Holocene sea level trend on the west coast of Bohai Bay, China: reanalysis and standardization
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Abstract: Using 110 newly revised Holocene sea level indicators categorized into three types, sediments (67), shelly cheniers (27) and oyster reefs (16), this paper firstly provides a Holocene relative sea level curve, based on multiple approaches of litho- and biostratigraphies and sedimentary faces analysis, for the west coast of Bohai Bay, China. Following considerations, including indicative meaning, the paleo tidal pattern and range and conversion from mean tidal level to mean sea level, an apparent relative mean sea level (RMSL) curve was further reconstructed. After systematical calibration using CALIB, those of the 48 reworked samples were further corrected for the residence-time effect. Similarly, the younger ages for another 35 samples were chosen at the subsample level. These result in a younger-oriented shift for about 0.5 ka. Three local spatial factors, including neotectonic subsidence (average rate about 0.1 mm/a), self-compaction of unconsolidated sediments (between a few decimeters to about 6 m) and subsidence due to groundwater withdrawal (between a few centimeters to about 2.5 m), were quantitatively corrected. Finally, the amended RMSL curve after eliminating all these local temporo-spatial factors is very likely to show non-existence of mid-Holocene highstand and imply potential influences of both ice-volume equivalent sea level and regional glacial isostatic adjustment. Although it is still unable to divide both global and regional factors, the slowdown of sea level rise, in 7.5–6.8 ka with a maximum height less than +1 m, may constrain the model effort in the near future.
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Key words:
- cheniers /
- oyster reefs /
- sediments /
- temporospatial corrections /
- local RMSL
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Figure 1. Basement tectonic map of the study area, depicted by a black rectangle, mainly belongs to the Bohai Bay Basin (Zhang et al., 2010; Huang et al., 2014; Liu et al., 2016). Four tidal gauge stations, located at the mouths of four rivers, are shown by blue solid squares. Inset: 1. Liaodong Bay; 2. Bohai Bay; 3. Laizhou Bay (modified from Li et al., 2015).
Figure 2. Map showing the geographic distribution of the sea level indicators in the coastal lowland and contiguous shallow sea area of the west coast of Bohai Bay (modified from Li et al., 2015).
Figure 3. Schematic illustration of a sedimentary model of the shelly cheniers in the Chenier Plain, west coast of Bohai Bay. Bar F, exposing the foot, was excavated in the wall of a shrimp pond and further Eijkelkamp penetrated, as shown in Figs 4a and b, while above the mid- or the rear-part can be seen in Figs 4c or f, respectively.
Figure 4. Photos showing the shelly cheniers and underlying and overlying muddy sediments in the Chenier Plain, the west coast of Bohai Bay. a. Chenier I, Houtangpu site, its crest covered by Jujuba shrubs, was perched on the surrounding muddy coast and formed the present native shoreline since last about 1 cal ka BP (Wang et al., 2000b). An excavation wall of a shrimp pond (bar F in Fig. 3), dug in the upper part of the present muddy tidal flat, shows the sediments above the front-base of the shelly chenier. b. Details of the wall in Fig. 4a. Thin layers, alternatively consisting of shell fragments and muddy shell hash, were revealed in this wall section. The indicator No. 84 (Table A4.2) was taken from the lower part of the wall-section. Eijkelkamp augering revealed a meter thick, muddy shell hash sediments, which show the very bottom of the chenier above its front-base and the underlying tidal mud. c. Chenier II-2 and the underlying mud, Gongnongcun, Shanggulin site, subsurface of the mid-part of chenier was visible about 30 cm below hammer. d. The underlying mud, below the subsurface in Fig. 4c, was further Eijkelkamp augured to a depth of 102 cm (from left-top to right-bottom), showing intertidal environment. The indicator No. 79 (Table A4.2), articulated in situ Sinonovacula constricta shells, was taken from the top of this underlying mud. e. The top of the underlying mud beneath the front-base, Chenier II-2, Apple Garden, Shanggulin site, was mixed with reworked single valves of Mactra veneriformis, Scapharca kagoshimensis and gastropoda Rapana, see the shells washed clean in a wooden box at right side, i.e., the indicator No. 75 (Table A4.2). f. Chenier II-1, Papadi, Shanggulin site, the rear-part of chenier body, showing fade-out landward (to right side), was covered by a thin darkish upper peat layer (i.e., indicator No. 23, Table A4.1). The geographical distribution of the sites here can also be found in Shang et al. (2016).
Figure 5. Schematic illustration of a sedimentary model for Holocene Crassostrea gigas reefs in the Oyster Plain, northwest coast of Bohai Bay. a. Reef body and its underlying and overlying muddy sediments. The reefs, about 2−6 m thick, were mainly composed of C. gigas shells, with a binary structure of the normal vertical building-ups of almost exclusively vertical posed and articulated individuals, and the horizontally intercalated muddy layers mixed with distorted individuals laying up horizontally. Such cyclicity, mostly repeated 6−7 times in the Oyster Group III only, about 5.8−4 cal ka BP, is a remarkable characteristic, although whether this characteristic was a response to sea level fluctuations still remains an open question (Wang et al., 2006). In this study, we picked the shell samples from the reef-top only as indicating MTL (mean tidal level). b. Two extreme and opposite patterns of the transition from reef top to the overlying upper intertidal muddy sediments: Bed 3(i) tranquil accumulation occurred first in the small depressions on the top surface and the shell-margin (ventral margin) of the individuals at the very top was still intact; Bed 3(ii) erosion and then deposition, the shell-margin on the very top was sharply truncated and a few individuals were removed by strong tides and then paved horizontally.
Figure 6. Buried Holocene Crassostrea gigas reefs, Oyster Plain, the northwest coast of Bohai Bay. a. Section 1, Dawuzhuang site, one of the largest reefs in Oyster Plain, was intermittently excavated from the 1990s to 2010s. By the end of digging work in the mid-2010s, the totally excavated area was about 150 m×100 m. Following such excavations, 11 sections were set up to study the reef itself and the overlying and underlying muds by our group (Fan, 2008, 2010; Liu, 2010; Wang et al., 2011c). Leveling shows the reef-top at 7 sections undulated in between −3.22 m and −1.94 m (undulation range 1.28 m), with an average elevation −2.48 m of National Vertical Datum 1985 (unpublished data). The indicator No. 97 was taken from the top part in this reef (Table A4.3). b. Biaokou site (Wang et al., 1995, 2006). The most concomitant species, Trapezium liratum, indicator No.101, was taken from 5 cm below the top surface in this reef (Table A4.3). c. Zengkouhe site. Dr. D. Surge, North Carolina University, stood on the bottom of excavating pit and Dr. Shang, one of the authors, stood with total station on a temporarily piled-dyke during the 2006 summer field work. Note a thin white line illustrating the boundary between the reef and the overlying muddy sediments, while the subsurface of reef was still a few decimeters below the pit bottom⑪⑫. The indicator No. 100 was taken from this reef (Table A4.3). d. The first type of transition (see 3(i) in Fig. 5b) from reef to the overlying intertidal mud revealed by Section 2, Dawuzhuang site, after carefully cleaning, no truncation was found from the ventral margin of the very top shells (except the one in the front of box ruler was artificially cut by cleaning). The lower part of overlying mud without laminar bedding structure is due to the stagnant qranquil microenvironment (i.e., the small depression), and gradually changed upwards to irregularly interbedded clayey and silty-fine sandy laminae, which are typically intertidal bedding structures. e. The second type of transition (see 3(ii) in Fig. 5b), Beihuaidian site. The shell margin was obviously truncated and even a few individuals were removed and paved on the boundary by strong floodings. f. A result for the Oyster-Museum-choosing-site investigation conducted in an area between Biaokou and Zengkohe sites. A three-dimensional diagram, based on 35 cores (the red vertical lines) in the area of 120 m×240 m, shows the reef-top (yellow) and reef-bottom (blue) depths, respectively. Ground surface, leveled against National Vertical Datum 1985, is shown by red color. The elevation of the reef-top observed undulates between −3.52 m and −2.26 m (Qin et al., 2017).
Figure 7. The primary evidence of the sea level change on the west coast of Bohai Bay. a. Distribution of the observed relative sea level (rsl) indicators, with the various symbols indicating different water levels as high (┬), low (┴), intertidal (□) and the mean tidal (+). b. Distribution of the relative mean sea level (RMSL) indicators, derived quantitatively from their originally observed rsl with the specific indicative meanings, shown as the three major types of sediments, cheniers and oyster reefs.
Figure 8. A series of temporospatial calibrations for the observed RMSL indicators on the west coast of Bohai Bay, China. a. Correction for the local residence time effects (RTC) for the 48 indicators, and the younger-age-selection at the subsample level for another 35 indicators are added to Fig. 7b. To date, two steps for time calibrations, CALIB+RTC corrections, have been completed in this study. b. A correction for the neotectonic subsidence, by compensating 0.1 mm/a, is added to Fig. 8a. c. A correction for the self-compaction of unconsolidated sediments is added to Fig. 8b. d. Further correction for the subsidence due to groundwater withdrawal is added to Fig. 8c. To date, all the local factors influencing the temporospatial distribution of the RMSL indicators have been corrected. Then, a solid black line describes approximately a local RMSL curve in the study area.
Figure 10. A diagram illustrates our RMSL curve (black solid line) in this study, the ESL curve of Lambeck et al. (red solid line), the model-predicted RMSL curves of Lambeck④ and Lambeck et al. (personal communication, 2014) (two green lines), and a RMSL band (light green shadow), redrawing from Fig. 4a-BB (Bohai Bay) of Bradley et al. (2016).
A1. Comprehensive diagram shows tidal gauge stations and the paleo bayhead evolution since the early mid-Holocene. Bayhead migrated gradually from the Oyster Plain in about 7 ka BP southeastward to the Chenier Plain and, finally, the present bayhead is located in the Jiyun River−Nanpai River section. Thin red lines, 0.58 and 0.64 of
$[(H_{{\rm O}_1}+H_{{\rm K}_1})/H_{{\rm M}_2}] $ in the shallow sea area, show less notable semidiurnal pattern⑥. Dotted+solid blue lines on the coastal lowland are paleoshorelines, determined by chains of both cheniers in the Chenier Plain and earthy mounds in the Oyster Plain. The earthy mound chains were alternated with the buried oyster reefs (Wang et al., 2006, 2010). Two red bars are approximate boundary separating modern bayhead and both sides of periphery while the thick black lines are rough boundary between the speculated ancient bayhead and peripheries.B1. Regression fit of the local porosity and depth, based on several key layers in Table B1.
B3. An Illustration showing comparison between decompacting value trends. For this study, differences are less than 1 m for shallow sediments normally less than 25 m in depth. Red circles: consolidation settlement is 400 m; green circles: consolidation settlement is 1 000 m. Blue circles are drawn by using slightly different values comparing with the red circles for porosity estimates as 45% for the basal peat, 40% for the hard soil horizon and 30% for the base of Quaternary sediments.
A1. The type of tides and tidal information collected from four gauge stations in the Bohai Bay⑥⑦ (Liu et al., 1986; HPL, 2007; EBC, 1989; HPL, 2007; Sun and He, 2013)
Tidal ranges Northeast periphery
(Northeast of Jiyun River Mouth)Bayhead
(Jiyun River Mouth−Napai River Mouth)Southeast Periphery
(Southeast of Nanpai River Mouth)Jianhekou Station Tanggu Station Qikou Station Dakouhe Station Mean tidal range
(MHW−MLW)about 2.3 m (1) 2.51 m, (2) 2.28 m,
(3) 2.48 m, (4) 2.40 m(1) 2.51 m,
(2) 2.3 m(1) 2.34 m, (2) 2.15 m,
(3) 2.30 maverage: about 2.42 m average: about 2.26 m Mean high tidal range
(MHHW−MLLW)2.80 m (1) 3.02 m, (2) 2.82 m,
(3) 2.9−2.8 m(1) 3.11 m (1) 2.88 m, (2) 2.7 m,
(3) 2.79 maverage: about 3.0 m average: about 2.79 m Mean high water
(MHW)about +1.13 m (1) +1.13 m, (2) +1.20 m,
(3) about +1.23 m(1) +1.23 m,
(2) about +1.23 mabout +1.08 m average: about +1.21 m Mean higher high water
(MHHW)about +1.18 m (1) +1.26 m
(2) +1.34 m(1) about +1.23 m,
(2) about +1.36 m+1.13 m average: about +1.3 m Mean low water (MLW) about −1.12 m (1) −1.15 m, (2) about −1.17 m about −1.07 m average: about −1.16 m Mean lower low water (MLLW) about −1.52 m (1) −1.56 m, (2) −1.66 m −1.47 m average: about −1.61 m Observed highest high weter (HHW) (1) +3.31 m, (2) +3.15 m,
(3) +3.11 m
average: +3.19 mNote: All the average values are calculated by this study and reaffirmed in Table A2. A2. Summary of the tides and geographic distribution for both the present and Holocene tidal situations in the Bohai Bay region, based on Table A1 and paleo geomorphology described in the main text and Fig. A1
Tidal properties The present tides and bay morphology Analogous Holocene tides and paleo bay morphology northeast periphery (Northeast of Jiyun River Mouth) bayhead (Jiyun River Mouth−Nanpai River Mouth) southeast periphery (Southeast of Nanpai River Mouth) paleo bayhead (Nanpai River Mouth−north most limit of the data) south periphery (Southeast of Nanpai River Mouth) Mean range 2.3 m 2.42 m 2.26 m 2.42 m 2.26 m Mean high range 2.80 m 3.0 m 2.79 m 3.0 m 2.79 m MHW +1.13 m +1.21 m +1.08 m +1.21 m +1.08 m MHHW +1.18 m +1.3 m +1.13 m +1.3 m +1.13 m MLW −1.12 m −1.16 m −1.07 m −1.16 m −1.07 m MLLW −1.52 m −1.61 m −1.47 m −1.61 m −1.47 m A3. The indicative meanings (RWL and IR) of the Holocene sea-level indicators on the west coast of Bohai Bay
