新疆中库鲁克塔格地区震旦系扎摩克提组沉积特征

扎摩克提组位于中库鲁克塔格震旦系上统底部,由砂岩、粉砂岩和泥页岩构成韵律武沉积,为不完整的玛鲍序列.砂岩层底面普遍发育槽模等底痕.有些砂岩呈纹层状,并有滑动构造和包卷层理等.构成砂岩的碎屑颗粒分选性差.根据粒度分布概率图、C-M图和碳、氧、硫等稳定同位素及Sr/Ba比值、硼含量等显示,该组形成于淡化海槽中.

SEDIMENTARY FEATURES OF SINIAN ZHAMOKETI FORMATION IN THE MIDDLE KURUKTAG AREA, XINJIANG

The Middle Kuruktag area is located at the northern margin of Tarim Basin In this area, Zhamoketi Formation overlying Tereeken Formation, is at the base of Upper Sinian Series. The sedimentary rocks of Zhamoketi Formation are characterized by cyclo-thems with incomplete Bouma sequences, which comprise sandstones, siltites, shales and a few conglomerates. Well-developed sole marks, such as flute groove and load casts, are found on the basal surface of graded conglomerate and sandstone beds. In the fine-grained clastic and muddy rocks, stratifications are common with some slumped and convoluted structures. In addition, the wave disturbing marks such as small-sized hummocky-like crossbedded structures, were observed-Sandstones are mainly lithoclastic greywackes with clastic grains moderately to poorly rounded and sorted. The pattern of C-M diagram and cumulative curves of grain-size distribution show analogies with some known turbidites formed in shallow water. According to the data of stable isotopes of C, O and S and the values of Sr/Ba ratio and boron, we have got the idea that the water of Kuruktag trough might have been desalinated for a while after Tereeken ice stage. Based on the field observation and the data from laboratory, a brief sedimentation model of Zhamoketi Formation is suggested as follows: there existed turbidity currents resulted from the reworking of the end-moraine of Tereeken glaciation. The sea-level arised during interglacial epoch accompanied by tectonic and/or storm activities. According to the data of palaeocurrent directions, It is concluded that two turbidite fans may have been formed in the research area . Overlying Zhamoketi Fomation turbidites is normal marine deposits, the Yukengou Formation.