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Geology topics

J.W. Harbaugh

Publications and source records attributed to J.W. Harbaugh.

4 recordsLinked to original sources
USGS2007

Reconstructing late Cenozoic stream gradients from high-level chert gravels in central Eastern Kansas

Interpreting the evolution of Kansas' landscape east of the Flint Hills provides major challenges. In the Neogene (late Tertiary) and perhaps part of the Pleistocene, streams transported a variety of sedimentary materials, including chert gravels derived from the Flint Hills. Gentle intermittent uplift stimulated the system system to cut down, locally removing and reworking the gravels to create stream-terrace deposits that consist mostly of chert pebbles, which now lie well above the floodplains of modern streams. By correlating the elevations of these gravels, the gradients of the trunk streams that deposited them can be reconstructed. Interestingly, these ancient streams flowed southeast at a little more than a foot per mile (0.2 m/km), roughly the same as the gradient of the trunk streams in the region today. The evolving landscape in eastern Kansas also has been strongly influenced by an extensive network of fractures that is widespread in the midcontinent region and may be worldwide in extent. In northeastern Kansas, glaciation during the Pleistocene disrupted the southeasterly drainage and established the present location of the Kansas River. South of the Kansas River and its immediate tributaries, however, the general southeasterly drainage has been preserved. We have made use of the wealth of topographic-elevation data now available in digital form known as DEMs or digital elevation models. Coupled with GIS procedures, the DEMs helped link the mapped distribution of chert gravels with hypothetical fitted surfaces that represent ancient stream gradients. Furthermore, DEM data placed in shaded-relief map form emphasize the influence of fractures in evolution of the drainage system.

Current Research in Earth Sciences↗
USGS1983

Statistical evaluation of oil and gas prospects in the outer continental shelf of the U.S. Gulf Coast

Areas of the U.S. Gulf Coast, both onshore and offshore, are among the petroliferous regions of the United States. In offshore Louisiana and Texas, most oil and gas is associated with structurally controlled traps on the crest or flanks of domes created by the diapiric movement of salt. These structures can be detected and mapped by seismic techniques that directly indicate favorable prospective areas. The characteristics of seismically defined structures provide information in advance of drilling about the probable size of reservoirs contained within these structures. Simple statistical relationships can be determined between the size, shape, and other attributes of structures detected by seismic mapping and the presence and size of petroleum and natural gas reservoirs. Gulf Coast OCS lease tracts presently are evaluated by the U.S. government using a Monte Carlo simulation procedure adapted from reservoir analysis. Specification of the parameters of the Monte Carlo model are obtained subjectively in advance of drilling and thus are highly uncertain. Comparisons of predrill predictions with postdiscovery reservoir evaluations show very low correlations. In contrast, predrill predictions based on regressions between seismic structural properties and reservoir volumes show highly significant correlations. In addition, statistical analysis of seismic structure is much simpler than the Monte Carlo procedure, and can be applied rapidly and inexpensively. A statistical analysis of the "Pleistocene Trend" of offshore Louisiana and Texas, an area of about 3 million acres, yielded results that are sufficiently encouraging to suggest that similar evaluations be made of the remaining Gulf Coast OCS and of OCS regions off of other coasts of the United States. ?? 1983 Plenum Publishing Corporation.

Journal of the International Association for Mathe↗
USGS1983

Reassessment of the rates at which oil from natural sources enters the marine environment

Previous estimates of the world-wide input of oil to the marine environment by natural seeps ranged from 0??2 to 6??0 million (metric) tonnes per year with a 'best estimate' of 0??6 million tonnes per year. Based on considerations of the availability of oil for seepage from the world's known and assumed oil resources, we believe that the world-wide natural oil seepage over geological time should be revised to about 0??2 million tonnes per year with a range upward or downward of a factor of ten leading to estimates between 0??02 and 2 million tonnes per year. Our estimate of the amount of oil eroding from the land and being transported to the oceans is about 0??05 million tonnes per year with an order of magnitude uncertainty. Therefore, while the uncertainties are large, we estimate that the total amount of oil entering the marine environment by natural, geological processes, is about 0??25 million tonnes per year, and the estimate may range from about 0??025 to 2??5 million tonnes per year. This rate applies over geological time, but episodic fluctuations in the input of oil to the marine environment may cause the rate to exceed this range in any one year.Previous estimates of the world-wide input of oil to the marine environment by natural seeps ranged from 0. 2 to 6. 0 million (metric) tonnes per year with a 'best estimate' of 0. 6 million tons per year. Based on considerations of the availability of oil for seepage from the world's known and assumed oil resources, the world-wide natural oil seepage over geological time should be revised to about 0. 2 million tons per year with a range upward or downward of a factor of ten leading to estimates between 0. 02 and 2 million tons per year. It is estimated that the amount of oil eroding from the land and being transported to the oceans is about 0. 05 million tons per year with an order of magnitude uncertainty. Therefore, the total amount of oil entering the marine environment by natural, geological processes, is about 0. 25 million tons per year, and the estimate may range from about 0. 025 to 2. 5 million tons per year. Refs.

Marine Environmental Research↗