Structural and Paleogeographic Controls on Sediment Transport Pathways in the Jurassic Eastern Gulf of Mexico: Implications for Along-Strike Provenance Variation Within the Norphlet Erg

Abstract

The Upper Jurassic Norphlet Formation is a highly prospective conventional eolian sandstone reservoir target that overlies the Middle Jurassic Louann Salt in the Eastern Gulf of Mexico (EGOM); recent discoveries in the Norphlet play indicate reservoir quality is dependent upon the distribution and variability of eolian dune facies. We present a regional model of paleotransport for Norphlet erg sands based on from the integration of seismic, well log, and sedimentary petrology data from the EGOM. The results indicate the proximal Norphlet erg paleogeography included structural highs with 1000's of feet of relief. Compositional and textural maturity of Norphlet erg sandstones increase away from these paleo-highs, indicating these paleohighs contributed sediment to the Norphlet erg. In addition, several alluvial, fluvial and wadi terrestrial depositional systems were routed toward through NE-SW oriented early Mesozoic rift graben systems into the proto-EGOM. As a result of NE-SW net sediment transport, the developing NW-SE oriented Norphlet erg exhibits an along-strike variability in provenance. In the Mississippi Interior Salt basin southeastward toward Mobile Bay, sediment input was entirely derived from Laurentian sources. In onshore southeastern Alabama, onshore Florida panhandle and offshore Florida, the provenance signature shows mixing of Laurentian and Gondwanan sources, and the proportion of Gondwanan input increases toward the Destin Dome and Pensacola federal lease blocks in the Apalachicola Embayment. This variability in provenance influences sandstone framework grain composition and abundances of labile accessory phases. Where these NE-SW oriented transport systems terminate, 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, with little mixing of sediment within the erg system. The down-dip limit was likely a pinch-out of the eolian system controlled by both sediment availability and eolian transport capacity; this model predicts that there is no shoreline facies that grade laterally with distal Norphlet erg sands but instead the basal facies of the Smackover Formation would onlap Norphlet erg sands during the incursion of the Oxfordian marine transgression into the EGOM.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015