鄂东地区上泥盆统五通组砂岩沉积相及其古地理特征

对鄂东地区上泥盆统五通组砂岩的成因，一直存在河流相和滨海相的不同认识。野外研究和室内分析表明：该组主要为一套成熟度较好纯净的石英砂岩和含海绿石石英砂岩。概率累积曲线斜率较大，以跳跃组分为主，悬浮组分和滚动组分含量低，有的砂岩跳跃组分具两段式，粒度参数属于分选好的滨海砂范围。微相和粒度分析都表明其具有明显的高能碎屑海岸的滨海沉积特征。砂岩中发育大型冲洗交错层理、大型不对称浪成波痕、不规则的坑凹面等典型的海滩沉积构造。纵向上为临滨下部一临滨上部一临滨下部一临滨上部一前滨一后滨沉积特征，上部为一个完整的退积型海滩沉积序列。区域古地理分析反映下扬子的鄂东地区晚泥盆世时期处于滨浅海环境，其北部可能与秦岭古海洋相通。

SEDIMENTARY FACIES AND PALEOGEOGRAPHY OF SANDSTONES OF WUTONG FORMATION OF THE LATE DEVONIAN IN EASTERN HUBEI PROVINCE

Fluvial facies and shore facies are two different viewpoints on the origins of sandstones of Wutong Formation of the Upper Devonian in the eastern Hubei Province. Based on the abundant and elaborate field investigations and laboratory analysis, it is suggested that the Wutong Formation is mainly pure quartz sandstone and glauconite-bearing quartz sandstone with great maturity. The cumulating curve of probability with a relative steep slopes shows that the sandstones are mainly made up of leaping components, some of which are made of the two-stage mode, and the contents of suspending and rolling components are quite low. It can be concluded that grain size parameter of the sandstones are limited within ranges of that of well-sorted shore sandstone. Microfacies and grain size analysis all indicate that the sandstones are significantly analogous to that of the high-energy clastic coast. The sandstones well developed the shore-deposit structure, such as flushing cross-bedding, great and asymmetrically wave-generated ripple and anomalistic concave. A sedimentary sequence evolutes from lower of shore face zone to upper of the shore face zone, foreshore zone and backshore zone vertically, upper parts of which there is a complete regressive sequence of the shore sediments. The analysis on the palaeogeography suggests that there was a shore environment in the eastern Hubei Province in the Late Devonian, which was perhaps open to ancient Qinling Sea northward.