鄂尔多斯盆地东缘中生代延长组浊流沉积的发现与意义

作者在鄂尔多斯盆地东缘发现了一套典型的浊积岩系．在露头剖面上连续发育的厚约２０ｍ的浊流沉积可划分为６４个鲍玛层序，既广泛发育有代表浊流沉积特征的递交砂和多种底痕构造，又有Ｔａ—Ｔｅ都发育的典型层序，在层序组合上呈周期性变化。浊流沉积形成于晚三叠世，其上被下侏罗统富县组和中侏罗统延安组所覆，与邻区对比，其间缺少一套三角洲前缘及三角洲平原沉积．表明印支运动使鄂尔多斯盆地抬升造成差异剥蚀和在深水－半深水湖盆条件下与三角洲发育有关的浊流沉积类型出现的广泛性．

DISCOVERY OF TURBIDITY DEPOSIT IN YANCHANG GROUP ALONG EASTERN MARGIN OF ORDOS BASIN AND ITS SIGNIFICANCE

iscovered by the authors in 1987, a set of very typical turbidite sequence along the eastern margin of the Ordos Basin is characterized. This kind of turbidite in the Mesozoic along the southern and western magins of the basin had been reported by other geologists in previous work. 64 Bouma sequences of the turbidity deposit are divided within the whole thickness of 20 meters along the eastern margin. Among the rocks, graded sands and various sole mark structures displaying turbidity sedimentary features are widely occurred, and the sequences from Ta to Te well developed. Periodic variations are shown by this Bouma sequence association. The turbidity deposit formed during the Late Triassic period are overlaid by the rock sequence of the Lower Jurassic Fuxian group and the Mid -Jurassic Yan'an group and absent of overlying delta front and plain deposits by comparison with adjacent regions. This implies differential erosion caused by uplift of the Ordos Basin in Indosinian movemont. The discovery of this turbidity deposit along the eastern margin of the Ordos Basin indicates the universality of turbidity deposit occurrence related to delta under the Conditions of relatively deep--water lake.