AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Sources of Earliest Clastic Input into the Eastern Gulf of Mexico and Their Control on Reservoir Prospectivity
(1) West Virginia University, Morgantown, WV.
(2) Geological Sciences, University of Alabama, Tuscaloosa, AL.
(3) Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN.
Provenance analysis of Uppper Jurassic Norphlet sandstone from the eastern Gulf of Mexico (EGOM) indicates sediment distribution in the EGOM was largely controlled by structural configuration of the underlying rifted basement. Ten core samples from onshore Alabama and 2 samples of cuttings from the Destin Dome offshore federal lease block were investigated using U-Pb detrital zircon geochronology and thin-section petrology. The Norphlet Fm. detrital zircon signature in southwestern/south-central Alabama is characterized by prominent zircon age populations of 360-760 Ma, 950-1900 Ma, and 2500-3000 Ma, consistent with derivation from Laurentian-affinity Appalachian sources. These zircon grains were eroded from remnant Appalachian orogenic highlands and recycled from synorogenic strata of the Black Warrior basin in the Appalachian pro-foreland. In contrast, samples from Destin Dome contain Laurentian-affinity zircon along with major populations of 540-580 and 2000-2200 Ma zircons consistent with derivation from the Gondwanan Suwanee terrane. Samples from Baldwin and Escambia counties of AL yield subequal proportions of both Gondwanan- and Laurentian-affinity zircons. These results indicate multiple sediment pathways with distinct catchments existed. An eastern transport system followed a pathway within a northeast-southwest trending graben that developed east of the Suwanee suture during Late Triassic to Early Jurassic rifting of Pangea, whereas a western system drained the southern terminus of the Appalachian orogen southward through the Mobile graben. Eolian transport by northeasterly trade winds transported Gondwanan-affinity sediment into the FL panhandle region, where it mixed with Appalachian-derived detritus. Implications for EGOM exploration from these results include: 1) increased Jurassic sandstone reservoir potential along the Florida Escarpment, and 2) widespread potential for secondary porosity development due to lithic grain dissolution in Jurassic reservoirs. Notably, Mesozoic zircon ages suggesting contribution of synrift magmatic rocks are rare; this may indicate that the mantle underlying the EGOM province was depleted due to previous episodes of Paleozoic melting, such that EGOM rifting processes were largely amagmatic. Additional U-Pb detrital zircon provenance analysis of Upper Jurassic EGOM units (i.e., Haynesville Formation and Cotton Valley Group) are on-going to test whether or not Norphlet transport pathways persisted through time.