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Weedon, Graham P; McCave, I Nick (1991): Grain size distribution of Oligocene and Miocene sediments from the Indus Fan. PANGAEA,, Supplement to: Weedon, GP; McCave, IN (1991): Mud turbidites from the Oligocene and Miocene indus fan at Sites 722 and 731 on the Owen Ridge. In: Prell, WL; Niitsuma, N; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 117, 216-220,

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The Owen Ridge south of Oman represents oceanic crust that was uplifted by compressional tectonic forces in the early Miocene. Build-out of the Indus Fan led to deposition of a thick sequence of turbidites over the site of the Ridge during the late Oligocene and early Miocene. Early Miocene uplift of the Ridge led to a pelagic cap of nannofossil chalks. Two short sequences of turbidites from the pre- and syn-uplift phases were chosen for detailed grain size analysis.
The upper Oligocene section at Site 731 is composed of thin (centimeter-decimeter scale) graded mud turbidites separated by relatively thick (decimeter-meter scale) intervals of homogeneous, non-bioturbated clayey siltstones. These finer intervals are unusually silt-rich (about 60%) for ungraded material and were probably deposited as undifferentiated muds from a series of turbidity current tails. By contrast, the lower Miocene section at Site 722 is comprised of a sequence of interbedded turbidites and hemipelagic carbonates. Sharp-based silt turbidites are overlain by burrow-mottled marly nannofossil chalks.
The Oligocene sequence may have accumulated in an overbank setting on the middle fan - the local topographic position favoring frequent deposition from turbidity current tails and occasional deposition from the body of a turbidity flow. Uplift of the Ridge in the early Miocene led to pelagic carbonate deposition interrupted only by turbidity currents capable of overcoming a topographic barrier. Further uplift eventually led to entirely pelagic carbonate deposition.
Median Latitude: 16.546150 * Median Longitude: 59.748900 * South-bound Latitude: 16.470500 * West-bound Longitude: 59.702500 * North-bound Latitude: 16.621800 * East-bound Longitude: 59.795300
Date/Time Start: 1987-09-08T12:00:00 * Date/Time End: 1987-10-09T16:45:00
117-722B * Latitude: 16.621800 * Longitude: 59.795300 * Date/Time Start: 1987-09-08T12:00:00 * Date/Time End: 1987-09-13T10:15:00 * Elevation: -2033.0 m * Penetration: 565.6 m * Recovery: 385.8 m * Location: Arabian Sea * Campaign: Leg117 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 59 cores; 565.1 m cored; 0 m drilled; 68.3 % recovery
117-731C * Latitude: 16.470500 * Longitude: 59.702500 * Date/Time Start: 1987-10-05T13:30:00 * Date/Time End: 1987-10-09T16:45:00 * Elevation: -2371.0 m * Penetration: 994.2 m * Recovery: 59.81 m * Location: Arabian Sea * Campaign: Leg117 * Basis: Joides Resolution * Device: Drilling/drill rig (DRILL) * Comment: 16 cores; 154.7 m cored; 0 m drilled; 38.7 % recovery
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