Types of indicators Modern and ancient bayhead Modern and ancient southeastern periphery Modern northeastern periphery
(rarely used) 1)Peaty layers subtracting (1.26±0.05) m subtracting (1.1±0.03) m subtracting (1.15±0.03) m Other sediments (1) when indicating MHHW or MHW: subtracting (1.3±0.5) m,
(2) when indicating MLLW:
adding (1.6±0.5) m,
(3) when indicating MLW:
adding (1.15±0.5) m,
(4) when indicating intertidal zone only: sample’s altitude ±1 m(1) when indicating MHHW or MHW: subtracting (1.1±0.5) m,
(2) when indicating MLLW: adding (1.45±0.5) m,
(3) when indicating MLW: adding (1.05±0.5) m,
(4) when indicating intertidal zone only: sample’s altitude ±1 m(1) when indicating MHHW or MHW: subtracting (1.15±0.5) m,
(2) when indicating MLLW: adding (1.5±0.5) m,
(3) when indicating MLW: adding (1.1±0.5) m,
(4) when indicating intertidal zone only: sample’s altitude ±1 mCheniers (1) front-part: sample’s altitude ±1 m,
(2) above the mid-subsurface: subtracting (1.2±0.5) m,
(3) above the rear-subsurface: subtracting (1.3±0.5) m(1) front-part: sample’s altitude ±1 m,
(2) above the mid-subsurface: subtracting (1.1±0.5) m,
(3) above the rear-subsurface: subtracting (1.1±0.5) m(1) front-part: sample’s altitude ±1 m,
(2) above the mid-subsurface: subtracting (1.1±0.5) m,
(3) above the rear-subsurface: subtracting (1.2±0.5) mOyster Reefs 2) (The reef-top-elevation+0.15 m) ± 0.7 m − − Note: All the values, based on Table A2, were rounded to the nearest 5 or 10. 1) Indicative meanings for the northeastern periphery are also listed though this coastal sector is rarely dealt with in this study. 2) Elevation of the top of oyster reef indicates mean tidal level (MTL) directly and 0.15 m is added to reconstruct a corresponding MSL. A4.1. The Holocene relative mean sea level (rmsl) indicators, derived from the sediments, on the west coast of Bohai Bay
Basic information Temporal distribution Spatial distribution No. Locality, stratigraphy and environment, material dated, sampling depth / ground surface elevation / (averaged) sample elevation Coordinate Lab code Measured 14C date δ13C
/‰PDBConventional 14C age/a BP Calibrated 14C age: median probability/2σ range/cal a BP Status of material
datedSub-sample RTC
/cal aAge of rmsl: single value
/range/cal ka BP)Elevation of the observed rmsl/m Corrections
of tectonics/
self-compa-
ction/water withdrawal /mElevation of rmsl after corrections for the three local factors /m 1 Zhakou, shelly layer, single valves of undetermined shells, about 2/-/about −1.75 m 39.4°N,
117.8°EGC175A 5 410±250 −2.68 5 769±253 6 375/
6 966−5 789reworked no −600 5.775/
6.36−5.19−1.75±1 +0.58/
+0.78/
+0.20−0.19±1 2 Lizigu, swamp, upper peaty layer, mud, articulated Arconaia contorta (?), about 2 m/about +1 m/−1 m 39.5°N,
117.4°ECG1394 3 990±80 −27 4 199±90 4 715/
4 473−4 446,
4 893−4 525,
4 960−4 898in situ (?) no − 4.715/
4.960−4.446−2.26±0.05 +0.47/
+0.78/
+0.12−0.89±0.05 3 idem, marine sediments, wood branch on the top, 2.3 m/about +1 m/about −1.3 m CG-? 6 680±110 −27 6 696±117 7 567/
7 355−7 333,
7 387−7 374,
7 791−7 414reworked no − 7.567/
7.791−7.333−2.60±0.5 +0.75/
+0.90/
+0.12−0.83±0.5 4 Maomaojiang, intertidal shelly layer, single valves of Mactra veneriformis mainly, about 2 m/-/about 0 m
idem, single valves of M. veneriformis mainly, about 2.3 m/-/about 0 m39.4°N,
117.7°ECG187,
TD55 320±75,
6 350±105−2.68 5 679±85,
6 709±1126 274/
6 481−6 019;
7 395/
7 604−7 162reworked no −600 5.674/
7.00−5.420±1.5 +0.56/
+0.78/
+0.12+1.46±1.5 5 Dawuzhuang, oyster reef, Section 9, the bottom of the overlying mud, semi-carbonized wood branch, about 5 m/-/−2.23 m 39.4°N,
117.9°EBA
091202− − 4 810±35 5 520/
5 558−5 471,
5 604−5 568reworked no − 5.520/
5.604−5.471−2.23±0.7 +0.55/
+1.95/
+0.52+0.79±0.7 6 Panzhuang, the upper peat, peaty mud, 0.5−1 m/about +2 m/+1.25 m 39.4°N,
117.5°EZK525,
CG1891 805±125,
1 275±95−27 1 773±131,
1 243±1031 697/
1 988−1 402;
1 158/
1 327−956in situ no −660,
−1001.047/
1.33−0.85−0.01±0.05 +0.10/
+0.29/
+0.09+0.47±0.05 7 Xingtuo, lagoon-salt marsh, garlic-structured clay, tests of Pseudononinella variabilis and Ammonia becarii vars., 0.58 m/+1.6 m/+1.02 m 39.3°N,
117.6°EAA
45906− −5.4 2 301±54 2 134/
2 339−1 892in situ (?) no − 2.134/
2.339−1.892−0.28±0.5 +0.21/
+0.22/
+0.70+0.85±0.5 8 idem, bottom of garlic-structured clay, articulated shells of Glauconome primeana, 2−2.1 m/+1.6 m/−0.45 m AA
45905− −4.8 3 428±49 3 505/
3 680−3 345in situ no − 3.505/
3.680−3.345−0.45±0.5 +0.35/
+0.78/
+0.70+1.38 ±1.5 9 Xingtuo Pit, the lower portion of intertidal zone, fine sandy-silty mud, articulated Mactra veneriformis shells, 3.8−4.0 m/about +1.6 m/about −2.3 m AA
45904− −4.5 4 169±52 4 489/
4 720−4 275,
4 766−4 753in situ no − 4.489/
4.766−4.275−0.7±0.5 +0.45/
+1.52/
+0.87+2.14±0.5 10 Core H1, basal peat, peaty mud, 16.57−16.63 m/+1.6 m/−15.0 m 39.3°N,
117.6°E00Y078 8 562±100 −27 8 530±108 9 520/
9 793−9 270,
9 816−9 808,
9 865−9 848,
9 885−9 877in situ no −660 8.860/
9.22−8.61−16.26±0.05 +0.88/
+4.81/
+0.87−9.7±0.05 11 Core H3, intertidal muddy sediments, single valves of Potamocorbula laevis, 4.4 m/+1.315 m/−3.09 m 39.3°N,
117.7°EBeta
3581643 640±30 −6.4 3 950±30 4 191/
4 377−4 009reworked no −600 3.591/
3.77−3.41−3.09±0.5 +0.36,
+1.46,
+1.40+0.13±0.5 12 Core HD21, lagoon-salt marsh, articulated Saliqua pulchella, 1.1−1.2 m/+0.71 m/−0.44 m 39.4°N,
117.6°EAA
45902− −7.6 1 579±48 1 310/
1 473−1 173in situ no − 1.310/
1.473−1.173−1.74±0.5 +0.13/
+0.40/
+0.45−0.76±0.5 13 Core NP3, salt marsh, Potamocorbula laevis fragments, 1.1 m/+2.134 m/+1.03 m 39.2°N,
118.0°EBeta
3053071 390±30 −0.8 1 790±30 1 524/
1 679−1 369reworked no −600 0.924/
1.08−0.77−0.12±0.5 +0.09/
0/
+1.72+1.69±0.5 14 idem, upper part of shallow sea, Nassarius variciferus, 9.3−9.4 m/+2.134 m/−7.22 m Beta
3053104 710±30 −6.3 5 020±30 5 558/
5 690−5 437reworked no −600 4.958/
5.09−4.83−5.72±0.5 +0.49/
+2.82/
+1.72−0.69±0.5 15 idem, charcoals from a shell hash layer, 17.75−17.87 m/+2.134 m/−15.65 m BA08832 − − 7625±40 8 417/
8 483−8 371,
8 520−8 490,
8 536−8 532reworked no − 8.417/
8.536−8.371−15.65±0.5 +0.84/
+4.87/
+1.72−8.22±0.5 16 Core HG81, basal peat, peaty mud, 16.65−16.68 m/about +2 m/−14.67 m 39.2°N,
117.8°E06Y084 8 160±250 −27 8128±253 9 040/
9 539−8 430in situ no −660 8.380/
8.88−7.77−15.93±0.05 +0.84/
+4.83/
+1.05−9.21±0.05 17 Core Beining Park, basal peat, plant debris (?), 16.89−17.09 m/about +2.46 m/about −14.53 m 39.2°N,
117.2°EZK601-I 8 035±120 −27 8035±120 8 902/
9 271−8 592in situ no − 8.902/
9.271−8.592−15.79±0.05 +0.89/
+4.93/
+0.37−9.6±0.05 18 Core CH114, basal peat, peaty mud, 12.0−12.1 m/about −3.90 m/about −15.95 m 39.1°N,
117.9°EBA
081875− − 8415±35 9 455/
9 351−9 320,
9 522−9 400in situ no −660 8.795/
8.86−8.66−17.21±0.05 +0.88/
+4.61/
+1.12−10.6±0.05 19 Core CH115, basal peat, charcoals and carbonized twigs, 17.41−17.43 m/−3.90 m/about −21.32 m 39.1°N,
117.9°EBA
081878− − 8 805±35 9 833/
9 946−9 682,
10 008−9 993,
10 127−10 063in situ (?) yes − 9.833/
10.127−9.682−22.58±0.05 +0.98/
+5.75/
+1.12−14.73±0.05 20 Core HDZ, basal peat, peaty mud, 18.05−18.15 m/about +2.5 m/−15.6 m 39.1°N,
117.7°ETD408 8 120±160 −27 8 088±165 8 998/
9 436−8 587in situ no −660 8.338/
8.78−7.93−16.86±0.05 +0.83/
+4.67/
+0.17−11.19±0.05 21 idem, basal peat, peaty mud, 18.81−19.0 m/about +2.5 m/−16.41 m 39.1°N,
117.7°ETD409 8 645±130 −27 8 613±136 9 644/
9 357−9 316,
9 962−9 399,
10 044−9 985,
10 152−10 052in situ no −660 8.984/
9.49−8.65−17.67±0.05 +0.90/
+4.90/
+0.17−11.7±0.05 22 Core Chentangzhuang, basal peat, peaty mud, 13.29−13.49 m/about +1.96 m(?)/−11.43 m 39.1°N,
117.21°ECG256 8 825±140 −27 8 793±146 9 858/
10 199−9 539in situ no −660 9.198/
9.54−8.88−12.69±0.05 +0.92/
+4.15/
+0.37−7.25±0.05 23 Papadi, Shanggulin, lagoon-salt marsh behind shelly chenier, the upper peat, peaty mud, about 1.2 m/about +2 m/+0.8 m 38.81°N,
117.1°E98Y076 1 827±80 −27 1 795±90 1 721/
1 904−1 529,
1 925−1 906in situ no − 1.721/
1.925−1.529−0.46±0.05 +0.17/
+0.47/
+0.75+0.93±0.05 24 Core BQ2, transitional zone, Potamocorbula laevis, 16.50 m/+1.57 m/−14.93 m 38.81°N,
117.51°EBA
04544− − 7 955±40 8 611/
8 841−8 430reworked yes − 8.611/
8.841−8.430−14.93±1 +0.86/
+4.78/
+1.0−8.29±1 25 Chuanganglu Pit, Section 7, Shell Bed B, articulated Potamocorbula laevis, 4.8/-/about −2.91 m 38.8°N,
117.5°EBeta
3636242 070±30 −3.7 2 420±30 2 271/
2 427−2 114reworked yes − 2.271/
2.427−2.114−2.91±1 +0.22/
+1.87/
+2.0+1.18±1 26 Chuanganglu Pit, Section 4, carbonized, fine plant twig, about 4/-/−2.46 m 38.8°N,
117.5°EBeta
3523312 830±30 −26.0 2 810±30 2 911/
2 999−2 844reworked no − 2.911/
2.999−2.844−3.76±0.5 +0.29/
+1.56/
+2.0+0.09±0.5 27 idem, Section 4, the bottom of Shell Bed A, articulated Mactra chinensis, about 4.4/-/−2.86 m 38.8°N,
117.5°EBeta
3523281 320±30 −1.3 1 710±30 1 436/
1 558−1 300reworked yes − 1.436/
1.558−1.300−2.86±1 +0.14/
+1.72/
+2.0+1±1 28 Chuanganglu Pit, Section 5, the mid-upper part of Shell Bed A, articulated Sinonovacula constricta, about 4/-/−2.46 m 38.8°N,
117.5°EBeta
3523251 570±30 −6.6 1 870±30 1 620/
1 786−1 482in situ yes − 1.620/
1.786−1.482−3.76±0.5 +0.16/
+1.56/
+2.0−0.04±0.5 29 Chuanganglu Pit, Section 1, coarse shell hash layer at the lower part of Shell Bed 1, Nassarius sp., about 4.2/-/about −2.4 m 38.8°N,
117.5°EBeta
3359101 520±30 −3.0 1 880±30 1 631/
1 795−1 494reworked yes − 1.631/
1.795−1.494−2.4±1 +0.16/
+1.64/
+1.5+0.9±1 30 idem, Section 1, thin shelly lamina at the upper part of Holocene marine muddy sediments, single valve of Potamocorbula laevis, about 4.5/-/−2.7 m 38.8°N,
117.5°EBeta
3359122 080±30 −1.2 2 470±30 2 339/
2 516−2 149reworked yes − 2.339/
2.516−2.149−2.7±1 +0.23/
+1.75/
+2.0+1.28±1 31 Chuanganglu Pit, Section 2, coarse shelly layer on the top of Shell Bed A, articulated Mactra venerifomis, about 4/-/about −2.2 m 38.8°N,
117.5°EBeta
3359071 410±30 −1.0 1 800±30 1 536/
1 686−1 387reworked yes − 1.536/
1.686−1.387−3.5±0.5 +0.15/
+1.56/
+2.0+0.21±0.5 32 idem, Section 2, the bottom of Shell Bed A, single valve of Potamocorbula laevis, about 5/−/about −3 m Beta
3359112 470±30 −2.2 2 840±30 2 794/
2 934−2 692reworked no −600 2.194/
2.33−2.09−3.0±0.5 +0.22/
+1.95/
+2.0+1.17±0.5 33 Chuanganglu Pit, Section 6, Shell Bed C, articulated Cyclina sinensis, about 5.5/-/−3.7 m; 38.8°N,
117.5°EBeta
3523232 100±30 −1.6 2 480±30 2 355/
2 542−2 156reworked yes − 2.318/
2.542−2.093−3.7±1 +0.23/
+1.87/
+2.00.4±1 idem, Section 6, Shell Bed C, articulated Potamocorbula laevis, about 5.5/-/−3.7 m; Beta
3636172 090±30 −5.9 2 400±30 2 246/
2 392−2 093idem, Section 6, Shell Bed C, articulated Mactra chinenesis, about 5.5/-/−3.7 m Beta
3636202 090±30 −1.4 2 480±30 2 355/
2 542−2 15634 idem, Section 6, Shell Bed C, copper coin, about 5.5/-/−3.7 m − − − − − in situ − − 2.119/
2.171−2.068−5.0±0.5 +0.21/
+1.87/
+2.0−0.92±0.5 35 idem, Section 6, Shell Bed D, Dupliaria dussumierii (?), about 6/-/−4.15 m Beta
3636231 950±30 +0.4 2 370±30 2 217/
2 341−2 060reworked yes − 2.217/
2.341−2.060−4.15±1 +0.22/
+2.04/
+2.0+0.11±1 36 Core BT113, single valve of Potamocorbula laevis, 4.4 m/+1.436 m/−2.96 m 38.8°N,
117.5°EBeta
2960051 180±30 −0.8 1 580±30 1 310/
1 436−1 180reworked no −600 0.710/
0.83−0.58−2.96±1 +0.07/
+1.52/
+1.50+0.13 ±1 37 idem, fragments of Potamocorbula laevis, 16.70 m/+1.436 m/−15.26 m Beta
2977427 520±40 −6.0 7 830±40 8 467/
8 599−8 341reworked no −600 7.867/
8.0−7.74−15.26±1 +0.78/
+4.70/
+1.50−8.28±1 38 Core BT115, basal peat, peaty mud, 11.1 m/−6.1 m/−17.2 m 38.7°N,
117.7°EBA
091538− − 8 190±40 9 137/
9 269−9 024in situ no −660 8.477/
8.61−8.36−18.46±0.05 +0.85/
+3.26/
+0.87−13.48±0.05 39 Core ZW15, basal peat, plant debris (subsample >180 μm), 12.6 m/+1.631 m/−10.97 m 38.7°N,
117.2°EBeta
3562087 450±40 −25.0 7 450±40 8 271/
8 358−8 186in situ yes − 8.271/
8.358−8.186−12.23±0.05 +0.83/
+3.90/
+0.95−6.55±0.05 40 Core G15, basal peat, peaty mud, 17.95 m/about +2.46 m/−15.49 m 38.7°N,
117.4°EZK1465 8 580±130 −27 8 548±136 9 548/
9 177−9 140,
9 223−9 203,
9 926−9 236,
10 117−10 069in situ no −660 8.888/
9.46−8.48−16.75±0.05 +0.89/
+5.20/
+0.22−10.44±0.05 41 idem, basal peat, peaty mud, 18.65 m/about +2.46 m/−16.19 m ZK1466 9 140±120 −27 9 108±127 10 288/
10 595−9 894, 10 650−10 624in situ no −660 9.628/
9.99−9.23−17.45±0.05 +0.96/
+5.41/
+0.22−10.86±0.05 42 Core BQ1, marine muddy sediments, intercalated coarse shelly layer, Corbicula fluminea, 18.22 m/+3.404 m/−14.81 m BA
04542− − 8 620±40 9 462/
9 576−9 305reworked no −600 8.862/
8.97−8.70−13.21±0.5 +0.88/
+4.98/
+1.12−6.23±0.5 43 Core TP23, single valve of Potamocorbula laevis, 5.7 m/+1.848 m/−3.85 m 38.7°N,
117.4°EBA
091539− − 3 450±35 3 528/
3 682−3 376reworked no −600 2.928/
3.08−2.77−3.85±1 +0.29/
+1.50/
+1.35−0.71±1 44 idem, peat layer, peaty mud, 14.1 m/+1.848 m/−12.25 m BA
091542− − 7 610±40 8 407/
8 462−8 350,
8 477−8 467,
8 513−8 495in situ no −660 7.747/
7.85−7.69−13.51±0.05 +0.77/
+3.80/
+1.75−7.19±0.05 45 idem, peat layer, peaty mud, 14.2 m/+1.848 m/−12.35 m BA
091543− − 8 160±40 9 096/
9 149−9 010,
9 254−9 162in situ no −660 8.436/
8.59−8.35−13.61±0.05 +0.84/
+3.83/
+1.75−7.19±0.05 46 Core Q7, lagoon-salt marsh (?), upper peat layer, peaty mud (<180 μm), 1.3 m/+3.458 m/+2.16 m 38.7°N,
117.5°EBeta
358054450±30 −20.4 530±30 540/
559−510, 630−600in situ no −100 0.440/
0.53−0.41+0.9±0.05 +0.04/
+0.12/
+1.0+2.06±0.05 47 idem, single valve of Ruditapes philippinarum, 16.3 m/+3.458 m/−12.84 m Beta
3571527 360±40 −2.7 7 730±40 8 371/
8 515−8 219in situ no −600 7.771/
7.91−7.62−12.84±1 +0.78/
+4.44/
+1.0−6.62±1 48 idem, peaty layer, plant debris (>180 μm), 17.2−17.23 m/+3.458 m/−13.76 m Beta
3571538 040±40 −28.0 7 990±40 8 868/
8 666−8 662,
9 005−8 705in situ yes − 8.868/
9.005−8.662−13.76±1 +0.89/
+4.70/
+1.0−7.17±1 49 idem, basal peat, organic matter (<180 μm), 18.85 m/+3.458 m/−15.39 m Beta
3571579 130±40 −24.6 9 140±40 10 287/
10 411−10 226in situ no −1320 8.967/
9.09−8.91−16.65±0.05 +0.96/
