龙门山甘溪土桥子组碳酸盐岩沉积相及其演化

Carbonate facies and sedimentary evolution of Upper Devonian Tuqiaozi Formation in Ganxi section of Longmen Mountain

依据野外实测剖面资料,对龙门山甘溪剖面上泥盆统土桥子组沉积相进行了分析,认为土桥子组以碳酸盐缓坡沉积为背景,该组沉积中期,随着海平面的短暂下降,碳酸盐缓坡发生短暂的台地化,其最直接的识别标志是生物礁前的角砾岩及塌积岩沉积的出现。该剖面土桥子组碳酸盐缓坡包括浅水缓坡和深水缓坡2种亚相类型;碳酸盐台地包括台地边缘礁滩和前缘斜坡2种亚相类型。土桥子组碳酸盐岩发育2个完整的沉积旋回,这2个旋回随着海平面的升降变化,表现出不同的沉积特征。龙门山上泥盆统甘溪剖面土桥子组碳酸盐缓坡沉积以微晶灰岩—泥灰岩组成的韵律层为特征。

Based on the data of cross sections, the Upper Devonian Tuqiaozi Formation in Ganxi section of the Longmen Mountain is considered to be carbonate ramp deposits. With the sea level of a brief fall in the middle sedimentary stage of Tuqiaozi Formation, the carbonate ramp transformed to carbonate platform, of which the most direct identification mark is the emergence of breccia and slump deposit in the front of reef. There are two types of subfacies including shallow ramp and deep water ramp in carbonate ramp and two types of subfacies including platform edge reef and beach and foreslope in carbonate platform. Two whole carbonate sedimentary cycles developed in Tuqiaozi Formation. There are different sedimentary features between the two sedimentary cycles with the changes of sea level rise and fall. The carbonate ramp of Tuqiaozi Formation in Ganxi section is characterized by rhythmite formed by micrite-marl.