Structural characteristics and tectonic division of the Zambezi Delta basin in the offshore East Africa: evidences from gravity and seismic data
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Abstract: The Zambezi Delta basin is a passive marginal basin located on the East African coast that has good oil and gas exploration potential. Due to the special geological evolutionary background of the Beira High in the Zambezi Delta basin, it has a low gravity anomaly, and the existing seismic survey lines do not cover the whole basin; therefore, it is difficult to interpret the structural characteristics of the whole basin based solely on gravity or seismic data. Based on satellite altimetry gravity anomaly data, this study infers the distribution characteristics of faults in the Zambezi Delta basin by using the normalized vertical derivative of the total horizontal derivative (NVDR-THDR) technique. Then, constrained by seismic data, the gravity anomaly at the Moho interface is extracted by using the fast forward method of the double-interface model of the gravity anomaly, and this anomaly is then removed from the Bouguer gravity anomaly to obtain the sedimentary layer gravity anomaly. The thickness of the sedimentary strata is obtained by inversing the sedimentary basement depth of the whole basin. Then, uplifts and depressions are divided based on a sedimentary layer thickness of 3 km. This research demonstrates that the Zambezi Delta basin mainly features nearly SN-trending and NE-trending faults and that these faults exhibit east‒west partitioning. The nearly SN-trending strike-slip faults controlled the sedimentary development of the basin, and the NE-trending tensile faults may have acted as migration channels for oil, gas and magma. The “overcompensation” effect of the Moho interface gravity anomaly on the gravity anomaly of the sedimentary layer is caused by the depression of the Moho interface beneath the Beira High, which results in a low gravity anomaly value for the Beira High. The pattern of uplifts and depressions trends NE and has the structural characteristics of east‒west blocks.
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Key words:
- Zambezi Delta basin /
- satellite altimetry gravity anomaly /
- Beira High /
- fault division /
- uplift and depression pattern
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Figure 13. Comparison of the geological profile (Mueller et al., 2016) and the gravity anomaly.
Table 1. Statistical table of the main strata densities (refer to Leinweber et al., 2013)
Main layer Layer Max thickness/km Main density(103 kg · m−3) Average density(103 kg · m−3) Water layer water layer 2.6 1.03 1.03 Cenozoic sediment layer sediment layer 1 0.9 1.95 2.30 sediment layer 2 0.8 2.18 sediment layer 3 1.8 2.39–2.46 sediment layer 4 1.8 2.40 Mesozoic sediment layer sediment layer 5 2.4 2.51–2.58 2.60 sediment layer 6 1.3 2.62 sediment layer 7 0.9 2.60 sediment layer 8 2.6 2.64 Crust upper crust onshore 4.7 2.69 2.90 middle crust onshore 32.0 2.91 lower crust 8.0 2.90–3.05 Mantle upper mantle - 3.27 3.27 Table 2. Statistical table of the inferred results for the main faults
Number Identifying characteristics Trend Position Nature Length/km DFZ NVDR-THDR continuous ridge value nearly SN east side of basin strike-slip – F3 NVDR-THDR continuous ridge value NE north side of basin tension 557 F4 NVDR-THDR continuous ridge value and local dislocation NE eastern part of the basin, which is centered tension 259 F5 NVDR-THDR continuous ridge value nearly SN mid-basin strike-slip 164 F6 NVDR-THDR continuous ridge value nearly SN northwestern basin tension 392 F7 NVDR-THDR continuous ridge value NE north side of Beira High tension 614 F8 NVDR-THDR continuous ridge value NE south side of Beira High tension 305 F9 NVDR-THDR continuous ridge value nearly SN west side of basin strike-slip 265 -
