Procedure
In the present work, use of the formal group names of the correlative Upper Palaeozoic succession of Svalbard has been extended to the southern Barents Sea because of the overall regional continuity and lithological similarities to the onshore succession. In addition, one new group has been introduced to include a thick succession of Permian cool-water carbonates in the offshore areas that are represented by the apparently condensed development of the Hambergfjellet Formation on BjГёrnГёya. All the offshore formations are new and are formally defined; well logs illustrate the type and reference sections and, where possible, sedimentological logs and photos of cored intervals are also presented. In accordance with the recommendations of the Norwegian Stratigraphic Committee (Nystuen 1986), wells with adequately cored intervals have been given precedence as type sections if these cored intervals are otherwise typical for the particular formation when compared to uncored reference sections with only electrical logs.
Because of the limited number of wells penetrating the Upper Palaeozoic succession, the new lithostratigraphic units are defined in relatively general terms in this paper and our proposals are open to further refinement when more wells are drilled. This is particularly the case for the basinal evaporite-dominated succession of the Gipsdalen Group. Unpublished descriptions of cores through the Upper Palaeozoic succession of Hopen drilled by Fina in the late 1960s and early 1970s and recent work in the northern sector of the Norwegian Barents Sea (Grogan et al. 1999) suggest that the same group divisions will also be applicable in those northern areas, but neither formational assignations nor definitions of new formational units are yet feasible there.
Presentation of data
Exploration well logs are presented with depths cited as metres relative to KB. Data from IKU shallow cores are referred to with depths below mean sea level (in contrast to Bugge et al. 1995, where depths refer to sea-bottom). The well logs display interpreted lithology together with gamma ray, density, neutron and sonic logs (lithological symbols are defined in Fig. 3). Text descriptions of unit boundaries are presented stratigraphically, i.e. with upward variation in log response across a boundary. For each group, a correlation scheme is presented giving a broad lithological overview of the formations and pictures of typical lithologies are shown throughout. Core descriptions of type sections are also presented.
Chronostratigraphic framework
Ages referred to in the text are generally at stage level, and more precise ranges are only presented when this is possible. Age designations for the different units are based on unpublished consultant and in-house reports and on data published by Nilsson (1993), Mangerud (1994), Bugge et al. (1995), Stemmerik et al. (1995, 1998) and Ehrenberg et al. (1998a, 2000, 2001). The published material is given preference. Age designations are based mainly on palynomorphs in the Lower Carboniferous and Upper Permian part of the succession and on fusulinids in the Upper Carboniferous and Lower Permian. Nomenclature in general corresponds to the time scale of Gradstein & Ogg (1996), including a twofold division of the Permian (Fig. 4).