+5.17/
+1.0−9.52±0.05 50 Core QX01, lagoon-salt marsh, organic mud (<180 μm), 5.52 m/+5.16 m/−0.36 m 38.7°N,
116.8°EBeta
3296474 260±30 −22.5 4 300±30 4 858/
4 892−4 829,
4 908−4 899,
4 917−4 913,
4 960−4 924in situ no −1320 3.538/
3.64−3.51−1.66±0.5 +0.35/
+1.76/
+1.0+1.45±0.5 51 idem, lagoon-salt marsh, organic mud (<180 μm), 6.35 m/+5.16 m/−1.19 m Beta
3296444 990±50 −23.6 5 010±50 5 750/
5 900−5 644in situ no −1320 4.430/
4.58−4.32−2.45±0.05 +0.44/
+1.82/
+1.0+0.81±0.05 52 idem, lagoon-salt marsh, organic mud (<180 μm), 7.2 m/+5.16 m/−2.04 m Beta
3296435 090±30 −25.0 5 090±30 5 813/
5 831−5 748,
5 912−5 843in situ no −1 320 4.493/
4.59−4.43−3.34±0.5 +0.45/
+2.11/
+1.0+0.22±0.5 53 idem, lagoon-salt marsh, plant debris (>180 μm), 8.2 m/+5.16 m/−3.04 m Beta
3296415 820±30 −24.6 5 830±30 6 647/
6 732−6 554in situ yes − 6.647/
6.732−6.554−4.34±0.5 +0.66/
+2.45/
+1.0−0.23±0.5 54 idem, lagoon-salt marsh, basal peat, plant debris (>180 μm), 8.7 m/+5.16 m/−3.54 m Beta
3296426 020±40 −24.3 6 030±40 6 875/
6 763−6 755,
6 981−6 778in situ yes − 6.875/
6.981−6.755−4.8±0.05 +0.69/
+2.62/
+1.0−0.49±0.05 55 idem, lagoon-salt marsh, basal peat, plant debris (>180 μm), 9.16 m/+5.16 m/−4.0 m Beta
3296456 160±40 −27.4 6 220±40 7 117/
7 133−7 006,
7 250−7 140in situ yes − 7.117/
7.250−7.006−5.26±0.05 +0.71/
+2.77/
+1.0−0.78±0.05 56 idem, lagoon-salt marsh, basal peat, plant debris (>180 μm), 11.39 m/+5.16 m/−6.23 m Beta
3296407 010±30 −25.3 7 010±30 7 855/
7 771−7 763,
7 935−7 786in situ yes − 7.855/
7.935−7.763−7.53±0.5 +0.78/
+3.22/
+1.0−2.53±0.5 57 Core QX03, peaty layer, plant debris (>180 μm), 2.9−2.92 m/+4.38 m/+1.47 m 38.7°N,
116.9°EBeta
3537922 280±30 −20.6 2 350±30 2 357/
2 461−2 326in situ) no − 2.357/
2.461−2.326+0.21±0.05 +0.23/
+0.74/
+0.90+2.08±0.05 58 idem, peaty layer, plant debris (>180 μm), 4.9−4.91 m/+4.38 m/−0.53 m Beta
3537943 370±30 −24.0 3 390±30 3 634/
3 699−3 569in situ no − 3.634/
3.699−3.569−1.83±0.5 +0.36/
+1.52/
+0.90+0.95±0.5 59 idem, articulated Sinonovacula sp., 7.28 m/+4.38 m/−2.9 m Beta
3538086 440±40 −9.5 6 690±40 7 380/
7 497−7 255in situ no − 7.380/
7.497−7.255−2.9±1 +0.74/
+2.13/
+0.90+0.87±1 60 idem. gleysoil (?), plant debries (>180 μm), 7.39−7.40 m/+4.38 m/−3.01 m Beta
353796NA NA 5 930±30 6 752/
799−6 671,
6 844−6 816in situ yes − 6.752/
6.844−6.671−3.01±1 +0.67/
+2.17/
+0.90+0.73±1 61 idem. organic mud, plant debris (>180 μm), 8.63−8.65 m/+4.38 m/−4.26 m Beta
3537986 440±40 −26.7 6 410±40 7 350/
7 420−7 271in situ yes − 7.350/
7.420−7.271−5.52±0.05 +0.73/
+2.59/
+0.90−1.3±0.05 62 Core QX02, intercalated organic mud (<180 μm), 5.68 m/+3.57 m/−2.11 m 38.6°N,
117. 0°EBeta
3327925 430±30 −24.0 5 450±30 6 247/
6 300−6 204in situ no −1320 4.927/
4.98−4.88−3.41±0.5 +0.49/
+1.78/
+0.95−0.19±0.5 63 idem, intercalated organic mud, plant debris (>180 μm), 7.27 m/+3.57 m/−3.70 m Beta
3333296 360±30 −25.7 6 350±30 7 283/
7 218−7 176,
7 331−7 240,
7 373−7 356,
7 413−7 390in situ yes − 7.283/
7.413−7.176−5.0±0.5 +0.73/
+2.10/
+0.95−1.22±0.5 64 idem, plant debris (>180 μm), 8.98 m/+3.57 m/−5.41 m Beta
3333306 620±30 −26.3 6 600±30 7 494/
7 522−7 434,
7 564−7 532in situ yes − 7.494/
7.564−7.434−6.71±0.5 +0.75/
+2.71/
+0.95−2.3±0.5 65 Core Yugong 3, basal peat, peaty mud, 14.72−14.92 m/about +1.26 m/−13.56 m 38.5°N,
117.6°ECG70 9 120±180 −27 9 088±184 10 240/
9 640−9 635, 10 711−9 661in situ no −660 9.580/
10.05−8.97−14.82±0.05 +0.96/
+4.59/
+0.06−9.21±0.05 66 Core 8-1, lagoon-salt marsh behind chenier, gleysol horizon, Gyraulus sp. and Assiminea sp., 1.55−1.59 m/+2.80 m/+1.23 m 38.2°N,
117.8°EAA
45899− −7.0 2 869±56 2 827/
3 018−2 689in situ yes − 2.827/
3.018−2.689+0.13±0.03 +0.28/
+0.60/
+0.15+1.16±0.03 67 Core LL1, basal peat, mainly charcoals, 15.22−15.35 m/+2.80 m/−12.48 m 03Y141 7 550±230 −27 7 550±233 8 368/
8 981−7 944in situ no − 8.368/
8.981−7.944−13.58±0.03 +0.84/
+4.44/
+0.15−8.15±0.03 to be continued No. Notes Explainations of the indicative meaning, RTC, the three spatial corrections and changes from the previous work (Li et al., 2015) 1 It is a shelly layer intercalated in intertidal muddy sediments (SQG, 1980). Two estimated sampling elevations were −2 m and −1.5 m (Han and Meng, 1996), so an average −1.75 m is used in this study. RTC was given (Li et al., 2015). “□” −1.75 m, msl (−1.75±1) m while error was ±1.5 m in Li et al. (2015). 2 An organic mud was formed in lagoon-swamp left by marine regression. This thin muddy layer, with fresh water mollusks including this dated Arcomaia contorta (?) and antler of Elaphodus davidianus, laid on the marine influenced sediments with oyster and razor clam shells (Zhao et al., 1989). Sampling depth and corresponding elevation were estimated on local topographic map (Zhao et al., 1989). “┬” −1m and (1.26±0.05) m (Table A3) should be subtracted for restoring msl, i.e., msl (−2.26±0.05) m. However, msl was (−2.5±0.5) m in Li et al. (2015) because MTL and MSL were confused at that time. 3 This thin twig was mixed into top part of marine sediments, buried by the upper peat layer, from which the sample CG1394 was obtained (Zhao et al., 1989). “┬” −1.3 m, (1.3±0.5) m should be subtracted (Table A3), i.e., msl (−2.6±0.5) m. However, 1.5 m was chosen in Li et al. (2015). 4 It was a shelly layer intercalated into intertidal muddy sediments (Han et al., 1980; Peng et al., 1980; Peng et al., 1984; Li and Zhao, 1990). The samples, taken from the lower to bottom part of the layer, indicate intertidal environemnt. However, the two ages are more than 1 100 cal a different and only sampling depths were given in the literature but without elevation. Correponding elevation has to be converted from topographic map. “□” 0 m, msl (0±1.5) m (Li et al., 2015). 5 This twig, 10 cm-long and 1.5 cm in diameter, was found mixed in the intertidal muddy sediments, immediately (only 1 cm) above the reef top. Foraminifera (abbreviated as “forams” below) analysis indicates that the muddy sample (10 g, dry), taken exactly from the same position with this twig, contains 14 different species and total 796 tests, mainly Ammonia beccarii vars., Elphidium nakanokawaense and E. magellanicum dominantly, indicating sea water influence in intertidal zone closing to estuary. Upwards, 10−20 cm above the reef-top, the mud consists of 18 species and about 1 600 tests, including A. beccarii, E. nakanokawaense and A. takanabensis. Both forams samples indicate the mid- to upper part of intertidal zone (Liu, 2010). Moreover, sedimentary facies analysis shows the mud sediments, overlying on the reef, remained intertidal environment for its lower 1.5 m thickness and further upward gradually changed to lagoon and salt marsh environment (Liu, 2010; Wang, 2012; Wang et al., 2011c). Elevation of the sampling position, −2.229 m, was given by Total Station measurement relative to the National Vertical Datum 1985 (Liu, 2010) (see the sea level indicator BA110343 for further details). So, “□” −2.23 m and directly indicates msl (−2.23±0.7) m. This reconstructed msl is same as Li et al. (2015) while the vertical error is changed from ±1.5 m to ±0.7 m in this study. RTC is not necessary because it is a macro plant fossil. 6 This terrigenous, 50−60 cm thick, peaty layer is 0.5−1 m below the ground surface and the sample was taken from the top part of the layer (IOA, 1983; Peng et al., 1980). Elevation of ground surface, about +2 m, is estimated from local topographic map by this study. The sampling position indicating “┬” about +1.25 m; two samples give a time range of 1988−956 cal a BP. After RTC it becomes about 1.33−0.85 cal ka BP. Contemporaneous msl was (−0.01±0.05) m, i.e., subtracting (−1.26±0.05) m (Table A3). However, (1.8±0.5) m was subtracted in Li et al. (2015). 7 The sampling layer shows a sudden increase of forams tests from less than a few hundred 60 cm below to about 3 630 at this position, where Pseudononinella variabilis and Ammonia beccarii vars. dominated, of which about 2 000 tests were picked out for AMS dating. On the other hand, 30 cm above, forams tests decreased to several tens only (Li et al., 2004; Wang et al., 2010). So, it indicates a flooding intrusion event of high sea water. “┬” +1.02 m, msl (−0.28±0.5) m, i.e., 1.3 m (an indicative meaning for sample deposited at MHHW in paleo bayhead, Table A3) is subtracted from +1.02 m. However, it was regarded as an equivalent of the upper peat, so 1.8 m was subtracted for msl reconstruction in Li et al. (2015). 8 The shells still kept their vertical growth position and were articulated (Li et al., 2004; Wang et al., 2010), and indicating intertidal muddy environment with freshwater input (Zhang, 2008; Okutani, 2000). RTC is not necessary for these in situ shells. “□” −0.45 m, msl (−0.45±0.5) m (Li et al., 2015). 9 Based on sedimentary facies analysis, forams study (Li et al., 2004) and the ecological description for this species (Zhang, 2008; Okutani, 2000), it was in the middle to lower intertidal and the upper subtidal zones. Five forams samples, from 2.8−4.8 m in depth, show 23 species and about 450 tests in average for each sample and maximum 30 species and 4 800 tests, mainly Quinqueloculina akneriana rotunda, Elphidium magellanicum, E. nakanokawaense, Ammonia beccarii vars. (Li et al., 2004). Ostrocoda of 2.5−4.5 m were mainly composed of Sinocytherdea impreaa, Tanella opima, Spinileberis sinensis, Eucyther serrata, Laxoconcha binhaiensis and totally 46 species with about 1 800 valves in average for each sample, indicating mid- to lower part of intertidal zone) (Lin et al., 2004). “┴” −2.3 m, msl (−0.7±0.5) m, i.e., adding (1.6±0.5) m (Table A3). RTC is not necessary for the in situ articulated shells. In Li et al. (2015), msl was (−0.8±0.5) m because 1.5 m was simply added. 10 Only rarely marine influenced Ostracoda Neomonoceratina dongtaiensis and Sinocytheridea impressa were found in the middle to upper part of this basal peat layer (Lin et al., 2004) but without forams (Li et al., 2004). Forams were found only from about 1 m above this layer with 48 tests of Ammonia beccarii indicating Holocene marine transgression started (Li et al., 2004). So, the sampling position roughly shows MHHW, i.e., “┬” −15.0 m, msl (−16.26±0.05) m ((1.26±0.05) m is subtracted, Table A3). After RTC, time range 9885−9270 cal a BP is corrected to 9.22−8.61 cal ka BP. However, (1.5±0.5) m was mistakenly subtracted from −15 m in Li et al. (2015). 11 Facies analysis and microbiological studies indicate that the sediments in depth 12−3 m were deposited in Holocene marine environments while this sample, at 4.4 m, was formed during the late Holocene marine regression. Microbiological sample at 4.8 m (40 cm below this sample), show (1) diatom: Coscinodiscus spp. and Diplonesis bombus; (2) forams: Quinqueloculina seminula and Massilina inaequalis; (3) ostracoda: Albileberis sinensis, Bicornucythere bisanensis, Metacytheropleron elliptica, Neomonoceratina dongtaiensis, Sinocytheridea impressa and Stigmatocythere dorsinoda. On the other hand, these analyses did at depth 4.0 m (40 cm above) also found marine fauna, in which diatom Coscinodiscus spp. reached 20 valves①. Ground elevation of the borehole was firstly estimated as about +1.5 m, afterwards the actually measured value +1.315 m was obtained1. “□” −3.09 m, msl (−3.09±0.5) m. RTC was given (Li et al., 2015). 12 +0.71 m of the ground elevation in this site was checked out from 1:10 000 map⑯. This articulated in situ razor clam was found just above the depositional boundary between lagoon-salt marsh and underlying open intertidal flat⑯. “┬” −0.44 m, msl (−1.74±0.5) m (Table A3). However, 1.8 m was subtracted in Li et al. (2015) when mistakenly made it as an equivalent as the upper peat. 13 Facies analysis indicates that the sedimentary environment of U5, from which this sample was taken, had changed from open intertidal to lagoon-salt marsh, caused by continuously increased accumulations of fluvial sediments (Chen et al., 2014). Forams show both Ammonia beccarii vars. and Elphidium magellanicum decreased but E. hugesi foraminosum, E. kiangsuensis, Pseudononionella variabilis and Cribrononion porisuturalis increased. Ostracoda assemblage shows Albileberis sheyangensis, Bicornucythere bisanensis, Neomonoceratina dongtaiensis, N. triangulata and Trachyleberis niitsumai disappered but Sinocytheridea impressa and Loxoconcha binhaiensis increased. All these indicate the sampling position was in the upper part of intertidal depth in lagoon-salt marsh environment (Chen et al., 2016).“┬” +1.03 m. msl (−0.12±0.5) m, i.e., (1.15±0.5) m should be subtracted because it is located in the northeast periphery (Table A3). However, it was mistakenly regarded as an equivalent of the upper peat, so 1.8 m was subtracted for msl reconstruction in Li et al. (2015). 14 This is a 10 cm-thick shell hash layer in marine facies U4, also with single valves of Chlamus forreri and other marine shells. Forams show A. beccarii vars. was domimant, while E. magellanicum decreased but Protelphid turberculatum and Quinqueloculina akneriana increased (Chen et al., 2014, 2016), indicating the lower limit of MLLW. “┴” −7.22 m. msl (−5.72±0.5) m, i.e., (1.5±0.5) m should be added because it is in the northeast periphery (Table A3). RTC was given. Although (1.5±0.5) m was also added in Li et al. (2015), it was considered as a half of MHHW−MLLW as a general value for the whole coast of the west Bohai Bay. However, there was lack of awareness of difference between MTL and MSL, and tidal regime difference beween bayhead and pheriphery at that time in Li et al. (2015). 15 The charcoal grains, >180 μm, picked out from a shelly layer, consisting of C. pestigris, P. laevis and Dosinia sp., intercalated into U3. It was formed in intertidal zone (Chen et al., 2014, 2016). RTC is not needed because of large charcoal grains. “□” −15.65 m, msl (−15.65±0.5) m while was (−15.65±1.5) m (Li et al., 2015). 