Morphology, internal structure, and sedimentation in indus fan as revealed by seismic investigations and piston core studies. [India]
The sea floor of the upper Indus fan is characterized by gradients less than 1/500, channels with levees approximately 100 m (330 ft) high, distinct echos with several continuous subbottom reflectors on 3.5-kHz records, and generally fine-grained sediments (Tc-e sequences) except in channels where coarse-grained sediments (Ta-e) are present. On multichannel and sparker seismic lines, the levee complexes are characterized by overlapping wedge-shaped reflections. Since the Oligocene and Miocene, several major episodes of extensive migration of the channels on the upper fan (with sediments more than 3 km, or 10,000 ft, thick) and of the feeder canyons on the Pakistan-India shelf are recognized. During the latest episode (Phil-Pleistocene), 3 distinct regions, each with numerous channel-levee complexes fed by the sediments of both the Indus and the now-extinct Hakra-Nara rivers on the Pakistan-India shelf, are identified. The middle fan has gradients of 1/500 to 1/1000, numerous channels with levees approximately 20 m (66-ft) high, and convex morphology due to extensive channel-levee buildup. Gradients less than 1/1000, channels with levees 8-20 m (26-66 ft) high, prolonged echos with few or no subbottom reflectors on 3.5-kHz records, smooth continuous reflections on seismic records, and the highest sand content in the sediments (Ta-e) of any fan region characterize the lower fan. Although unchannelized sheetflow turbidite deposition was the dominant mode, channelized and overbank deposition also played a significant role in the sedimentation of the lower fan. On a gross scale, 2 extensive Quaternary sand-rich deposits (lobes), primarily laid down by sheet flows, are mapped on the lower fan.
- Research Organization:
- Superior Oil Co., Houston, TX
- OSTI ID:
- 6555742
- Report Number(s):
- CONF-8405216-
- Journal Information:
- Am. Assoc. Pet. Geol., Bull.; (United States), Vol. 68:4; Conference: AAPG annual convention, San Antonio, TX, USA, 20 May 1984
- Country of Publication:
- United States
- Language:
- English
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