Locality 96-25. 69° 19' 53"N 162° 33' 29" W
Corwin Formation
Specimens: 96 RAS 120, 120, 121, 122, 122b, 122c, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 132b, 133, 134
Description. Large bluffs on north side of Kukpowruk River. The basal exposed succession consists of poorly indurated gray silts and mudstones with abundant ironstone nodules containing Equisetites, Podozamites, branch and trunk wood. Ginkgo occurs in the coarser units, together with rare Birisia and Pityophyllum. This capped by a coal which thickens downstream to more than 1.5 m. Overlying this, with an erosional contact, is a fine to coarse cross-bedded gray to yellow sand containing some pebble conglomerates and wood fragments, plant debris and charcoal. At least three lenticular sand bodies make up a package that is estimated at about 25 - 30 m thick. Brown silty mudstones up to approximately 1 m thick separate the sand bodies. No shelly fauna was seen but there are rare burrows in the siltstone.
All specimens (96 RAS 120 - 134) come from ironstones originating in a gray silty mudstone underlying the coal. The thickness of this mudstone unit is more than 30 m.
Interpretation. This succession represents both interfluve and near-channel environments. The interfluves with extensive long-lived woody mires were subsequently inundated and eroded by large river channels of the upper delta floodplain. The fluvial sandstones of locality 96-25 are probably the same as those at locality 96-23 where they have been downfaulted against the underlying mudstones.
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