Clay mineralogy of the first and second members of the Nenjiang Formation, Songliao Basin: Implications for paleoenvironment in the Late Cretaceous  

作　　者：GAO Yuan XI DangPeng QIN ZuoHuan MA PengFei WANG ChengShan 

机构地区：[1]State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences [2]School of Earth Sciences and Resources, China University of Geosciences [3]State Key Laboratory of Marine Geology, Tongji University

出　　处：《Science China Earth Sciences》2018年第3期327-338,共12页中国科学（地球科学英文版）

基　　金：supported by the Fundamental Research Funds for the Central Universities of China(Grant No.2652015387);the National Basic Research Program of China(Grant No.2012CB822000)

摘　　要：The first and second members ofthe Nenjiang Formation （K2n1＋2） in the Songliao Basin, northeast China, are an interval of dark-colored mudstone. Paleoenvironmental studies of these strata are useful for understanding the terrestrial environment under a greenhouse climate and hydrocarbon accumulation in lake basins. In this study, clay mineralogy of the K2n1＋2 from four borehole or outcrop sections is investigated to understand terrestrial paleoenvironment during the depositional period in the Late Cretaceous. In the mudstone samples, smectite and illite are the predominant clay minerals, and were derived from weathering of parent rocks in a temperate, sub-humid to sub-arid climate; kaolinite and chlorite are minor clay species. The difference in the clay-mineral assemblages between the eastern and western margins of the basin was primarily controlled by provenance lithology, and the high smectite content in the western basin resulted from alteration of volcanic rocks exposed in the Greater Xing＇an Range area. The increasing illite content and ratio of illite/smectite percentages in the upper part of the first member of the Nenjiang Formation indicate paleoenvironmental change. This temporal change in the clay-mineral composition was primarily caused by a regionally cooler and drier paleoclimate, consistent with previous paleoenviroumental reconstructions.The first and second members of the Nenjiang Formation(K_2n^(1+2)) in the Songliao Basin, northeast China, are an interval of dark-colored mudstone. Paleoenvironmental studies of these strata are useful for understanding the terrestrial environment under a greenhouse climate and hydrocarbon accumulation in lake basins. In this study, clay mineralogy of the K2 n1+2 from four borehole or outcrop sections is investigated to understand terrestrial paleoenvironment during the depositional period in the Late Cretaceous.In the mudstone samples, smectite and illite are the predominant clay minerals, and were derived from weathering of parent rocks in a temperate, sub-humid to sub-arid climate; kaolinite and chlorite are minor clay species. The difference in the clay-mineral assemblages between the eastern and western margins of the basin was primarily controlled by provenance lithology, and the high smectite content in the western basin resulted from alteration of volcanic rocks exposed in the Greater Xing'an Range area. The increasing illite content and ratio of illite/smectite percentages in the upper part of the first member of the Nenjiang Formation indicate paleoenvironmental change. This temporal change in the clay-mineral composition was primarily caused by a regionally cooler and drier paleoclimate, consistent with previous paleoenvironmental reconstructions.

关 键 词：Clay mineral Nenjiang Formation Songliao Basin PALEOENVIRONMENT Late Cretaceous 

分 类 号：P534.53[天文地球—古生物学与地层学] P618.13[天文地球—地质学]