渭北地区晚三叠世深水重力流沉积特征  

Sedimentary characteristics of Late Triassic deep water gravity flow in Weibei Area

作　　者：李宗霖 李红[1,2] 李文厚[1,2] LI Zonglin;LI Hong;LI Wenhou(Department of Geology,Northwest University,Xi’an 710069,China;National Key Laboratory of Continental Dynamics,Northwest University,Xi’an 710069,China)

机构地区：[1]西北大学地质学系,陕西西安710069 [2]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《西安科技大学学报》2023年第1期135-142,共8页Journal of Xi’an University of Science and Technology

基　　金：国家自然科学基金项目(41272115,41572086)。

摘　　要：晚三叠世鄂尔多斯盆地处于洋盆收缩末期,受印支运动影响广泛发育深湖-半深湖沉积,是湖盆由鼎盛期向衰退期发展的转折时期和湖盆发育的重要调整期。为明确深水砂体形成机理,通过野外露头观察、岩芯观察及钻测井资料,对鄂尔多斯盆地渭北地区延长组长6深水沉积特征、重力流类型、重力流沉积模式进行探讨。结果表明:渭北地区延长组长6沉积期发育富有机质深水缺氧还原环境细粒沉积物,见灰黑色、灰色、灰白色岩屑长石砂岩和长石岩屑砂岩,发育滑塌、泥岩撕裂、砂枕、火焰状构造、重荷模、槽模等沉积构造;发育滑动-滑塌沉积、砂质(泥质)碎屑流沉积、浊流沉积3种类型的重力流沉积物,各类型沉积物特征明显,重力流形成过程可分为三角洲前缘沉积阶段、滑动-滑塌变形阶段、砂质(泥质)碎屑流形成阶段及浊流形成阶段。研究结果对分析同一盆地或同一时期的深湖-半深湖沉积特征、重力流特征具有指导作用,对目前国际地学界广泛开展的大陆边缘沉积物“从源到汇”过程的研究有积极意义。Ordos Basin was at the end of oceanic basin contraction in Late Triassic, and deep lake and semi-deep lake deposits were extensively developed under the influence of the Indo-China movement.It was the transition period from the heyday to the decline period of the lake basin and an important adjustment period for the development of the lake basin.In order to clarify the formation mechanism of deep-water sand bodies, based on the field outcrop observation, core observation and drilling and logging data, the deep-water sedimentary characteristics, gravity flow types and gravity flow deposition models of Chang 6 of Yanchang Formation in Weibei Area of Ordos Basin were discussed.The results show that the organic-rich deep-water fine-grained sediments developed in the Chang 6 member of Yanchang Formation in Weibei Area, and gray-black, gray and gray-white lithic feldspar sandstone and feldspathic lithic sandstone were mostly seen during the deposition period, developing the sedimentary structures such as slumping, mudstone tearing, sand pillows, flame-like structures, heavy load models, and trough models.There are three types of sliding-slump deposition, sandy(mud)debris flow deposition, and turbidity current deposition.Gravity flow sediments have obvious characteristics of various types of sediments.The formation process of gravity flow can be divided into delta front sedimentation stage, sliding-slip deformation stage, sandy(mud)debris flow formation stage and turbidity current formation stage.The results have a guiding role in analyzing the sedimentary characteristics and gravity flow characteristics of deep lakes and semi-deep lakes in the same basin or the same period, and have positive significance for the research on the “source-sink” system of continental margin sediments widely carried out by the international geoscience community currently.

关 键 词：鄂尔多斯盆地 延长组 细粒沉积 重力流 

分 类 号：TD121[矿业工程—矿山地质测量]