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The
Aggradational to Retrogradational Stacking Pattern of the Hugin
Formation (Callovian - Early Oxfordian) Southern Viking Graben, North Sea*
By
Atle Folkestad1, Nicholas Satur1, Torben Olsen1, and Arnfinn Rømuld1
Search and Discovery Article #50002 (2003)
*Adapted from “extended abstract” for presentation at the AAPG Annual Meeting, Houston, Texas, March 10-13, 2002.
1Statoil, Norway (www.statoil.com)
The aggradational to retrogradational part (200 m thick) of the Hugin Formation has been studied in the Sleipner Field in the South Viking Graben, North Sea (Figure 1). The formation was deposited in the Middle Jurassic during the opening and finally drowning of the Viking Graben (Thomas and Coward, 1996)(Figure 2). The Hugin Formation consists of shallow marine sediments deposited during overall transgressive and aggradational conditions. Regionally, the Hugin Formation represents the termination of the southward retreat of the Brent system.
uGeneral setting uFigure captions uDepositional environments uApplication uReferences
uGeneral setting uFigure captions uDepositional environments uApplication uReferences
uGeneral setting uFigure captions uDepositional environments uApplication uReferences
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Click to view sequence of palaeogeographic maps.
Click to view sequence of Figures 3 and 4.
Depositional Environments and SequencesFrom 26 cored wells, 17 facies associations have been identified and grouped into 6 genetic depositional sub-environments: coastal plain fines, tidal channel fill and bars, tidal flat, prograding mouthbars, shoreface, and offshore mudstones. Interpretation of facies associations in uncored intervals was followed by a detailed well-to-well correlation based on both sedimentological and biostratigraphic evidence. The correlations reveal that the Hugin Formation consists of 8 transgressive/regressive sequences where the transgressive parts of sequences consists of tidal channel fills, tidal bars, tidal flats and coastal plain fines deposits whereas the regressive part consists of coastal plain fines in the form of palaeosols, with associated prograding mouthbars and shoreface deposits. Offshore mudstones occur in both parts as the distal component of the depositional systems (Figure 3). The regressive and transgressive parts of sequences have characteristic thickness trends (Figure 4). The regressive segments of a sequence increase in thickness basinward until a point where the sandstone gives way to offshore mudstone of the Heather Formation. The transgressive segments of the sequences have a minimum thickness in basinal areas and increase in thickness in the landward direction until a point where the sandstone gives way to shales and coals of the continental Sleipner Formation. These thickness trend observations can be explained when considering mass-balance in the depositional profile (Shanley and McCabe, 1994; Willis, 1997). Regression occurs as a result of lack of accommodation space and excess in sediment supply in a landward position that forces the coastline to prograde seaward, so the majority of sediments are trapped in a seaward position. During transgression, the majority of sediments are trapped in a landward position due to an increased accommodation space in that location.
ApplicationApplication of this concept to interwell areas provides a powerful predictive tool for the thickness and facies type of Hugin Formation sandstones.
ReferencesCope, J.C., Ingham, J.K. & Rawson, P.F., (1992). Atlas of palaeogeography and lithofacies. The Geological Society of London Memoir No. 13, 155 p. Shanley, K.W., and McCabe, P.J., (1994). Perspectives on the sequence stratigraphy of continental strata. Report of a working group at the 1991 NUNA Conference on high resolution sequence stratigraphy: AAPG Bulletin, v. 78, no. 4, p. 544-568. Thomas, D. W., and Coward, M. P., (1996). Mesozoic regional tectonics and South Viking Graben formation: evidence for localised thin-skinned detachments during rift development an inversion. Marine and Petroleum Geology, v. 13, no. 2, p. 149-177. Willis, B.J., (1997). Architecture of fluvial-dominated valley-fill deposits in the Cretaceous Fall River Formation. Sedimentology, v. 44, p. 735-757. |