STRUCTURAL CONTROLS ON SEDIMENT TRANSPORT PATHWAYS IN THE JURASSIC EASTERN GULF OF MEXICO

The Upper Jurassic Norphlet Formation is a highly prospective conventional eolian sandstone reservoir target in the Eastern Gulf of Mexico (EGOM), and reservoir quality is dependent upon the distribution and variability of eolian dune facies. We present a regional model based on the integration of seismic, well log, and sandstone petrography data in which paleotransport of Norphlet Formation sediment is structurally-controlled by a NE-SW trending Early Mesozoic horst and graben system in the proto-EGOM. These structures had 1000’s of feet of topographic relief and controlled the transport pathways and depositional loci of Norphlet Formation dunes. The compositional and textural maturity of Norphlet sandstones increase away from these paleo-highs, indicating these paleo-highs contributed sediment to the Norphlet erg. Facies distribution indicates that alluvial, fluvial and wadi terrestrial depositional systems were routed through the NE-SW trending grabens. In SE Mississippi toward Mobile Bay, sediment input was entirely derived from Laurentian sources, which is supported by the distribution of facies and dipmeter net eolian transport vectors. Southward eolian transport dominated much of SW Alabama. In SE Alabama, onshore Florida panhandle and offshore NW Florida, the provenance signature shows mixing of Laurentian and Gondwanan sources, and the proportion of Gondwanan input increases toward the Destin Dome and Pensacola blocks in the Apalachicola Embayment. Dipmeter net transport vectors in the Destin Dome block indicate primarily westward transport. The seismic data show normal fault systems and incised basement geometries on top of the Middle Ground Arch that funneled sediment westward into the basins of the proto-EGOM. In addition, structural paleo-highs, like the Middle Ground Arch, are bounded by the NE-SW trending graben faults, which controlled the location of sediment shed into the proto-EGOM basins. Where the graben transport system terminates, S-oriented winds in the Mississippi-Alabama region and W to NW-oriented winds in the Florida region reworked sediment locally into thick accumulations of eolian sands. This model permits a wide distribution of Norphlet reservoirs in the EGOM and is consistent with thick eolian sands discovered in wells in the Desoto and Mississippi Canyons.