Facies pattern and depositional motif in an immature trench-slope basin, Eocene Mithakhari Group, Middle Andaman, India
Facies pattern and depositional motif in an immature trench-slope basin, Eocene Mithakhari Group, Middle Andaman, India
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印度安达曼中部始新世 Mithakhari 群未成熟海沟斜坡盆地的相格局和沉积主题
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发表时间：
1999
影响因子：
1.3
通讯作者：
K. S. Gupta
中科院分区：
文献类型：
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作者：
P. Chakraborty;T. Pal;T. D. Gupta;K. S. Gupta
通过对始新世Mithakhari群的详细相分析，揭示了八种具有广泛古地理意义的岩相。这些相是i）无序基质支撑砾岩，ii）分级基质支撑砾岩，iii）分级含砾砂岩，iv）块状厚层砂岩，v）平面层状和交错层状砂岩，vi）砂岩和泥岩互层，vii）块状至微弱层状页岩和viii）页岩和煤互层;它们被分为五个不同的相组合（FA）。即水下冲积平原（FA 1）、浅水、浪控陆棚（FA 2）、三角洲斜坡（FA 3）、前三角洲斜坡（FA 4）和海底扇（FA 5）。不整合地位于大洋基底（蛇绿岩片？）这些沉积物构成了短截的层序。三个独立剖面的岩性测量，即Kaushalyanagar。Sagwannala和Rangat-Nimbutala揭示了广泛变化的相序列模式。频繁的相变，质量流沉积物的优势，同沉积盆地的干扰和广泛的古地理变化的签名表明，在一个不成熟的沟坡设置在小的孤立的盆地沉积。研究剖面中丰富的前陆沉积旋回和出露证据提供了这些盆地充填史中前缘加积和构造变浅的指示。
Detailed facies analysis in Eocene Mithakhari Group reveals eight different lithofacies of wide ranging paleogeographic significance. These facies are i) disorganised matrix-supported conglomerate, ii) graded matrix-supported conglomerate, iii) graded pebbly sandstone, iv) massive and thick-bedded sandstone, v) plane laminated and cross-stratified sandstone, vi) interbedded sandstone and mudstone, vii) massive to faintly laminated shale and viii) interbedded shale and coal; which are grouped into-five different facies associations (FA). viz. Subaerial alluvial plain (FAl), Shallow water, wave dominated shelf (FA2), Delta slope (FA3), Prodelta slope (FA4) and Submarine fan (FA5). Lying unconformably on oceanic basement (ophiolite slices?) these sediments constitute short truncated successions. Litholog measurement in three isolated sections viz. Kaushalyanagar. Sagwannala and Rangat-Nimbutala reveal widely varying facies succession pattern. Frequent facies change, predominance of massflow deposits, signatures of synsedimentary basinal disturbance and wide paleogeographic variation indicate sedimentation in small isolated basins in an immature trench-slope setting. Profusion of progradational depositional cycles and evidences of emergence in the studied sections provide indication of frontal accretion and tectonic shoaling in the filling history of these basins.