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Holocene tephra deposits in the northern Okinawa Trough
LIU Yanguang, OLE Bjφrslev Nielsen, ZHANG Deyu, DU Dewen, JAN Heinemeier, WU Yonghua
2006(1): 78-89.
Keywords: Okinawa Trough, Holocene, tephra deposits
The mineralogical and geochemical characteristics of sediments of Core CSH1,which was collected from the northern Okinawa Trough,indicate that large amounts of volcanic materials have deposited in the northern Okinawa Trough during the Holocene.On the basis of down-core variations in mineral and element contents of sediments,two layers in the uppermost section of Core CSH1 characterized by high quartz,Na2O,MnO,K2O,uranium contents and low contents of clay minerals,volatiles,Fe2O3,MgO,CaO and strontium,have been identified as the tephra deposits.Systematic grain-size measurements also suggest that sediments from the northern Okinawa Trough are made up of terrigenous materials and volcanic ashes with different proportion during the Holocene.The sediments of tephra layers in Core CSH1 show bi-modal patterns in grain-size distribution with modal grain-sizes of 74.3 and 7.81 μm,respectively.According to the radiocarbon dating on shells of zooplankton foraminifera,two tephra layers in Core CSH1,formed at 7 250 and 10 870 a BP (cal),approximately correspond to the K-Ah tephra[7 300 a BP (cal)] and the eruption of Kuju Volcano (12~10 ka BP),respectively.
Paleoenvironmental implications of Holocene long-chain n-alkanes on the northern Bering Sea Slope
ZHANG Haifeng, WANG Rujian, XIAO Wenshen
2017, 36(8): 137-145. doi: 10.1007/s13131-017-1032-0
Keywords: Bering Sea, terrestrial input, long-chain n-alkanes, vegetation structure, Holocene
The records of high-resolution terrestrial biological markers (biomarkers) from Core B2-9 from the northern Bering Sea Slope over the last 9.6 ka BP were presented in the study. Variations in input of terrestrial long-chain n-alkanes (referred to as n-alkanes) and vegetation structure in their source regions were investigated. The results show that the nC27 is the main carbon peak and has the greatest contribution rate of the total n-alkane content; this might be related to the abundance of woody plants and their spatial distribution in the source region. nC23 is another n-alkane having a relatively high content; this was mainly derived from submerged plants widespread along the coastal areas in the northern hemisphere. Total n-alkane content dropped quickly at ca. 7.8 ka BP, ca. 6.7 ka BP and ca. 5.4 ka BP, and was followed by four relatively stable stages mostly controlled by sea-level rise, climate change and vegetation distribution in the source region. Variation in carbon preference index (CPI) indicates that the n-alkanes primarily originated from higher land plants, and the average chain length (ACL) and nC31/nC27 ratio reveal the relatively stable presence of woody/herbaceous plants during the Holocene, and dominate woody plants in most of the time. Simultaneous variation in total n-alkane content, nC27 content and its contribution, CPI, ACL and nC31/nC27 ratio over several short periods suggest that the growth rate of the woody plant n-alkane contribution was lower than that of herbaceous plants and fossil n-alkanes under the particular climatic conditions of the source region.
Environmental record from the mud area on the inner continental shelf of the East China Sea since the midHolocene
LIU Shengfa, SHI Xuefa, LIU Yanguang, WU Yonghua, YANG Gang
2011(4): 43-52. doi: 10.1007/s13131-011-0132-5
Keywords: Holocene, East China Sea, mud area, major element, palaeoclimate, East Asia monsoon
Paleoclimate record was revealed in Core MZ01 covering the mid-Holocene in age, located in the mud area of the inner continental shelf of the East China Sea. The ancient environment featured low-energy shallow sea shelf deposition formed mainly by coastal currents. The results show that temporal variation in geochemistry corresponds with the climate changes inferred from historical record. Relatively low MgO/Al2O3, CaO/K2O and high Al2O3/Na2O, K2O/Na2O, MnO/CaO values reflected a warm and humid climate in general, and vice versa. Therefore, these chemical indices could be applied to identify the variation of palaeoclimate in eastern China. The authors reconstructed the history of mid-Holocene climatic variation of the inner continental shelf of the East China Sea. From 8 300 a BP to 4 200 a BP, the climate was moderately warm and humid. From 4 200 a BP to 2 000 a BP, the climate turned cool and dry, and the regional climate frequently fluctuated in alternation of cool-dry periods (3 700 a BP, 2 850 a BP and 2 400 a BP) and warm-wet periods (3 250 a BP and 2 650 a BP). After 2 000 a BP, the climate of the study area gradually turned warm again, while the Little Ice Age, a cold event centered at around 250 a BP was indicated by those geochemical indices as mentioned above.
Holocene strata along the coastal area of eastern Guangdong
Li Pingri, Huang Zhenguo, Zhang Zhongying, Zong Yongqiang
1988(1): 104-114.
The data of about 1700 drill holes are correlated, of which 47 drill sections are discussed comprehensively for chronology and sedimentology, and the characteristics and changes of sporo-pollen are analysed. The authors consider that the Holocene strata along the coast of eastern Guangdong can be divided into five formations. The Holocene began 12 000 years ago; the fluvial facies gravel, the striped weathered clay and the "old red sand" serves as the boundary between the Holocene and the Pleistocene.
Issues of the Holocene transgression on the southern plain of the Changjiang Delta
Yan Qinshang, Hong Xueqing
1988(4): 578-590.
The paper deals with the question of Holocene transgression on the southern plain of the Changjiang Delta.
At the beginning of the transgression, the paleovalleys of the Changjiang and Qiantang Rivers were covered by sea water at first.The shoreline of 8000-7500 yr BP coincided with the -7m isobath of paleotopography.Sea level had already been the present level about 7000-6500 years ago, and the Holocene transgression reached its maximum extent.During the period, the Changjiang and Qiantang Rivers and the Dongtiaoxi valley were turned into estuaries; the eastern area of Shanghai became a shallow sea; some of the bays and lagoons were distributed on the Hang-Jia-Hu and Tao-Ge Plain; the hilly region around the Taihu Lake was coastal marsh and freshwater swamp.Gangshen on the west of Shanghai was formed 7000-4000 yr BP, and during the last 4000 years, the eastern coastal plain of Shanghai advanced quickly toward the sea, and partial clear land of the western Taihu Lake was enclosed and charged into a freshwater lake.
Palaeoceanological significance of Holocene ostracean banks in Tianjin area
Wang Qiang, Li Xiuwen, Zhang Zhiliang, Li Fenglin, Shao Jun, Bai Dezhong, Shang Xuexi, Tang Ruolu
1991(2): 249-262.
On the basis of the study of ostracean banks in Tianjin area,the present study recognized that the ostracean banks at Ninghe County in Tianjin area are well developed along the west coast of the Bohai Sea; they consist of thanato-coenose and taphocoenose from Crassistrea gigars and C.revularis.From the 14C datings it can be known that the banks had formed from early Middle-Holocene and continued up to over 2 ka BP (14C age).The top has different reliefs.Although there is an effect of spatial shift of estuary position,the top is only distributed in the range of -0.50~-2.50 m(Huanghai elevation minus National elevation system).The banks cannot explain the sea-level fluctuation.As the string ostracean banks are distributed near E-W direction,it suggests that the direction of tidal currents was then similar to that of the present day.
Holocene sea level changes and coastline snitts in Zhejiang Province, China
Feng Huaizhen, Wang Zongtao
1989(1): 101-111.
In the present paper, the Holocene sea level changes and coastline shifts in Zhejiang, China are discussed, based on the ancient coastline evidence related with sea level changes and 21 14C datings of shell, peat or mud and wood samples along the Zhejiang coast. The development of Zhejiang coastline during the Holocene period can be divided into four stages. A lot of data of historical period and modern times have shown that tracing coastline shifts back to its source, we have to consider tremendous effects of man's activities besides natural factors, such as elevation and subsidence of the earth crust, sea level changes, supply of sediment, and littoral hydrodynamics.
Holocene shelf-coastal sedimentary systems associated with the Changjiang River:An overview
GAO Shu
2013, 32(12): 4-12. doi: 10.1007/s13131-013-0390-5
Keywords: Transport-accumulation processes, Holocene sedimentary systems, process-product relationships, sedimentary records, East China Sea
The fate of the terrestrial sediment supplied by rivers is a critical issue for understanding the patterns of Holocene environmental change on continental shelves. The East China Sea is a typical broad continental shelf with abundant sediment supply from large rivers. Here, a variety of sedimentary records were formed during the Holocene period. The sedimentary systems associated with these records have unique characteristics in terms of spatial distribution, material composition, deposition rate and the timing of deposition, which are related to active sediment transport processes induced by tides and waves, shelf circulations and sediment gravity flows. The sedimentary records thus formed are high resolution slices, i.e., each record has a temporal resolution of up to 100-10-1 a, but only covers a limited part of the Holocene time. In terms of the spatial distribution, these records are scattered over a large area on the shelf. Further studies of these systems are required to understand the underlying process-product relationships. In particular, the mid-Holocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, as well as the Holocene mud deposits off the Zhejiang-Fujian coasts, should be investigated in terms of the material supply (from both seabed reworking during the sea level rise event and river discharges), transport-accumulation processes, the sediment sequences and the future evolution of the sedimentary systems. Advanced numerical modeling techniques should be developed to meet the needs of these studies.
Sedimentary facies and paleoenvironmental interpretation of a Holocene marsh in the Gironde Estuary in France
WANG Jianhua, MASSE Laurent, TASTET Jean-Pierre
2006(6): 52-62.
Keywords: marsh, sedimentation, benthic foraminifera, 14C dating, Holocene sea-level fluctuation, paleoenvironment
The Monards Marsh is located on the northeastern bank of the Gironde Estuary in France.Lithological, sedimentological and micropalaeontological investigations were made on four cores to determine the evolution of Holocene sedimentary environments and processes in this area over the last 6 000 a.Three main lithological facies are distinguished from bottom to top:(1) grey laminated silty-sandy clay; (2) homogeneous dark grey silty clay; and (3) compact silty clay.About 26 benthic foraminifera species are identified and divided into six groups according to their ecological characteristics.In association with lithology, sedimentary structures and grainulometry, the distribution of foraminifera group is used to define external slikke, internal slikke, external schorre, internal schorre, and continental marsh facies.Combined with 14C (AMS) dating, these data indicate four successive paleoenvironments in the Monards Marsh:(1) Holocene transgression resulted in the development of a basal schorre facies overlying fluvial deposits that transformed to slikke facies sedimentation; the transgression maximum occurred around 5 600 to 5 400 a BP and was inferred to be associated with the last phase of the rapid Holocene sea-level rise; (2) post-trangressive maximum sedimentation resulted in a regressive sequence of deposits prograding towards the estuary, corresponding to the stabilisation of sea level after 5 400 a BP; (3) a slight positive tendency in the sea level around 2 800 a BP recorded in the central part of the marsh; and (4) the wetland to a continental marsh environment.The sequential pattern for the evolution of wetlands in this estuarine area during the Holocene is fluvial facies-blackish schorre facies-slikke facies-blackish schorre facies-continental marsh facies.Characteristics of sedimentary facies distribution and evolution reveal that the development of Holocene salt marsh in this area was controlled by the sea-level change and tidal range.The sedimentary facies show an obvious surficial and vertical banding distribution in which the texture and structure, authigenic mineral, foraminifera distribution and bioturbation indicate many distinct difference characteristics.
THE CHARACTERISTICS AND DISTRIBUTION OF HOLOCENE SAND BODIES IN THE CHANGJIANG DELTA AREA
LI CONGXIAN, LI PING
1983(1): 84-96.
The holocene sand bodies in Changjiang delta area may be classified genetically as river mouth sand, marine sand and river channel-filled sand, which are different in external geometry, internal characteristics, spatial distribution and contact with overlying and underlying beds, The sand bodies ate distributed in two-storeyed beds in vertical sequence. The transgressive sands are overlain by regressive ones, and there is a wedge of marine clay between them.
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