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Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
1 British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 OET, UK
2 Scott Polar Research Institute, University of Cambridge, Lensfield Road, Cambridge CB2 1ER, UK
The late Precambrian succession of the fjord region of East Greenland is characterized by two glacigenic formations. The lower one, the Ulvesø Formation, rests on different members of the Limestone-Dolomite ‘series’ (Eleonore Bay Group), and comprises diamictite, conglomerate, sandstone, and rhythmite, all with a high dolomite content. Few beds can be traced for more than a few hundred metres, and erosional breaks are sometimes present. Clasts are predominantly intrabasinal. A turbiditic dolomitic sandstone-mudstone succession, the Arena Formation, lies above. The upper glacigenic horizon, the Storeelv Formation, contains a similar range of facies as the Ulvesø Formation, but is less dolomitic and contains exotic gneiss, granite and volcanic clasts, as well as intrabasinal carbonates.
The Ulvesø and Storeelv formations contain facies characteristic of a low-level terrestrial to marine glacial environment, including: basal tillite, waterlain tillite, debris-flow deposits, ice proximal to distal glacimarine sediments, glaciolacustrine and glacimarine rhythmites with ice-rafted material, permafrost features, aeolian sands and evaporites.
The bulk of the glacigenic sediment appears to have been associated with an ice sheet of continental proportions, which in terms of its thermal regime was probably below the pressure melting point but sliding on its bed. Our interpretation of large parts of the succession as waterlain till implies that floating, debris-bearing ice was an important part of the system, probably in the form of outlet glaciers or ice streams, coalescing as an ice shelf in a tectonically controlled marine basin beyond an irregular coastline. Considerable current activity, both beneath the ice shelf, and sedimentation controlled by iceberg drifting in distinct lanes existed. The succession further illustrates the response of glacimarine sedimentation to ice-retreat onto land, with marked changes from facies with obvious glacial affinities to those devoid of them.
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