甘肃皋兰—白银—靖远地区早白垩世沙漠沉积的特征及其古风带恢复

Early Cretaceous desert and the reconstruction of palaeowind belts in Gaolan-Baiyin-Jingyuan area,Gansu Province

在前人对甘肃白银—靖远地区早白垩世河口群(K1H)沙漠研究的基础上,对皋兰地区的河口群进行了沉积结构、构造和石英砂颗粒表面特征等综合对比分析,确认皋兰地区亦存在沙漠沉积。首次通过系统测量研究区风成沙丘的前积层的产状,对当时的古风向、古风带进行了恢复,结果表明,早白垩世晚期研究区盛行西风,与东部鄂尔多斯盆地早白垩世罗汉洞组(K1l)沙漠沉积风向记录完全一致。岩性特征与古风向的一致性表明,研究区与鄂尔多斯盆地均处于北半球西风带中,研究区可能为"古鄂尔多斯沙海"的一部分。

Based on previous researches on Early Cretaceous desert of Hekou Group（K1H） in Baiyin-Jingyuan area,the authors made a synthetic comparative analysis of sedimentary texture and structure as well as typical eolian grain surface texture of Hekou Group in Gaolan area,and reached the conclusion that there must also exist desert sediments in Gaolan area.Then,the palaeowind direction and palaeowind belt were reconstructed by systematical measurement of the dips of the eolian dune foresets in the study area.The results indicate that west winds were prevailing during late Early Cretaceous in the study area,being consistent with the palaeowind direction recorded in the Luohandong Formation（K1l） in Ordos basin.The consistency of the lithologic character and palaeowind direction recorded in K1H and K1l indicates that the study area and Ordos basin were then located within the same westerlies in the northern hemisphere and the study area might have been part of the Ordos palaeodesert sea.