Chapter 4 The Central Basin

Abstract

Svalbard rocks conveniently divide into younger and older rocks at about the initial 'Carboniferous' boundary. There are, however, latest Devonian strata in places continuous with Carboniferous sedimentation. The older rocks are tectonically as well as stratigraphically complex. Beginning with the sub-Carboniferous (peneplane) unconformity resting variously on Devonian and pre-Devonian strata, it expressly excludes any older rocks. The term basin as in Central Basin applied here is used in a structural sense for what amounts to a broad brachysyncline. The accumulated strata were also formed in sedimentary basins with shifting depocentres. The most obvious is the Paleogene sedimentary and structural basin commonly referred to as the Tertiary Basin. The Central Basin excludes the western and southwestern areas (Chapters 9 and 10) where older and younger rocks are caught up in the Paleogene West Spitsbergen Orogeny. It also excludes the areas, mainly in the islands in the east, where subsidence was less marked at first and tectonic platform conditions prevailed. The younger succession, Tournaisian through Paleogene (a span of about 330 million years) has suffered only minor diastrophism in contrast to earlier events. Central Basin thus refers to the whole post Devonian cover or platform sequence in this study area. Most mineral prospects of economic interest in Svalbard belong to these younger rocks, from the many coal deposits of which Early Carboniferous and especially Early Paleogene horizons have been exploited. Furthermore, in the search for petroleum, source rocks of Late Carboniferous Early Permian, Early to Mid-Triassic and Jurassic age have been identified