川南下志留统石牛栏组沉积体系与岩相古地理

Depositional system and lithofacies and paleogeography of the Silurian Shiniulan Formation in the southern Sichuan Basin,China

四川盆地南部下志留统石牛栏组为在缓坡陆棚基础上发育起来的碳酸盐台地的沉积,可划分出4个岩性段和2个沉积旋回。沉积体系在空间展布特征上表现为由南向北的从碎屑滨岸→局限台地→开阔台地→生物礁/滩→台地边缘斜坡→浅水陆棚浅滩→泥质浅水陆棚→深水陆棚变化,在垂向上则由泥/灰质深水→浅水陆棚→碳酸盐台地的变化;海平面变化是控制沉积体系发育和空间分布的重要因素。

The Silurian Shiniulan Formation in the south of the Shichuan Basin was deposited on the carbonate platform developed based on a flat shelf. Four lithologic segments and two sedimentary cycles can be identified in the formation. The depositional system tracts formed in the environments including, from south to north, clastic seashore, localizing platform, open platform, biogenic reef or beach, slope of platform edge, shallow shelf beach, argillaceous shallow shelf and deep-water shelf. Temporally, the whole sedimentary environment changed from argillaceous or calcite deep-water to shallow shelf and to carbonate platform. The most important factor of controlling the spatial and temporal evolution of depositional system is sea level fluctuation.