16 Although terrigenous Bithynia sp. and Gyraulus sp. shells were found about 30 cm below this layer, broken Crasostrea shell and other marine shell fragments appeared 60 cm above it (Liu, 2007). So, it can be roughly recognized at MHHW level, i.e., “┬” −14.67 m, msl (−15.93±0.05) m (subtracting (1.26±0.05) m, Table A3), though msl was (−16.4±0.5) m in Li et al. (2015), i.e., subtracting (1.8±0.5) m when the sampling elevation was roughly determined as −14.6 m. RTC was given (Li et al., 2015). 17 Although it was immediately under the marine sediments the ground elevation +4 m (IOA, 1983) is doubtful, i.e., without definite indication of which elevation system was used. This study guesses it should be the 1950 Dagu System (the local system). So, 1.543 m is subtracted from the original +4 m. Thus, “┬” −14.53 m, msl (−15.79±0.05) m, i.e., subtracting (1.26±0.05) m (Table A3) though (1.8±0.5) m was subtracted in Li et al. (2015). RTC is not needed because the sample was described as plant peat (IOA, 1983) though it was given in Li et al. (2015). 18 Scattered fragments of marine diatom Coscinodiscus spp. were found in this peat layer, i.e., upper part of the diatom Assemblage Zone 1. This basal peat layer was eroded at 11.2 m by overlying marine mixed deposits of black-brown shell hash of Chlamus farreri (?), Crassostrea sp. and Anomia chinesis, with silty sand, consisting of diatom Zone 2, including Cyclotella striata/stylorum, Coscinodiscus perforates, C. subconcavus, Actinoptychus undulates, C. argus, C. radiates, Thalassionema nitzschioides and Grammatophora oceanica (Shang, 2011). Sedimentary facies analysis and diatom assemblages indicate this basal peat had been slightly influenced by sea water as salt marsh environment and then eroded by shallow sea deposits⑨ (Shang, 2011). So, “┬” −15.95 m. msl (−17.21±0.05) m, i.e., (1.26±0.05) m should be subtracted because at bayhead (Table A3). RTC was given (Li et al., 2015). However, (1.8±0.5) m was subtracted in Li et al. (2015). 19 This 2 cm-thick bulk sample, then subdivided into two subsamples, was taken from a dark muddy peaty layer in depth of 17.4−17.6 m. This layer consists of Gyraulus sp., Cincinnatia alticonula, Stenothyra glabra and Assiminea lutea, and seeds, semi-carbonized plant debris, and fresh water Ostracoda Cypris decaryi, Candonirlla albicans, Ilyocypris radiate and I. subbiplicata but without forams, indicating this is fresh water peat (unpublished data of the authors’ group). However, Assiminea sp. appeared in overlying mud at 15.05−17.4 m, indicating the beginning of sea water influence. This subsample of charcoals and twigs is about 1 330 cal a younger than another subsample: 11 167 cal a BP/BA081877, shells of Gyraulus sp. and Bithynia sp. (Li et al., 2015). On the other hand, this peaty layer was gradually formed from the underlying hard mud, i.e., the late Pleistocene soil horizon formed in LGM (Last Glacial Maximum). This in situ characteristic and being much younger than another subsample mean that RTC is not necessary. “┬” −21.32 m and (1.26±0.05) m should be subtracted (Table A3). So, msl (−22.58±0.05) m. However, (1.8±0.5) m was subtracted in Li et al. (2015). 20 Although marine sediments existed immediately above this basal peat layer, elevation of the borehole is approximately estimated only (Li and Zhao, 1990; Wang and Tian, 1999). So, “┬” −15.6 m, msl (−16.86±0.05) m (Table A3). However, it was (−17.4±0.5) m in Li et al. (2015) because (1.8±0.5) m was subtracted. RTC was given (Li et al., 2015). 21 Comparing with indicator TD408, this is a lower peat layer (Wang and Tian, 1999) and also enables to approximately indicate arrival of rising water. So, “┬” −16.41 m, msl (−17.67±0.05) m (i.e., subtracting (1.26±0.05) m), though it was (−18.21±0.5) m (i.e., subtracting (1.8±0.5) m) in Li et al. (2015). RTC was given as subtracting 660 cal a from two end dates of 10 152 and 9 316 cal a BP, respectively (Li et al., 2015). 22 This basal peat layer was covered by marine muddy sediments with a marine shell hash layer of 12.7−13 m and also a shell-concentrated lamina was just above this basal peat (Luo et al., 1983). However, the borehole elevation of +3.5 m is estimated to be the local datum, so 1.543 m shoule be subtracted in this study to be +1.96 m. As to the Borehole elevation of +1.6 m in Peng et al. (1980), it is probably wrong because Luo et al. (1983) was personally responsible for this drilling work. So, “┬” −11.43 m, msl (−12.69±0.05) m (Table A3), though it was −13.23 m (i.e., subtracting 1.8 m) in Li et al. (2015). RTC was given (Li et al., 2015). 23 A 10 cm-thick, in situ, black clayey peaty mud, as the upper peat layer, was revealed by a transverse section cutting Chenier II-1 in this site. The layer covered from chenier-crest landward to its lee side till the chenier rear-end (Fig. 4f). Such a tilted peaty layer is +1.7 m high on the chenier-crest and +0.7 m high on the rear-end. This sample was taken at about +0.8 m. Sedimentary analysis indicates this peaty sample was formed above the level of poured high sea waters (Wang et al., 2000c). So, “┬” +0.8 m and msl (−0.46±0.05) m, i.e., subtracting (1.26±0.05) m (Table A3). However, in Li et al. (2015), 1.8 m was subtracted and was perceived as reworked deposit and RTC of 660 a was given. 24 It is a 33 cm-thick transitional layer in depth of 16.63−16.3 m in between the Holocene marine transgressive sediments and the underlying terrigenous muddy sediments. This subsample is about 610 cal a younger than another subsample, freshwater Arconaia contorta shell: 9 225 cal a BP/BA04543 (Li et al., 2015) and, therefore, RTC is not necessary. This indicates intertidal environment, i.e., “□” −14.93 m, msl (−14.93±1) m while was (−14.93±1.5) m (Li et al., 2015). 25 It is also a beach face layer and about 130 cal a younger than another subsample of single valve of Mactra chinensis: 2 397 cal a BP/Beta363625 (Li et al., 2015; Shang et al., 2015; 2016). The sampling position is about 75 cm below the average top elevation of −2.16 m. So, “□” −2.91 m, msl (−2.91±1) m. RTC is not necessary. The reconstructed msl is more accuracy than (−3±1.5) m in Li et al. (2015). 26 It is a totally 30 cm-thick, horizontally alternative deposits between shelly hash laminae and muddy laminae with very fine, carbonized herbaceous twigs. It was formed in between the Shell Bed A and the overlying salt marsh-lagoonal mud (Shang et al., 2016), indicating a remained influence of sea water. It might indicate high waters rather than the intertidal as Li et al. (2015) used. The sampling position is 30 cm below the average top elevation of −2.16 m. So, “┬” −2.46 m and msl should be (−3.76±0.5) m, i.e., (1.3±0.5) m is subtracted (Tables A2 and A3). However, it was believed as intertidal environment and reconstruceted msl was (−2.46±1.5) m in Li et al. (2015). RTC is not necessary because it is macro plant though RTC calibration was given in Li et al. (2015). 27 This is a beach face in intertidal depth, Shell Bed A, and about 1 260−0 cal a younger than another two subsamples of single valves of Moerella sp.: 2 695 cal a BP/Beta352329, and Potamocorbula laevis: 1 436 cal a BP/Beta352330 (Li et al., 2015; Shang et al., 2015, 2016). The sampling position is 70 cm below the average top elevation of −2.16 m. Thus, “□” −2.86 m, msl (−2.86±1) m though msl was (−2.86±1.5) m in Li et al. (2015). RTC is not necessary (Li et al., 2015). 28 This in situ razor clam is still in vertical position and articulated. The species is in lower, or middle to lower, intertidal environment based on conchologists such as Okutani (2000) and Zhang (2008). However, sedimentalogically, this individual probably survived in a small depression with poured high waters in the Shell Bed A, top layer of the Holocene marine sediments (Shang et al., 2016), therefore, it may roughly indicate high position of the intertidal environment rather than its normally growing environment. It was 210−70 cal a younger than another two subsamples of the same layer as Umbonium sp.: 1 830 cal a BP/Beta352327, and single valve of Scapharca kagoshimensis: 1 689 cal a BP/Beta352326 (Li et al., 2015). The sampling position is about 30 cm below the average top elevation of −2.16 m (Li et al., 2015; Shang et al., 2015, 2016). So, “┬” −2.46 m and msl (−3.76±0.5) m (i.e., subtracting (1.3±0.5) m, Table A3), while msl was (−2.46±1.5) m in Li et al. (2015) because the conchlogists’ idea was simply followed. RTC is not necessary (Li et al., 2015). 29 This shell bed, as a cover of the Holocene marine sediments, was formed in intertidal zone and it is about 390 cal a younger than another subsample of single valve Potamocorbula laevis: 2019 cal a BP/Beta335908 (Shang et al., 2015, 2016). So, “□” −2.4 m, msl (−2.4±1) m (Table A3), though it was (−2.4±1.5) m (Li et al., 2015). RTC is not necessary. 30 It was in the intertidal flat during the Holocene marine regression period and is about 470 cal a younger than another subsample of single valve of Corbicula: 2 812 cal a BP/Beta335909 and RTC is not necessary. Elevation of the outcrop was Total Station and RTK measured relative to the National Vertical Datum 1985. “□” −2.7 m, msl (−2.7±1) m while it was (−2.7±1.5) m (Li et al., 2015). 31 It was a 10 cm-thick, coarse shelly layer, having high-angle foreset bedding, in the top part of Shell Bed A, Section 2, and is about 650−290 cal a younger than another two subsamples of single valve of Scapharca kagoshimensis (1 830 cal a BP/Beta335913) and shell hash (2 198 cal a BP/Beta335914) (Shang et al., 2016; Li et al., 2015). In this pit (about 200 m×120 m, cf., Shang et al., 2016), top elevations of the Holocene marine sediments and the ground surface were Total Station measured and then connected with the National Vertical Datum 1985 by RTK, showing the average elevation (−2.16±0.2) m (simply as −2.2 m) for top of the Holocene marine sediments (12-spot average, but only six sites were shown in Shang et al. (2016) and +1.93 m of the local ground surface elevation, unpublished data of the authors’ group). In this paper, elevations of sea level indicators in this pit were then calculated as a vertical distance from the average top elevation (−2.16±0.2) m (or (−2.2±0.2) m). As to this sample, it was probably formed by MHHW. “┬” −2.2 m. So, (1.3±0.5) m should be subtracted and msl (−3.5±0.5) m. RTC is not necessary compared with another two subsamples (Li et al., 2015). However, msl was (−2.2±1.5) m because it was approximately regarded as intertidal depth and without further compensation for msl reconstruction in Li et al. (2015). 32 It was formed in intertidal environment (Li et al., 2015; Shang et al., 2016). Sampling position is about 80 cm lower than the average top elevation of −2.16 m in this site. “□” about −3.0 m, msl (−3.0±0.5) m. RTC was given (Li et al., 2015). The indicative meaning was same while error was ±1.5 m in Li et al. (2015). 33 These three articulated shells, as three subsamples, taken from the same thin shelly layer in the shell beach, Shell Bed C, show the exactly same or highly overlapping ages of their 2σ range, and are about 1 130 cal a younger than the fourth subsample of single valve of Dosinia corrugate: 3 450 cal a BP/Beta352324 (Li et al., 2015; Shang et al., 2015, 2016). The sampling position is about 1.5 m below the average top elevation of −2.16 m (Li et al., 2015). This layer is considered as shelly beach in intertidal environment. So, “□” −3.7 m, msl (−3.7±1) m. Such three subsamples give the same ages and are 1 150 cal a younger than the fourth one, RTC is therefore not necessary (Li et al., 2015). In Li et al. (2015), vertical error was ±1.5 m. 34 This coin was found mixed with shells and muds at the same beach face layer, Shell Bed C (Li et al., 2015). Based on the two independent experts, this coin was cast during 221−118BC, i.e., 2 171−2 068 cal a BP. Numerous shards of pottery, 8 pottery fishnet sinkers and a 37 cm-long artifact of edge-truncated cattle-shoulder, as a spade/cooking utensil (?), were found altogether with this coin in this layer (Shang et al., 2015, 2016). The archaeological evidence indicates this beach face was soon exposed above MHHW during 221−118 BC (Shang et al., 2015, 2016). So, “┬” −3.7 m, and (1.3±0.5) m should be subtracted (Table A3). As a result, msl (−5.0±0.5) m. However, 1.8 m was subtracted in the light of the peat layer in Li et al. (2015). 35 This Shell Bed D is another beach face layer and about 0.45 m below the Shell Bed C and was also intercalated into fine sandy-/muddy marine sediments. About 420 cal a younger than another subsample of single valve Dosinia corrugate: 2 639 cal a BP/Beta363622 (Li et al., 2015; Shang et al., 2015, 2016). “□” −4.15 m, msl (−4.15±1) m, while the error was ±1.5 m in Li et al. (2015). 36 It was taken from the upper part of U5, consisting of abundant Potamocorbula laevis, and Ammonia confertitesta, Quinqueloculina akneriana rotunda, A. beccarii vars., A. annectens; Sinocytheeridea impressa, Bicornucythere bisanensis and Neomonoceratina dongtaiensis. It was in intertidal environment. The overlying sediments, at least 2 m thick, were still affected by high waters as salt marsh (Chen et al., 2012a, b, 2016). The borehole elevation was measured by Total Station and connected with the present-day National Datum. So, “□” −2.96 m, msl (−2.96±1) m. RTC was given. The sampling elevation was miscaculated as −2.94 m (Li et al., 2015). 37 This is the U2, 16.9−16.0 m, deposited in the estuary or tidal flat with fresh water influence, see notes of the previous indicator. The underlying U1, 20.0−16.9 m, fine sand and silt with land snail Cathaica sp. and carbonized plant debris, showing terrestrial environment (Chen et al., 2012a, b, 2016). So, this sample indicates intertidal environment, i.e., “□” −15.26 m, msl (−15.26±1) m. RTC was given (Li et al., 2015). However, the vertical error was ±1.5 m in Li et al. (2015). 38 Definitely marine influenced shelly hash layer with Scapharca kagoshimensis was found only 0.8 m above this peaty layer. This basal peat was formed in coastal salt marsh based on seismic investigations and sedimentary analysis (Tian et al., 2017). So, it was just above high waters. “┬” −17.2 m, msl (−18.46±0.05) m (Table A3). RTC was given (Li et al., 2015). 39 11.3−11.45 m: marine shell layer, with >10 cm fragmentary shells of Crassostrea sp., eroded the underlying sediments. 