Controls of carbonate slope morphology on mixed siliciclastic and carbonate basinal sedimentation, Delaware Basin, southeast New Mexico and west Texas, USA
Abstract
Few studies exist on mixed carbonate-siliciclastic slope morphology, down-dip sediment transport, and basinal deposition. Early Permian (Wolfcampian and Leonardian) intervals in the Delaware Basin of west Texas and southeast New Mexico provide examples of mixed basinal deposits associated with highly variable carbonate slopes. Core description, outcrop analogs, and detailed subsurface well-log mapping reveal basinal sedimentation patterns and facies distributions controlled by specific slope and margin characteristics.
Highstand basinal carbonate strata range from individual debrites and turbidites to mixed carbonate and siliciclastic submarine fans. Mapping indicates significant downdip carbonate resedimentation and potential fan growth require sediment focusing mechanisms on the margins and/or confinement on the slopes, such as antecedent topography, margin re-entrants, or tectonic alteration. As the carbonate margins evolve, input locations systematically migrate over time resulting in migration of fan locations. Shallow gradients (3-6 degrees) and lower platform to basin relief promote progradation of the margins and allow transport of sediment to the basin creating the most significant carbonate fans. During lowstands siliciclastic intervals bypass upper slopes and onlap middle to lower slopes. More significant onlap and greater proximal extent exists over lower gradient carbonate profiles. Dominant point sources of sediment are absent. Instead multiple sediment entry points form, likely due to the irregularity in carbonate margins and slopes and inability to incise significant canyons during short lived icehouse lowstands. Steeper slopes often lack significant confining mechanisms, which result in variable sediment input points, bypass of siliciclastics, and ponding of thick sand bodies at the toe of slope. Siliciclastics deposited over lower gradients often form 1-5 km wide, 15-50 m deep channel and feeder systems likely confining flows before transitioning to unconfined deposition farther downdip. Feeder systems may coalesce deeper in the basin to form large submarine fans. Results should add depth to existing depositional models and define facies associations and play concepts for oil and gas reservoirs in analog systems.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP41C1587P
- Keywords:
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- 1039 Alteration and weathering processes;
- GEOCHEMISTRY;
- 1051 Sedimentary geochemistry;
- GEOCHEMISTRY;
- 4217 Coastal processes;
- OCEANOGRAPHY: GENERAL;
- 4912 Biogeochemical cycles;
- processes;
- and modeling;
- PALEOCEANOGRAPHY