Deglacial Control on Sedimentation and Basin Evolution of Permo-Carboniferous Talchir Formation, Talchir Gondwana Basin, Orissa, India
Deglacial Control on Sedimentation and Basin Evolution of Permo-Carboniferous Talchir Formation, Talchir Gondwana Basin, Orissa, India
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DOI：
10.1016/s1342-937x(05)70788-7
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发表时间：
2004-04
影响因子：
6.1
通讯作者：
W. Maejima;R. Das;K. Pandya;M. Hayashi
中科院分区：
文献类型：
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作者：
W. Maejima;R. Das;K. Pandya;M. Hayashi
塔尔希尔盆地东南部石炭-二叠系Talchir组以厚约260m的碎屑序列为代表，分布在东高止群前寒武纪基岩上。初步将层序自下而上划分为AI、A-II、B、C四个岩石地层单位。AI单元由泥质基质、分选极差的硅质岩和薄砂岩与泥岩互层组成，产生下垂岩。它们揭示了前冰期湖泊环境中的沉积，在这种环境中，冰排和悬浮沉积以及融水下溢过程产生了各种不同的相。A-II单元的层序以卵石-巨砾砾岩和砂岩为主。它们主要来自各种水下和水下的高能沉积重力流，并在盆地边缘形成陡峭的扇三角洲。单元B显示湖缘斜坡和坡基环境中的浊积沉积，发育湖下河道-扇体系。湖缘边坡被河道切割，并伴有漫滩和堤防沉积。从河口运来的沉积物在斜坡底部沉积，形成扇叶，并向湖盆底部推进。C单元主要由泥岩组成，夹层为粉砂岩和砂岩，形成一个大规模的向上粗化的三角洲层序，最终被喀哈尔巴里组的河流沉积所覆盖。在受冰川影响的沉积作用之后，Talchir序列显示出垂直相序，表明湖盆逐渐加深，并最终由于快速三角洲进积而被填满。这样的演替代表了塔里尔时期对盆地演化的去冰期控制。在冰川退缩初期，冰川崩塌和山地冰湖崩塌频繁，引发高含沙量泥石流和特大洪水，给湖泊带来了丰富的粗碎屑，在盆地边缘形成了扇三角洲。冰川的持续退缩和消失导致大量的冰融水进入地堡，同时海平面上升，是湖平面上升的原因。随后的三角洲快速进积和最终的湖盆充填表明湖盆加深后湖平面迅速下降。这可能是由于冰期后均衡反弹引起的区域隆升所致。通过地堡快速排出湖水，建立了轴向排水系统，该系统以轴向供给三角洲的形式迅速填满了湖盆。
Abstract The Permo-Carboniferous Talchir Formation in the southeastern part of the Talchir basin is represented by about 260 m thick clastic succession resting on the Precambrian basement rocks of the Eastern Ghats Group. The succession is tentatively subdivided into four lithostratigraphic units, namely AI, A-II, B and C from base to top. Unit AI comprises mud-matrixed, very poorly sorted diamictites and interbedded thin sandstone and mudstone yielding dropstones. They reveal deposition in a proglacial lake environment in which ice rafting and suspension sedimentation, as well as meltwater-underflow processes, produced variety of facies. The succession of unit A-II is dominated by pebble to boulder conglomerates and sandstones. They were deposited mostly from various kinds of high-energy sediment gravity flows, both subaerial and subaqueous, and formed steep-faced fan-delta on the margin of the basin. Unit B demonstrates turbidite sedimentation in lake-margin slope and base-of-slope environments, in which a sublacustrine channel-fan system developed. The lake-margin slope was dissected by channels which were accompanied by overbank and levee deposits. Sediments delivered from the mouth of a channel were deposited at the base-of-slope, forming a fan lobe which prograded onto the lake basin floor. Unit C dominantly consists of mudstone with intercalations of siltstone and sandstone and forms a large-scale coarsening-upward deltaic sequence eventually covered by the fluvial deposits of the Karharbari Formation. Following the glacially influenced sedimentation, the Talchir succession shows a vertical facies progression suggesting gradual deepening of the lake basin and eventual filling up of it due to rapid delta progradation. Such a succession represents deglacial control on basin evolution during the Talchir time. In the initial stage of glacial recession, collapse of a glacier and failure of montane glacial lakes frequently occurred and gave rise to generation of a highly sediment-laden debris flow and a catastrophic flood, which brought abundant coarse clastics into the lake and built a fan-delta on the basin margin. The continued recession and disappearance of glacier resulted in abundant supply of ice-melt water into the graben as well as eustatic sea-level rise, being the cause of the rise in lake-level. Subsequent rapid delta progradation and eventual filling-up of the lake basin suggest rapid lake-level fall after deepening of lake basin. It was possibly caused by the regional uplift due to post-glacial isostatic rebound. Rapid draining of lake water through the graben gave rise to the establishment of an axial drainage system which rapidly filled the lake basin in form of an axially fed delta.