11.45−12.6 m: mud, without definite marine-influenced evidence. So, this sample, taken from the peaty layer of 12.6−12.7 m, approximately shows that corresponding msl must be lower. It is about 630 cal a younger than another subsample (portion <180 μm): 8 899 cal a BP/Beta355822, so RTC is not necessary (Li et al., 2015). “┬” −10.97 m, and (1.26±0.05) m was subtracted (Table A3), so msl (−12.23±0.05) m. Howwver, (1.8±0.5) m was subtracted in Li et al. (2015). 40 This basal peat layer was immediately overlaid by Holocene marine sediments with suddenly increasing of forams and marine ostracoda, 100−200 individuals, respectively, per sample (Wang et al., 1986). However, the borehole elevation could be only approximately estimated as +4 m relative to the local datum and so 1.543 m is therefore subtracted by this study to convert to the National Vertical Datum 1985 system. So, “┬” −15.49 m, and (1.26±0.05) m should be subtracted (Table A3), i.e., msl (−16.75±0.05) m. RTC was given (Li et al., 2015). However, the ground elevation was estimated as +2 m of the local datum and 1.8 m was subtracted by Li et al. (2015) and thus, reconstructed msl was even about 2.5 m lower than this study. 41 It was taken from the lower part of the same basal peat layer with the sample ZK1465 (Wang et al., 1986). This sample was even less marine-influenced than the overlying one (ZK1465), So, “┬” −16.19 m, msl (−17.45±0.05) m, i.e., subtracting (1.26±0.05) m (Table A3). However, msl was (−19.96±0.5) m in Li et al. (2015), see the notice of indicator ZK1465. RTC was given (Li et al., 2015). 42 It was taken from the lower part of Bed 2. This bed, yellowish brown (10YR 4/3) silt, is composed of Potamocorbula laevis, Scapharca subcrenata, Arcopsis sp., Sinonovacula aonstricta and Nassarius sp., with brackish water species such as Corbicula fluminea, Parafossarulus exiguous, Assiminea latericea. Forams increased to >5 000 tests while marine ostracoda reached to >1 760 valves per sample. This was a fluctuation of sea level rise named as Ib④, formed in estuary in intertidal depth to subtidal depth (Yan et al., 2006a, b). So, it may indicate “┴” −14.81 m, msl −13.21 m, i.e., adding (1.6±0.5) m (Table A3). RTC was given (Li et al., 2015). However, (1.5±0.5) m, a half of mean high tidal range, was simply added in Li et al. (2015). 43 It was deposited on the top part of Holocene marine sediments, with abundant shell hash mixed in mud, indicating intertidal environment following marine regression process (unpublished data of the authors; Sun et al., 2011). “□” −3.85 m, msl (−3.85±1) m (Table A3). RTC was given (Li et al., 2015). 44 This and the following data all have a few forams, including Elphidium nakanokawaense and Ammonia beccarii, which suggest a coming of sea water (unpublished data of the authors’ group). So, “┬” −12.25 m, msl (−13.51±0.05) m, i.e., (1.26±0.05) m should be subtracted (Table A3). RTC was given (Li et al., 2015). However, (1.8±0.5) m was subtracted in Li et al. (2015). 45 This is same as the overlying BA091542 (unpublished data of the authors’ group). “┬” −12.35 m, msl (−13.61±0.05) m, i.e., (1.26±0.05) m should be subtracted (Table A3). However, 1.8 m was subtracted in Li et al. (2015). RTC was given (Li et al., 2015). 46 Many shelly hash and scattered articulated Mactra chinensis (?) were also found in this peaty layer and the layer was considered as the upper peat layer, i.e., “┬” +2.16 m. So, msl (+0.9±0.05) m (Table A3). RTC was given (Li et al., 2015). However, (1.8±0.5) m was subtracted in Li et al. (2015). 47 Forams at the sampling position of 16.3 m show less than 50 tests but rapidly booming upward to >500 tests at 16 m. It indicates an ongoing rising-fluctuation of sea level. Unfortunately, there is only a test-counting but without species identification. So, it is better to think it was in intertidal zone, i.e., “□” −12.84 m, msl (−12.84±1) m. RTC was given (Li et al., 2015). The sampling position was considered at low tidal environment and 1.5 m, as a half range between MHHW and MLLW, was added to restore msl as (−11.34±0.5) m in Li et al. (2015). However, difference between MTL and MSL was not realized three years ago. 48 As an intercalated thin peaty layer, it was found in the lower part of Holocene marine muddy sediments. Based on facies analysis, this layer was in salt marsh in intertidal depth with forams tests nearly 350 a sample. Although it was perhaps reworked peaty-concentrated layer, this subsample (>180 μm) is about 420 cal a younger than another one (i.e., the portion <180 μm): 9 287 cal a BP/Beta358055 (Li et al., 2015). Therefore, RTC seems to be not necessary. “□” −13.76 m, msl (−13.76±1) m (Table A3), though the error was ±1.5 m in Li et al. (2015). 49 It immediately overlay on the early Holocene terrigenous, yellowish brown mud, with a small amount of forams (<50 tests), indicating onset of marine transgression. “┬” −15.39 m, msl (−16.65±0.05) m, i.e., (1.26±0.05) m should be subtracted (Table A3). RTC should be given. This is a new indicator in this study. 50 Forams in Zone VI were nearly disappeared from 5.6 m upwards, only very few Ammonia beccarii vars. and Nonion glabrum remained in euryhaline and brackish environment as a small depression where only very high sea waters may enter. Facies analysis indicates this was in transition between Holocene marine environment and overlying salt marsh (Wang et al., 2015). So, it can be used to indicating a position of MHHW, i.e., “┬” −0.36 m, thus msl (−1.66±0.5) m (subtracting (1.3±0.5) m, Table A3). Only the portion <180 μm was dated and the empirical estimation of 1 320 cal a should be subtracted for RTC. 51 This sample was taken from the very bottom of Forams Zone VI. Comparing to huge amount of forams as >17 000 tests at 6.6 m and >38 000 at 6.8 m of Zone V-2, howevr, this sample is composed of 57 tests as being Ammonia beccarii dominant only (Wang et al., 2015), and CaCO3 illuviation existed at 6.1−6.3 m. Such a calcium precipitation was abundant but without clear boundary showing short and not mature condition. All these suggest this sample was formed at around MHHW level, perhaps a small depression in saltmarsh environment with an increased evaporation upwards. So, “┬” −1.19 m, msl (−2.45±0.05) m (subtracting (1.26±0.05) m, Table A3). However, 1.8 m was subtracted in Li et al. (2015). RTC was given to subtracting 1 320 cal a (Li et al., 2015). 52 Formas Zone V-2. a salt marsh-lagoonal environment occasionally inundated by high water from open bay and has Ammonia beccarii, Pseudononion minitum, Nonion glabrium and Cribrononion porisuturalis (Wang et al., 2015). Stratigraphical transition from the immediately underlying hydromorphic soil to this faint, darkish layer also indicates this seawater reoccupied environment. So, “┬” −2.04 m and (1.3±0.5) m should be subtracted (Table A3), i.e., msl (−3.34±0.5) m. However, in the early study (Li et al., 2015) this sample was believed as in the intertidal depth, so no further vertical compensation was given. RTC was given (Li et al., 2015). 53 It is a faint, darkish layer belonging to the start of Forams Zone V-1. A very small amount of forams of Nonion glabrum (12 tests) and Ammonia beccarii (1 test) was found in a 20 g dry sample taken from this layer, showing brackish environment (Wang et al., 2015). This subsample was about 360 cal a younger than another subsample (portion <180 μm): 7 005 cal a BP/Beta331456 (Li et al., 2015). “┬” −3.04 m, msl (−4.34±0.5) m (subtracting (1.3±0.5) m, Table A3). It was classified to the “upper peat layer” in Li et al. (2015), or more precisely, a layer transformed from the immediately underlying hydromorphic gley horizon in salt marsh-lagoon environment behind shoreline and was occasionally inundated by high water. 54 A faint darkish layer in the bottom of Zone IV, 8.7−7.8 m. Two samples were without forams and only one sample had 13 tests, and colour become yellowish with weakly mottling structure, all indicating increased terrestrial influence, i.e., sea level drops for a short time. So, this sample was in the upper part of intertidal zone in between MHHW and MHW and can be treated as an intercalated organic-rich layer. It was about 210 cal a younger than another subsample (portion <180 μm): 7 088 cal a BP/Beta331457 (Li et al., 2015). So, “┬” −3.54 m and (1.26±0.05) m (Table A3) should be subtracted, i.e., msl (−4.8±0.05) m. However, 1.8 m was subtracted in Li et al. (2015). 55 Zone III, 9.2−8.7 m in depth and 2 forams samples show 68 and 338 tests, respectively, and Nonion glabrum dominated (Wang et al., 2015;). About 1 050 cal a younger than another subsample (portion <180 μm): 8 162 cal a BP/Beta331458 (Li et al., 2015). Downwards, core logging and forams study of Zone II, 10.6−9.2 m, having 7 forams samples with tests in between 0−18, showing a saltmarsh occasionally influenced by high water. So this sample can also be roughly treated as an intercalated organic-rich layer. “┬” −4.0 m, msl (−5.26±0.05) m, though (1.8±0.5) m was subtracted in Li et al. (2015). 56 Although freshwater diatoms were still dominant such as Eunotia spp. and Synedra unla, more marine and brackish species, including planktonic Cosinodiscus spp. and Actinocyclus spp., were found. The freshwater diatoms also changed from benthic (e.g., Eunotia spp. and S. unla) to planktonic taxa (e.g., Melosira spp.). On the other hand, forams in this sample downward to the basal peat at about 13.1 m, 8 010 cal a BP (Beta329646) were very rare for 4 forams samples (0−3 tests per sample). However, forams sadenly boomed from above 11.2 m upward (Wang et al., 2015). Therefore, this sample itself can be reconnized as being highwater influenced and indicating an arrival of sea water to the area. This subsample is about 160 cal a younger than another subsample (portion <180 μm): 8 016 cal a BP/Beta331455 (Li et al., 2015). So, “┬” −6.23 m, msl (−7.53±0.5) m (i.e., subtracting (1.3±0.5) m, Table A3) and RTC was given (Li et al., 2015). However, 1.8 m was subtracted in Li et al. (2015). 57 It was a peaty layer, with fragments of Gyraulus sp. and small CaCO3 concretions, formed in lagoon-salt marsh environment and may indicate a maximum height of MHHW (unpublished data of the authors’ group). RTC is not necessary because only the plant debris was used for dating. “┬” +1.47 m, and (1.26±0.05) m (Table A3) should be subtracted because it shows influence by MHHW. So, msl (+0.21±0.05) m. However, (1.8±0.5) m was subtracted in Li et al. (2015). 58 A dark organic layer, 4.9−5.1 m, was formed in salt marsh-lagoonal muddy environment and this sample was taken from the very top of the layer. Forams in this layer have >500 tests a 20 g dry sample and then sharply decreased upward to less than 50 in the overlying sediments, implying an end of seawater fluctuation upwards. So, this layer was probably influenced by MHHW. “┬” −0.53 m, subtracting (1.3±0.5) m to restore msl, i.e., msl (−1.83±0.5) m. RTC is not needed (Li et al., 2015). However, 1.8 m was subtracted in Li et al. (2015). 59 6−7.9 m: mud, dull yellow orange (10YR 7/2), clearly mottling structure with scattered Fe/Mn nodules of mm scale. This is different with both underlying and overlying brownish gray mud (10YR 5/1) and indicating more oxidized environment. Conchologically, this razor clam usually lives in mid- and lower intertidal zone with fresh water input, according to Zhang (2008) and Okutani (2000). The 13C value, −9.5‰PDB, of this clam shell supports freshwater poured in. On the other hand, forams had suddenly booming from about 7.4 m, i.e., 12 cm below the clam position, upward, indicating this articulated razor shell was also seawater influenced. So, most probably, this razor clam lived in lagoon-salt marsh within intertidal depth where both high tidal waters and freshwater can pour into. So, “□” −2.9 m, msl (−2.9±1) m. However, it was considered to be survived by high waters and 1.8 m was subtracted for msl reconstruction in Li et al. (2015). Indeed, survived by high waters was true but it was in intertidal depth. 60 A 1 cm-thick gleysol horizon, light grey, 10YR 7/1, was in muddy sediment. Forams started to bloom from this position upward till 6.7 m in depth, within which five forams samples all show >500 tests, indicating seawater came from this horizon. 820 cal a younger than another subsample (part <180 μm): 7 572 cal a BP/Beta355244 (Li et al., 2015). So, this horizon can be considered as a sudden but endurable filling of high sea waters into lagoon-salt marsh (see explanation of Beta 353808). “□” −3.01 m, msl (−3.01±1) m. However, this age is about 630 a younger than the overlying razor clam (Beta353808). A doubt remains with this reversal time sequence. It is a new indicator in this study. 61 Forams analysis indicates a sudden high sea water fluctuation with >500 tests a sample at about 8.8 m, i.e., only a decimeter lower than this sampling position. It means this sample was high tide influenced. It is 955 cal a younger than another subsample (<180 μm): 8 305 cal a BP/Beta355245 (Li et al., 2015). “┬” −4.26 m, as being an equivalent of basal peat, so (1.26±0.05) m should be subtracted, msl (−5.52±0.05) m. RTC is not needed. It is a new indicator in this study. 62 This sample was taken from a thin peaty layer intercalated in between two mainly marine influenced beds (Wang et al., 2015). A forams sample, just 2 cm below this sample, shows 2 tests only. Another three forams samples, 6.2 m, 6 m and 5.8 m in depths, have foraminifera tests 5 600, 6 016 and 304, respectively. Upwards, tests were found as much as 5 360, 7 456 and 8 512 in depths of 5.6 m, 4.6 m and 4 m, respectively. These clearly indicate only the sampling position at around 5.68 m was nearly nothing but both the underlying and overlying were fully abundant with forams. It suggests that this sample was in a short term during which sea water was little bit far away. Thus, this peaty layer was formed above high waters. So, “┬” −2.11 m, msl (−3.41±0.5) m (i.e., subtracting (1.3±0.5) m, Table A3). The sample is <180 μm and RTC correction of 1 320 cal a was given (Li et al., 2015). However, (1.8±0.5) m was subtracted in Li et al. (2015). 