西秦岭直合隆地区三叠系深水水道沉积模式分析

西秦岭三叠系地层主要由深水沉积物组成。选取西秦岭直合隆地区出露较好的三组剖面进行研究，按重力流类型及静水条件下所发生的沉积现象，总结出六种岩石相类型，即滑塌岩相（F1）、碎屑流相（F2）、超高密度流相（F3）、高密度浊流相（F4）、低密度浊流相（F5）、深海泥岩相（F6）。通过对三处剖面的横向追踪对比，结合不同沉积环境下表现出特定的岩石相占比及砂体堆叠样式，共识别出限制性水道、弱限制性水道及水道天然堤三类沉积单元。限制性水道中砂体叠置关系复杂，以超高密度流相占主导地位，次为碎屑流相；弱限制性水道中砂体叠置较规整，以超高密度流相占主导地位，次为低密度浊流相；而水道天然堤表现为砂泥互层（总厚度约15 m），主要为低密度浊流相和深海泥岩相。最后建立了研究区内深水水道沉积演化阶段模式图——早期限制性环境下水道较顺直，水道较窄，砂体叠置关系复杂；中期限制性环境相对早期有所减弱，水道弯曲度增大，水道变宽，出现溢岸沉积，砂体叠置关系复杂；晚期为弱限制性环境，弯曲水道两侧发育天然堤，砂体叠置规整。本次研究利用野外露头建立的深水水道沉积演化模式，在一定程度上还原其相关的重力流演化过程及发育期次，对全球其他类似研究具有一定的参考意义。

Sedimentary Model Analysis of Triassic Deep?water Channels in Zhihelong,West Qinling Mountains

The Triassic strata of West QinLing Mountains are mainly composed of deep?water deposits. This study takes three well?exposed profiles in the Zhihelong area as the research objects and comprehensively summarizes six types of lithofacies by types of gravity flow and sedimentary phenomena under hydrostatic conditions. The six lithofacies are slump facies （F1）， debris?flow facies （F2）， ultra?high?density flow facies （F3）， high?density turbidity current facies （F4）， low?density turbidity current facies （F5） and deep?sea mudstone facies（ F6）. By tracking and correlation of three outcrop profiles， and combining the analysis of lithofacies proportion and sand stacking style in the different sedimentary environments， three types of sedimentary units were recognized: confined channel， weakly?confined channel and levee deposit. Confined channels feature complex amalgamation of sands， in which ultra?high?density flow facies are predominant， with sporadic debris?flow facies. In weakly?confined channels， the amalgamation of sands is relatively regular， within which ultra?high?density flow facies are dominant， with sporadic low?density turbidity current facies. Levee deposits are characterized by sand/mud interbeds （total thickness 15 m）， dominated by low?density turbidity current facies and deep?sea mudstone facies. Finally， this study proposes a sedimentary evolution model of deepwater channels in the study area. Channels are straight and narrow in the early confined background， accompanied by complex sand amalgamation. In the middle stage of decreased confinement， the sinuosities and widths of the channels increase， commonly with the occurrence of overbank deposits and complex sand amalgamation. In the late stage， as the background becomes more weakly confined， levee deposits tend to occur on both sides of channels and sand amalgamation becomes relatively regular. This sedimentary evolution model of deepwater channels was inferred from observation of outcrops， and to some degree reconstructs the evolution and development process of gravity flows and is a significant reference for similar studies around the world.