Skip to Main Content

ABSTRACT

A contour map on a prominent mid-Jurassic surface (MJS) outlines four crustal types in the northeastern Gulf of Mexico basin: 1) continental crust underlying northern Florida, 2) thick transitional crust characterized by large E-W trending basement highs and lows (Wiggins uplift, Apalachicola basin, Middle Ground arch-Southern platform, Tampa embayment, and Sarasota arch), 3) thin transitional crust underlying the West Florida basin, and 4) oceanic crust underlying the deep central Gulf basin. This basin configuration developed during the early breakup of Pangea, as South America-Africa separated from North America. Over much of the area the MJS is a prominent unconformity that truncates Late Triassic-Early Jurassic rift sediments as well as all older Paleozoic and Precambrian sedimentary, igneous and metamorphic rocks. It is overlain by mid-Jurassic pre-marine evaporites (Louann salt and equivalent rocks), which are thick in basinal areas and thin or absent over adjacent highs. The evaporites were deposited toward the end of the period of crustal attenuation and the formation of transitional crust but prior to the emplacement of oceanic crust.

This crustal structure and basin configuralion of the MJS influenced the distribution and development of the overlying Upper Jurassic and Lower Cretaceous sequences. During Smackover time a broad shelf to prograding ramp partially filled the basinal areas, while scattered carbonate buildups developed along the surrounding basement highs. In areas of thick salt sediments thicken into small basins formed along listric growth faults caused by salt withdrawal (salt rollers). The shelf margins continued to prograde basinward during Haynesville time, depositing a thick section in the Tampa embayment, while a starved carbonate margin (Gilmer?) developed in the western Apalachicola basin. During the latest Jurassic-earliest Cretaceous (Cotton Valley time) a broad, dominantly clastic, prograding ramp filled the basins and overlapped the highs, while a deep-sea fan system developed in the adjacent West Florida basin. Cotton Valley deposition culminated with the development of the Knowles carbonate margin along a tectonic hinge-zone (THZ) at the thick/thin transitional crust boundary.

During the Lower Cretaceous a rimmed carbonate margin controlled by the THZ continued to develop along the present-day Florida escarpment. This margin became steeply-dipping to the south, separating a broad carbonate platform from a relatively starved basin. To the north in the De Soto canyon area, the margin remained gently-dipping, reflecting the influence of a narrow shelf and the influx of terrigenous clastics to the adjacent slope. In the West Florida basin mounded and lobate geometries are interpreted as deep-sea fan systems. Low velocity channel fills on the adjacent platform suggest that siliciclastic sediments may have bypassed the Lower Cretaceous carbonate margin during sea level lowstands and been deposited as potential siliciclastic reservoir rocks within portions of the deep-sea fan systems.

As the carbonate margin adjacent to the West Florida basin continued to aggrade and steepen during the Early Cretaceous, southward-flowing deep-sea currents intensified and became focused along the base of the margin, altering depositional patterns and processes and culminating in the deposition of a large southward-prograding contourite mound. Near the end of the Early Cretaceous, extremely intense currents, possibly due to sea level drops, preferentially eroded these lobes and mounds, culminating in the widespread mid-Cretaceous sequence boundary (MCSB). A subsequent rise in relative sea level terminally drowned the Lower Cretaceous platform margin and caused the retreat of the margins to more landward positions during the Upper Cretaceous.

You do not currently have access to this chapter.

Figures & Tables

Contents

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal