重庆合川地区吴家坪期海水进退与腕足动物多样性

在分析重庆合川吴家坪期地层的沉积环境和腕足动物化石地层分布的基础上,运用海水进退沉积旋回和物种多样性综合指数相结合的定性定量分析方法,对本区吴家坪期腕足类物种多样性演变规律进行了综合研究.结果表明:本区吴家坪期腕足类物种辐射起步于吴家坪初期,共出现了4次高潮期和4次低潮期.在整个吴家坪期,物种辐射的高峰主要出现在前期,而物种辐射低潮则主要出现在后期,总体呈现出物种多样性不断下降的趋势;在正常的海进海退层序中,海进序列中的腕足类物种多样性要明显高于海退序列.但在快速短暂的海水进退的变化环境下,则海退序列腕足类物种多样性要高于海进序列,反映海水深度和环境的稳定性是物种多样性高低的重要影响因素.

Marine Transgression-Regression and Brachiopod Diversity from the Wujiapingian in the Hechuan Area of Chongqing

Based on analyzing sedimentary environment and Brachiopod stratigraphic distribu-tion of Wujiapingian in Hechuan, Chongqing, the Brachiopods species diversity changes in this area was investigated combining the transgression-regression cyclothems and species diversity integrate index with qualitative and quantitative analysis. The results show that Wujiapingian Brachiopods species radiation appeared in early Wujiapingian, which contained four fastigiums and four low tides. During the Wujiapingian, species radiate fastigiums mostly appeared in pro-phase, while the radiate low tides in anaphase, with the trend of species diversity descend con-tinuously. In normal transgression-regression sequence, Brachiopods species diversity in trans-gression is visibly higher than that in regression. But in fast-transitory transgression-regression sequence, Brachiopods species diversity in regression is higher than that in transgression, which reflected that seawater depth and environment stability are important impact factors of species diversity.