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USGS1993

Allogenic and autogenic controls on sedimentation in the central Sumatra basin as an analogue for Pennsylvanian coal-bearing strata in the Appalachian basin

Recent sedimentation patterns in the central Sumatra basin, Republic of Indonesia, may help to explain the cyclic stratigraphy of the Pennsylvanian System of the eastern United States. Modern influx of fluvial siliciclastic sediment to the epeiric seas of the Sunda shelf, including the Strait of Malacca, appears to be highly restricted by rain forest cover within the ever-wet climate belt of equatorial Sumatra. As a result, much of the marine and estuarine environments appear to be erosional or nondepositional except for localized deposition of sediment in slack water areas, such as the down-stream end of islands. Contemporaneously, thick (>13 m), laterally extensive (>70,000 km 2 ), peat deposits are forming on poorly drained coastal lowlands. Modern peat formation in this study, therefore, is not coeval with aggrading fluvial siliciclastic systems, a situation that commonly is assumed in many depositional models of coal formation. The stratigraphy of Pleistocene and Holocene sediments on the Sunda shelf, as well as those of the Pennsylvanian System, appears to be better explained by the allocyclic controls of climate and sea-level change on sediment flux rather than by depositional models that are based on autocyclic processes. The objective of this paper is to evaluate allocyclic and autocyclic controls on sedimentation in an epeiric setting in a humid (ever-wet) tropical region. Of particular interest are the factors that control peat formation and siliciclastic sediment flux in rivers, estuaries, and open marine environments.

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USGS1990

Coal resources available for development; a methodology and pilot study

Coal accounts for a major portion of our Nation's energy supply in projections for the future. A demonstrated reserve base of more than 475 billion short tons, as the Department of Energy currently estimates, indicates that, on the basis of today's rate of consumption, the United States has enough coal to meet projected energy needs for almost 200 years. However, the traditional procedures used for estimating the demonstrated reserve base do not account for many environmental and technological restrictions placed on coal mining. A new methodology has been developed to determine the quantity of coal that might actually be available for mining under current and foreseeable conditions. This methodology is unique in its approach, because it applies restrictions to the coal resource before it is mined. Previous methodologies incorporated restrictions into the recovery factor (a percentage), which was then globally applied to the reserve (minable coal) tonnage to derive a recoverable coal tonnage. None of the previous methodologies define the restrictions and their area and amount of impact specifically. Because these restrictions and their impacts are defined in this new methodology, it is possible to achieve more accurate and specific assessments of available resources. This methodology has been tested in a cooperative project between the U.S. Geological Survey and the Kentucky Geological Survey on the Matewan 7.5-minute quadrangle in eastern Kentucky. Pertinent geologic, mining, land-use, and technological data were collected, assimilated, and plotted. The National Coal Resources Data System was used as the repository for data, and its geographic information system software was applied to these data to eliminate restricted coal and quantify that which is available for mining. This methodology does not consider recovery factors or the economic factors that would be considered by a company before mining. Results of the pilot study indicate that, of the estimated original 986.5 million short tons of coal resources in Kentucky's Matewan quadrangle, 13 percent has been mined, 2 percent is restricted by land-use considerations, and 23 percent is restricted by technological considerations. This leaves an estimated 62 percent of the original resource, or approximately 612 million short tons available for mining. However, only 44 percent of this available coal (266 million short tons) will meet current Environmental Protection Agency new-source performance standards for sulfur emissions from electric generating plants in the United States. In addition, coal tonnage lost during mining and cleaning would further reduce the amount of coal actually arriving at the market.

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