塔里木北部库车前陆盆地晚白垩世和古新世的钙质超微化石组合

LATE CRETACEOUS AND PALEOCENE CALCAREOUS NANNOFOSSIL ASSEMBLAGES FROM KUCHE FORELAND BASIN IN THE NORTHERN TARIM BASIN

库车前陆盆地是中国大型油气基地之一,盆地中的白垩系及古近系为盆地油气的主要储层。对本区白垩系的时代划分和沉积环境的精确确定直接关系到对油气田的规模、储量和分布范围的正确评价。本研究在前人划分为陆相下白垩统巴什基奇克组的顶部首次发现了由10属15种组成的晚白垩世海相钙质超微化石组合Arkangelskiellacymbiformis—Quadrumgartneri。此外,在由前人定为古新统—始新统的塔拉克组下段也发现了晚白垩世Arkangel skiellacymbiformis—Quadrumgartneri组合,在该组上段发现了古新世化石Biantholithussparsus。该成果既为准确确定这两个岩组的地质时代提供了可靠的古生物证据,又为本区存在晚白垩世地层和海相沉积提供了佐证,表明巴什基奇克组顶部存在晚白垩世的海相沉积,塔拉克组下段属于上白垩统,上段属于古新统。

A biostratigraphic study on calcareous nannofossils from the Cretaceous Bashijiqike Formation and Paleocene Talake Formation in the northern Tarim Basin was carried out to obtain reliable biostratigraphic assignment.A Late Cretaceous calcareous nannofossil assemblage, _Arkangeleskiella cymbiformis-Quadrum gartneri,_ was found in sediments on the top of the Bashijiqike Formation in the northern Tarim Basin, indicating a Late Cretaceous age for the sediments. The occurrence of the calcareous nannofossil assemblage also suggests a marine sedimentation environment in the Late Cretaceous in the studied area.This assemblage was also found in sediments from the lower sections of the Talake Formation, assigning the sediments into Upper Cretaceous._Biantholithus sparsus,_ which is commonly used for marking the bottom of Tertiary, was found in the upper sequences of the Talake Formation, which suggests an age of Paleocene for the upper sequences of the Talake Formation.