The Kapp Lyell Diamictite (Late Proterozoic), Bellsund, Spitsbergen: Sedimentological Evidence for its Non-Glacial Origin

• Autorzy: Birkenmajer K.
• Języki publikacji: EN

Abstrakty

EN

The Kapp Lyell diamictite complex south of Bellsund, Spitsbergen, believed so far to represent tillites of the Late Proterozoic (Vendian) glaciation, was investigated by the present author in 2002. It was found that sedimentological evidence for glacial erosion and/or deposition active during formation of the diamictite, is missing from the whole Kapp Lyell metasedimentary pile. Diamictites, the predominant rocks of this pile, represent terrestrial debris-flow and slope-creep covers derived from frost-shattered rocky margins of depositional basin. They consist mainly of dolostone, limestone and quartzite clasts. Greenstone clasts and lenses, and granitoid clasts, appear in stratigraphically higher part of the succession (in green diamictite). This clast distribution resembles that known from metaconglomerates (diamictites) of the Slyngfjellet Formation (base of Upper Proterozoic) in Wedel Jarlsberg Land, suggesting a close age correlation between the two. Uncommon finer-grade varved deposits with mainly dolostone and quartzite dropstones probably formed in restricted fresh-water reservoirs that froze during winter. During summer, drifting winter ice provided a mechanism for dispersion of clasts (ice-rafted dropstones) from lake beach/coast to water reservoir. Shallow erosional channels filled with sandstone, which occur in the diamictites, might be an evidence for ephemeral braided river systems that were active during summer. There are also some evidences for proximity of a high-energy, probably marine, beach. The Late Proterozoic Kapp Lyell diamictite complex was deposited mainly as talus aprons in a wide valley rimmed by rocky ridges, under seasonally differentiated, moderate-cool climate, comparable with the modern Subarctic periglacial zone, however outside reach of glaciers or ice-sheet. Frost-shattering during winter was probably the main factor of disintegration of source rocks.

Słowa kluczowe

EN

Spitsbergen; Late Proterozoic; diamictite; periglacial sedimentary palaeoenvironment

• Wydawca: Centrum Upowszechniania Nauki PAN
• Czasopismo: Bulletin of the Polish Academy of Sciences. Earth Sciences
• Rocznik: 2003
• Tom: Vol. 51, nr 1
• Strony: 65--78
• Opis fizyczny: Bibliogr. 16 poz.

Twórcy

autor

Birkenmajer K.

• Institute of Geological Sciences, Polish Academy of Sciences, Kraków, Poland