彰武盆地东、西物源—沉积体系差异:来自沙海组(K_1s)岩芯的证据

利用钻井取芯的岩石组成、碎屑粒度特征及岩性-岩相的差异分析,研究彰武盆地下白垩统沙海组东、西物源物质组成和沉积体系特征。结果表明,东部物源火山碎屑占45%～85%,其中原生火山碎屑占70%,风化火山碎屑占30%,空落碎屑占杂基的10%～25%;西部物源火山碎屑占25%,风化碎屑占75%,空落碎屑占杂基5%～10%。CVL图解显示,东部物源的火山岩屑(L)和玻屑(V)含量均高于西部物源,而晶屑(C)含量低于西部物源。东部为受大型断裂控制的火山斜坡-扇三角洲环境。西部为缓坡区,发育辨状河三角洲环境,接受部分来自于东部的空落火山物质。Dickson图解显示,物源均来自火山弧和造山带物源区。区域早白垩世地壳拉张、火山喷发和同期盆地沉积,是形成不同物源-沉积体系的主要原因。

Differences between provenance-depositional systems in eastern and western Zhangwu Basin: evidences from drilling cores of Lower Cretaceous Shahai Formation

On the basis of petrographic composition, detrital grain size and lithology-lithofacies variance analysis of cores, the material composition and sedimentary system of eastern and western provenance-depositional systems of the Lower Cretaceous Shahai Formation in Zhangwu Basin have been studied. The results indicate that volcanic debris accounts for 45%~85% in eastern provenance, of which primary volcanic debris is 70%, weathered volcanic debris is 30%, air fall debris accounts for 10%~25% of the matrix contents. The volcanic debris accounts for 25% in western provenance, of which volcanic debris is 25%, weathered detritus is 75%, air fall debris accounts for 5%~10% of the matrix content. The CVL illustration shows that the contents of volcanic detritus (L) and vitroclastic (V) in eastern provenance are higher than that in western provenance, whereas the content of crystal pyroclast (C) in eastern provenance is lower than that in western provenance. The eastern system is a volcanic slope-fan delta system controlled by a large fault. The western system is a gentle slope area, in which the braided river delta develops and there is a small amount of air fall pyroclastic from the eastern system. The Dickson illustration shows that the fragments are from volcanic arc and orogenic belt provenances. The Early Cretaceous crustal extension, volcanism and corresponding basin development in this area are the primary causes for the formation of different provenances-depositional systems.