Microfossil-based biostratigraphy of the Precambrian Hecla Hoek sequence, Nordaustlandet, Svalbard
Summary The Precambrian Murchisonfjorden Supergroup of Nordaustlandet, Svalbard, contains approximately 6000 m of folded, but essentially unmetamorphosed, shallow marine sedimentary rocks. The abundant microfossils found through much of the section allow confident biostratigraphic subdivision of the...
| Published in: | Geological Magazine |
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| Main Author: | |
| Format: | Article in Journal/Newspaper |
| Language: | English |
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Cambridge University Press (CUP)
1982
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| Online Access: | http://dx.doi.org/10.1017/s001675680002608x https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S001675680002608X |
| Summary: | Summary The Precambrian Murchisonfjorden Supergroup of Nordaustlandet, Svalbard, contains approximately 6000 m of folded, but essentially unmetamorphosed, shallow marine sedimentary rocks. The abundant microfossils found through much of the section allow confident biostratigraphic subdivision of the succession and correlation with contemporaneous sequences in East Greenland and Scandinavia. Diamictite-bearing rocks of the Gotia Group (uppermost in the sequence) contain a depauperate assemblage of acritarchs dominated by Bavlinella Javeolata . A Vendian age of deposition is indicated. Carbonates of the immediately underlying Ryssö Formation contain a wide variety of microfossils including stromatolitic associations of several types, planktonic acritarchs, and, near the top of the formation, vase-shaped heterotrophic protists. The acritarchs, including Chuaria circularis, Kildinella hyperboreica, K. sinica, Trachysphaeridium spp., and others, and the protistan remains indicate a latest Riphean age. The underlying Hunnberg Formation is similarly fossiliferous. A typically Late Riphean acritarch suite is present, and in addition double-walled forms and large (500 μm), thick-walled spheroids bearing club-shaped 10 μm diameter spines are found. Thus, it appears that the entire carbonate sequence of the Roaldtoppen Group was deposited late in Late Riphean time. The thick detrital succession comprising the lowermost part of the unmetamorphosed Nordaustlandet sequence, the Celsiusberget and Franklinsundet groups, contains fossils at various levels. Although microfossils are often somewhat coalified, identifiable Late Riphean taxa such as Chuaria circularis and Kildinella spp. are present in rocks as low as the middle Westmanbukta Formation. The presence of the distinctive carbonaceous macrofossil Tawuia dalensis in the Kapp Lord Formation permits an age estimate of 850–900 Ma for this formation. All told, the entire Murchisonfjorden Supergroup of Nordaustlandet appears to have been deposited during the Late Riphean and ... |
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