陕南奥陶纪圆尾虫类三叶虫的丰度及海平面变化

RELATIVE ABUNDANCE CHANGES OF CYCLOPYGID TRILOBITES DURING THE MIDDLE TO UPPER ORDOVICIAN IN SOUTHERN SHAANXI WITH REFERENCE TO SEA-LEVEL FLUCTUATIONS

上扬子区北缘米仓山地区 3个宝塔组剖面的远岸水中浮游圆尾虫类三叶虫丰度变化研究表明 ,该区海域在兰维恩晚期至阿什极尔早期曾出现 4次海平面跌落和 3次海平面上升 ,与同期全球海平面变化有一定的可比性。证明圆尾虫类丰度变化的研究可能是揭示奥陶纪全球海平面变化规律的一个有效手段。

The relative abundance changes of mesopelagic cyclopygid trilobites through the Pagoda Formation in the Micangshan area of southern Shaanxi, northwestern margin of the Yangtze Block, indicate that 4 ma jor falls and 3 major rises in sea level may have taken place in the Yangtze Sea during the late Llanvirn—early Ashgill. These relative abundance change approximate coincide with global sea level fluctuations as revealed by Ross and Ross (1992) and Fortey (1984). This suggests that the alternation of the relative aboundances of cyclopygids may be closely related to the eustatic changes of sea level.