中国黑龙江东部鸡西盆地白垩纪多期砾岩特征及古地理意义

对鸡西盆地白垩纪不同时期砾石统计结果显示:下白垩统城子河组和穆棱组砾石主要成分为石英岩和花岗岩,与盆地周缘露头前中生代基底主要岩性相吻合;上白垩统猴石沟组砾石成分流纹岩、安山岩、凝灰岩增多,出现石英砂岩和少量泥岩,砾石很大一部分来源于下白垩统。6个统计点的砾石主要为次棱角状到圆状,长短轴之比集中在1~2,粒径以小砾为主,粒径长度符合正态分布;沉积环境判别函数显示砾石主要属于河流(三角洲)成因。研究表明城子河组沉积时期,盆地西部的张广才岭和盆地内的古隆起为盆地提供物源,城子河组到穆棱组的沉积过程是一个水体不断扩大的过程;穆棱组沉积中晚期,盆地西部成为盆地主要物源区。晚白垩开始,在强烈的逆冲作用下,盆地及周缘发生区域抬升,抬升区遭受强烈剥蚀,为盆地提供物源,低洼处沉积猴石沟组。

Features of Multistage Cretaceous Conglomerate Deposition and Its Palaeogeographic Significance in Jixi Basin of Eastern Heilongjiang,NE China

The results of gravel counting in different periods of cretaceous in Jixi basin shows that lower cretaceous gravel mainly consist of quartzite and granite,which is consistent with the outcrop lithology of pre-mesozoic basement in its periphery.In the contrast,rhyolite,andesite,tuff are growing in number in upper cretaceous Houshigou formation,and quartz sandstone and boulder clay can be found,hence indicating that the early mesozoic strata partly supply sediments.The shape of gravels chiefly changes from subangular to round,and the ratios between its long axis and short axis vary within 1–2 mostly,in small gravel primarily,particle size length conforms to the normal distribution.Sedimentary environment discriminant function displays that gravel mainly belong to rivers(delta) causes.Based on the analysis of gravels,the west of the basin and paleo-uplift supply sediments during the sedimentary stage of the Chengzihe formation.The deposition from Chengzihe formation to Muleng formation is the course of water expending.In the middle and late sedimentary stage of the Muleng formation,the western becomes the mainly continental provenance followed by the further expansion of the transgressive range.During late cretaceous,the basin and its periphery occurs uplift and subjects to erosion because intensely fold-thrusting,deposit Houshigou formation in the low-lying region.