尼日尔Termit盆地及其周缘晚白垩世古地理演化

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。

Palaeogeographic evolution of the Upper Cretaceous in Termit Basin and its adjacent areas,Niger

The Termit Basin and its adjacent areas are the typical Mesozoic Cenozoic rift basin of West African Rift System (WARS), and they are also the most potential risk exploration area for CNPC overseas. However, because of the complex tectonic movement, the study area is lack of system analysis in paleogeographic evolution of the Upper Cretaceous. In this article, we take the Termit Basin and its adjacent areas as our study area. On the basis of tectonic evolution, we comprehensively utilize geochemistry, stratigraphy and geophysics to analyze the paleo sedimentary environment and Paleogene provenance in the study area. The study suggested that during the early Cenomanian in the study area the transgression began to occur, and it achieved maximum transgression in the Santonian, then the sea level began to descend. Because of the regional tectonics, the uplifting movements occurred in the Termit Basin and the west part. The geochemical, lithological and seismic data show that the Termit Basin and its adjacent areas were in shallow shelf deposition during the Cenomanian Santonian period, and the provenance mainly came from the NE direction; during the second period, the sedimentary facies of marine deposit transited to transitional facies, and the provenance came from the NE and SW directions; and all of this had provided the theoretical basis for the analysis of sedimentary systems and sand body prediction.