Abstract
The Caledonian structures in the late Proterozoic Eleonore Bay Supergroup of the Ardencaple Fjord area were controlled by the position and shape of the contacts with older basement rocks. Those contacts that are not late faults are likely to have been extensional shear zones of Vendian age which were reactivated in compression during the Caledonian orogeny. This interpretation may aIso be applied to the other large tracts of low grade Eleonore Bay Supergroup sediments in East Greenland, and explains their preservation at the present erosion level, surrounded by Precambrian basement rocks.
Highlights
The Caledonian structures in the late Prolerozoic Eleonore Bay Supergroup of the Ardencaple Fjord area were conlrolled by the position and shape of the contacts with older basemenl rocks
The Eleonore Bay Supergroup (EBG) is one of the major clastic sequences of Late Proterozoic age that are prcserved within the North Atlantic Caledonides
Il is exposed in Easl Greenland belween latitudes 72° and 76°N in a number of tracts that arc surrounded by earlier Proterozoic and Archaean schists and gneisses (Fig. I); the outcrops around Ardencaple tJord (Fig. 2) make up the northernmost of these tracts
Summary
The most northerly occurrence of Eleonore Bay Supergroup rocks in East Greenland occupies a 75 by 40 km area centred on Ardeneaple Fjord and its two inner branches, Smallefjord and Bredet]ord (Fig. 2); northwards the main tract reaches almost to Bessel Fjord while detached outcrops are present in the southem part af Hochstetter Forland and in a fault-bounded strip in northem Kuhn ø (Fig. l). The Ardeneaple Fjord tract of EBG rocks was discovered during sledge trips and reconnaissance flights in the 1930s, but the only detailed fieldwork prior to 1988 was one month, undertaken by Max Sommer in 1955 and supplemented by reconnaissance flights with Norseman aircraft (Sommer, 1957) He was able to establish correlation with the EBG of the central fjord zone and define the principal folds and faults. At least 2 km of the Nathorst Land Group ('lower EBG') is present, forrning the high mountainous terrain north of Bredet]ord (Fig. 2). It consists of altemating units of quartz arenite, interbedded sandstone and mudstone, and black silty mudstone. Other major structures in the EBG tract (Fig. 2) include a syncline along Ejnar Mikkelsen Gletscher and Knæksø
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