Palaeovalleys at the basal unconformity of the Palaeoproterozoic Karrat Group, West Greenland

In the Rinkian belt of West Greenland, reworked Archaean gneisses are overlain by supracrustal successions of the Palaeoproterozoic Karrat Group, defined by Henderson & Pulvertaft (1967) as comprising two formations: the Qeqertarssuaq Formation and the Nûkavsak Formation. The group was later extended to include the Mârmorilik Formation (Henderson & Pulvertaft 1987) originally considered to be of Archaean age (Henderson & Pulvertaft 1967) but later shown to be Palaeoproterozoic, resting with a depositional unconformity on Archaean gneiss (Garde 1978). Henderson & Pulvertaft (1987) suggested that the carbonatedominated Mârmorilik Formation in the south was laterally equivalent to the siliciclastic-dominated Qeqertarssuaq Formation in the north, the two subbasins being separated by a basement topographic high.