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Carboniferous Coal Deposition Associated with Flood-Plain and Limnic Environments in Nova Scotia

By
Peter A. Hacquebard
Peter A. Hacquebard
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J. Roger Donaldson
J. Roger Donaldson
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Published:
January 01, 1969

In the Sydney coalfield, normal-banded autochthonous coals accumulated in a flood-plain environment. Lithofacies maps show the existence of two main river channels in this plain. The interaction between fluvial sedimentation and peat deposition, which caused the splitting and digitation of seams, is illustrated. The environmental changes in the peat swamps have been interpreted from petrographic variations within the coals. By arranging the latter in “fades triangles,” it was possible to plot these changes in cross sections of eight seams. They show that forest-moor and reed-moor environments predominated throughout, but were interrupted occasionally by open moor conditions. Changes in environment were accompanied by changes in vegetation. This was concluded from variations in the spore florules within seams, particularly in the ratios of Punctatosporites and Lycospora. Rapid subsidence with early burial of peat beds is indicated for Sydney basin, by type of clastics and excellent preservation of coal macerals.

In the Pictou coalfield, micro-banded hypautochthonous coals accumulated in a narrow intermontane lake basin. A lithofacies map shows lacustrine sediments, with coal seams up to 44 feet thick, in the central part of the basin and more fluviatile deposits at the margin. Rapid megascopic changes are illustrated between coal and detrital sediments, which caused lateral “lithification” rather than digitation of seams. Uniform ecological conditions are indicated by uniformity in petrographic composition and by constancy of the spore florule within each seam. A slowly subsiding basin with simultaneous accumulations of peat and clastic materials is postulated by the type and preservation of the coal macerals and the presence of numerous, minute quartz grains.

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Contents

GSA Special Papers

Environments of Coal Deposition: Papers Presented at a Symposium by the Coal Geology Division of The Geological Society of America at the Annual Meeting Miami Beach, Florida, 1964

Edward C. Dapples
Edward C. Dapples
Editors
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M. E. Hopkins
M. E. Hopkins
Editors
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Geological Society of America
Volume
114
ISBN print:
9780813721149
Publication date:
January 01, 1969

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