相对海平面变化对腕足动物群落取代的影响——以吐哈盆地北缘桃西沟上石炭统祁家沟组—奥尔土组剖面为例

THE INFLUENCE OF RELATIVE SEA LEVEL CHANGES TO THE REPLACEMENT OF BRACHIOPODS COMMUNITIES:A CASE STUDY OF TAOXIGOU CARBONIFEROUS SECTION OF THE NORTH MARGIN OF TURPAN-HAMI BASIN

相对海平面的升降变化引起的相对水深及相关生态条件的改变对腕足动物群具有影响。相对海平面变化的速度和幅度是引起腕足动物群面貌变化的重要因素。相对海平面的持续缓慢上升有利于腕足动物丰度的增加和分异度的提高,海平面的大幅度快速变化对腕足动物群落则是一个不利的因素,是造成腕足动物物种丰度下降、新种增加量减少乃至彻底死亡的重要原因。吐哈盆地北缘晚石炭世发育的5个腕足动物群落全部与相对海平面上升期有关。在海平面的持续缓慢上升期,腕足动物的丰度不断增加,分异度迅速提高;而在相对海平面下降期,本区陆源粗碎屑物大量注入,不适合腕足动物的生存。

Relative sea level change may result in the change of water depth and all the other ecological factors related, so it is a key factor for controlling the succession and replacement of brachiopods communities. The speed and extension of sea level rising and descending greatly control the species richness and diversity of brachiopods community. In the area of the north margin of Turpan-Hami basin, totally three third-order relative sea level changes can be recognized from the Upper Carboniferous, and all the 5 brachiopods communities developed during this period are closely related to the sea level risings. There is no brachiopods fossil found during the marine regression, this may result from the quick descending of relative sea level changes and too much clastic sediment swarmed into. During the period of sea level rising, the rapid rising of primary sea level is in favor of early brachiopods communities but may restrain the development of later comers. Constant and slow rising of sea level is helpful to the flourish of the species richness and diversity of brachiopods, but may delay the process of the replacement of brachiopods communities.