Collection 60ACr130, composed of several very small horn corals, probably represents the Siksikpuk formation. Both genera identified by Helen Duncan are reported elsewhere from the Siksikpuk and Tachylasma is not known from pre-Permian rocks.

Of the remaining 5 collections, one contains essentially coralline and bryozoan material (60ACr78) like that found low in the Alapah and its equivalents. This would suggest a correlation with the lower part of unit Ml₃.

The other collections contain elements of what appears to be a single fossil assemblage, composed predominantly of brachiopods, with abundant Leiorhynchus. This is a facies fauna that occurs in the "Culm" lithology nearly everywhere it is present. In relation to the measured section, these fossils could represent either the lower part of Ml₃ or Ml₁. It is quite possible that a shaly facies represents the entire Ml₁ - lower Ml₃ interval in other parts of the Lisburne peninsula.

On the other hand, because there are apparently Devonian and Permian rocks in the same general area, structural complications may have made the identification and distinction among shaly units very difficult.

Collection part of scattered localities, statigraphic position determined by field-mapping correlations (from faunal list given on Table 2, pp. 8-9 in Campbell, 1967)

Fossil locality shown on Plate 1 )

Four formations of Mississippian age are shown on the geologic map (pl. 1). The lowermost is an unnamed poorly exposed mudstone-sandstone-limestone sequence, the oldest exposed within the map area. It overlain by the relatively pure limestone and dolomite beds of the Lisburne Group. .... The undivided sequence of mudstone, sandstone, and limestone of Early and Late Mississippian age crops out in the wester part of the mapped area. (from Campbell, 1967, p. 5).

The collections of marine fossils have been identified by J.T. Dutro, Jr., and Helen M. Duncan, of the Geological Survey, who report (written commun., 1961) that the fauna in the collections from near Cape Thompson is Early Mississippian in age. About 12 miles to the north, however, in the upper reaches of Nalakachack Creek, fossil collections from the mudstone-sandstone-limestone sequence (60ACr-129, 60ACr-132, and 60ACr-132A of table 2) are reported to be lower Upper Mississippian (Helen M. Duncan, written commun., 1963; J.T. Dutro, Jr., written commun., 1965). This suggests that teh contact between this predominantly terrigenous clastic unit and the relatively pure limestone of the Lisburne Group may transgress with time, becoming progressively younger from south to north. ..... The collections from the Nalakachak area were first thought to be faunally equivalent to part or all of the Lower Mississippian part (basal 500 ft) of the Nasorak Formation (Dutro and Duncan, written commun., 1962) and earlier papers (Campbell, 1965a, Campbell, 1966) reported the unit to be Early Mississippian. The collections have subsequently been reported as most likely lower Upper Mississippian (Helen M. Duncan, written commun., 1965; J.T. Dutro, Jr., written commun., 1965) so that the map unit must now be regarded as of Early and Late Mississippian age (from Campbell, 1967, p. 6).