湖北松滋刘家场地区寒武系叠层石沉积特征及其古环境意义

湖北松滋刘家场地区寒武系覃家庙组三段发育层状、不规则层状和柱状叠层石,三游洞组发育柱状和半球状叠层石。从层状、不规则层状、柱状到半球状叠层石,内部灰泥含量不断减少,纹层特征从明显到断续,反映了水动力条件加强的变化环境。从沉积岩石学角度与叠层石分类观点讨论得出,研究区不同沉积环境的叠层石组合类型有所差异,不同类型的叠层石主要沉积相带不同:潮上带主要分布层状(包括不规则层状)和柱状叠层石,潮间带主要分布柱状、半球状叠层石;层状叠层石主要分布于水动力条件较弱的潮上带,而柱状和半球状叠层石主要分布于水动力条件较强的潮间带下部。部分后生动物的大量灭绝导致叠层石微生物生长繁殖是松滋寒武系叠层石发育的主要原因。

Sedimentary characteristics and their palaeoenvironment significance of Cambrian stromatolites in Liujiachang of Songzi City, Hubei Province

In the Cambrian strata in Liujiachang of Songzi City, stratiform, irregularly stratiform and columnar stromatolites develop in the third member of the Qingjiamiao Formation, and columnar and hemispherical stromatolites develop in the Sanyoudong Formation. From the stratiform, irregularly stratiform, columnar stromatolites to hemispherical stromatolites, the internal stucco content is decreasing. The decrease of laminated features reflect that the hydrodynamic force is gradually strengthening. From the perspective of sedimentary petrology and the classification of stromatolites, it is concluded that the combination of stromatolite types in different sedimentary environments is different. They have different sedimentary facies belt:Stratiform (including irregularly straiform)and columnar stromatolites are mainly distributed in the supratidal zone, Columnar and hemispherical stromatolites are mainly distributed in the intertidal zone; The stratiform stromatolites mainly develop in the supratidal zone with weak hydrodynamic force, while the columnar and hemispherical stromatolites mainly develop in the lower intertidal zone with powerful hydrodynamic condition. A mass extinction of part of the metazoan is the main reason for the growth of stromatolites microorganism, which results in the growth of stromatolites in Cambrain strata in Songzi.