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Stratigraphy of Linked Submarine Minibasins in Laboratory Experiments

Viparelli, Enrica *1; Yeh, Tzu-hao 1; Cantelli, Alessandro 2; Leslie, Edgar 1; Robertson, Alec 1; Parker, Gary 3
(1) Department of Civil and Environmental Engineering, University of Illinois Urbana-Champaign, urbana, IL.
(2) Shell, Houston, TX.
(3) Department of Civil and Environmental Engineering and Department of Geology, University of Illinois Urbana-Champaign, urbana, IL.

Minibasins in the deep sea on the North Slope of the Gulf of Mexico are prime locations for the deposition by turbidity currents of sediment with the potential to form hydrocarbon reservoirs. Laboratory experiments on two linked submarine minibasins with three-dimensional geometries and non-uniform sediment have been performed at the University of Illinois, Urbana-Champaign to study 1) the role of the geometry on the deposition of coarse sediment in the updip portion of the first (or updip) basin; 2) the fate of both the sand and the mud as the updip basin fills; and 3) the evolution of the deposit in the downdip (or second) basin as the first basin fills. Salt-induced subsidence has not been modeled. Three sets of experiments have been performed with different inflow discharges. i.e. high, medium, and low. In each set, repeated and sustained turbidity currents have been released to fill the updip basin. A downdip-migrating entrance deposit, which might be interpreted as the analog of an apron, formed in the updip portion of the first basin, while the deposit in its downdip part can be reasonably characterized as ponded. At the end of each experiment the deposit in both the basins has been dried and sliced, and core samples have been taken to quantify the stratigraphy. At the moment, data have been processed for the experiments with medium and high inflow rate, showing that: 1) the deposit in the updip basin in the experiment with the high inflow rate is coarser than the deposit in the experiment with the medium inflow rate; 2) as the updip basin fills, the pattern of trapping of coarser sediment in the apron deposit causes a mild tendency for upward fining in the ponded zone; and 3) the apron deposit shows a downstream fining profile. Finally, detailed measurements of one event in the first basin show a massive ponded deposit (i.e. no significant vertical variation of grain size distribution) bounded by two thin layers of fine drape. The deposit in the downdip basin is mostly fine-grained and draped, but its grain size distribution is coarser for the experiment with the high inflow rate.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California