Triassic rift sedimentation and palaeogeography of central East Greenland

Abstract

The majority of the investigated Triassic (upper(?) Scythian – Rhaetian) rocks apparently formed in continental environments comprising alluvial fans, braided rivers, aeolian deserts, flood plains, saline playa lakes and freshwater shallow lakes. In the Middle Triassic a brief but widespread marine transgression affected large parts of the basin and resulted in the deposition of barrier limestones and lagoonal mudstones. Details of sedimentary structures, bed types, facies sequences and vertical and lateral variations are discussed for each of these environments. Special emphasis is given to the remarkable variety of lacustrine facies associations. The Triassic sediments probably accumulated in a N-S trending rift valley. This fault controlled depositional basin apparently formed in connection with overall rifting of the 'Laurasian' megacontinent. Tectonic movements along N-S trending fault lines appear to have been an important control on the thickness and nature of the Triassic facies, and the basal alluvial fan sediments formed simultaneously with or slightly after tectonic uplift of the borderlands. The climate throughout the Middle-Late Triassic period was warm and subtropical with alternating dry and wet seasons. The basin was under the influence of dominant north-east trade winds (winter) and less common south-east trade winds (summer). The vertical succession of climate-sensitive rocks further suggests a gradual shift towards increased humidity during the Middle-Late Triassic times. This climate trend is explained by a northwards continental drift of the area.

Episodic burial and exhumation in North-East Greenland before and after opening of the North-East Atlantic

“…The development of the East Greenland margin was also characterised by episodic processes prior to break-up as it is well documented in numerous studies of the post-Caledonian geology (Surlyk 1978a(Surlyk , 2003Clemmensen 1980;Stemmerik 2000;Larsen et al 2008a). In particular, three phases of uplift and denudation that affected North-East Greenland and Scandinavia in the late Carboniferous, Middle Triassic and Early-Middle Jurassic, appear to be part of widespread epeirogenic uplifts that accompanied fragmentation of Pangaea (Section 9.1).…”

“…The uplift and erosion at this time led to the deposition of coarse-grained siliciclastic sediments across the region: the Pingo Dal Group on Jameson Land (Fig. 18; Clemmensen 1980;Oftedal et al 2005), the Middle-Upper Triassic Skagerrak Formation (or Hegre Formation) around southern Scandinavia (Bertelsen 1980;Goldsmith et al 2003) and the Triassic Sherwood Sandstone across the British Isles. In a review of published Triassic stratigraphic nomenclatures for North-West Europe, Goldsmith et al (2003) noted that the precise chronostratigraphic equivalence of these units is uncertain.…”

“…Creek Group above a pronounced unconformity, for example in northern Jameson Land (Clemmensen et al 2020). The deposition of the Pingo Dal Group was the result of a major phase of basin-margin uplift and rapid fault-controlled basin subsidence in Early Triassic time (late Scythian) leading to the formation of a northsouth-trending intermontane graben, about 300 km long and 75 km wide (Clemmensen 1980;Surlyk 1990).…”

“…18). These units overly the marine mudstones of the Wordie Creek Group on northern Jameson Land (Clemmensen 1980;Bjerager et al 2006). Extensive C1 cooling in the basement areas west of these basins (C1 in Fig.…”

The Permian to Cretaceous succession at Permpasset, Wollaston Forland: the northernmost Permian and Triassic in North–East Greenland

“…The Permian and Triassic have received much attention where spectacularly exposed in Jameson Land, Scoresby Land, Traill Ø, Geographical Society Ø, Hold with Hope and Clavering Ø (Clemmensen 1980a(Clemmensen , 1980bSurlyk et al 1986;Christiansen et al 1993;Stemmerik 2001;Andrews et al 2019, www.geusbulletin.org 2020a, 2020bClemmensen et al 2020). However, those sections lying further north on Wollaston Forland have seen little, if any, concerted study (Fig.…”