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Termit盆地及其周缘是中西非裂谷中典型的中、新生代裂谷盆地,也是中石油海外最具潜力的风险勘探区,但由于多期构造运动的复杂性,研究区晚白垩世的古地理演化缺乏系统的分析研究。本文将Termit盆地及其周缘作为研究区域,在构造演化的基础上利用地球化学、地层学及地球物理等手段进一步分析了研究区的古沉积环境、古气候及古物源,最终明确了晚白垩世的古沉积演化。研究认为,晚白垩世早期的森诺曼阶(Cenomanian)研究区开始发生海侵,三冬阶(Santonian)时期达到最大海侵范围,之后开始逐渐海退的过程。马斯特里赫特阶(Maastrichtian)时期的区域构造挤压事件使盆地形态发生改变,该构造事件最终以区域不整合结束。地球化学资料、岩性资料以及地震资料综合表明,森诺曼阶(Cenomanian)—三冬阶(Santonian)时期研究区处于偏还原的浅海陆架沉积,属典型的热带气候,接受来自北东向的物源供给;至坎潘阶(Campanian)—马斯特里赫特阶(Maastrichtian)时期,伴随着海平面的下降,研究区由海相沉积逐渐转变为海陆过渡相沉积,且物源主要来自于北东及南西两个方向。本次研究明确了Termit盆地及其周缘在晚白垩世的古沉积演化过程,这为进一步明确研究区的沉积体系及砂体的预测提供了理论依据。
The Termit Basin and its peripheries are typical Mesozoic and Cenozoic rift basins in the Rift Valley and are also the most potential risk exploration areas overseas. However, because of the complexity of multistage tectonic movement, the paleogeographic evolution of the Late Cretaceous in the study area Lack of systematic analysis. Based on the tectonic evolution, the Termit Basin and its periphery are used as the study area. Based on the tectonic evolution, the paleo-sedimentary environment, paleoclimate and ancient provenance in the study area are further analyzed by means of geochemistry, stratigraphy and geophysics. Finally, the Late Cretaceous Ancient sedimentary evolution. The study suggests that the transgression began to occur in the Cenomanian study area in the early Late Cretaceous and reached its maximum transgression range during the Santonian period and then began to recede gradually. The regional tectonic extrusion in the Maastrichtian period changed the shape of the basin, and the tectonic event ended up as a regional unconformity. The geochemical data, lithological data and seismic data show that the Cenomanian-Santonian study area is under the partial reefs of shallow shelf deposits, which belongs to the typical tropical climate and receives the data from the NE direction In the period from the Campanian to Maastrichtian to the Campanian-Maastrichtian, the sea area was gradually changed from marine sediment to marine-continental transitional facies with the sea-level decrease. The source mainly came from North East and South West in both directions. The study identified the evolution of paleoclimate evolution of the Termit Basin and its periphery in the Late Cretaceous, which provides a theoretical basis for further clarifying the sedimentary system and the prediction of sand bodies in the study area.