Morphological features in the Bay of Bengal
Morphological features in the Bay of Bengal
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发表时间：
2000
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通讯作者：
K. Sarma;M. V. Ramana;V. Subrahmanyam;K. Krishna;T. Ramprasad;M. Desa
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作者：
K. Sarma;M. V. Ramana;V. Subrahmanyam;K. Krishna;T. Ramprasad;M. Desa
孟加拉球迷是世界上最大的潜艇风扇之一，面积为2.8-3.0x10 6平方公里。它从北纬20°左右的恒河/雅鲁藏布江三角洲延伸到7°S以南，最大宽度在北纬15“附近约1000公里。恒河和雅鲁藏布江向孟加拉湾排放了大量的大陆沉积物，更细的沉积物颗粒甚至达到了S纬度7°。沉积物位于早白垩世洋底，以中生代M11至M0异常为特征。泥沙沉积模式，追踪泥沙运动的印记，浑浊水流。通过相识别，可以利用古河道及其时空迁移和海平面波动恢复扇体的发育历史。在印度与欧亚板块的软碰撞之后，这些事件可能对孟加拉湾自始新世晚期以来的各种地貌特征的形成起到了关键作用。目前沿西北-东南走向30海里的长剖面收集的12千赫回声测深仪数据有助于改善孟加拉湾的水深图。回波图像显示了海底的一些重要的地理地貌特征。其中一个特征就是“无地样本”，它看起来像一个深峡谷/海峡/山谷。几条纵向河道似乎将恒河和雅鲁藏布江的沉积物排入孟加拉扇区。海床上也有堤坝和废弃的河道。东部大陆边缘具有陆架狭窄、坡度陡峭的特点。邻近的孟加拉扇的水深从4000米不等。沿某些剖面的回声图描绘了紧接在陆架断裂之后的不规则而崎岖的地形。海底非常稳定和平坦，除了少数几个地方外，陆架断裂。在远孟加拉扇区的一些地方，孤立的局部高压控制着海底，与平均海床的正起伏距离为500至900米，这些特征与正磁异常有关。新报道的测深高(R)具有三个峰的特征，并与正磁异常有关。这个积极的地形高地被废弃的河道和堤坝和扇形隔板所包围。
Bengal Fan is one of the world's largest submarine fans having an area of 2.8-3.0 xl0 6 sq.km. It extends from Ganges/Brahmaputra delta around 20° N latitude to south of 7° S, with a maximum width of about 1000 km around 15" N latitude. Large volume of continental sediments are being discharged by Ganges and Brahmaputra Rivers into the Bay of Bengal and the finer sediment particles reach even 7° S latitude. The sediments rest on the early Cretaceous ocean floor characterized by the Mesozoic anomalies M11 through M0. Pattern of sediment deposition, tracing the imprints of sediment movement, turbidity current flows. paleo channels, their migration in time and space and sea level fluctuations by facies identification can be used to reconstruct the development history of the Fan. After India's soft collision with the Eurasian plate, these events may have played a critical role in shaping various morphological features since late Eocene in the Bay of Bengal. The present 12 kHz Echo sounder data collected along the NW-SE trending long profiles spaced at 30 nautical miles aided to improve the bathymetry chart of the Bay of Bengal. The echograms show some important geo-morphological features of the seafloor. One such feature is the "Swatch of no ground" which resembles a deep Canyon/Channel/ valley. Several longitudinal channels appear to drain the sediments from the mighty rivers Ganges and Brahmaputra into the Bengal Fan. Levees and abandoned channels are also present on the seafloor. The eastern continental margin is characterized by narrow shelf followed by steep slope. Bathymetry in the adjacent Bengal fan varies from 4000 m. The echograms along some profiles depict an irregular and rugged topography immediately beyond the shelf break. The seafloor is very stable and smooth except few places beyond shelf break. At some locations in the distal Bengal fan, isolated local highs dominate the seafloor with a positive relief of 500 to 900 m from the mean seabed and these features are associated with positive magnetic anomalies. The newly reported bathymetric high (R) is characterized with three peaks, and associated with a positive magnetic anomaly. This positive topographic high is surrounded by abandoned channels with levees and the fan divisions.