四川华蓥山地区晚二叠世生物礁中“板状水螅”化石的初步研究

A PRELIMINARY STUDY OF PLATE-SHAPED HYDROZOANS FROM UPPER PERMIAN REEFS IN HUAYING MOUNTAINS,SICHUAN,CHINA

所讨论的“板状水螅”是一类分类位置尚有争议的化石，为华蓥山地区上二叠统生物礁的主要造礁生物之一。这里描述了３属３种．其中包括２新属和３新种．它们是Ｐｓｅｕｄｏｐａｌａｅｏａｐｌｙｓｉｎａｈｕａｙｉｎｇｅｎｓｉｓ，Ｐｈｒａｇｍｏｒｐｈａａｓｉａｔｉｃａ和Ｃｎｉｄｏｐｏｒａｔｕｂｅｒｃｕｌｏｓａ。

Since 1983. numerous Upper Permian reefs have been discovered in the HuayingMountains, Central Sichuan, which are similar in textures, structures and developing process, with such main reef--building organisms as calcareous sponges, hydrozoans and bryozoans, and encrusting organisms such as Archaeolithoporella and Tulephytes. Associatedin great amounts with the reef building organisms are reef dwelling organisms, such as brachiopods, foraminifers, gastropods. crinoids, ostrocods and various calcareous algae. In sedimentological and palaeontological characteristics of these reefs, the Upper Permian reefsdeveloped in central Sichuan represent the typical organic reefs in South China. All of thesereefs occurred in the Upper Permian Changhsing Formation which is overlain by the LowerTriassic Feixianguan Formation. The tops of the reefs are covered with tidal flat depositsattaining about l--7 m in thickness and made up of micritic dolomites accompanied bysome evaporitic remnants in which specialized ostrocods and stromatolites can be found. Itis not very clear whether the tidal flat deposits belong to Triassic or to Permian. The decline of the Permian reefs corresponds to the mass extinction of various Permian organismsacross the Permo--Triassic boundary, and therefore the reefs in this area can be regarded asthe 'latest Palaeozoic reefs in the world.