63 The sampling position was almost no forms found. However, 40 cm above, forams increased to 9 000 tests a 20 g dry sample (Wang et al., 2015). About 460 cal a younger than another subsample (<180 μm): 7 739 cal a BP/Beta332793 and RTC is not necessary (Li et al., 2015). “┬” −3.70 m, msl (−5.0±0.5) m, i.e., an intercalated organic layer formed at high waters (Table A3). 64 The diatom assemblage at 9.0−8.39 m shows from more benthic to more planktonic species upwards, indicating marine inundation had started (Wang et al., 2015). However, abundance of foraminifera had decreased from >500 tests in about 9.2 m to disappeared in this sampling depth of 8.98 m, then reoccurred at about 8.6 m (i.e., about 40 cm above this sample). So, it can be roughly considered as only influenced by high waters. “┬” about 5.41 m, and (1.3±0.5) m should be subtracted because is was an intercalated organic layer indicating high waters (Table A3). So, msl (−6.71±0.5) m. This is about 460 cal a younger than another subsample (<180 μm): 7952 cal a BP/Beta332794 (Li et al., 2015), so RTC is not needed. This is a new indicator in this study. 65 It is composed of euryhaline forams, brackish ostracoda and molluscan shells (Peng et al., 1984) and so it was influenced by high sea waters. The borehole elevation of +2.8 m (Peng et al., 1984) was classified to the National Vertical Datum 1985 in Li et al. (2015). Nevertheless, in this study, it is reconsidered as the local datum only and 1.543 m has to be subtracted. So, “┬” −13.56 m, msl (−14.82±0.05) m, i.e., subtracting (1.26±0.05) m (Table A3). RTC was given (Li et al., 2015). 66 This is about 10 560 cal a younger than another subsample of bulk organic mud (gley horizon): 13 477 cal a BP/KIK12257 (Wang et al., 2004; Li et al., 2015), from which the in situ gastropoda shells were picked out and dated (Wang et al., 2003). “┬” +1.23 m, msl (+0.13±0.03) m, i.e., subtracting (1.1±0.03) m because it was located in the ancient southwest periphery as an upper peat layer (Fig. A1 and Table A3). However, 1.8 m was subtracted in Li et al. (2015). RTC correction is not necessary (Li et al., 2015). 67 This basal peat was eroded by marine muddy sediments, in which Potamocorbula sp., Scapharca subcrenata, Mactra veneriformis, Assiminea sp., Nassarius sp., Corbicula sp. and Ammonia beccarii, Elphidium advenum and Quinqueloculina seminula were found (Li et al., 2006). “┬” −12.48 m, msl (−13.58±0.03) m, i.e., (1.1±0.03) m was subtracted as it was basal peat in the ancient southwest periphery (Fig. A1 and Table A3). RTC seems to be not necessary because it was in situ and mainly charcoals though it was given in Li et al. (2015). Note: The measured 14C dates, signified in italics in Column 4, were changed from their original dates with the Libby half life of 5 730 a by subdiving 1.029 in this study. The 13C values, signified in italics in Column 5, were either recommended by Mook and van de Plassche (1986) or used with the local empirical mean value of −2.68‰ PDB (Wang, 1994; Wang and van Strydonck, 1997; Li et al., 2015) for the marine shells. Correspondingly, such calibrated approximate conventional ages in Column 6 were given in italics. A4.2. Holocene relative mean sea level (rmsl) indicators, derived from the shelly cheniers, in the west coast of Bohai Bay
Basic information Teomporal distribution Spatial distribution No. Locality, stratigraphy and environment, material dated, sample-depth / ground surface elevation / (averaged) sample elevation Coordinate Lab code Measured 14C date δ13C
/‰PDBConventional 14C age/a BP Calibrated 14C age: median probability/2σ range/cal a BP Status of material
datedSub-sample RTC
/cal aAge of rmsl: single value/ range/cal ka BP Elevation of the observed rmsl/m Corrections of tectonics
/self-compaction/water withdrawal/mElevation of rmsl after corrections for the three local factors/m 68 Qingtuozi, shelly chenier, Section 1, Umbonium sp., 2.90/-/about−0.20 m 39.1°N,
117.8°EBeta
3053141 940±30 −3.6 2 290±30 2 123/
2 292−1 972reworked no −600 1.523/
1.69−1.37−1.4±0.5 +0.15/
+1.13/
+1.57+1.45±0.5 69 idem, shelly chenier, Section 4, single valves of Potamocorbula laevis, about 2/-/about +0.22 m Beta
3053122 180±30 −0.2 2 590±30 2 505/
2 677−2 341reworked no −600 1.905/
2.07−1.74−0.98±0.5 +0.19/
+0.78/
+1.57+1.56±0.5 70 Xinlicun, chenier, single valves of undetermined shells, about 1.5/-/about +1 m 39.1°N,
117.4°EGC
172(2)3 040±120 −2.68 3 399±127 3 476/
3 827−3 138reworked yes −600 2.876/
3.23−2.54−0.2±0.5 +0.29/
+0.58/
+0.25+0.92±0.5 71 Jugezhuang, shelly chenier, Eijkelkamp core Site JN341-2, very bottom of chenier, single valves of Mactra veneriformis, about 4/-/−0.4 m 39.0°N,
117.3°EBA
101095− − 3 350±25 3 417/
3 285−3 270,
3 560−3 290reworked yes − 3.417/
3.560−3.270−1.0±0.5 +0.34/
+1.56/
+1.75+2.65±0.5 72 idem, Site JN341-2, very top of the underlying mud, single valves of M. veneriformis and Scapharca kagoshimensis, about 4/-/about −0.6 m BA
101097− − 3 500±25 3 590/
3 753−3 438reworked yes − 3.590/
3.753−3.438−1.2±0.5 +0.36/
+1.56/
+1.75+2.47±0.5 73 Yucenzi, shelly chenier, bottom, single valve of Crassostrea sp., about 1.5/-/about +0.39 m 38.9°N,
117.0°EBA
110865− − 4 415±35 4 808/
4 967−4 611reworked yes − 4.808/
4.967−4.611−0.81±0.5 +0.48/
+0.58/
+2.36+2.61±0.5 74 Banqiao, shelly chenier, Eijkelkamp core, just above the subsurface in its front side, Nassarius sp., 2.4−2.5 m/+2.311 m/about −0.14 m 38.9°N,
117.5°EBeta
3052941 490±30 −6.0 1 800±30 1 536/
1 687−1 386reworked no −600 0.936/
1.08−0.78−0.14±0.5 +0.09/
+0.94/
+2.19+3.08±0.5 75 Apple Garden, Shanggulin, shelly chenier, top of the underlying mud, single valves of Scapharca kagoshimensis and Mactra veneriformis, about 4/-/about −1.5 m 38.8°N,
117.5°EUtC7038 − −1.70 1 850±35 1 597/
1 760−1 430reworked yes − 1.597/
1.760−1.430−1.5±0.5 +0.10/
+1.56/
+1.56+1.72±0.5 76 idem. chenier, above the front-base, Umbonium sp. and Terebridae, -/-/about −1 m UtC2240 − 0.0 2 350±100 2 190/
2 478−1 894reworked yes − 2.19/
2.478−1.894−1±0.5 +0.22/
+1.56/
+1.56+2.34±0.5 77 Papadi, Shanggulin, shelly chenier, middle part, articulated Mactra veneriformis, 1.2 m/about +2 m/+0.8 m 38.8°N,
117.5°EUtC7037 − −4.03 2 125±40 1 919/
2 096−1 701reworked no − 1.919/
2.096−1.701−0.5±0.5 +0.19/
+0.47/
+1.56+1.72±0.5 78 idem. shelly chenier, bottom, just above its subsurface at its seaward side, Umbonium sp., 2 m/about +2 m/0 m 98Y075 2 410±140 −2.68 2 769±146 2 705/
3 080−2 319in situ no − 2.28/
2.66−1.900±0.5 +0.23/
+0.78/
+1.56+2.57±0.5 79 Gongnongcun, Shanggulin, shelly chenier, top of the underlying mud, articulated Sinonovacula constricta, about 4/-/about −0.5 m 38.8°N,
117.5°E03Y79 − − 850±80 605/
767−468in situ no − 0.605/
0.767−0.468−0.5±0.5 +0.06/
+1.56/
+1.56+2.68±0.5 80 Qikou, shelly chenier, lower part, single valves of undetermined shells, 5.32 m/+6.22 m/about +0.9 m 38.6°N,
117.6°ESH217 2 000±70 −2.68 2 402±81 2 250/
2 524−1 986reworked no −600 1.650/
1.92−1.38+0.9±0.5 +0.16/
+1.81/
+0.17+3.04±0.5 81 idem, shelly chenier, about 0.5 m above the rear-base of subsurface, single valves of undetermined shells, -/-/about +1 m CG73 2 020±100 −2.68 2 379±108 2 225/
2 573−1 917reworked no −600 1.625/
1.97−1.31+0.2±0.5 +0.16/
+0.78/
+0.17+1.31±0.5 82 Zhaizhuang, shelly chenier, top of the underlying mud, articulated Sinonovacula constricta, 4−5 m/-/about −3 m 38.6°N,
117.2°ECG328 5 130±85 −2.68 5 489±94 6 070/
6 295−5 845in situ no − 6.070/
6.295−5.845−3±0.5 +0.61/
+1.75/
+0.09−0.55±0.5 83 Zhangjuhe, shelly chenier, bottom, shells, 1.8/-/about +0.6 m 38.6°N,
117.6°EYS265 2 495±65 −2.68 2 854±76 2 819/
3 064−2 609reworked no −600 2.219/
2.46−2.01−0.7±0.5 +0.22/
+0.70/
+0.15+0.37±0.5 84 Houtangpu, shelly chenier, Eijkelkamp core, chenier foot above its front-base, Umbonium sp. and Terebridae, −2/-/about −0.5 m 38.5°N,
117.6°EUtC2237 − +0.7 820±90 586/
762−426reworked no −100 0.486/
0.66−0.32−0.5±0.5 +0.05/
+0.78/
+0.15+0.48±0.5 85 Zhaojiapu, a thin shelly layer remained in the present-day muddy intertidal flat, shell hash, 0.1 m/-/about +0.48 m 38.5°N,
117.6°ESH200 1 030±60 −2.68 1 389±72 1 121/
1 281−937reworked no −100 1.021/
1.18−0.83+0.48±0.5 +0.10/
0/
+0.10+0.68±0.5 86 Jiajiapu, shelly chenier, Eijkelkamp core, lower part, Scapharca kagoshimensis, Corbulidae and Nassarius sp., about 4/-/about +1.8 m 38.5°N,
117.6°EUtC2239 − −0.1 810±70 579/
709−453reworked yes − 0.579/
0.709−0.453+0.6±0.5 +0.06/
+1.56/
+0.11+2.33±0.5 87 Jilingbo, shelly chenier, undetermined shells, 1.45/-/about +0.5 m 38.4°N,
117.7°ESH247 2 860±70 −2.68 3 219±81 3 255/
3 482−2 988reworked no −600 2.655/
2.88−2.39−0.8±0.5 +0.26/
+0.56/
+0.21+0.23±0.5 88 Wuditai, shelly chenier, undetermined shells, 1.1/-/about +1.1 m 38.4°N,
117.5°EGC-? 3 920±120 −2.68 4 279±127 4 629/
4 969−4 243reworked no −600 4.029/
4.37−3.64−0.2±0.5 +0.40/
+0.43/
+0.10+0.73±0.5 89 Yangjiapu, shelly chenier, undetermined shells, 1.05/-/about +1.1 m 38.4°N,
117.7°EYS248 2 205±70 −2.68 2 564±81 2 477/
2 724−2 253reworked no −600 1.877/
2.12−1.65−0.2±0.5 +0.19/
+0.41/
+0.09+0.49±0.5 90 Qianmiaozhuang, shelly chenier, middle-upper part, single valves of Meretrix meretrix, about 2.5/-/about +1.8 m 38.3°N,
117.4°ECG
176(1)4 205±105 −2.68 4 564±112 5 013/
5 319−4 675reworked yes − 5.013/
5.319−4.675+0.5±0.5 +0.50/
+0.97/
+0.05+2.02±0.5 91 idem. shelly chenier, lower part, single valves of Meretrix meretrix and Mactra veneriformis, about 3.3/-/about +0.35 m CG177 4 740±105 −2.68 5 099±112 5 648/
5 336−5 334,
5 370−5 349,
5 906−5 384reworked no −600 5.048/
5.30−4.73−0.85±0.5 +0.50/
+1.29/
0.05+0.99±0.5 92 Laolangtuozi, Pit 1, shelly chenier, top of the underlying mud, Terebridae and Nassarius sp., about 5/-/about +0.7 m 38.3°N,
117.8°EAA
45901− −1.6 1 687±52 1 416/
1 566−1 272reworked no −600 0.816/
0.96−0.67−0.6±0.5 +0.08/
+1.94/
+0.12+1.54±0.5 93 idem, Pit 1, shelly chenier, bottom, Terebridae and Nassarius sp., about 5/-/about +0.8 m AA
45900− −0.8 1 455±47 1 191/
1 321−1 034reworked no −600 0.591/
0.72−0.43−0.5±0.5 +0.06/
+1.94/
+0.12+1.62±0.5 94 idem, Pit 4, shelly chenier, bottom, fragments of Potamocorbula sp., Corbicula and Dosinia sp., about 4/-/+1.7 m 99Y007 2 740±80 −2.68 3 099±90 3 104/
3 358−2 840reworked no −600 2.504/
2.76−2.24+0.4±0.5 +0.25/
+1.56/
+0.12+2.33±0.5 to be continued No. Notes Explainations of the indicative meaning, RTC, the three spatial corrections and changes from the previous work (Li et al., 2015) 68 Redeposited on the middle part of subsurface of chenier (Su, 2012; Shang et al., 2013). Elevation of the sampling position was measured by Total Station connected with the National Vertical Datum 1985 benchmark (Su, 2012). “┬” −0.20 m, msl (–1.4±0.5) m, i.e., subtracting (1.2±0.5) m as it was above the mid-subsurface (Table A3). However, it was roughly treated as being formed in intertdal depth only and thus reconstructed msl is (−0.2±1.5) m in Li et al. (2015). RTC was given (Li et al., 2015). 69 Redeposited on the middle part of subsurface of chenier (Su, 2012; Shang et al., 2013). Elevation of the sampling position was measured by Total Station connected with the National vertical Datum 1985 benchmark (Su, 2012). “┬” +0.22 m, msl (−0.98±0.5) m, i.e., subtracting (1.2±0.5) m because it was above the mid-subsurface (Table A3). RTC was given (Li et al., 2015). However, it was simply judged to be just in intertidal depth in Li et al. (2015). 70 Detailed information is lacking except its approximate elevation It is treated to be taken from above the mid-subsurface, so (1.2±0.5) m should be subtracted, i.e., msl (−0.2±0.5) m (Table A3). However, it was simply considered at intertidal zone in Li et al. (2015). RTC was given (Li et al., 2015). 71 It was just above the chenier subsurface at its middle to seaward side. 720−310 cal a younger than another 3 subsamples: 3 731 cal a BP/BA101094, 3 766 cal a BP/BA101093 and 4 140 cal a BP/BA101112 (Su, 2012; Shang et al., 2016). Forams assemblages, for the lower part of chenier and the immediately underlying muddy sediments, indicate that the uppermost 1 m of the muddy sediments was dominantly composed of Ammonia beccarii, A. confertitesta, A. granuloumbilica, Elphidium simplex, A. granuloumbilica and Pseudononionella variabilis, based on four forams samples. Upwards in the mud column to closing the chenier subsurface, the assemblage shows size of the reworked individuals increased, i.e., tests become bigger and much broken. These suggest the chenier subsurface was subject to erosion and close to MHW environment (Li et al., 2016b; Su, 2012). Elevation of the ground surface was Total Station measured and then connected to the National Vertical Datum 1985 (Su, 2012). “┬” −0.4 m, msl (−1.0±0.5) m, i.e., 0.6 m could be subtracted because the sampling position is just in between the forepart and the mid-subsurface (the former is without vertical compensation but 1.2 m should be subtracted for the latter, Table A3). However, 1.8 m was subtracted in Li et al. (2015) since the compensation value of 1.8 m for basal peat was misused. 72 The sampling position was in between the mid-subsurface and the forepart. 720−340 cal a younger than another 3 subsamples: 3 927 cal a BP/BA101096, 4 089 cal a BP/BA101113 and 4 313 cal a BP/BA101098 (Su, 2012; Shang et al., 2016). Forams assemblages (Li et al., 2016; Su, 2012) and indicative meaning can be referred to the indicator BA101095 aforementioned. “┬” −0.6 m, msl (−1.2±0.5) m (Table A3). However, 1.8 m was subtracted in Li et al. (2015) because the compensation value of 1.8 m for basal peat was misused. 73 This age is 510 cal a younger than another subsample of Nassarius sp.: 5 318 cal a BP/BA110864 (Shang et al., 2016; Li et al., 2015; Su, 2012) though Crassostrea shells are usually able to bear stronger or longer reworking processes. Total Station measurement, connecting with RTK leveling, was given for elevation of the sampling position, which is only about 10 cm above the mid-subsurface (Su, 2012). So, (1.2±0.5) m should be subtracted, i.e., msl (−0.81±0.5) m (Table A3). However, the sampling position was just simply determined as intertidal depth in Li et al. (2015). 