Facies model for a coarse‐grained, tide‐influenced delta: Gule Horn Formation (Early Jurassic), Jameson Land, Greenland

Abstract

Tide-dominated deltas have an inherently complex distribution of heterogeneities on several different scales and are less well-understood than their wave-dominated and river-dominated counterparts. Depositional models of these environments are based on a small set of ancient examples and are, therefore, immature. The Early Jurassic Gule Horn Formation is particularly well-exposed in extensive sea cliffs from which a 32 km long, 250 m high virtual outcrop model has been acquired using helicopter-mounted light detection and ranging (LiDAR). This dataset, combined with a set of sedimentological logs, facilitates interpretation and measurement of depositional elements and tracing of stratigraphic surfaces over seismic-scale distances. The aim of this article is to use this dataset to increase the understanding of depositional elements and lithologies in proximal, unconfined, tide-dominated deltas from the delta plain to prodelta. Deposition occurred in a structurally controlled embayment, and immature sediments indicate proximity to the sediment source. The succession is tide dominated but contains evidence for strong fluvial influence and minor wave influence. Wave influence is more pronounced in transgressive intervals. Nine architectural elements have been identified, and their internal architecture and stratigraphical distribution has been investigated. The distal parts comprise prodelta, delta front and unconfined tidal bar deposits. The medial part is characterized by relatively narrow, amalgamated channel fills with fluid mud-rich bases and sandier deposits upward, interpreted as distributary channels filled by tidal bars deposited near the turbidity maximum. The proximal parts of the studied system are dominated by sandy distributary channel and heterolithic tidal-flat deposits. The sandbodies of the proximal tidal channels are several kilometres wide and wider than exposures in all cases. Parasequence boundaries are easily defined in the prodelta to delta-front environments, but are difficult to trace into the more proximal deposits. This article illustrates the proximal to distal organization of facies in unconfined tide-dominated deltas and shows how such environments react to relative sea-level rise.

Basin-scale architecture of deeply emplaced sill complexes: Jameson Land, East Greenland

“…5). Further sea-level rise led to gradual backstepping and later abandonment of the deltaic system in the study area, and deposition of the dark, mudstone-rich, offshore deposits of the Albuen Member Eide et al 2016). A rapid forced progradation of the shallow-marine system Ziegler (1988) and Doré (1992).…”

“…The outcrop is oriented obliquely along-strike of this delta system, and the southern part is further away from an inferred sediment input point located to the west of Harris Fjeld (Fig. 1), leading to gradually more distal and mudstone-rich deposits in the south part of the study area Eide et al 2016;Fig. 5).…”

“…The tide-dominated delta of the Elis Bjerg Member (Ahokas et al 2014a;Eide et al 2016) mainly consists of sandy heteroliths (Fig. 5), which are brittle, well-cemented, dominantly sandy deposits comprising interbedded sandstone and mudstone, with sandstone beds generally ranging from 1 to 60 cm thick, and mudstone beds and laminae ranging from 0.1 to 10 cm thick (Fig.…”

“…4). Relative sea-level rise in the latest Pliensbachian led to marine flooding of the basin and deposition of the Neill Klinter Group in a mainly tide-influenced, shallow-marine, structurally controlled embayment Eide et al 2016;Fig. 1a).…”

“…Larsen & Marcussen 1992;Mathiesen et al 2000;Hansen et al 2001). The section is at a scale comparable with that for typical offshore seismic data, but includes data from extensive outcrop work including six logs, and at the decimetre scale in the virtual outcrop model (Eide et al 2016). The combination of detailed logs and the high-resolution lidar model facilitates recognition of magma emplacement features that reveal the mode of emplacement, such as steps, bridges, fingers and peperites (Fig.…”