Abstract Northern Greenland underwent within-plate deformations in Tertiary time in response to a rather complex and incompletely understood displacement history associated with the opening of Labrador Sea – Baffin Bay, the Arctic Ocean basins, and the North Atlantic. Because post-Ellesmerian cover sequences are not widely preserved in the region, it is frequently difficult to differentiate these “Eurekan” structures from earlier deformations, or to establish their precise age. Nonetheless, three sets of structures and two geotectonically important magmatic events of Cretaceous-Paleogene age have been recognized Fig. 16.1. Since these have been subject to speculative and often conflicting geotectonic interpretations, in this account we concentrate on the available factual information, following the review by Soper et al. (1982) and references therein, plus new information derived from 1984 fieldwork. We allude briefly to geotectonic implications, referring the reader to the Nares Strait symposium volume (Dawes and Kerr, 1982) for fuller discussion. A dense swarm of approximately north-south trending (coast-normal) dolerite dykes occurs along the north coast of Greenland between about 38°W and 48°W (Nansen Land, westernmost Johannes V. Jensen Land and the intervening islands). Scattered examples are also present throughout Johannes V. Jensen Land. The swarm is most dense at sea level, approaching 50 per cent of the rock in places, with individual dykes up to 25 m in width and occasionally much larger. Dyke density diminishes both upward and to the south, the swarm being confined to the region north of the Harder Fjord fault zone (see below). The dykes cut lower Paleozoic

Abstract As outlined above (Chapters 7, 8), the sedimentary subprovince of the Franklinian deep water basin (Hazen Trough) extends eastward from the Canadian Arctic Islands (Chapter 8C) into northern Greenland (Chapter 7), and the pulses of deformation which affected the Canadian sector (Hazen Fold Belt) in Late Silurian or Devonian to Early Carboniferous time (Chapter 12) likewise extended into Greenland producing an east-west striking mobile zone, known traditionally as the North Greenland fold belt. The fold belt has an exposed width of up to 100 km on the north coast of Greenland and is flanked to the south by the weakly deformed lower Paleozoic platform sequence described in Chapter 7. Figure 11.1 shows that several distinct tectonic zones can be recognized in the fold belt, and Figure 11.2 illustrates how these are spatially related to the geometry of the deep water basin (Hazen Trough). A southern fold and thrust zone coincides with a region which was transitional between the platform and trough for much of the Cambrian and Ordovician. It is bounded to the south by the Navarana Fjord lineament, which represents the position to which the platform margin had retreated by Early Silurian time. The structure of the southern zone is of thin skinned fold and thrust type, with an approximately east-west strike and southerly vergence. A northern orthotectonic zone is developed on the site of the trough proper with its thick fill of dominantly Lower Cambrian turbidites. It forms the mountainous regions of Johannes V. Jensen Land, Nansen Land,

Abstract The volcanic succession in the inland Prinsen af Wales Bjerge contains the oldest known onshore lava flows (61 Ma) of the Palaeogene East Greenland flood basalt province. These flows and interbedded sediments define the Urbjerget Formation and are found in the southernmost part of Prinsen af Wales Bjerge. Flows of the Urbjerget Formation are chemically similar to the coastal Vandfaldsdalen Formation flows and the two formations may be chronostratigraphical equivalents. The Urbjerget Formation is overlain by the < 57 Ma tholeiitic basalts of the Milne Land Formation. Four regional volcanic formations are found along the Blosseville Kyst, but the Milne Land Formation is the only one present in the southern Prinsen af Wales Bjerge. Flows of the absent formations (Geikie Plateau, Rømer Fjord and Skrænterne formations) may not have been able to enter the area due to local uplift, more distal located eruption sites or possibly topographic features. A high-Si (SiO 2 > 52 wt%) lave flow succession in the Milne Land Formation consists of crustally contaminated magmas which were arrested in crustal chambers as the magma supply rate from the mantle decreased, either due to a general lowering of potential mantle temperatures or a decrease in the rate of continental rifting. Tholeiitic high-Ti flows (MgO: 10–15 wt%, TiO 2 : 5–6 wt%) within the Milne Land Formation are unique to the Prinsen af Wales Bjerge region, and equivalents have not been reported from other flood basalt provinces. Local flow composition variations in the Milne Land Formation can be explained as the result of melting under lithosphere of variable thickness, small-scale variations in mantle composition and mixing in small magma chambers. Unconformably overlying the Milne Land Formation is a succession of c. 53 Ma alkaline flows, known as the Prinsen af Wales Bjerge Formation. Several crater sites are known from this flow succession and this suggests that the Prinsen af Wales Formation was only covered locally by later volcanic or sedimentary units. The duration of alkaline volcanic activity in the Prinsen af Wales Bjerge is not well constrained but may have been less than 2.5 Ma. The hiatus between the Urbjerget and Milne Land formations is a regional feature in the North Atlantic as it occurs at a similar stratigraphic level at Nansen Fjord, the Faroe Islands and in the ODP Leg 152 volcanic succession off SE Greenland at c. 63°N. It represents a 3–4 Ma long cessation of, or very low frequency of activity in East Greenland/Faroese volcanism and may be explained as the time interval between two pulses in the palaeo-Icelandic plume.