Seabed Sediment Mobilisation In The Deep Ocean - An Example From The Southeastern Indian Ocean
Abstract
The spatial resolution of maps covering most of the deep ocean seabed is usually too coarse to enable the identification of seabed features recording the mobilisation of fine-grained sediment that accumulates over vast areas. To examine seabed morphology, we utilised multibeam echosounder, sub-bottom and sidescan sonar data for a large area centered on Broken Ridge in the Southeast Indian Ocean. Water depths mapped range between 634 and 6,300 m, and the sedimentary section typically comprised up to hundreds of metres of oceanic ooze. The data were acquired to assist in the search for is Malaysia Airlines Flight 370 (MH370) and have a horizontal spatial resolution from sub-meter to 100 m. Seabed morphology indicates that sediment has eroded from the southern side of bedrock outcrops on the crest of Broken Ridge (≥634 m water depth), resulting in moats forming on the southern side of the outcrops, and preferentially accumulating on the northern sides. These features indicate that northward flowing bottom currents appear to accelerate as they flow over the crest of the ridge. The northern flank of Broken Ridge and margin of the adjoining plateau (1,200 - 3,000 m water depth) are dissected by numerous cross-cutting retrogressive slumps and debris flows running northwards for ≥150 km into the adjoining basin. In the ocean basin south of Broken Ridge (>2,200 water depth) are areas with pockmarks and seabed scours (200 - 800 m diameter, 1 - 10 m deep). These features appear to record erosion by bottom currents in combination with fluid and gas escape. Farther south, fracture zones, such as the Geelvinck Fracture Zone, include fault valleys (≤900 m deep and ≤8 km wide) that are partially infilled and include chaotically bedded deposits that suggest a past period of sediment flow. The thinning of sediment along the margins of the valleys also reflects the influence of bottom currents on the pattern of valley infill. Areas of sediment erosion and accumulation indicate modes of seabed failure and pathways of benthic sediment transport, and point to a range of hydrodynamic regimes in this mid-ocean, deep-water benthic environment.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMOS24B..03P
- Keywords:
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- 1910 Data assimilation;
- integration and fusion;
- INFORMATICSDE: 3045 Seafloor morphology;
- geology;
- and geophysics;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3094 Instruments and techniques;
- MARINE GEOLOGY AND GEOPHYSICSDE: 3099 General or miscellaneous;
- MARINE GEOLOGY AND GEOPHYSICS