Deep-sea fan valleys, channels, lobes and fringes of the Silurian Peary Land Group, North Greenland

Abstract

The Silurian Peary Land Group in North Greenland is possibly one of the largest known ancient deep-sea fan turbidite complexes (terminology after Mutti and Normark 1987). Fan deposition was initiated very rapidly in the Early Silurian (Late Llandovery) after onset of fine-grained turbidite deposition in proximal areas close to the Ordovician-Silurian boundary. The Peary Land fan complex extended throughout the Franklinian Basin from eastern North Greenland far westward into the Canadian Arctic Islands. The provenance area was the rising Caledonian mountain belt in north-east Greenland and the main source of the huge thickness of quartzose turbidites was undoubtedly the thick successions of Proterozoic sandstones exposed in central and eastern North Greenland and their correlatives. The fan system was elongate, parallel to the margin of the east-west trending Franklinian carbonate platform and was of the order of 2000 km long, including the down-current extension in Canada, and more than 200 km wide. The maximum preserved thickness is c. 5 km and the total fan volume is estimated at more than 2 × 106km3. The Peary Land fan occupies a similar plate tectonic setting to that of the largest modern fan, the Bengal Fan, being sourced from a rising orogen and building out along a passive margin perpendicular to the mountain belt. The nature of the crust beneath the Peary Land fan is assumed to be thinned continental crust transitional to oceanic crust along the passive margin of the Franklinian Basin. Excellent exposures in deeply incised steeply walled fjords and valleys show large-scale structures representing original fan topography. Canyons, wide inner-fan valleys, smaller mid-fan channels, outer-fan lobes and the basin plain are clearly recognized, making it possible to bridge the scale and terminology problem between modern and ancient fans. It is extremely sand-rich and bottom-hugging contour currents possibly played a role in transporting very fine-grained sediment further westward outside the fan area.