Abstract:

The Songkan section in Tongzi County of Guizhou Province， with a complete development of the Lower and Middle Triassic， abundant fossils and favorable exposure is an ideal section for the study of marine strata in the  Upper Yangtze area. According to the stratigraphic division and correlation， the Lower Triassic is divided into the Yelang and Maocaopu Formations， and the Middle Triassic comprises the Guanling Formation. Carbonate rocks and clastic rocks dominate the Lower and Middle Triassic with the former one making up 67％ of the entire section and the latter one  24％ respectively. Carbonates are distributed in the Yelang， Maocaopu and Guanling Formations， while clastics are confined to the Yelang Formation. The research results show that the Lower and Middle Triassic was characterized by a multicycle deposition. The Yelang Formation includes two transgressiveregressive cycles with sedimentary environments of tidal flat， open platform and shoal， and the Maocaopu Formation includes three cycles with sedimentary environments of open platform and restricted platform. The Guanling Formation is mainly a regressive succession， with sedimentary environments of restricted platform and tidal flat. Upon these researches， the sedimentary model of the Lower and Middle Triassic is established， ie., tidal flat-restricted platform-shoal-open platform pattern.

Key words: Guizhou Province, Songkan section, Lower and Middle Triassic, petrological characteristic, sedimentary environment, sedimentary model

摘要：

贵州桐梓松坎剖面中、下三叠统发育齐全，化石丰富，出露良好，是研究上扬子地区海相地层的理想剖面之一。根据地层划分与对比，将其分为下三叠统夜郎组、茅草铺组和中三叠统关岭组。该剖面以碳酸盐岩和碎屑岩为主，其中碳酸盐岩占67％，在夜郞组、茅草铺组和关岭组均有分布；碎屑岩占24％，主要分布于夜郎组。研究表明，松坎剖面中、下三叠统是一套多旋回沉积，其中夜郎组包括2个海进海退旋回，属于潮坪、开阔台地和浅滩沉积环境；茅草铺组包括3个海进海退旋回，属于开阔台地和局限台地沉积环境；关岭组总体上为海退沉积，属于局限台地和潮坪沉积环境。在沉积环境分析的基础上，建立了松坎剖面中、下三叠统的沉积模式，即潮坪—局限台地—浅滩—开阔台地沉积模式。

关键词: 贵州松坎剖面, 中、下三叠统, 岩石特征, 沉积环境, 沉积模式