Architecture and sequence stratigraphic perspectives of the Dunlin Group formations and proposal for new type- and reference-wells

Marjanac, Tihomir (1995) Architecture and sequence stratigraphic perspectives of the Dunlin Group formations and proposal for new type- and reference-wells. In: Sequence Stratigraphy on the Northwest European Margin, Proceedings of the Norwegian Petroleum Society Conference Stavanger, Norway, 1–3 February 1993. Norwegian Petroleum Society Special Publications, 5 . Elsevier B.V., pp. 143-165. ISBN 978-0-444-81863-8

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Abstract

The Lower Jurassic Dunlin Group is formally subdivided into the Amundsen, Johansen, Burton, Cook and Drake Formations, and these are proposed redefined herein on the basis of the well-logs and cores from the Veslefrikk Field. The Johansen sandstones are reinterpreted as a northwestward prograding delta7 and the Cook Formation is broadened in stratigraphic span to include all thick sandstone bodies which are at present informally referred to as the “lntradunlin” and “lntradrake” sandstones. The Cook sandstones of the Veslefrikk Field are interpreted in terms of tidal bars in an estuarine setting. In order to provide better correlatability and wider applicability of the Dunlin Group formations, and a better match with the recent high-resolution well-logs, new type- and reference-wells are proposed. These are the 3018-2 (type-well) and 30,’3-3, 34;'10-21, 34,’10-9, 34./4-3 (reference-wells). The suggested type-well is selected in the Veslefrikk Field because it is centrally located in the Early Jurassic basin and all of the Dunlin Group formations are developed here. A large number of extensive Bonding surfaces is recognized within the Amundsen, Burton and Drake Formations, and some are attributed to the stage of “maximal flooding”. These surfaces are assumed horizontal and thus used as datum lines for the well-log correlation. Seven depositional units bounded by erosional surfaces are recognized. The erosional surfaces bound incised valleys which were created during sea-level lowstands, whereas the overlying sediments are interpreted as late lowstand (locally), transgressive and highstand deposits. These are recognized as the Cook Formation that typically comprises fine-grained sandstones of tide- and wave-influenced origin, followed by coarser, tidally-constructed sandstone bodies which in turn are capped by a ravinement surface and overlain by shales and heterolithic deposits ofthe Drake Formation.

Item Type: Book Section
Date: 1995
Number of Pages: 608
Subjects: NATURAL SCIENCES > Geology
Divisions: Faculty of Science > Department of Geology
Corporate Creators: Norwegian Petroleum Society Conference
Publisher: Elsevier B.V.
Depositing User: Sonja Borak
Date Deposited: 20 Feb 2014 12:29
Last Modified: 03 Mar 2014 08:34
URI: http://digre.pmf.unizg.hr/id/eprint/447

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