Collection 128 from the nonmarine portion of this unit contains only a crush carbonized plant fragment which is indeterminate.

Collection 59ACu30f, not from the measured section, ressembles 116f and likely represents about that level in the formation.

Coarse clastic rocks and nonmarine facies appear higher in the sequence in the Cape Thompson area than in the Brooks Range to the east. In the central Brooks Range, the nonmarine facies is probably all of late Devonian age while near Cape Thompson it may well include Kinderhook equivalents as well.

This clastic phase has been assigned to the Noatak sandstone (restricted) and the Utukok formation in the western DeLong Mountains. The boundary between these two units is at the breakover to marine deposition. I would say this some 300 to 400 hundred feet below the base of Ml₁ in the measured section. In a section that I measured in 1951, near or possibly at the same place as your measured section, I found plant fragments in carbonaceous sandstone beds up to about 800 ft. below the base of Ml₁. Nearly 500 ft. of shale with ironstone nodules separate the plant-bearing beds from the lowest marine fossils.

I would suggest that the lower 1500 feet of so of the sandstone-shale unit is a Noatak sandstone equivalent and that the upper 300 or so feet, plus unit Ml₁ is a Utukok formation equivalent.

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).