TY - JOUR

T1 - Upper Jurassic – Lower Cretaceous of eastern Wollaston Forland, North-East Greenland

T2 - a distal marine record of an evolving rift

AU - Hovikoski, Jussi

AU - Ineson, Jon R.

AU - Olivarius, Mette

AU - Bojesen-Koefoed, Jørgen A.

AU - Piasecki, Stefan

AU - Alsen, Peter

N1 - Publisher Copyright: © 2023, GEUS - Geological Survey of Denmark and Greenland. All rights reserved.

PY - 2023

Y1 - 2023

N2 - Two drill cores spanning the Upper Jurassic – Lower Cretaceous succession in Wollaston Forland, North-East Greenland, offer an insight into mud accumulation in an evolving distal fault block. Previous studies have revealed the presence of long-lasting black mudstone accumulation extending through the oxygen-restricted early rift and rift climax phases (Bernbjerg and Lindemans Bugt Formations). Here, we present a detailed description of the sedimentary succession extending into the late syn-rift settings (Palnatokes Bjerg and Stratumbjerg Formations). The results indicate that the Kimmeridgian – lower Volgian early rift-phase was characterised by suspension settling and millimetre-scale event deposition in a tectonically affected, prodeltaic offshore setting. The event-related depositional processes are recorded by starved wave ripples, scour-and-fill structures, putative mud-floccule ripples and mud-dominated gravity-flow deposits. During the middle Volgian – Ryazanian rift climax, the depositional environment evolved into a narrow half-graben that was detached from the proximal depocentre flanking the deltaic coastline, itself dominated by coarse sediment. The correlative sedimentary facies in the detached half-graben are bioclastic and pyrite-rich black mudstones, which document suspension settling and gravity-flow or mass-wasting deposition in sub-storm wave-base slope and basin-floor environments. Black mudstone sedimentation ended abruptly in the late Ryazanian when the accumulation of condensed, bioturbated deep marine marls coincided with broader oceanographic reorganisation concomitant with waning rift activity in the west. Deposition of red bioclastic mudstones with a common gravity-flow component characterised the Hauterivian, potentially representing final draping of the submerged fault block crest. The top of the cored succession is demarcated by dark grey bioturbated mudstones of Barremian age, reflecting the onset of regionally continuous deep marine mud accumulation in thermally subsiding basins. Although superficially monotonous, the mudstone-dominated succession reveals a highly dynamic depositional system that reflects changing sediment transport processes during almost a full rift cycle.

AB - Two drill cores spanning the Upper Jurassic – Lower Cretaceous succession in Wollaston Forland, North-East Greenland, offer an insight into mud accumulation in an evolving distal fault block. Previous studies have revealed the presence of long-lasting black mudstone accumulation extending through the oxygen-restricted early rift and rift climax phases (Bernbjerg and Lindemans Bugt Formations). Here, we present a detailed description of the sedimentary succession extending into the late syn-rift settings (Palnatokes Bjerg and Stratumbjerg Formations). The results indicate that the Kimmeridgian – lower Volgian early rift-phase was characterised by suspension settling and millimetre-scale event deposition in a tectonically affected, prodeltaic offshore setting. The event-related depositional processes are recorded by starved wave ripples, scour-and-fill structures, putative mud-floccule ripples and mud-dominated gravity-flow deposits. During the middle Volgian – Ryazanian rift climax, the depositional environment evolved into a narrow half-graben that was detached from the proximal depocentre flanking the deltaic coastline, itself dominated by coarse sediment. The correlative sedimentary facies in the detached half-graben are bioclastic and pyrite-rich black mudstones, which document suspension settling and gravity-flow or mass-wasting deposition in sub-storm wave-base slope and basin-floor environments. Black mudstone sedimentation ended abruptly in the late Ryazanian when the accumulation of condensed, bioturbated deep marine marls coincided with broader oceanographic reorganisation concomitant with waning rift activity in the west. Deposition of red bioclastic mudstones with a common gravity-flow component characterised the Hauterivian, potentially representing final draping of the submerged fault block crest. The top of the cored succession is demarcated by dark grey bioturbated mudstones of Barremian age, reflecting the onset of regionally continuous deep marine mud accumulation in thermally subsiding basins. Although superficially monotonous, the mudstone-dominated succession reveals a highly dynamic depositional system that reflects changing sediment transport processes during almost a full rift cycle.

KW - Bernbjerg Formation

KW - Early Cretaceous

KW - Greenland

KW - Late Jurassic

KW - Lindemans Bugt Formation

KW - mudstone

KW - Palnatokes Bjerg Formation

KW - Stratumbjerg Formation

U2 - 10.34194/geusb.v55.8349

DO - 10.34194/geusb.v55.8349

M3 - Journal article

AN - SCOPUS:85180718679

VL - 55

JO - GEUS Bulletin

JF - GEUS Bulletin

SN - 2597-2162

M1 - 8349

ER -