陇中盆地中部下白垩统下岩组沉积相及其构造意义  

Sedimentary facies of the lower formation of the lower cretaceous and their tectonic significance in the Longzhong Basin

作　　者：刘海娇[1,2] 戴霜[1] 张明震[1] 汪禄波[1] 张文防[1] 张莉莉[1] 张瑞[1] 

机构地区：[1]兰州大学西部环境与气候变化研究院,西部环境教育部重点实验室,兰州730000 [2]大庆市博物馆,黑龙江大庆163000

出　　处：《兰州大学学报（自然科学版）》2013年第5期581-591,597,共12页Journal of Lanzhou University(Natural Sciences)

基　　金：国家自然科学基金项目(41272127;40972025;41021091);甘肃省科技重大专项(1203FKDA038);国家科技支撑计划项目(2011BAK12805)

摘　　要：通过对临夏盆地和民乐—兰州盆地下白垩统河口群下岩组地层序列和沉积环境分析,在2个盆地中鉴别出了7个沉积相:冲积扇相、辫状河相、曲流河相、辫状河三角洲相、三角洲相、滨湖相、浅湖相.同时发现临夏盆地下岩组沉积物总体显示从下向上由粗变细、古水流向南.砾石成分下部以花岗岩、闪长岩、变质岩为主,上部以花岗岩和变质岩为主及少量英安斑岩.民乐—兰州盆地下岩组沉积物则发育2个粗—细旋回、古水流向北,砾石成分及变化与临夏盆地类似.结合两盆地内广泛分布上岩组湖相沉积的事实,说明临夏盆地和民乐—兰州盆地至少在河口群下岩组沉积时处于分隔状态,大致以雾宿山一线为界分为南北2个盆地,在上岩组沉积时盆地连通,属于统一的陇中盆地,沉积物源区分析显示,盆地在下岩组沉积时沉积物主要来源于中部雾宿山,代表早白垩世一次强烈的构造隆升过程.民乐—兰州盆地和临夏盆地沉积环境与沉积旋回的差异,是盆地发生时间不同还是山体在南、北两侧隆升过程的差异,还有待于进一步研究.Through an analysis of the stratigraphic sequence and sedimentary environment in the Linxia and the 1Viinhe-Lanzhou Basin, seven sedimentary facies were identified i.e. alluvial facies, braided fluvial facies, meandering fluvial facies, braided fluvial delta facies and delta facies, shore-lake facies, shore-shallow lake facies, from lower formation of the lower cretaceous, respectively. In the Linxia Basin, the sediments of the lower formation varied from being coarser below to being finer above, the palaeocurrent was totally southward, and the lower part of gravel component was dominated by granite, diorite, quartzite veins and metamorphic rock, but a small amount of the dacitic porphyry occurred in the upper part. In the Minhe-Lanzhou Basin, the sediments of the lower formation were characteristic of two sedimentary cycles being from coarser to finer upwardly, and the palaeocurrent was totally northward, the change of gravel composition was similar to that of the Linxia Basin. All these suggest that the Linxia and the Minhe-Lanzhou Basins were separated when the lower formation was deposited. The paleocurrent and the gravel component data show that the Suwushan Mt was the sediment supply of the two basins, which separated the two basins from the north to south at that time, whereas thetwo basins were connected, belonging to the Longzhong Basin when lacustrine sediment was widely distributed over the two basins. In general, the basins went through a strong tectonic uplift in these region during the early cretaceous. Whether the reason for the variances in the sedimentary environment and sedimentary cycles between the two basins are due to the different formative times or to the discrepancies in the tectonic uplift between the south and north of the the Suwushan Mt, a further study is still needed in future research.

关 键 词：沉积相 构造隆升 陇中盆地 早白垩世 

分 类 号：P53[天文地球—古生物学与地层学] P54[天文地球—地质学]