PARCELL, WILLIAM C., Department of Geology, University of Alabama, Tuscaloosa, AL

Abstract: Stratigraphic Architecture of Upper Jurassic (Oxfordian) Reefs in the Northeastern Gulf Coast, U.S. and the Eastern Paris Basin, France

The Late Jurassic was a major period of reef expansion. Many Jurassic reefs are potential hydrocarbon reservoirs, but their stratigraphic distribution has been difficult to predict. Examination of the stratigraphic architecture of Oxfordian reefs in the northeast U.S. Gulf Coast and the eastern Paris Basin, France affords a comparison of mixed coral-algal-sponge reefs versus algal-dominated reefs.

The Smackover Formation in the northeastern Gulf Coast contains algal-dominated reefs. The Smackover represents deposition during a major transgression. The Smackover algal-dominated reefs occur within late transgressive system tract (TST) deposits.

The Oxfordian of the eastern Paris Basin is characterized by reefs of mixed corals, algae and sponges. In the Ardennes-Lorraines, reefs appear after the maximum flooding event of a stratigraphic sequence and are maintained through the highstand systems tract (HST) and into the overlying stratigraphic sequence. In Burgundy, reefs occur in association with the maximum flooding event of the upper sequence. Reef growth begins in the TST and is dominated by platy microsolenids. This interval is traditionally called the lower reef complex. More diverse reef growth (the upper reef complex) continues above the maximum flooding event through the early HST. Reef growth ceases by the late HST with the introduction of grainstones and other high energy lithologies.

All reefs in this examination, regardless of biota, are associated with maximum flooding events. The sequence stratigraphy of the Oxfordian reefs in France and the Gulf Coast provides a framework for studying Jurassic reefs of both mixed and algal-dominated assemblages. 

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana