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Deposits of Fine Grained Meandering Rivers, With Large Discharge Variations, in the Carboniferous of the Maritime Provinces, Canada: Abstract
A series of fining-upward sequences, up to 11 m thick and interpreted as point bar deposits, occur in the lower part of the Shepody Formation (mid-Carboniferous) in the Chignecto Bay area of New Brunswick and Nova Scotia. The sandstones are predominantly of fine to very fine sand grade but have a maximum grain size of medium sand grade. Plane parallel lamination and ripple lamination are the dominant sedimentary structures in the sandstones. The sandstones pass upward into siltstone with climbing ripple or parallel lamination and clay mudrock. Small, steep-sided channels, infilled with rippled sandstones and siltstones, cut into the upper parts of the fining-upward sequences. These are interpreted as chute-fill deposits. Desiccation features occur in the upper third of the fining-upward sequences and in the chute channels. The presence of chute channels in such a fine-grained sequence and the desiccation structures suggest rivers with considerable stage fluctuations.
In the underlying Maringouin Formation, fining-upward sequences are similar to those in the Shepody but are thinner (up to 5 m) and finer (virtually all very fine sandstone or finer). Ripple lamination is the dominant sedimentary structure. Desiccation features are seen throughout most of the fining-upward sequences and it is probable that many of the river channels were ephemeral.
Acknowledgments and Associated Footnotes
1 Department of Geology, University of Nebraska, Lincoln, Nebraska 68588
Copyright © 2009 by the Canadian Society of Petroleum Geologists