T. Markham Puckett

Upper Jurassic (Oxfordian) Smackover carbonate petroleum system characterization and modeling, Mississippi Interior Salt Basin area, northeastern Gulf of Mexico, USA

The Upper Jurassic (Oxfordian) Smackover Formation is a prolific oil and gas reservoir in the northern Gulf of Mexico, including the Mississippi Interior Salt Basin area. The Smackover petroleum system is categorized as a giant petroleum system and ranks fourth among recognized Upper Jurassic petroleum systems. In the Mississippi Interior Salt Basin area, the components of the Smackover petroleum system include pre rift, syn rift and post rift siliciclastic, evaporite, and carbonate underburden and overburden rocks, Smackover subtidal lime mudstone source rocks, uppermost Smackover anhydrite and Buckner Anhydrite Member subaqueous saltern and sabkha seal rocks, and upper Smackover shoal complex and tidal flat complex packstone, grainstone, boundstone and dolostone reservoir rocks. The critical events include the initiation of the generation of crude oil, the commencement of hydrocarbon expulsion, the initiation of hydrocarbon migration, and the entrapment of hydrocarbons during the Early to Late Cretaceous. The critical moment for the Smackover petroleum system is the time of peak hydrocarbon expulsion in the mid to late Early Cretaceous in basin center areas and mid to latest late Cretaceous in areas along the northern basin margin. *** DIRECT SUPPORT *** A00QA034 00003

Absolute paleobathymetry of Upper Cretaceous chalks based on ostracodes-Evidence from the Demopolis Chalk (Campanian and Maastrichtian) of the northern Gulf Coastal Plain

The presence of abundant and diverse sighted ostracodes in chalk and marl of the Demopolis Chalk (Campanian and Maastrichtian) in Alabama and Mississippi strongly suggests that the Late Cretaceous sea floor was within the photic zone. The maximum depth of deposition is calculated from an equation based on eye morphology and efficiency and estimates of the vertical light attenuation. In this equation, K , the vertical light attenuation coefficient, is the most critical variable because it is the divisor for the rest of the equation. Rates of accumulation of coccoliths during the Cretaceous are estimated and are on the same order as those in modern areas of high phytoplankton production, suggesting similar pigment and coccolith concentrations in the water column. Values of K are known for a wide range of water masses and pigment concentrations, including areas of high phytoplankton production; thus light attenuation through the Cretaceous seas can be estimated reliably. Waters in which attenuation is due only to biogenic matter-conditions that result in deposition of relatively pure chalk-have values of K ranging between 0.2 and 0.3. Waters rich in phytoplankton and mud-conditions that result in deposition of marl-have K values as great as 0.5. Substituting these values for K results in a depth range of 65 to 90 m for deposition of chalk and a depth of 35m for deposition of marl. These depth values suggest that deposition of many Cretaceous chalks and marls around the world were deposited under relatively shallow conditions.

New Ostracoda species from an Upper Cretaceous oyster reef, northern Gulf Coastal Plain, U.S.A.

This paper describes new species of Ostracoda from Late Cretaceous (late Santonian) oyster reefs of the Eutaw Formation of eastern Alabama. The reefs are composed almost exclusively of Ostrea cretacea Morton, with rarer occurrences of the oysters Exogyra upatoiensis Stephenson and Lopha ucheensis (Stephenson) and the bivalve Anomia preolmstedi Stephenson. Total thickness of the reefs is about 30 m, and the reefs are a major topographic feature across most of Macon and Russell Counties, Alabama, a distance of about 60 km. The reefs are interpreted to have been backbarrier sediments deposited under brackish conditions. Eight species of ostracodes are identified, including five new species described herein. The fauna is typically well preserved, and includes males, females, and juveniles. New species include Haplocytheridea ? eutawensis, Antibythocypris dimorphicus, A. nephotrema, Brachycythere asymmetrica , and Eocytheropteron mutafoveata. Also discussed and illustrated are Cytherella tuberculifera Alexander, Haplocytheridea renfroensis renfroensis Crane, and Fissocarinocythere gapensis (Alexander).

Basin Analysis of the Mississippi Interior Salt Basin and Petroleum System Modeling of the Jurassic Smackover Formation, Eastern Gulf Coastal Plain, Final Report and Topical Reports 5-8 on Smackover Petroleum system and Underdevelopment Reservoirs

The Smackover Formation, a major hydrocarbon-producing horizon in the Mississippi Interior Salt Basin (MISB), conformably overlies the Norphlet Formation and is conformably overlain by the Buckner Anhydrite Member of the Haynesville Formation. The Norphlet-Smackover contact can be either gradational or abrupt. The thickness and lithofacies distribution of the Smackover Formation were controlled by the configuration of incipient paleotopography. The Smackover Formation has been subdivided into three informal members, referred to as the lower, middle and upper members.