An Yulin, Zhang Minghua, Huang Jinming, et al. 2010. The computation scheme and computation process for gravity correction values within the pure spherical coordinate system. Geophysical and Geochemical Exploration (in Chinese), 34(6): 697–705 Castelino J A, Reichert C, Klingelhoefer F, et al. 2015. Mesozoic and Early Cenozoic sediment influx and morphology of the Mozambique Basin. Marine and Petroleum Geology, 66: 890–905, doi: 10.1016/j.marpetgeo.2015.07.028 Cox K G. 1992. Karoo igneous activity, and the early stages of the break-up of Gondwanaland. Geological Society, London, Special Publications, 68(1): 137–148 Cui Ge, Jin Aimin, Wu Changwu, et al. 2020. Tectonic evolution of East Africa coast and comparison of hydrocarbon accumulation conditions in the north and south petroliferous basins. Marine Geology & Quaternary Geology (in Chinese), 40(1): 104–113, doi: 10.16562/j.cnki.0256-1492.2018080103 Cui Zhihua, Lou Zhanghua, Zhu Zhenhong, et al. 2016. Petroleum geological characteristics and exploration prospect of Mozambique basin. Marine Geology Frontiers (in Chinese), 32(6): 1–8,22, doi: 10.16028/j.1009-2722.2016.06001 Feng Xuliang, Zhang Gongcheng, Wang Wanyin, et al. 2018. An integrated study on distribution of Cenozoic basins in the South China Sea based on gravity, magnetic and seismic data. Chinese Journal of Geophysics (in Chinese), 61(10): 4242–4254, doi: 10.6038/cjg2018L0567 He Tao, Wang Wanyin, Bai Zhizhao, et al. 2023. Integrated gravity and magnetic study on patterns of petroleum basin occurrence in the China seas and adjacent areas. Acta Oceanologica Sinica, 42(3): 201–214, doi: 10.1007/s13131-022-2139-5 IHS. 2018. International energy oil & gas industry solutions. http://www.ihs.com/industry/oil-gas/internation.aspx Ji Xiaolin, Wang Wanyin, Qiu Zhiyun. 2015. The research to the minimum curvature technique for potential field data separation. Chinese Journal of Geophysics (in Chinese), 58(3): 1042–1058, doi: 10.6038/cjg20150329 Jin Chong, Chen Anqing, Lou Zhanghua, et al. 2012. Tectonic evolution and hydrocarbon accumulation principle in East Africa. Journal of Jilin University (Earth Science Edition) (in Chinese), 42(S2): 121–130, doi: 10.13278/j.cnki.jjuese.2012.s2.012 Jourdan F, Bertrand H, Féraud G, et al. 2009. Lithospheric mantle evolution monitored by overlapping large igneous provinces: case study in southern Africa. Lithos, 107(3-4): 257–268, doi: 10.1016/j.lithos.2018.10.011 Jourdan F, Féraud G, Bertrand H, et al. 2007. Distinct brief major events in the Karoo large igneous province clarified by new 40Ar/39Ar ages on the Lesotho basalts. Lithos, 98(1-4): 195–209, doi: 10.1016/j.lithos.2007.03.002 König M, Jokat W. 2010. Advanced insights into magmatism and volcanism of the Mozambique Ridge and Mozambique Basin in the view of new potential field data. Geophysical Journal International, 180(1): 158–180, doi: 10.1111/j.1365-246X.2009.04433.x Lei Shoumin. 1984. Calculation of generalized topographic and isostatic gravity corrections. Marine Geology & Quaternary Geology (in Chinese), 4(1): 101–111, doi: 10.16562/j.cnki.0256-1492.1984.01.013 Leinweber V T, Klingelhoefer F, Neben S, et al. 2013. The crustal structure of the Central Mozambique continental margin - Wide-angle seismic, gravity and magnetic study in the Mozambique Channel, Eastern Africa. Tectonophysics, 599: 170–196, doi: 10.1016/j.tecto.2013.04.015 Li He. 2021. Crustal architecture and Tectonic-sedimentary evolution of the transform continental margin: insights from the Southern Mozambique Margin, East Africa (in Chinese)[dissertation]. Hangzhou: Zhejiang University, doi: 10.27461/d.cnki.gzjdx.2021.002613 Li Jinbo, Wu Guiqian, Xu Chuang, et al. 2023. Influence of gravity stripping in the South China Sea area on Moho inversion. Progress in Geophysics (in Chinese), 38(1): 0031–0046, doi: 10.6038/pg2023gg0083 Li Yuejun, Yang Haijun, Zhang Guangya, et al. 2012. Redivision of the tectonic units of tabei rise in tarim basin, NW china. Acta Petrologica Sinica (in Chinese), 28(8): 2466–2478 Luo Xin’gang, Wang Wanyin, Chen Ying, et al. 2023. Study on the distribution characteristics of faults and their control over petroliferous basins in the China seas and its adjacent areas. Acta Oceanologica Sinica, 42(3): 227–242, doi: 10.1007/s13131-022-2138-6 Mahanjane E S. 2012. A geotectonic history of the northern Mozambique Basin including the Beira High - A contribution for the understanding of its development. Marine and Petroleum Geology, 36(1): 1–12, doi: 10.1016/j.marpetgeo.2012.05.007 Mahanjane E S. 2014. The Davie Fracture Zone and adjacent basins in the offshore Mozambique Margin – A new insights for the hydrocarbon potential. Marine and Petroleum Geology, 57: 561–571, doi: 10.1016/j.marpetgeo.2014.06.015 Mahanjane E S, Franke D, Lutz R, et al. 2014. Maturity and petroleum systems modelling in the offshore Zambezi Delta depression and Angoche Basin, northern Mozambique. Journal of Petroleum Geology, 37(4): 329–348, doi: 10.1111/jpg.12589 Mueller C O, Jokat W. 2017. Geophysical evidence for the crustal variation and distribution of magmatism along the central coast