龙门山地区泥盆纪碳酸盐与硅质碎屑的混积相与混积机理

HYBRID FACIES AND MECHANISM FOR THE FORMATION OF THE MIXED DEVONIAN CARBONATE-SILICICLASTIC SEDIMENTS IN THE LONGMEN MOUNTAIN AREA,SICHUAN

关键词:  混积相  混积类型  混积机理  碳酸盐与硅质碎屑的混合沉积  泥盆纪  龙门山地区

Key words:  hybrid facies  hybrid type  mechanism of hybrid processes  mixed carbonate-siliciclastic sediments  Devonian  Longmen Mountain area

摘要:

碳酸盐与陆源碎屑的混合沉积研究至今尚未引起足够重视,文献屈指可数。扬子西缘龙门山地区泥盆纪发育了这类良好的混合沉积。作者根据实际材料,首次从这-思路出发,识别出该区泥盆纪Emsian期到Givetian早期的混积相四种,混积亚相约14种,阐明了其优势混积作用;根据混积作用特征、沉积背景关系,划分出两大混积类型,即泥质背景下的混积Ⅰ型和砂灰质背景下的混积Ⅱ型;对混积作用机理进行了探讨;并指出不同级次的混积层序类型、混积成因方式受不同因素控制。

Abstract:

Four hybrid facies and fourteen hybrid subfacies are recognized in the Emsian to early Givetian (Devonian) mixed siliciclastic-carbonate sediments from the frontal zone of the Longmen Mountain area,Sichuan on the westren Yangtze platform.They may be assigned, on the basis of hybrid processes and background sediments,to two types;the hybrid type Ⅰ sediments dominative of shelf shales controlled by punctuated mixing,in-situ mixing and source mixing,and the hybrid type Ⅱ sediments dominated by sandy and limy littoral and shallow shelf deposits. The authors contend that the punctuated mixing of the hybrid type I sediments is re-lated to the processes of storm wave and reflux,while the in-situ mixing has a connection with birth growth and death of biological communities after the storms ceased.The mixing of the main hybrid facies in the hybrid type Ⅰ sediments is in general governed by relative sea level fluctuations and the supply cycles of different orders are also discussed in the pre-sent paper.