Provenance of the Upper Jurassic Norphlet and Surrounding Formations from U-Pb Detrital Zircon Geochronology

Lisi, Andrea; Weislogel, Amy

U-Pb detrital zircon geochronology supplemented by dense mineral analysis, thin section petrography, and well log correlation of the Upper Jurassic Norphlet Formation, overlying Mesozoic formations, and basement rock in the eastern Gulf of Mexico has been used to constrain the provenance of Jurassic sediments. The results have helped to reconstruct paleogeography, sediment transport pathways, and sandstone distribution of the Norphlet Formation, an important hydrocarbon reservoir in the eastern Gulf of Mexico. Previous work regarding the depositional environment of these sediment packages often assume a northern Appalachian and Talladega slate belt source. However, the Gondwanan, Suwannee terrane makes up the northern Florida basement and has also sourced the Norphlet and surrounding formations according to zircon ages. Appalachian zircon populations include Laurentian (2500-2800, 1600-1900, and 1360-1500 Ma), Grenville (900-1300 Ma), Rodinia rifting (550-800 Ma), the Taconic orogeny (350-490 Ma), and the Alleghanian orogeny (300-325 Ma). Distinct Gondwanan zircon age populations observed in the eastern Gulf of Mexico include the Trans-Amazonian/Eburnean (1900-2250 Ma) and the Pan-African/Brasiliano events (~530-680 Ma) when in combination with the Trans-Amazonian/Eburnean event.

This study used sandstone samples from 3 onshore and 2 offshore Florida wells and 5 wells from the offshore federal lease blocks, Mobile Bay, Pensacola, Destin Dome, St. Petersburg, and Florida Middle Ground. Results suggest a primary Appalachian source for the Mobile Bay offshore federal lease block, mixed affinity in the western Florida Panhandle, and a primary Gondwanan affinity for the remaining offshore lease blocks and eastern Florida Panhandle. Thicker intervals of Norphlet are found within the NW/SE trending rift grabens associated with the initial rifting of Pangea. Some Norphlet-like deposits were identified just south of the Middle Ground Arch, far east of the current up-dip limit of the Norphlet. These sands were likely deposited similarly to the Norphlet in sourrounding areas in the Gulf of Mexico and were predominantly derived from the nearby paleo-high, the Middle Ground Arch.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013