74 It was just above the subsurface at chenier’s seaward margin, indicating intertidal environment (Su, 2012; Li et al., 2015). “□” −0.14 m, msl (−0.14±0.5) m (Table A3) and RTC was given (Li et al., 2015). The vertical error was ±1.5 m in Li et al. (2015). 75 The sample, lying on the top of the underlying mud, is only 10 cm beneath the chenier subsurface at its fore-base (Wang et al., 2000c). This age is about 590−900 cal a younger than another two, 2 190 cal a BP/UtC2240 and 2 505 cal a BP/Beta305320, obtained from the bottom of the chenier at its fore-base (Li et al., 2015; Shang et al., 2013a). Elevation of the sampling position, about −1.5 m, was measured relative to a local benchmark. Considering all the three were reworked, this age as the youngest is chosen by this study indicating “□” at −1.5 m, so msl (−1.5±0.5) m (Table A3). RTC is not given because the age used was much younger than another two. Notes 6 ages of the chenier, including 2 190 cal a BP and 2 506 cal a BP, in this site are 550−1 100 cal a older than this age from the underlying mud. In general, ages in chenier may be older than those from the underlying mud because of reworking, but the time-gap of 550−1 100 cal a is too much. Therefore, it raised doubt that this age, 1 597 cal a BP, may be slightly younger. Thus, the following age, UtC2240, is still retained though both ages give self-contradictory time determination for the two indicators. 76 Another sample was taken from the similar position but age of 2 505 cal a BP/Beta305320. Therefore, RTC is not necersary. Elevation of subsurface at the fore-base here is −1.4 m and this sample was taken from about −1 m (Su et al., 2011). “□” −1 m, msl (−1±0.5) m (Table A3). 77 The dated M. veneriformis specimen, with very fresh shell surface decoration and still articulated, were mixed with wrecked single valves of Scapharca sp., Dosinia sp. and Meretrix sp. Although the dated M. veneriformis shells were also reworked, they must not be far away from their original living place and were quickly dumped into the chenier in here (Wang et al., 2000c). So, RTC is not necessary. Ground elevation is about +2 m relative to a local benchmark and the chenier subsurface is 2 m below it in this profile. The sampling position is about 0.8 m above the chenier subsurface (unpublished data of the authors’ group). The sample could be transported by MHHW and so (1.3±0.5) m should be subtracted, i.e., “┬” +0.8 m, msl (−0.5±0.5) m. Comparing to Li et al. (2015), this indicator is newly added in this study. Notes that this sample was not taken immediately from above the subsurface of chenier. Instead, it was taken from 0.8 m above it, therefore, it was piled up by high waters, i.e., subtracting (1.3±0.5) m, Table A3. 78 The shells dated still keep their glittered surface ornamentation and were lay in situ as thin shelly laminae intercalated with clayey laminae at the very bottom of chenier at fore-base in this site (Wang et al., 2000c). Concomitant were Terebridae shells and also with fresh decoration surface. It is considered to be formed during initial stage of chenier at intertidal depth in semi-closed bay environment (Li et al., 2015). Elevation of the sampling position was measured relative to a local benchmark. However, in this site two subsamples, UtC7037 and 98Y077 of articulated Mactra veneriformis shells from the same bulk sample, were separately dated by two labs and the 98Y077 is about 420 cal a older than UtC7037 (Wang et al., 2000c; Li et al., 2015). Another two pairs, given also by our inter-laboratory comtrastive test at subsample-level, show the Y is about 1 260 or about 5 180 cal a older than the UtC results, respectively, in Biaokou Oyster Reef⑩. As a result, 400 a are subtracted. Based on Table A3, msl is (0±0.5) m though it was (0±1.5) m in Li et al. (2015). 79 Although 8 shell samples were dated in this site (Wang et al., 2007), only this in situ articulated razor clam sample is a most believable indicator. Conchologically, this species lives in mid to lower intertidal depth (Zhang, 2008; Okutani, 2000). The sampling elevation is estimated based on the measurement in Apple Garden, about 2 km north along the same chenier ridge (Shang et al., 2013). “□” −0.5 m, msl (−0.5±0.5) m (Table A3) though it was (−0.5±1.5) m in Li et al. (2015). 80 The sample, with definite sampling depth and elevation, was taken from the very bottom of chenier and its sampling position is closed to the present-day high tidal shoreline (Xu, 1994; Xu et al., 1986). Normally, chenier foot wadges seaward below the shoreface of late muddy sediments, so this suggests the sampling position is above the fore-base along its traverse section (i.e., a section perpendicular to the strike direction of chenier chain; Wang and van Strydonck, 1997). So, msl (+0.9±0.5) m (Table A3), though it was (+0.9±1.5) m in Li et al. (2015). RTC was given (Li et al., 2015). 81 Landward subsurface in the sampling position is about +1 m (Wang, 1994), while the sampling position is about 0.5 m above it (Zhao et al., 1980), i.e., about +1.5 m. So, msl (+0.2±0.5) m, i.e., subtracting (1.3±0.5) m (Table A3), while it was (−0.4±0.5) m in Li et al. (2015) because elevation was mistakenly cited from literature. RTC was given (Li et al., 2015). 82 Three radiocarbon-dated shell samples are available in this site (Zhao and Zhang, 1981). Based on Zhao and Zhang (1981) and personal discussion with the author, only this in situ articulated razor clam sample is believable but the another two were picked up from the upper part of chenier. However, Zhao and Zhang (1981) only indicated this razor shell was taken 4−5 m below the ground surface, while radiocarbon lab gave the sampling elevation as +1.5 m (Peng et al., 1984). However, local topographic map shows the ground surface here is about +1.5 m. So, Peng et al.’ estimation is wrong (we guess Peng et al. confused ground surface elevation with the sampling elevation for this sample) and thus this study uses the sampling elevation as about −3 m (considering sampling depth of 4−5 m). “□” −3 m, msl (−3±0.5) m (Table A3). However, sampling elevation was +1.5 m in Li et al. (2015) because simply accepted Peng et al.’ +1.5 m. RTC is not necessary (Li et al., 2015). 83 This sample was taken from the very bottom of chenier, i.e., just above the subsurface, with an approximate sampling elevation of +0.6 m (Xu, 1994). Beneath the subsurface here, underlying mud is composed of Ammonia beccarii vars., A. annectens, Candoniella albicans and pollen assemblage Chenopodiaceae-Pinus-Pteredum. On the other hand, A. beccarii vars., A. annectens and Chenopodiaceae-Querecus were found from the surficial muddy sediment along the present-day high tidal shoreline in the same site. So, the bottom material of chenier here was formed at high tidal environment influenced by fresh water input (Xu and Liu, 1991; Xu, 1994). “┬” +0.6 m, msl (−0.7±0.5) m, i.e., (1.3±0.5) m was subtracted (Table A3). RTC was given. However, Li et al. (2015) put the sampling position simply in intertidal depth without further compensation for msl reconstruction. 84 The sampling position is about 1 m above the chenier subsurface at its seaward margin of −1.5 m in elevation. Chenier foot was fully wedged into muddy tidal flat. Sediments in this part were composed of alternation between shelly hash laminae and muddy laminae, with penecontemporaneous deformation structure, and much dark-staining downwards, indicating intertidal environment (Wang et al., 2000a, b). The subsurface tilted seaward for about 2.8 m within about 100 m distance from its landward to seaward margin (Wang et al., 2000a, b; Su, 2012). So, “□” −0.5 m, msl (−0.5±0.5) m (Table A3) and RTC was given (Li et al., 2015). 85 Nowadays, it was found as a linear shoal, only 10 cm thick, consisting of well-sorted, very fine shell hash, about 2 200 m out of the present-day shoreline. This remaining shoal is about 70−80 m wide and about 10 cm beneath the intertidal flat surface of clayey silt and floating mud. Elevation was measured relative to local bench mark (Xu et al., 1986; Xu, 1994). This shoal was probably a remnant of Chenier S-T (Sui-Tang) (Wang et al., 2000b; Shang et al., 2016). RTC was given. “□” +0.48 m, msl (+0.48±0.5) m. However, msl was (+0.48±1.5) m in Li et al. (2015). 86 Due to landward digging by local fishermen from the sea side of chenier here, the core portion of chenier was exposed and a bulk sample was taken from the lower part, about 1 m above the subsurface. Elevation of subsurface in the sampling position is about +0.8 m based on comparison with the present-day MHHW shoreline which is 31 m east of the sampling pit (Wang, 1994). This is similar with subsurface elevation of +0.657 m measured by Xu and Liu (1991) and Xu (1994) in this site. So, “┬” +1.8 m, msl (+0.6±0.5) m (Table A3). This subsample is 100 cal a younger than another subsample of Umbonium sp. and Terebridae: 679 cal a BP/UtC2238 (Wang, 1994; Wang and van Strydonck, 1997; Shang et al., 2016; Li et al., 2015). However, the elevation of sampling position was roughly determined as (+2±1.5) m and thought to be msl directly in Li et al. (2015). 87 It was taken from lower-middle part of chenier and elevation was approximately obtained from topographic map (Xu, 1994). So, “┬” +0.5 m, msl (−0.8±0.5) m (Table A3). RTC was given. As indicator YS265, the sampling position was only simply recognized as intertidal depth in Li et al. (2015). 88 It was taken from the lower part of chenier because still having 0.4 m-thick shelly sediments below this sampling poition, and elevation was approximately obtained from topographic map (Xu, 1994). So, “┬” +1.1 m, msl (−0.2±0.5) m, i.e., (1.3±0.5) m was subtracted (Table A3). RTC was given. However, this sampling position was simply believed as intertidal depth (Li et al., 2015). 89 The chenier ridge was occupied by local residents long ago (Xu, 1994), implying that this site was a relatively high mound. The sampling position is about +1.1 m in elevation (Xu, 1994). “┬” +1.1 m, msl (−0.2±0.5) m (Table A3). RTC was given. In Li et al. (2015), reconstructed msl was −0.7 m because 1.8 m was subtracted from +1.1 m. This was misused when considering the sampling layer is an equivalent of the upper peat. 90 This is about 1 160 cal a younger than another subsample of Crassostrea gigas shell CG176(2) and the sampling position is about +1.8 m (Peng et al., 1980; Zhao et al., 1980; Xu, 1994), which is believed to be the position of MHHW. “┬” +1.8 m, msl (+0.5±0.5) m, i.e., (1.3±0.5) m should be subtracted (Table A3). However, 1.8 m was subtracted in Li et al. (2015) due to misuse of the upper peat. 91 Peng et al. (1980) gave the age and sampling elevation of about 0 m, which is about 0.5 m above the chenier subsurface which lay on the underlying grayish marine silty mud. However, Zhao et al.(1979) and Xu (1994) both gave another approximate elevation of the sampling position as +0.7 m. This study uses average +0.35 m of both, though it was 0 m in Li et al. (2015), i.e., only accepted Peng et al. (1980). The original authors mentioned above did not indicate the sample is from the chenier’s landward or seaward part (i.e., rear part or front foot of chenier). Considering its huge scale excavated by the local fishermen (unpublished data of our group), the sample could be taken from middle of subsurface and speculating the sample, being 0.5 m above the subsurface, was formed in the upper part of intertidal depth, though was only in intertidal zone simply in Li et al. (2015). So, “┬” +0.35 m and (1.2±0.5) m (Table A3) should be subtracted, i.e., msl (−0.85±0.5) m. RTC was give in Li et al. (2015). 92 This underlying mud is dull yellowish brown (10YR 5/3) clay, indicating much oxidized environment in the upper part of intertidal flat① (Wang et al., 2003). However, the authors thought previously it was formed just in intertidal depth (Li et al., 2015), but now it is further restricted to the upper part of intertidal zone. So, “┬” +0.7 m and (1.3±0.5) m should be subtracted (Table A3), i.e., msl (−0.6±0.5) m. However, msl was reconstructed as (+0.7±1.5) m in Li et al. (2015). RTC was given (Li et al., 2015). Elevations of three indicators, including the following two, in this site were leveled relative to a local benchmark with National Vertical Datum 1985 (Wang et al., 2003). 93 This gastropoda sample, picked from fine shelly hash, immediately lying on the chenier subsurface, is about 10 cm above the sample AA45901①. It was thought to be formed in intertidal depth (Li et al., 2015) but now in this paper is restricted to the upper intertidal zone. So, “┬” +0.8 m, msl (−0.5±0.5) m (Table A3). RTC was given (Li et al., 2015). 94 The sample was taken just above the subsurface at the mid- to rear part of the chenier17. So, “┬” +1.7 m, msl (+0.4±0.5) m, i.e., (1.3±0.5) m should be subtracted (Table A3). However, 1.8 m was subtracted from the sampling elevation in Li et al. (2015) because it was incorrectly treated as an equivalent of the peat layer. RTC was given (Li et al., 2015). Note: The measured 14C dates, signified in italics in Column 4, were changed from their original dates with the Libby half life of 5 730 a by subdiving 1.029 in this study. The 13C values, signified in italics in Column 5, were either recommended by Mook and van de Plassche (1986) or used with the local empirical mean value of −2.68‰PDB (Wang, 1994; Wang and van Strydonck, 1997; Li et al., 2015) for the marine shells. Correspondingly, such calibrated approximate conventional ages in Column 6 were given in italics. A4.3. Holocene relative mean sea level (rmsl) indicators, derived from the oyster reefs, in the west coast of Bohai Bay
Basic information Temporal distribution Spatial distribution No. Locality, stratigraphy and environment, material dated, sample-depth / ground surface elevation / (averaged) sample elevation Coordinate Lab code Measured 14C date δ13C
/‰PDBConventional 14C age/a BP Calibrated 14C age: median probability/2σ range/cal a BP Status of material