of Mozambique. Tectonophysics, 712–713: 684–703, doi: 10.1016/j.tecto.2017.06.007 Mueller C O, Jokat W. 2019. The initial Gondwana break-up: a synthesis based on new potential field data of the Africa-Antarctica Corridor. Tectonophysics, 750: 301–328, doi: 10.1016/j.tecto.2018.11.008 Mueller C O, Jokat W, Schreckenberger B. 2016. The crustal structure of Beira High, central Mozambique-Combined investigation of wide-angle seismic and potential field data. Tectonophysics, 683: 233–254, doi: 10.1016/j.tecto.2016.06.028 Ponte J P, Robin C, Guillocheau F, et al. 2019. The Zambezi delta (Mozambique channel, East Africa): high resolution dating combining bio- orbital and seismic stratigraphies to determine climate (palaeoprecipitation) and tectonic controls on a passive margin. Marine and Petroleum Geology, 105: 293–312, doi: 10.1016/j.marpetgeo.2018.07.017 Rajesh R, Kumar K S, Tiwari R K. 2020. Regional and residual gravity anomaly separation using singular spectrum based frequency filtering methods: a case study of shallow subsurface modeling from Nagpur, India. Pure and Applied Geophysics, 177(2): 977–990, doi: 10.1007/s00024-019-02289-y Salman G, Abdula I. 1995. Development of the Mozambique and Ruvuma sedimentary basins, offshore Mozambique. Sedimentary Geology, 96(1–2): 7–41, doi: 10.1016/0037-0738(95)00125-R Sandwell D T, Müller R D, Smith W H F, et al. 2014. New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure. Science, 346(6205): 65–67, doi: 10.1126/science.1258213 Senkans A, Leroy S, d’Acremont E, et al. 2019. Polyphase rifting and break-up of the central Mozambique margin. Marine and Petroleum Geology, 100: 412–433, doi: 10.1016/j.marpetgeo.2018.10.035 Shi Buqing, Ding Liangbo, Ma Hongxia, et al. 2023. Characteristics of hydrocarbon accumulation in deep-water depositional system in offshore East Africa. Lithologic Reservoirs (in Chinese), 35(6): 10–17, doi: 10.12108/yxyqc.20230602 Solomon S, Bureau-Cauchois G, Ahmed N, et al. 2014. CO2 storage capacity assessment of deep saline aquifers in the Mozambique Basin. Energy Procedia, 63: 5266–5283, doi: 10.1016/j.egypro.2014.11.558 Wang Buqing, Huang Zhibin, Ma Peiling, et al. 2009a. Establishment of division standard, evidence and principle of structural units in Tarim Basin. Geotectonica et Metallogenia (in Chinese), 33(1): 86–93, doi: 10.16539/j.ddgzyckx.2009.01.024 Wang Wanyin, Pan Zuoshu. 1993. Fast solution of forward and inverse problems for gravity field in a dual interface model. Geophysical Prospecting for Petroleum (in Chinese), 32(2): 81–87,123 Wang Wanyin, Pan Yu, Qiu Zhiyun. 2009b. A new edge recognition technology based on the normalized vertical derivative of the total horizontal derivative for potential field data. Applied Geophysics, 6(3): 226–233, doi: 10.1007/s11770-009-0026-x Watts A B. 2001. Gravity anomalies, flexure and crustal structure at the Mozambique rifted margin. Marine and Petroleum Geology, 18(4): 445–455, doi: 10.1016/s0264-8172(00)00079-9 Wen Zhixin, Wang Zhaoming, Song Chengpeng, et al. 2015. Structural architecture difference and petroleum exploration of passive continental margin basins in East Africa. Petroleum Exploration and Development (in Chinese), 42(5): 671–680, doi: 10.11698/PED.2015.05.16 Xu Zhigang, Han Wenming, Sun Yumei. 2014. Tectonic evolution and petroleum exploration prospect of East Africa. Geology in China (in Chinese), 41(3): 961–969 Xu Chuang, Luo Zhicai, Sun Rong, et al. 2018. Multilayer densities using a wavelet-based gravity method and their tectonic implications beneath the Tibetan Plateau. Geophysical Journal International, 213(3): 2085–2095, doi: 10.1093/gji/ggy110 Yu Xuan, Hou Guiting, Dai Shuanghe, et al. 2015. Tectonic evolution and hydrocarbon pooling patterns analysis in East Africa continental margin. Geological Science and Technology Information (in Chinese), 34(6): 147–154,158 Zhang Gongcheng, Feng Yangwei, Qu Hongjun. 2022. Characteristics of petroleum geology of global five deep-water basin belts. China Petroleum Exploration (in Chinese), 27(2): 11–26, doi: 10.3969/j.jssn.1672-7703.2022.02.002 Zhang Yimi, Wang Wanyin, Li Linzhi, et al. 2023. Influence of the Moho surface distribution on the oil and gas basins in China seas and adjacent areas. Acta Oceanologica Sinica, 42(3): 167–188, doi: 10.1007/s13131-022-2136-8 Zhou Xinhuai, Yu Yixin, Tang Liangjie, et al. 2010. Cenozoic offshore basin architecture and division of structural elements in Bohai sea. China Offshore Oil and Gas (in Chinese), 22(5): 285–289