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The Kapp Lyell diamictites (Upper Proterozoic) at Bellsund, Spitsbergen: rock-sequence, sedimentological features, palaeoenvironment

Birkenmajer K.

Studia Geologica Polonica

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2010

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Vol. 133

7-50

EN

The Upper Proterozoic meta-diamictites (Kapp Lyell Formation) exposed south of Bellsund, central Spitsbergen, believed by many authors to represent the Vendian (Varangian) glacial tillites, have been investigated. Character of their relictic sedimentary features does not confirm, however, its glacial origin. The diamictites formed mainly as debris-flow and slope-creep terrestrial covers derived from frost-shattered steep rocky margins of a predominantly fresh-water depositional basin. The deposition took place under seasonally differentiated moderate-cool climatic conditions comparable to the modern Subarctic periglacial zone, however outside the reach of glaciers and ice-sheet. Uncommon finer-grade varved deposits containing haphazardly distributed clasts (drop- stones) probably formed in shallow fresh-water lakes that froze during winter; the clasts were subsequently dispersed during summer in the lakes as ice-rafted dropstones. Shallow erosional channels infilled with sandstone within the diamictite complex, might be evidences for braided river systems that were active during summer. Rare, well-rounded cannonball-size cobble/boulder beds represent a fossil high-energy, probably marine beach.Uncommon thin limestone intercalations, found in a predominantly coarse-clastic suite, might suggest occasional incursions of a shallow sea.

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The Magnethogda Sequence (Hecla Hoek Succession), NW Torell Land, Spitsbergen: a Revision of Lithostratigraphy and Age

Birkenmajer K.

Bulletin of the Polish Academy of Sciences. Earth Sciences

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2002

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Vol. 50, nr 2

175-191

EN

Martinfjella, a submeridional mountain chain which divides the glaciers Antoniabreen from Recherchebreen, NW Torell Land, Spitsbergen, was so-far believed to consist of Middle Proterozoic rocks attributed to the "Magnethogda sequence". In the present author's opinion, this sequence consists of rock-units comparable with the Lower Ordovician Sorkapp Land Group (Wiederfjellet and Luciapynten formations), the Cambrian Sofiekammen Group (Gnalberget Fm.), and the Upper Proterozoic Sofiebogen Group (Gashamna and Hoferpynten formations), as defined in the Hornsund area, south Spitsbergen. A stratabound iron-ore unit, here distinguished as the Jarnbekken Formation (new unit), divides the Wiederfjellet from the Luciapynten formations. A separate tectonic unit thrust over the above ones, consists of phyllites and quartzite's with pink migmatite (augen-gneiss, feldspathite) intercalations and bands. The present author considers this unit as a variety of the Gashamna Formation metasomatised by K-rich solutions, probably related to Caledonian magmatism. The Luciakammen Formation and the migmatite-bearing Gashamna Formation, continue eastwards across Antoniabreen to reappear in Aldegondaberget, Berzeliuseggene, Berzeliustinen and Hermelinberget. Within the "Recherchebreen sequence" of Chamberlindalen, three lithostratigraphic units of the Upper Proterozoic Sofiebogen Group have been distinguished: the Gashamna, the Hoferpynten and the Slyngfjellet formations.

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Caledonian Basement (Hecla Hoek Succession) at Midterhuken, Bellsund, Spitsbergen: a Revision of Lithostratigraphy and Age

Birkenmajer K.

Bulletin of the Polish Academy of Sciences. Earth Sciences

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2002

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Vol. 50, nr 2

165-173

EN

Caledonian basement (Hecla Hoek Succession) of the Carboniferous through Tertiary platform coyer is exposed at Midterhuken, Bellsund, Spitsbergen. It consists of three rock-units, so far attributed to the "Magnethogda sequence" believed to represent Middle Proterozoic. In the present author's opinion, these units correlate well with Upper Proterozoic and Cambrian lithostratigraphic units of the Hornsund area, south Spitsbergen. At Midterhuken, there occur: (1) the Hoferpynten Formation (Upper Proterozoic Sofiebogen Group: dolostones, more than 600 m thick); (2) the Gashamna Formation (Upper Proterozoic Sofiebogen Group: phyllite and quartzite, about 300 m thick); (3) the Gnalberget Formation (Cambrian Sofiekammen Group: phyllitic limestone, probably more than 300 m thick). Small thickness of the Gashamna Formation, and the lack of the oldest lithostratigraphic units of the Sofiekammen Group (i.e., the Blastertoppen, the Vardepiggen and the Slaklidalen formations) at Midterhuken, seem to be mainly a result of Caledonian folding and thrusting.