The Jurassic of East Greenland: a sedimentary record of thermal subsidence, onset and culmination of rifting

Abstract

The Late Palaeozoic -Mesozoic extensional basin complex of East Greenland contains a record of deposition during a period of Rhaetian -Early Bajocian thermal subsidence, the onset of rifting in the Late Bajocian, its growth during the Bathonian-Kimmeridgian, culmination of rifting in the Volgian -Early Ryazanian, and waning in the Late Ryazanian -Hauterivian. The area was centred over a palaeolatitude of about 45°N in the Rhaetian and drifted northwards to about 50°N in the Hauterivian. A major climate change from arid to humid subtropical conditions took place at the Norian-Rhaetian transition. Deposition was in addition governed by a long-term sea-level rise with highstands in the Toarcian-Aalenian, latest Callovian and Kimmeridgian, and lowstands in the latest Bajocian -earliest Bathonian, Middle Oxfordian and Volgian.The Rhaetian -Lower Bajocian succession is considered the upper part of a megasequence, termed J1, with its base in the upper Lower Triassic, whereas the Upper Bajocian -Hauterivian succession forms a complete, syn-rift megasequence, termed J2. The southern part of the basin complex in Jameson Land contains a relatively complete Rhaetian-Ryazanian succession and underwent only minor tilting during Middle Jurassic -earliest Cretaceous rifting. Rhaetian -Lower Jurassic deposits are absent north of Jameson Land and this region was fragmented into strongly tilted fault blocks during the protracted rift event. The syn-rift successions of the two areas accordingly show different long-term trends in sedimentary facies. In the southern area, the J2 syn-rift megasequence forms a symmetrical regressive-transgressive-regressive cycle, whereas the J2 megasequence in the northern area shows an asymmetrical, stepwise deepening trend.A total of eight tectonostratigraphic sequences are recognised in the Rhaetian-Hauterivian interval. They reflect major changes in basin configuration, drainage systems, sediment transport and distribution patterns, and in facies and depositional environments. The sequences are bounded by regional unconformities or flooding surfaces and have average durations in the order of 10 Ma. They are subdivided into conventional unconformity-bounded depositional sequences with durations ranging from tens of thousands of years, in the Milankovitch frequency band, up to several million years. Deposition was alluvial and lacustrine in the Rhaetian-Sinemurian, but almost exclusively marine during the Pliensbachian-Hauterivian time interval when a marine strait, up to 500 km wide and more than 2000 km long, developed between Greenland and Norway, connecting the Arctic Sea and the North Sea. Coal-bearing fluvial and paralic deposits occur, however, at the base of the onlapping Middle Jurassic succession in the central and northern part of the basin complex. The sedimentary development is similar to that in the Northern North Sea and on the Norwegian shelf, and East Greenland offers important onshore analogues for virtually all of the types of deeply buried Jurassic depositional systems of these ar...

Seismic Interpretation of Sill-Complexes in Sedimentary Basins: The ‘Sub-Sill Imaging Problem’

“…2) in East 164Greenland(Eide et al, 2017). The host-rock was deposited in the Early-Middle Jurassic 165 during a post-rift thermal sag phase(Surlyk, 2003), and comprises a variety of shallow-marine 166 tide-influenced deposits, deposited close to the basin margin(Dam and Surlyk, 1998; Ahokas 167 et al, 2014; Eide et al, 2016). The Jameson Land Basin was a minor sub-basin in the 168 Mesozoic seaway between Norway and Greenland, and the sedimentary host rocks are 169 time-and facies equivalent to the Båt Group, which is a prolific reservoir interval on the 170 conjugate Haltenbanken area on the Norwegian Continental Shelf (Martinius et al, 2001; 171 Ichaso and Dalrymple, 2014; van Capelle et al, 2017).…”

Descriptive text to Geological map of Greenland, 1:500 000, Dove Bugt, Sheet 10

“…Cretaceous (Hauterivian). This rifting was associated with northward transgression across crystalline basement terrain that brought parts of the present-day Kuhn Ø, Hochstetter Forland, Shannon and Store Koldewey in the Dove Bugt map area within the depositional basin (Surlyk 2003). Sedimentary rocks of Jurassic-Cretaceous age are preserved in a 40 km long N-S-trending zone on the east side of the island Store Koldewey, and in three small fault-bounded occurrences on the east side of Koefoed-Hansen Brae in the western part of Nordmarken (Stemmerik & Piasecki 1990;Piasecki et al 1994).…”

“…The Mesozoic sedimentary rocks of eastern Store Koldewey (Stemmerik & Piasecki 1990) [CB]. Note that recent lithostratigraphic revisions (Surlyk 2003) have upgraded the 'Vardekløft Formation' to the Vardekløft Group, and that the Bernbjerg Formation now becomes part of the Hall Bredning Group. These changes reflect the interpretation of the Jurassic -Early Cretaceous succession as part of a syn-rift megasequence.…”

The Jurassic of Denmark and Greenland: key elements in the reconstruction of the North Atlantic Jurassic rift system

“…In East Greenland, the Rhaetian -Early Bajocian time interval was characterised by regional subsidence following rift events in the Late Permian and Early Triassic (Surlyk 1990(Surlyk , 2003. The depositional basin was centred over Jameson Land and stratigraphic units have a more or less basinwide extent and sheet-like geometry, reflecting the relatively uniform subsidence and the absence of major faulting (Dam & Surlyk 1995.…”

“…The seven North Sea tectonostratigraphic sequences of Rattey & Hayward (1993) are equivalent to six sequences for the correlative interval in East Greenland (Surlyk & Noe-Nygaard 2000;Surlyk 2003, this volume). The main difference between the two regions seems to be the delayed onset and culmination of rifting in East Greenland compared to the North Sea and the apparent lack of a tectonostratigraphic sequence boundary roughly at the Oxfordian-Kimmeridgian boundary in East Greenland.…”