10.1594/PANGAEA.756773
Weedon, Graham P
Graham P
Weedon
McCave, I Nick
I Nick
McCave
0000-0002-4702-5489
Grain size distribution of Oligocene and Miocene sediments from the Indus Fan
PANGAEA
1991
Drilling/drill rig
Leg117
Joides Resolution
Ocean Drilling Program (ODP)
1987-09-08T12:00:00/1987-10-09T16:45:00
en
Supplementary Publication Series of Datasets
10.2973/odp.proc.sr.117.140.1991
2 datasets
application/zip
Creative Commons Attribution 3.0 Unported
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.
Supplement to: Weedon, Graham P; McCave, I Nick (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
59.7025
59.7953
16.4705
16.6218
Arabian Sea