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Abstract

The Jarlsbergian unconformity at the Late Proterozoic-Early Cambrian boundary, is expressed in the Hecla Hoek Succession of South Spitsbergen as a regional low-angle unconformity, the result of folding and subsequent erosion of the Late Precambrian Jarlsbergian Basin deposits. The unconformity pre-dates the Bonnia-Olenellus trilobite zone; the sedimentary hiatus covers the lowest Cambrian Fallotaspis and Nevadella trilobite zones, and a closer undefined uppermost part of the Late Proterozoic. There are no Varangian (latest Proterozoic) tillites present in south Spitsbergen at the top of the Late Proterozoic metasediment column which is represented by the Gashamna Formation phyllites and associated rocks.
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Abstract

Anthracite coal matter fills irregular voids in dolostones of the Upper Proterozoic Höferpynten Formation in the Hornsund area, south Spitsbergen. The coals are of organic origin, as indicated by a variety of coal-petrographic studies, and by association with algal structures. They probably derived from bitumina accumulated in voids of dolostone at an early diagenelic stage. The degree of coalification (graphitization) is high but diversified, suggesting several coalification stages, probably related t o successive metamorphic events. The oldest changes may correspond to initial stage of t h e greenschist-amphibolite phase of regional metamorphism, with temperatures of over 500°C and pressure of over 20,000 MPa . Multiphase graphite crystallites which occur in t h e coal are mainly fibrous. There are also crystallites which precipitated from gaseous phase, and pyrolitic graphite; they may have originated due to action of mesothermal solutions which had produced ore-bearing veins.
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