Polyphase deformation at the Harder Fjord Fault Zone (North Greenland)

Abstract

In North Greenland, the E–W-trending Harder Fjord Fault Zone represents a major lineament which cuts through Cambrian to Silurian deep-water sediments of the Franklinian Basin over a distance of 300 km. On both sides of the fault zone, these successions were affected by two stages of folding (F1, F2) during Devonian to Early Carboniferous (Ellesmerian) deformation. No field evidence was found that the Harder Fjord Fault Zone was active prior to Ellesmerian folding. Early movements along the fault zone are indicated by post-Ellesmerian sedimentation of coarse red-beds (Depot Bugt conglomerate) which represent the oldest of the Wandel Sea Basin sediments. They were probably deposited in narrow, fault-controlled (?)Late Carboniferous basins similar to those described from Svalbard. During Late Cretaceous times, 500 m thick fluvial and marine clastic sediments were unconformably deposited over the folded Cambro-Ordovician units. Although no direct field evidence suggests that sedimentation was controlled by displacements along the Harder Fjord Fault Zone, the intrusion of Upper Cretaceous mafic sills and dykes indicates a phase of important crustal extension related to reactivation of the fault zone during this period of time. This stage was followed by post-late Santonian (Eurekan) N–S compression (D3) which affected the Franklinian Basin deposits, Wandel Sea Basin sediments and mafic intrusions. In general, it was concentrated along the Harder Fjord Fault Zone and probably caused the reactivation of pre-existing (?)Carboniferous and younger fault lines. The entire deformation and its timing are comparable with the Eurekan structures found at the Kap Cannon Thrust Zone in northernmost Greenland and are related to intracontinental compression prior to the separation of Svalbard from Greenland.