Paleoenvironmental and stratigraphic changes in Paleocene and lower Eocene strata, eastern Gulf Coastal Plain, USA

The depositional history of the eastern Gulf Coastal Plain of the United States during the Paleocene and early Eocene was dominated by deltaic, marginal marine, and marine sedimentation (Fig. 1). A major, fluvial-dominated delta complex developed during the Paleocene and continued into the early Eocene, and this system had a profound influence on the depositional patterns in the region. The source area for the deltaic sediment was to the northwest, and sediment influx was related to Laramide orogenic pulses in the Rocky Mountain region (Galloway 1989). The Paleocene (Danian, Selandian, and Thanetian) and lower Eocene (Ypresian) strata of the eastern Gulf Coastal Plain consist of 431 m of marine carbonates, marlstones, and glauconitic sandstones and marginal marine to fluvial-deltaic tial Range Zone (P0), Parvularugoglobigerina eugubina Total Range Zone (Pα), Parvularugoglobigerina eugubina–Praemurica uncinata Interval Zone (P1), Praemurica uncinata–Morozovella angulata Interval Zone (P2), Morozovella angulata–Globanomalina pseudomenardii Interval Zone (P3), Globanomalina pseudomenardii Total Range Zone (P4), Morozovella velascoensis Partial Range Zone (P5), and Morozovella subbotinae Partial Range Zone (P6) (Mancini & Oliver 1981; Mancini 1984; Olsson & Lui 1993). Using the planktonic foraminiferal zones, the Danian/Selandian Stage boundary occurs at the base of the Matthews Landing, and the Selandian/Thanetian Stage boundary is probably at the base of the Nanafalia (Fig. 2). The Thanetian/Ypresian Stage boundary is at the base of the Hatchetigbee, and the Paleocene/Eocene boundary is recognized at the base of the Hatchetigbee using planktonic foraminiferal criteria. A total of nine unconformity-bounded units of 0.5 to 3.5 million years in duration have been observed in these strata (Mancini & Tew 1991). The depositional sequences are characterized by distinct lowstand, transgressive, and highstand systems tract deposits and by mappable physical surfaces, including sequence boundaries, first transgressive surfaces, and maximum flooding surfaces. The Paleocene and lower Eocene strata can be mapped regionally in the eastern Gulf Coastal Plain area utilizing sequence stratigraphic relationships in combination with biostratigraphic data. Global correlation of these strata to European sections is possible employing the biostratigraphic zones recognized in these Paleocene and lower Eocene strata. GFF volume 122 (2000), pp. 99–100. “Early Paleogene Warm Climates and Biosphere Dynamics”

EXTENDED ABSTRACT: Stratigraphic framework of the Mesozoic sediments of the Mississippi Interior Salt Basin

ABSTRACT The stratigraphic framework of the Mississippi Interior Salt Basin (MISB) was studied to determine the burial and thermal history of the basin. Wireline logs, predominantly SP and resistivity but supplemented by gamma ray, sonic, and neutron/density logs, and lithologic and sample logs from 48 wells comprise the information base. Five cross sections were generated, including a strike section and four dip sections. The geographic extent of the dip sections allows tracking formational changes in the basin, particularly the change from predominantly siliciclastic to carbonate sediments which most of the formations display, and the diachroneity of the formational contacts. Figure 1. Time-stratigraphic cross section of Mississippi Interior Salt Basin along generalized line from Yazoo County to the Wiggins Arch in George County, Mississippi. The change from siliciclastic to carbonate sediments presents special problems when correlating from onshore to offshore regions of the Gulf of Mexico. Typically, formational boundaries in onshore areas can be recognized on the basis of characteristic wireline log signatures that reflect lithologic disparities. South of the Wiggins Arch, where much of the Mesozoic section is carbonate, biostratigraphy is increasingly used to define formational boundaries. Although the presence of microfossils is reported in sample and lithologic logs from many wells and formations in the MISB, very little of this paleontological information has been published and remains an area of future study. Tectonic subsidence of the MISB occurred largely during the Jurassic and Early Cretaceous, as variances of the thicknesses of these two systems are much greater than that of the Upper Cretaceous System. The literature indicates that other salt basins occurring on thick transitional crust have analogous depositional systems, suggesting that stratigraphic models developed in one basin can be applied to other, less studied salt basins. End_of_Record - Last_Page 25-------

Comparison of Upper Cretaceous and Paleogene Depositional Sequences in the Eastern Gulf Coastal Plain

ABSTRACT Genetic depositional sequences representing durations of 0.5 to 11 million years, their component systems tracts and associated physical surfaces have been identified and mapped in Upper Cretaceous and Paleogene strata of the eastern Gulf Coastal Plain. The time duration in which these sequences were deposited appears to have little impact on sequence development in that the component systems tracts can be recognized in all of the sequences. However, the Upper Cretaceous sequences represent longer periods of time, resulted from slower sedimentation rates, experienced lower subsidence rates, and, generally, reflect more marine paleoenvironmental conditions. In the eastern Gulf Coastal Plain, the Late Cretaceous was characterized by warm climates, relatively high sea levels, and stable depositional conditions. Conversely, Paleogene sequences represent shorter durations of time and were greatly affected by differential rates of sedimentation and subsidence. In Paleogene sequences, usually only the transgressive systems tracts were characterized by marine depositional conditions. In the eastern Gulf Coastal Plain, the Paleogene was typified by widely fluctuating climates and dynamic changes in depositional conditions. Generally, Upper Cretaceous sequences span more than one biozone, whereas Paleogene sequences usually are restricted to a single biozone. The sedimentation rates and patterns, the stable depositional conditions, and high biologic productivity during the Late Cretaceous results in a stratigraphic section that is useful for high resolution sequence analysis. Thus, the diachroneity of sequence boundaries and first transgressive surfaces and the synchroneity of maximum flooding surfaces are more easily discerned by mapping Upper Cretaceous system tracts and associated physical surfaces in the eastern Gulf Coastal Plain. The study of Upper Cretaceous depositional sequences, therefore, is potentially more helpful in identifying the factors affecting global sea level change.