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Abstract:
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The structures along the Atwater Fold belt form important deep -water hydrocarbon traps in the northern Gulf of Mexico . The purpose of this study is to map and quantify the morphology , sedimentology and architecture of Plio -Pleistocene basin floor fan systems outboard of the Poseidon Minibasin , located along the Atwater deep -water fold belt (mid -Miocene to Pliocene ) , and apply that information to determine the temporal and spatial nature of the fill and its implications as a reservoir analog . The data set includes ~2200 km sq . of 3D seismic data , along with information from several wells . Wireline logs show the Tertiary age deposits outboard of the Sigsbee Escarpment to be several hundred feet thick , sharp -based , dominantly coarse -grained (sandy ) but fining up cycles composed of sandy basin floor fans , mass transport complexes and leveed channels developed in a confined setting within deep -water “valleys .”
The largest valley formed in five main stages : initiating from narrow channel incision , widening through lateral incision and sidewall slumping , straightening , and finally flooding and infilling . The valley system is ~20 ,000 feet across and ~ 1 ,400 feet deep , with what look like well -developed levees ranging from 700 to 1300 feet at their thickest point extending ~19000 feet away from the channel . This system is underlain by a ~700 foot thick mass transport complex and overlain by younger , low sinuosity leveed channel systems . Both of these systems appear to have been sourced by large submarine drainages , originating from a shelf edge sediment source system to feed the rugose slope with deep -water channel pathways uninhibited by salt wall inflation at the time of valley deposition .
Major phases of salt thrusting along the southern edge of the Atwater were contemporaneous with the formation of these large , through -going valley system , which appear to be associated with the period of sheet thickening and development of monoclinal basinward dip related to rafted mini -basin docking .
Well log signatures show evidence for armored clay drapes along the valley margins as well as a flattening of lateral accretion packages toward the distal end of the system . The flattening of these packages seems to signal proximity to the fan terminus , which would serve as an important indicator of spatial extent of plays in deep -water . |