Abstract
Previous geological descriptions of the Adams Gletscher region (fig. 9) have been given by J. C. Troelsen (unpublished field notes in GGU) and Dawes (1976) - the latter based on a three day reconnaissance during 1975. The sequence contains a much fuller record of the Cambrian system than is present in the geologicaIly better described area near Jørgen Brønlund Fjord to the east (Christie & Peel, 1977; Jepsen, 1971), where only Lower Cambrian strata are present. A sample with trilobites collected by Dawes established the occurrence of Middle Cambrian rocks near Adams Gletscher (Peel in Dawes, 1976), but it would now appear that a substantial part of the sequence is of this age. In addition, the location in 1978 of early Late Cambrian trilobites near the base of a 900 m thick unit overlain by the Wandel Valley Formation of Early-Middle Ordovician age, suggests that the upper sub-division of the Cambrian is also well represented. An unconformity of regional extent separates the Cambrian from the overlying Wandel Valley Formation. This formation maintains the same generallithology at Adams Gletscher as that described by Christie & Peel (1977) to the east, although a tentative lithologicallink to the late Lower Ordovician of western North Greenland is established.
Highlights
An unconformity of regional extent separates the Cambrian from the overlying Wandel Valley Formation
Strata on both sides of Adams Gletscher generally dip at about 5-8° to the north, the Cambrian beneath the unconformity with overlying Wandel Valley Formation is shallowly flexured with dips locally reaching a maximum of 20° to the north
The Brønlund Fjord Group includes, but is not exactly equivalent to, strata previously referred to the Brønlund Fjord Formation (Troelsen, 1949; Christie & Peel, 1977) in its type area north of Jørgen Brønlund Fjord
Summary
The Portfjeld Formation (Jepsen, 1971) is the oldest rock unit exposed in the Adams Gletscher - J. About 180 m of strata are exposed (locality 5) and can be tentatively correlated with the type sequence at Portfjeld, to the east. Of notable interest is the change in character of Jepsen's bed 18, a 5 m thick orthoquartzite, which at Adams Gletscher consists of at least 20 m of dark, cross-bedded, coarse-grained, conglomeratic sandstone (see discussion by O'Connor, this report). It is relatively simple to recognise the equivalence between unit A (180 m) of Dawes (1976) and the Portfjeld Formation section of similar thickness measured in 1978 on the opposite side of Adams Gletscher. The rusty weathering, coarse-grained sandstone is common to both units, as is the underlying dolomite breccia
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