The samples that showed evidence of silicification were etched in hydrochloric acid. The etching was continued long enough to reveal what silicified fossils were present, but not enough to destroy the samples. Several samples showed no evidence of silicification, and no indication of presence of macrofossils. Three samples contained identifiable material that suggests a Permian age. These have been assigned P&S Branch numbers, and are being retained for future reference. The others are being returned as requested.

***
Brief statement of problem and remarks (from collector):
Information needed to decipher post-Mankomen stratigraphy in eastern Alaska Range. In area shown on sketch map 3 distinct and continuous lithologic units overlie the Mankomen Formation south of the great Denali Fault. These are, in order of decreasing age: 5000-7000 feet of dark amygdaloidal basalt, 0-500 feet of massive reef-like limestone, and 7000-9000 feet of argillite, sandstone, conglomerate, and minor limestone. In Moffit's early reconnaissance mapping (1954) all of these units, together with schistose varieties north of the Denali Fault, were lumped in an undifferentiated Paleozoic unit. Geologic work to date has differentiated the 3 units, but we have no data as to the age of the rocks. The amygdaloidal basalt is similar in appearance to the Nikolai Greenstone. All fossils [corals and brachiopods] listed above have been collected from the limestone which overlies and inpart is intra-formational with the amygadaloidal basalt.