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Facies Model for an Ancient Tide-Dominated Delta: The Early Jurassic Gule Horn Formation, Jameson Land, Eastern Greenland


Tide-dominated deltas are inherently complex with heterogeneities on several different scales. Depositional models of such environments are based on a relatively small set of ancient examples and they are less well understood than their wave- and river-dominated counterparts and facies models for such systems are immature. Despite the relatively poor understanding, tidal delta deposits act as significant reservoirs in a number of systems. These reservoirs are typically complex and challenging. Outcrop analogs of such systems are typically rare. The tide-dominated, Early Jurassic Gule Horn Formation of the Neill Klinter Group is exposed in extensive sea-cliffs in Jameson Land, East Greenland. A 30 km long, 250 m thick virtual outcrop model of these cliffs have been acquired using oblique helicopter-mounted lidar data. The virtual outcrop dataset, combined with a set of sedimentological logs, allows for accurate interpretation and measurement of depositional elements and stratigraphic surfaces over significant distances. The tide-dominated, Early Jurassic Gule Horn Formation was deposited in a structurally controlled embayment. Immature sediments indicate that it was deposited close to the sediment source. The succession is tide dominated but contains evidence for subordinate wave and fluvial processes. The distal part of the outcrop is dominated by prodelta, delta front and mouthbar deposits, while the more proximal parts of the outcrop is dominated by tidal channel and tidal flat deposits. The medial parts of the outcrop is characterized by relatively narrow 80 m to more than 1.5 km wide, amalgamated channels filled with upward-sanding deposits interpreted as tidal bars. The proximal tidal channels are filled by either laterally migrating tidal bars or forward migrating compound dunes. The sandbodies of the proximal tidal channels are wider than the expsures in all cases, and are several kilometers wide. The channels show little lateral change in thickness. The Gule Horn Formation is composed of three parasequence sets, the two lowermost are progradational while the uppermost is retrogradational. Parasequence boundaries are relatively straightforward to define in the prodelta to delta front environments, but are difficult to trace into the more proximal delta top deposits.