南秦岭淅川地区上石炭统周营组生物群特征

The biotic fossils from the Upper Carboniferous Zhouying Formation in the Xichuan district,southwestern Henan

关键词:  南秦岭  周营组  生物  豫西南

Key words:  South Qinling  Zhouying Formation  biota  southwestern Henan

摘要:

南秦岭淅川地区上石炭统周营组有多门类化石共生,类为晚石炭世的标准分子,菊石、腕足、珊瑚、双壳、腹足类多具泥盆纪生物群特征。岩石组合、岩性特征、层序特征、沉积环境演变及构造古地理、生态的综合研究表明,周营组为晚石炭世沉积地层,其内的晚石炭世、中晚泥盆世古生物组合是在有障壁的局限滞留盆地这一特殊的古地理和生态环境下形成和发展起来的,是南秦岭淅川地区特有的组合,不具有搬运再沉积的物质条件,不是搬运再沉积的结果。每一次海侵,海水的加深和有机质的富集,是周营组生物群得以发生和发展的有利条件。海水的退出、咸化和相对闭塞环境下食物的缺乏,是生物群绝灭,并很好保存埋藏的主要原因。

Abstract:

There occur various biotic fossils in the Upper Carboniferous Zhouying Formation in the Xichuan district,southwestern Henan. They are fusulinids,ammonites,corals,brachiopods,bivalves,gastropods,crinoids,bryozoans,foraminifera and plant remains. The fusulinids appear as the Late Carboniferous standard fossils,while the ammonites,corals,brachiopods,bivalves and gastropods are generally characteristic of the Devonian biotic fossils. The integration of lithology,sequences,ecology and sedimentary environments suggests the Late Carboniferous sedimentary strata of the Zhouying Formation. The Late Carboniferous,Middle and Late Devonian biotic assemblages are the characteristic products in the Xichuan district developed in the barried restricted lag basins. The sea water encroachment and deepening and enrichment of organic matter are favourable for the generation and development of the biotas in the Formation. The marine regressions,salification of sea water and lack of food in the relatively enclosed conditions are responsible for the extinction of the biotas and burial and preservation of their fossils.