四川乐山大佛砂岩的成因

四川乐山地区上白垩统夹关组红色砂岩到底是水成的还是风成的已经争论了很久。许多人根据它宏观的沉积构造特征认为是风成砂岩,但并未提出令人信服的证据。为了解决这一问题,本文作者从沉积构造、垂向序列、粒度分布特征,石英砂表面特征等四个方面详细论证了这套砂岩的确形成于干旱的沙漠环境,但不时受到间歇性河流的影响。 该区典型的垂向序列由粒度明显不同的两套岩石组成。中到下部为细到中粒长石石英砂岩具巨型斜层理,属内陆砂丘成因。上部粉砂岩具沙纹层理,含钙质结核和泥质纹层,属间歇性片流沉积。粒度分析和石英砂扫描电镜分析有力地支持了这一结论。 综合分析区域地层学和岩相古地理资料可知,晚白垩世时乐山地区处于干旱气候下距西部山前冲积扇不远的沙漠环境。

THE ORIGIN OF LESHAN GREAT BUDDHA SANDSTONE IN SICHUAN PROVINCE

The historic famous city--Leshan is located in the, southwestern part of Sichuanbasin. Three rivers--Mingjiang, Daduhe and Qingyi,yiang converge here, and theworldfamous Leshan great Buddha with:、thickness of 70m is serenelly siting on the cliff bythe Ming jiang river, facing the distant city. The red sandstone from which the staiue was carved is very attractive and interesting togeologists for its large-scale cross-beddines and unique seq,uences.In this paper, the originof the red sandstone will be discussed in detail.