四川盆地东北部长兴期沉积特征与沉积格局

Characteristic and Framework of the Changxingian Sedimentation in the Northeastern Sichuan Basin

四川盆地东北部长兴组(大隆组)为海洋环境的产物,根据沉积特点,可以分为碳酸盐台地沉积体系和盆地沉积体系。碳酸盐台地沉积体系又可进一步分为局限台地、开阔台地、台地边缘礁滩及缓坡等沉积相。在详细研究分析各沉积体系的沉积特点的基础上,探讨了该期沉积相带的空间分布,提出了不存在“开江—梁平”海槽的认识。笔者等认为在“开江—梁平海槽”区域内,长兴组只是水体相对台地较深环境(台棚环境)的产物,为碳酸盐缓坡,不宜称为海槽。指出台地边缘浅滩及生物礁是储层最有利相带,礁白云岩及颗粒白云岩等是储层的有利微相。研究区的生物礁为碳酸盐台地边缘缓坡点礁群,沿着台地边缘断续分布。

The Changxing Formation in the northeastern Sichuan Basin is in a marine environment, and can be divided into a carbonate platform sedimentary system and a basin sedimentary system based on sedimentary characteristics. The carbonate platform sedimentary system is further divided into such facies as restricted platform, open platform, platform margin reef and ramp. In this paper we discuss spatial distribution of the sedimentary facies belts, and argues that the Kaijiang-Liangping ocean trough does not exist. The Changxing Formation is the result of a deep-water environment relative to platform, and it is located on a carbonate ramp, instead of an ocean trough. We point out that platform margin shoals and organic reefs are the best favorable facies belts of reservoirs, and reef dolomite and grain dolomite are the favorable microfacies of reservoirs. Organic reefs in the study region form a patch reef group on the carbonate platform margin ramp and they are interruptedly distributed along the platform margin.