datedSub-
sampleRTC
/cal aAge of rmsl: single value/ range/cal ka BP Elevation of the observed rmsl/m Corrections of tectonics
/self-compa-
ction/water withdrawal /mElevation of rmsl after corrections for the three local factors /m 95 Mengzhuang oyster reef, articulated C. gigas, 4.5 m/-/about −2.5 to −3.3 m (?) 39.4°N,
117.8°ETD342 5 070±115 −2.68 5 429±122 6 008/
6 280−5 704in situ no − 6.008/
6.280−5.704−2.65±0.7 +0.60/
+1.75/
+0.37+0.07±0.7 96 Dawuzhuang, oyster reef, Section 6, top, articulated C. gigas, about 4.5/-/about −2.58 m 39.4°N,
117.9°EBA
091172− − 5 360±35 5 926/
6 096−5 752in situ no − 5.926/
6.096−5.752−2.43±0.7 +0.59/
+1.75/
+0.60+0.51±0.7 97 Dawuzhuang, oyster reef, Section 1, top, articulated C. gigas, 0−0.3 m below the top surface, about 5/-/−3.22 to −3.5 m 39.4°N,
117.9°EBA
110343− − 5 625±35 6 223/
6 365−6 061in situ yes − 6.223/
6.365−6.061−3.07±0.7 +0.62/
+1.95/
+0.60+0.1±0.7 98 Shizhuang, oyster reef, top (?), articulated Crassostrea gigas, about 4/about +2.5 m/−1.4 to −2 m; 39.4°N,
117.5°ETD344 5 860±95 −2.68 6 219±103 6 879/
7 161−6 613in situ no − 6.414/
7.161−5.614−1.55±0.7 +0.64/
+1.56/
+0.11+0.76±0.7 Jiangzhuang-Shizhuang oyster reef, articulated C. gigas, about 4/about +2.5 m/−1.4 to −2 m CG181 5 020±140 −2.68 5 379±146 5 950/
6 267–5 614in situ no − 99 Lingtou, oyster reef, top, articulated C. gigas, 3.1−3.3 m/+0.87 m/−2.23 to −2.43 m 39.3°N,
117.6°EBA
110339− − 3 980±30 4 234/
4 404−4 069in situ yes − 4.234/
4.404−4.069−2.08±0.7 +0.42/
+1.25/
+0.62+0.21±0.7 100 Zengkouhe, oyster reef, top, articulated C. gigas, 2.8 m/about +0.5 m/about −2.3 m 39.3°N,
117.6°EBA
110317− − 3 965±30 4 212/
4 399−4 047in situ no − 4.212/
4.399−4.047−2.15±0.7 +0.42/
+1.09/
+0.67+0.03±0.7 101 Biaokou, oyster reef, top, articulated Trapezium liratum, 4.2 m/+2.38 m/−1.82 m 39.3°N,
117.6°EUtC7036 − −1.23 3 865±35 4 067/
4 251−3 882in situ no − 4.067/
4.251−3.8821.67±0.7 +0.41/
+1.64/
+0.56+0.94±0.7 102 Yujialing, oyster reef, articulated C. gigas, about 3.1/-/about −1.4 to −1.6 m 39.2°N,
117.7°ETD356 1 830±100 −2.68 2 189±108 2 000/
2 296−1 720in situ (?) no − 2.000/
2.296−1.720−1.5±1.5 +0.20/
+1.21/
+0.52+0.43±1.5 103 Konggang, oyster reef, a transition zone between reef-top and the overlying mud, articulated Trapezium liratum, about 5.5/-/−2.85 to −2.90 m 39.1°N,
117.4°EBA
101110− − 3 800±25 3 980/
4 140−3 825in situ yes − 3.980/
4.140−3.825−2.7±0.7 +0.40/
+1.87/
+1.05+0.62±0.7 104 idem, reef-top, articulated C. gigas, about 5.5/-/about −2.9 to −3.0 m; idem, the same individual of BA101108 39.2°N,
117.4°EBA
101108,
Beta
305302−
3 440±30−
−3.93 800±25,
3 790±303 980/
4 140−3 825;
3 967/
4 140−3 811in situ yes − 3.973/
4.140−3.811−2.78±0.7 +0.40/
+1.87/
+1.05+0.54±0.7 105 Binhaihu, oyster reef, top, articulated C. gigas, about 3.3/-/about 3.15 to −3.5 m 39.2°N,
117.6°EBA
110340− − 2 265±30 2 088/
2 276–1 939in situ yes − 2.088/
2.276−1.939−3.16±0.7 +0.21/
+1.29/
+0.75−0.91±0.7 106 Core CH79, oyster reef, articulated C. gigas, 8.75−8.80 m/−3.4 m/about −12.18 m 39.2°N,
117.9°EBA
08822− − 6 935±35 7 588/
7 702−7 466in situ no − 7.588/
7.702−7.466−10.58±0.5 +0.76/
+3.78/
+1.87−4.17±0.5 107 idem, articulated C. gigas, 9.90−9.95 m/−3.4 m/−13.33 m BA
08823− − 7 275±40 7 912/
8 048−7 762in situ no − 7.912/
8.048−7.762−11.73±0.5 +0.79/
+4.13/
+1.87−4.94±0.5 108 idem, articulated C. gigas, 11.50−11.55 m/−3.4 m/−14.93 m BA
08824− − 7 625±35 8 268/
8 388−8 146in situ no − 8.268/
8.388−8.146−13.33±0.5 +0.83/
+4.63/
+1.87−6.0±0.5 109 Beitang, oyster reef, articulated Crassostrea gigas, about 2/-/about −1 m 39.1°N,
117.7°EZK507-I 975±85 −2.68 1 334±94 1 067/
1 281–850in situ no − 1.067/
1.281−0.850−0.85±0.7 +0.10/
+0.78/
+0.19+0.22±0.7 110 Tongju, oyster reef (?), single valve of Crassostrea gigas, about 2/-/about +1 m 38.6°N,
117.2°ECG180 4 460±160 −2.68 4 819±165 5 327/
5 679−4 857in situ (?) no − 5.327/
5.679−4.857+1.15±0.7 +0.53/
+0.78/
+0.10+2.56±0.7 to be continued No. Notes Explainations of the indicative meaning, RTC, the three spatial corrections and changes from the previous work (Li et al., 2015) 95 The sample is about 1 m below the reef top (Wang et al., 1991) while the top elevation is confused as −1.5 m (Wang et al., 1991), −2.3 m or −1.5 m (Han and Meng, 1996). This study uses average of about −2.8 m as the sampling elevation. The age is considered approximately as its top age. So, msl (−2.65±0.7) m while it was (−2±1.5) m in Li et al. (2015). Usually, the reef-top can grow up to MTL but 15 cm lower than the corresponding msl in the study area (see Section 4.3 and Table A3). Thus, all the oyster indicators here have been treated by adding 15 cm to the observed reef-top elevation in order to fulfil the conversion from MTL to msl (the same below). 96 Elevation of this sampling position was not measured and we then use −2.58 m, the 7-spot-average of the reef-top elevations in this site (Li et al., 2015). msl (−2.43±0.7) m. 97 In this big pit, elevation measurement was given by using Total Station connected with the National Vertical Datum 1985. As a result, elevations of the 7 spots on the reef top were obtained, among which the top surface at this sampling position is −3.22 m. Furthermore, totally, 19 top-spots, including another two reef sites in Binhai Lake and Konggang, were leveled and showed that an average undulation of the reef-top is ±0.7 m (Fan et al., 2005a; Liu, 2010; Wang et al., 2011c, 2012a; Shang et al., 2013). This is similar to 0.5−1 m of the top undulation of the modern living oyster reef in Xiaomiaohong site, Jiangsu Province (Zhang, 2004). In this study, ±0.7 m has been used as an error range for the top undulation for all oyster reefs (Li et al., 2015). So, msl (−3.07±0.7) m (Table A3). However, it was (−3.4±0.7) m in Li et al. (2015) because −3.4 m is a rounding value of middle point of the sampling range of −3.22 m to −3.5 m. 98 C. gigas were with coexisting Trapezium sp., Assiminea sp. and Cerithidea sp. shells (Peng et al., 1980). Five independent investigations were carried out and five ages, dated by four different labs, were obtained for these two closed reef sites (Peng et al., 1980; ICP, 1987; IOA, 1983; Li and Zhao, 1990). Ages of TD344 and CG181 listed are the oldest and youngest, respectively, among the five (Li et al., 2015). Elevations of the reef top were quite different from about +0.5 m (ICP, 1987), −1.5 m (Wang et al., 1991), −1.4−−1.5 m (Han and Meng, 1996) to about −2 m (Wang et al., 2011c). Considering less precise estimation for the elevations and the inherent undulation of reef top, this study uses −1.7 m, an average of the latter three (Li et al., 2015). So, msl (−1.55±0.7) m in this study (Table A3) while it was (−1.7±1.5) m in Li et al. (2015). 99 This individual was taken from the top of reef in this site. Elevation of ground surface was leveled relative to a local benchmark (Li et al., 2015) and msl (−2.08±0.7) m (Li et al., 2015). 100 The ground elevation is +0.71 m of Core HD21, about 1 km west of this reef site and a 7-spot-average, given by RTK leveling in 2016, is +0.385 m, about 0.5 km north of this reef site (Qin et al., 2017). This is flattened lagoon-salt marsh lowland② (Qin et al., 2017; see indicator No. 12). So, the ground elevation in this reef site is about +0.5 m approximately. This sample was taken from the top of the reef, which is 2.8 m below the ground surface① (Shang et al., 2013). So, the reef-top is −2.3 m and msl (−2.15±0.7) m. However, the sampling elevation, about −3.1 m in Li et al. (2015), was only reckoned by an estimation of elevation difference between the reef-tops of Biaokou and this site (the latter is based on Wang et al., 1991). 101 T. liratum is a most important associated species in the C. gigas reefs in the study area and this sample was taken from 5 cm below the reef top. Ground elevation was leveled relative to the local benchmark (Wang et al., 2006; Li et al., 2015). msl (−1.67±0.7) m (Li et al., 2015). 102 Top and/or upper part of oyster reef in this site was destroyed by bridge construction and the reef-bottom was not dug out (Wang et al., 1991). So, it is impossible to know from which part of reef column the sample was taken exactly. Approximately, it is considered to be in middle part of the reef body in this site and was in intertidal depth. So, ‘□’ −1.4−−1.6 m, msl (−1.5±1.5) m. 103 The sample, in the bottom of transitional zone, was immediately above the reef-top. Another in situ subsample is articulated Ruditapes philippinarum, which was a later burrowed animal showing reasonably 480 cal a younger age: 3 500 cal a BP/BA101109 (Wang, 2012; Wang et al., 2012a; Li et al., 2015). MTL (−2.85±0.7) m while msl should be (−2.7±0.7) m. 104 The top elevation fluctuated between (−2.70 to −3.16) m based on leveling at 3 spots in this site and the average is −2.93 m (Wang, 2012). A bulk sample, as a part of the ligamental resilium of LV of the same individual, taken from the reef-top, was divided and separately AMS dated by two labs and gave the exact same ages (Wang, 2012; Wang et al., 2012a; Li et al., 2015). msl (−2.78±0.7) m (Li et al., 2015). 105 The top part of reef in this site is composed of intact oyster individuals and oyster hash, also fragments of Rapana venosa, and Trapezium liratum, Mitrella bella (?), Pseudoliotia pucchella, Assiminea latericea, Barbatia sp., Potamocorbula laevis, Ruditapes philippinarum. Forams were Ammonia confertitesta (dominant species), Quinqueloculina akneriana rotunda, Protelphidium granosum, Elphidium nakanokawaense. Ostracoda were Sinocytheridea impressa, Loxoconcha binhaiensis and so on. These indicate intertidal environment with occasionally input of freshwater③ (Fan et al., 2008; unpublished data of the authors’ group). Nine spot levelling indicates the top elevation is in between −2.96 to −4.36 m③ and average −3.31 m has been used (Li et al., 2015). So, msl (−3.16±0.7) m. Another individual taken from the top is about 290 cal a older: 2 380 cal a BP/06Y082③. 106 The reef body, 8.45−11.63 m below sea floor, was revealed by this underwater borehole. This sample is only about 30 cm below the top of this buried reef. It therefore may roughly indicate environment of the reef-top. Two microbiological samples, 8.5−9.0 m, of Assemblage Zone 4-1, having huge amount of forams of about 3 000−4 000 tests per 20 g dry sample, mainly Ammonia beccarii vars., A. annectens and E. limpidum, indicating shallow sea environment closing to estuary. Also, forams assemblages of 4 samples, Zone 3, taken from the overlying muddy sediments, mainly A.beccarii vars. and P. tuberculatum with Q. akneriana rotunda, E. magellanicum, Cribrononion incertum and Buccella frigida, indicating shallow sea environment (Li, 2010). So, ‘┴’ −12.18 m and (1.6±0.5) m as a compensation value for MLLW (Table A3) should be added for restoring msl, i.e., msl (−10.58±0.5) m, though 1.5 m, as a half of mean high tidal range, was simply added in Li et al. (2015). 107 This sample, taken from the middle part of the reef column, belongs to the foraminifera assemblage Zone 4-2 in 9.6−11.5 m. Forams can reach 3 000−4 000 tests of 20 g dry sample, mainly Pseudoeponides compressum, Ammonia beccarii vars., P. enderssen and P. tuberculatum, A. convexidorsa, indicating estuary environment in lower intertidal to upper subtidal depth with salt and fresh water mixture (Li, 2010). ‘┴’ −13.33 m and (1.6±0.5) m (Table A3) should be added for restoring the contemporaneous msl. So, msl (−11.73±0.5) m, though 1.5 m was added in Li et al. (2015). 108 This articulated shell, taken from the reef-bottom, gives an initial age of this reef. Concomitant forams, 3 000−4 000 tests per 20 g dry sample, were composed of mainly Ammonia beccarii and shallow sea species such as A. flevensis, Elphidium limpidum, Pseudoeponides enderssen and A. convexdorsa, indicating estuary environment in lower intertidal to upper subtidal depth (Li, 2010). Downwards, two forams samples, taken from the underlying mud, 12−14.9 m, show mainly A. beccarii vars., indicating marine influence had started from this underlying mud and sea water become deeper upwards. So, ‘┴’ −14.93 m, msl (−13.33±0.5) m, i.e., (1.6±0.5) m should be added (Table A3). However, msl was (−13.43±0.5) m because 1.5 m was simply added in Li et al. (2015). 109 It seems to be taken from the reef top though more detailed information, including elevations for both ground surface and reef top, were deficient in original literature (Zhao et al., 1979). So, msl (−0.85±0.7) m and RTC is not necessary (Li et al., 2015). 110 This possible oyster reef, or at least an oyster bank, existed exceptionally in Chenier Plain (Peng et al., 1980) and with a numerous Trapezium liratum (Wang et al., 2007), one of a few coexisting species within C. gigas reefs in the area. So, it is probably a less developed reef occurred in Chenier Plain. ‘□’ +1 m, MTL +1 m and msl +1.15 m. The oyster sample is considered in situ and RTC is not necessary (Li et al., 2015). It was thought to be chenier with a vertical error of ±1.5 m (Li et al., 2015). Now it is reclassified to oyster reef and vertical error is changed to ±0.7 m as the local reef top undulation. Note: The measured 14C dates, signified in italics in Column 5, were changed from their original dates with the Libby half life of 5 730 a by subdiving 1.029 in this study. The 13C values, signified in italics in Column 6, were either recommended by Mook and van de Plassche (1986) or used with the local empirical mean value of −2.68‰PDB (Wang, 1994; Wang and van Strydonck, 1997; Li et al., 2015) for the marine shells. Correspondingly, such calibrated approximate conventional ages in Column 7 were given in italics. B1. Estimated porosity for this study, modified from Li et al.③
Key layer Average depth/m Porosity/% Surface 0 60 Basal peat 18 50 Hard soil horizon, LGM 21 45 Subsurface of sediments 400 30 B2. Relationship of self-compaction and depth
Depth/m Self-compaction,
Δ (m), modelSelf-compaction Δ (m),
empirical0 0.00 0.00 5 1.94 1.91 10 3.39 3.42 15 4.66 4.67 20 5.79 5.77 25 6.83 6.84 30 7.79 7.79 35 8.69 8.71 40 9.53 9.57 -
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