Several analogs of known ancient depositional patterns are observed in modern turbidite systems of the northern Gulf of Mexico (GOM). Bryant Canyon/Fan feeds through a chain of mini-basins (2 to 15 kilometers in diameter) that exhibit seismic facies of: 1) mass-transport deposit (MTD) wedges of chaotic mud and sheets of chaotic mud and sand, 2) incised, ponded, and perched turbidites, and 3) bypass channelized facies. The mini-basin pathway of Bryant Canyon, which traps mud, has resulted in non-bifurcated aggrading channels that extend 200 kilometers across the sand-rich Bryant Fan to feed single distal depositional lobes which are approximately 30 kilometers in length. The Bryant mini-basin and fan patterns provide analogs for the Miocene systems in the Mississippi Canyon area. In contrast, the mud-rich Mississippi Delta and its associated 20-kilometer-wide gullied canyon sediment source have resulted in multiple mid-fan channel bifurcations and outer fan channel splays in 200-kilometer-long lobes of the mud-rich Mississippi Fan.

Extensive MTDs, ranging in size from 400-kilometer-long debris sheets to 10-centimeter thick MTD beds, were deposited during lowering and rising sea level episodes and are intermixed with the channel and lobe turbidite deposits. Similar to Bryant Canyon and Mississippi Fan, the intermixing of turbidites and extensive MTDs is found in some subsurface turbidite systems of the GOM margin. The Rio Grande Fan is a contrasting braided fan analog for some Paleogene subsurface

Seafloor relief map by Lui and Bryant.

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petroleum plays in the northwestern GOM. Multiple canyons provide coarse-grained sediment from adjacent mountain sources to deposit the fan on a continental-slope plateau. The seismic facies relatively steep fan gradient (1:250) and incised channels, rather than leveed channels, throughout the surface and subsurface show that the Rio Grande Fan is a braided sandrich fan.

Seismic Line across Beaumont Basin along the Bryant Canyon Pathway.

Mini-basin depositional patterns, mass transport deposits.

Northern Gulf of Mexico submarine fans: Bryant – Sand-rich, fed by canyon with mini-basins that trap muds; single sinous channel and lobe; limited MTD’s & splays. Rio Grande – Sand-rich from mountain sources: multiple canyons & braided channels; lacks lobes & MTD’s. Mississippi – Mud-rich, gullied canyon, meandering channels; multiple splays & lobes; half turbites and half MTD’s.

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