重庆北碚老龙洞二叠－三叠系界线层中的全脐螺侏儒化: 环境突变中的机会群落?     

姜红霞  吴亚生  刁建波  陈建阳 《地球学报》2010,31(2):163-169

本文首次报道重庆北碚老龙洞剖面二叠－三叠系界线附近的全脐螺科的微型腹足类动物群。全脐螺科个体微小, 多为盘形、圆锥形, 具明显的脐, 方解石质的壳壁。区分出研究层内的两类全脐螺, 一类是碗形, 脐宽而大, 脐部深凹; 壳壁厚度变化很大, 螺环可能上有棱、角或瘤等装饰。另一类是胎壳呈平旋状, 呈开放式旋绕; 壳壁厚度均匀, 未见装饰特征显示。全脐螺类为优势分子的群落在二叠纪末大绝灭事件后盛极一时, 如此异常现象可能与浅海区在缺氧之后暂时改善为有氧环境有关, 此后随着早三叠世腹足类的全面复苏, 它们只能退居为极次要的角色。  相似文献   

Microgastropod records in paleoceanographical environment of southern shelf of South China Sea since 14 ka     

冯伟民 《中国科学D辑(英文版)》2002,45(3):241-249

Very diversified and abundant benthic microgastropods and planktonic microgastropods (pteropods) from core NS93-12-25 could provide a glance of change of the sea level in the south continental shelf of the South China Sea since last 14 ka. Research shows that general sea level changes of this sea area were rising and later rising after a short period of falling in this period. In the range from the bottom of the core to the core depth of 200 cm, individuals in big size are common in microgastropods and Turritella filiola is very rich, signifying the environment of the inner continental shelf in the last deglaciation stage. In the core depth range of 200–150 cm the continuously getting light of the δ¹⁸O, the regularly decreasing of the percentage content of T. filiola and the high diversification of microgastropods indicate the rising of the sea level. Especially at the core depth range of 175–150 cm the pteropods became dominant, making sure the fact that the high sea level possibly occurred in the early Holocene. Channels of surrounding straits connecting the adjacent sea thus were opened. But at the core depth of about 100 cm T. filiola became very rich again. This possibly implies that there was a short term of the sea level falling, resulting in the temporal closure of the channels. In the core depth range of 55–50 cm the Scaliola’s representatives relatively develop and this may be inferred to the cooling of climate.  相似文献