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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
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Title: Coal
-Bed Discontinuities: ABSTRACT
Author(s):
Abstract:
Predictive models that characterize coal
bed discontinuities enable mine operators to be better judges of the size, geometry, and influence of these features in unmined portions of the
coal
bed. An analysis of depositional environments in initial geologic studies of prospective mine properties will indicate the specific types of
coal
bed discontinuities that can be anticipated.
The type of coal
bed discontinuity and the frequency of occurrence are functions of the depositional environment. Peat, the precursor of
coal
, accumulated in swamps that may form on fluvial plains, on delta plains, and in littoral areas. Using generalized depositional models for these environments, the types of
coal
bed discontinuities that can be expected and an estimate of the likelihood of their occurrence can be determined.
Coal
beds deposited on fluvial plains generally are thin, erratic, and discontinuous because of the highly oxidizing character of this environment. Discontinuities due to irregular topography and fluvial channel activity are common, as displayed by Upper Pennsylvanian and Permian
coal
beds of the Dunkard basin.
Coal
beds formed in deltaic settings are generally
thick and laterally extensive, as they commonly infill broad interdistributary areas. These
coal
beds are typically plagued by discontinuities associated with distributary channels (e.g., avulsion, splays). The Freeport and Kittanning
coal
beds in west-central Pennsylvania demonstrate features characteristic of delta-plain coals and the discontinuities that beset them.
Coal
beds deposited landward of barrier bar sequences generally are irregular and are interrupted by tidal channels and washover deposits. The Pocahontas 3
coal
bed of southern West Virginia exhibits many of the characteristics of this paralic setting. Although some clastic dikes may be depositionally related, such discontinuities, as well as faulting, may be overprinted by tectonic activity on
coal
beds from any depositio
al environment.
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