Bituminous Carbon Research Articles

Preliminary Assessment of Organic Carbon Content and Petroleum Source Rock Potential of Cretaceous and Lower Tertiary Carbonate Rocks, South Florida Basin: ABSTRACT

ABSTRACT Analyses of core samples obtained from oil and gas tests in the South Florida basin indicate that the Cretaceous carbonates of Comanchean age are relatively richer in average organic carbon (0.41%) than those of Coahuilan age (0.20%) and Gulfian age (0.18%), and richer than those of Paleocene age (0.20%). They are also nearly twice as rich as the average for carbonates worldwide (0.24%). The majority of carbonates have organic carbon values less than 0.30 percent, but the presence of many beds relatively rich in organic matter composed of highly bituminous, argillaceous, highly stylolitic, and algal- or sapropel-bearing limestone and dolomite accounts for the higher percentage of organic carbon in some of the stratigraphic units. Carbonate rocks that contain greater than 0.4 percent organic carbon and that might be considered as possible petroleum source rocks were noted in almost every subdivision of the Lower Cretaceous section, and particularly in units of Fredericksburg `B' of Exxon (Dollar Bay Formation of Winston), Trinity `A' and `F'(of Exxon) and Sunniland Limestone. Rocks of Gulfian and Paleocene age are generally relatively low in organic carbon; however, bituminous carbonates having as much as 3.2 percent or more of organic carbon were observed in the lowermost Gulfian Series. Oil stains and dead and live oil have been noted by others in the uppermost Gulfian and uppermost Paleocene. The South Florida basin is sparsely tested and, to date, produces hydrocarbons only from the Sunniland Limestone at an average depth of 11,500 ft. (3,500 m). Because the Sunniland contains good reservoir rocks and apparently adequate source rocks, and because the rate of new oil-field discoveries has increased in recent years, the chances of finding additional oil reserves in the Sunniland seem promising. Furthermore, the presence of reservoir rocks and possible source rocks in many additional stratigraphic units, such as those of Fredericksburg age, should provide incentive for exploring these additional units.

Certain aspects of geochemistry of copper in Dzhezkazgan

The microbiological factor, in its different forms, is found to be enriched and effective throughout the stratified hydrochemical profile of the orefield, below the ground water table, in extraction of stable Cu-organic compounds from bituminous carbonate rocks, in liberation of Cu from such compounds in solution, and in precipitation of Cu as sulfide by the continuously evolving biogenic H2S.

Realms of Permian Tectonism and Sedimentation in Western Utah and Eastern Nevada

Realms of sedimentation of Permian rocks include basins, troughs, platforms, and shelves within or adjacent to the Cordilleran miogeosyncline. Peripheral tectonic uplands (Antler and Sonoma orogenic belts on the west, Utah-Wyoming and other shelves on the east), as well as intrageosynclinal positive areas (Northeast Nevada high, Western Utah high, Southern Nevada high, Emery uplift, and others), varied in degrees of tectonism and thus provided different types of detritus and material removed in solution to accumulate in the several depocenters. Oquirrh, Wood River, Bird Spring, Ely, Hamilton-Elko, Ferguson, Pequop-Diamond Creek, Montello-Sublett, Ruby, and Park City basins are the more negative parts of the geosyncline, whereas several shelves and the Riepe Spring, Callvi le, Pakoon, and Kaibab platforms identify the less negative repositories. Starved basins of relatively short geologic duration were present locally. The study area, embracing western Utah, eastern Nevada, and a part of southern Idaho, is about 300 mi (483 km) wide in an east-west direction and about 525 mi (845 km) long north-south. The Permian includes slightly more than 17,000 ft (5,182 m) of sedimentary rocks in northwestern Utah, but thins to featheredges toward the orogenic belts on the west and the craton on the east. Most basinal accumulations exceed 5,000 ft (1,524 m), and many aggregate 6,000-10,000 ft (1,829-3,048 m). Rocks include a vast spectrum of limestone, dolostone, orthoquartzite, siltstone, sandstone, mudstone, gypstone, redbeds, and minor shale. They are of Wolfcampian, Leonardian, and Guadalupian ages. Fusulinids and some corals are abundant and are excellent guide fossils in Wolfcampian and Leonardian rocks, w ereas mollusks (including some ammonoids), brachiopods, sponges, and conodonts have stratigraphic value in younger sedimentary rocks. Conodonts in particular are of index and correlation value in Guadalupian rocks. During Wolfcampian time a thick sequence of orthoquartzite and shelly limestone accumulated in the Oquirrh, Wood River, and Hamilton-Elko basins, whereas bituminous carbonate rocks formed in the Ferguson basin. Clean carbonate sediments and various arenites typified the shelves and platforms. The Leonardian was a time of diversification into deeply subsiding troughs, basins, and areally extensive shelves and platforms; orthoquartzite, limestone, dolostone, some evaporites, redbeds, and related sediments formed. During Guadalupian time basinal carbonate rocks accumulated locally. Very cherty mudstone and carbonate sediment formed in other depocenters, whereas patch reefs, redbeds, sandstone, and evaporites were deposited in other depositional realms. Ochoan rocks, as identified elsewhe e by certain ammonoids and advanced fusulinaceans, are not recognized in the eastern Great Basin, but it cannot be stated with assurance that they are absent. Lower Triassic nonmarine (and marine) rocks disconformably overlie Permian rocks in several places within the study area. Oil is produced in limited quantity from Permian rocks within the study area in Utah, and hydrocarbon shows in wells have been very common. This vast area, however, has not been tested adequately. It is a structurally complex area, and exploration for oil and gas will be hazardous and costly.