AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Regional Norphlet Formation Facies Correlation, Analysis and Implications for Paleo-Structure and Geologic Provenance, Eastern Gulf of Mexico
(1) Department of Geological Sciences, University of Alabama, Tuscaloosa, AL.
(2) Dept of Geology & Geography, West Virginia University, Morgantown, WV.
(3) Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN.
Despite significant hydrocarbon discoveries, the eastern Gulf of Mexico (EGOM) has remained understudied due to a multi-decade drilling moratorium in that region. Many elements of the EGOM’s early structure are unknown because they are sub-salt and have not been extensively investigated. This structural fabric developed during Late Triassic and Early Jurassic time as the EGOM opened. Salt formed in the shallow sea that developed. After the deposition of the Louann Salt, siliciclastic input into the EGOM filled the low regions to form the Jurassic Norphlet Formation, followed by deposition of the carbonate Smackover and siliciclastic Haynesville formations. Core and log analyses reveal that the primary facies of the Norphlet Fm. are: a lower unit of black shale, wadi deposits, and eolian sands, and an upper unit of marine sands reworked by a transgression. Eolian deposits can be found nearly everywhere the Norphlet Fm. is present, while wadi facies are less consistently found in the offshore but are present are far out as Desoto Canyon. Thickness of the Norphlet Fm. is variable: up to 500’ in Mississippi, 600’ in onshore Alabama, 600’ to 800’ in offshore Alabama and Florida and up to 800’ in parts of Desoto Canyon. In this study, well logs from approximately 60 offshore wells located in Destin Dome, Mobile, Pensacola, and Desoto Canyon as well as a similar number of onshore wells are used to extend Norphlet Fm. facies, described in onshore cores, into the offshore EGOM. The distribution and thickness of the different facies indicates paleo highs and lows which were not concealed by the Louann Salt. These trends have implications for the nature of the rifting in the EGOM.
One way to understand the sediment source is to analyze the sediment for characteristic detrital zircon U-Pb age distributions. Detrital zircon provenance studies reveal that Norphlet Fm. sands originated from both Laurentian and Gondwanan source terranes during Late Jurassic time. This study contains new provenance data from the Haynesville Formation in the EGOM revealing the evolution of source terranes during Late Jurassic time. The facies distribution indicates potential candidates for sediment input pathways for the Laurentian and Gondwanan sediments. The sediment input pathways and distribution of the facies during Late Jurassic time provide a clearer picture of the extent of the reservoir facies within the Norphlet Formation and decreases uncertainty for hydrocarbon exploration.