Unknown
PANGAEA
In:
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, https://doi.org/10.2973/odp.proc.sr.117.140.1991
Publication Date:
2024-05-18
Description:
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.
Keywords:
117-722B; 117-731C; Arabian Sea; DRILL; Drilling/drill rig; Joides Resolution; Leg117; Ocean Drilling Program; ODP
Type:
Dataset
Format:
application/zip, 2 datasets
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