ABSTRACT: Salt-Withdrawal Mini-Basins as Proven Producers Along Present and Paleo-Louisiana Slope
MACKENZIE, MICHAEL, EMMITT GUDERIAN, RHETT HAMITER, and ALLEN LOWRIE
The basinward salt extrusion along the Louisiana margin, with lateral and isostatic motions, creates mini-basins between rising salt ridges, generally along upper and middle slope. Mini-basins grow with salt-withdrawal.
Sedimentation includes gravity-driven, high-energy, turbid currents; debris flows and slumps, often originating along the outer shelf/shelfbreak and descending the slope, depositing an alternating coarse-to-fine-grained reservoir, on multiple time scales ranging from annual through 4th order, and punctuated by catastrophic (irregularly timed) turbidites and megaturbidites, all modified by pelagic deposition. Efficient sediment sorting yields clean sands of a Bouma sequence, sand sourcing being almost ubiquitous. These deposits are found in numerous slope and continental-rise deposits, examples will be provided along with their seismic and well-log signatures.
Neogene-Quaternary deposition along productive mini-basins results from 4th order sea level oscillations of some 2(104) to 105 year durations, clustered into more easily recognizable 3rd order oscillations of (approx.) 106year durations, promoting energetic sediment movements and yielding reservoir-grade deposits.
Trapping mechanisms within mini-basins are generally structural, aided by stratigraphy. Growth faults, basinward and counter regional, bracket slope mini-basins. A compendium of possible traps from existent fields and marine geologic analogues is included.
AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana