辽东苏子河盆地聂尔库组沉积相与沉积环境研究

辽东苏子河盆地是早白垩世形成的小型断陷盆地,盆地内发育了相对连续的陆相沉积,是研究白垩纪陆地环境及气候演化的理想地区。早白垩世晚期沉积的聂尔库组地层出露连续,沉积现象典型。通过分析聂尔库组沉积岩类型、沉积构造、古生物化石及垂向沉积序列,可识别出扇三角洲相和湖泊相,其中扇三角洲相包括扇三角洲平原亚相、扇三角洲前缘亚相和前扇三角洲亚相,湖泊相主要为滨浅湖泥砂沉积。研究表明,聂尔库组形成于断陷盆地边缘陡坡带,属于间歇性洪水控制的扇三角洲—湖泊沉积体系,经历了扇三角洲—湖泊—扇三角洲的沉积环境变化,代表了断陷湖盆由深陷扩张期—抬升收缩早期的沉积充填过程。根据沉积岩与沉积相特征,结合古生物、特殊沉积、黏土矿物及地球化学资料,认为早白垩世晚期辽东地区总体与当时全球"温室气候"的大背景相一致,处于高温干旱/潮湿的气候条件,但这种高温气候具有不均一性,存在气候波动。

Study of Sedimentary Facies and Environment of the Nieerku Formation,Suzihe Basin,Eastern Liaoning

The Suzihe Basin is a Lower Cretaceous small fault basin in eastern Liaoning Province. The continental deposits in the basin offer unique conditions for the study of the evolution of the paleoenvironment and paleoclimate of terrestrial settings during the Cretaceous. The sediments of the late Lower Cretaceous Nieerku Formation in the Suzihe Basin contain various clastic and mud rocks, typical deposits and divers terrestrial fossils. An analysis of the sedimentary rock types, the sedimentary structure, fossils and sedimentation sequence, recognized fan delta facies and lake facies. The fan delta facies are divided into fan delta plain subfacies, fan delta front subfacies and pre-fan delta subfacies. The lake facies primarily contain shore to shallow-lake mudstones and sandstones. It was found that the Nieerku Formation formed on the steep slope of a faulted lacustrine basin in a fan delta/lake sedimentary system that underwent intermittent flooding. The Nieerku Formation evolved in a sedimentary environment from fan delta to lake, then to fan delta, indicating that the faulted lacustrine basin experienced two evolutionary stages: a deep depressional period and an early shrinkage period. The characteristics of the sedimentary rocks and facies, combined with paleontological data, specific sediments, clay minerals and geochemical data, confirm that the climate was generally hot and dry/humid in eastern Liaoning during the late Lower Cretaceous, which corresponds to a “greenhouse” climate, but the warm climate was not static. This supports the generally held view that the Cretaceous climate was turbulent.