The map on the right shows the localities along the Kukpowruk River sampled both by Smiley (reported in Smiley 1969a), Spicer and Herman (1996) and by Bob and Andrew Spicer in 1998. Click on the locality numbers to see further details of the sites and the fossil floras.
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| Field photograph of Locality 96-27 showing an in situ tree stump impression (right side of the image) rooted in a 'lumpy' gray siltstone. |
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Locality 96-27. 69° 20' 11" N 162° 34' 21" W
Corwin Formation
Specimens: 96 RAS 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158
Description. Two coals separated by gray silty mudstone. Each coal approximately 1 m thick. A "lumpy" gray siltstone overlies the upper coal and this contains an impression of an upright tree approximetely 25 - 30 cm diameter. This tree appears to be rooted in the siltstone. Above the tree is a fine gray/yellow cross bedded sandstone with abundant woody debris, including drifted coalified logs, and several prominant pebble stringers. The sandstone is approximately 5 m thick with no obvious well developed ripples or burrows. This passes up into a series of interbedded gray/brown mudstones and thin sandstones. These mudstones and thin sandstones contain abundant large-leaved ginkoes and Desmiophyllum. Ferns are rare. Equisetites is apparently absent. Silty mudstones contain numerous ironstone nodules with Desmiophyllum, Podozamites and fern fragments.
The coal beds were traceable across the river to the northeast where they outcropped stratigraphically below locality 96-26. Here the sequence continues upwards towards the axis of Howard Syncline with interbedded gray silty mudstones and gray to orange/yellow weathering fine sandstones. Sandstones contain Equisetites rhizomes, Desmiophyllum, and vertical and horizontal, sometimes branched, mud-filled burrows approximately 1 cm diameter (not "U" shaped). This sequence passes up into more carbonaceous-rich mudstones with iron nodules and then to a coal more than 1.5 m thick. This coal is covered by gray mudstones containing ironstone nodules in bands.
The ironstones yielded some rare ginkgoes, Desmiophyllum in abundance, rare Pagiophyllum triangulare, Birisia, cf. Arctopteris/Cladophlebis, branchwood, some cones and a very large-leaved Pseudocycas cf. P. unjiga. Equisetites is frequent in overlying fine to medium gray sandstones with abraded wood fragments on some bedding planes. Above this 1.5 m thick sandstone is a thin weathered bentonite approximetely 5 cm thick.
Interpretation. Floodplain interfluves with mires, near-channel crevasse splays and channel sands. The channel influence wanes upsection and there is a return to predominanlty interfluve depositional environments.
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