Glacial erratics on the Arctic Ocean margin of North Greenland: implications for an extensive ice-shelf

Abstract

Glacial erratics of high-grade metamorphic and plutonic rocks occur on the northern coast of Peary Land on the edge of the Arctic Ocean. Crystalline terrain is not exposed in Peary Land; sample sites are 250 km distant from the present-day Inland Ice which covers the nearest potential source - the Greenland shield. The dominant till clasts are locally derived from a northern ice-cap that coalesced during the late Wiscon- sinian glacial maximum with the Inland Ice at about 82°30'N. Recent Quaternary mapping by the Geological Survey of Greenland failed to locate crystalline erratics in northernmost Peary Land; consequently prominence is given to early observations. The present paper describes a collection of erratics made in 1969. Conveyance mechanisms, viz. ice-cap regime (glacier or ice-shelf) contra drifting ice (icebergs or sea ice) are discussed and possible transportation paths are sum­marised. Based on rock type and mineralogy, the Greenland shield is the most likely source of the erratics and derivation from an expansion of the Inland Ice around eastern Peary Land the most logical glacial model. However, such a provenance contravenes with the presently available on-shore data which indicate an eastwards Weichselian ice flow along the coast. Instead of invoking a rather complicated glacial history for Peary Land, involving different land ice regimes, an alternative glacial model based on an extensive Greenland - Ellesmere Island ice-shelf is outlined.