Evidence for a glacial origin of Neoproterozoic III striations at Oaibaččannjar'ga, Finnmark, northern Norway
| Autor: | C.-C. Hofmann, A. H. N. Rice |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Geological Magazine. 137:355-366 |
| ISSN: | 1469-5081 0016-7568 |
| DOI: | 10.1017/s0016756800004222 |
| Popis: | The origin of the famous late Precambrian striated pavement at Oaibaččannjar'ga (Bigganjargga), northern Norway, remains controversial. Most investigators have accepted a glacial formation, but some prefer a soft-sediment mechanism. However, a newly discovered c. 2.5 mm thick zone of brecciation under rare polished striations indicates a hard substrate during formation and thus a glacial origin for the striations. Other points indicating that the striations formed in a hard substrate are: (1) the striated platform (in the Veidnesbotn Formation) is c. 150 Ma older than the overlying diamictite (Smalfjord Formation); having been buried to c. 2.5 km depth, cementation should have started before Smalfjord times; (2) the marked irregularity of the sub-Smalfjord Formation palaeotopography on Skjåholmen; (3) the presence of rounded Veidnesbotn Formation boulders in the diamictite above the striations. Imprints of clasts appearing to lie across the striations are re-interpreted as relicts of mud-flakes within the Veidnesbotn Formation which were cut across and quarried-out during pavement formation. The origin of the overlying diamictite (tillite vs. debris-flow) is not constrained by the presence of glacial striations and most probably was deposited some time after striation formation. |
| Databáze: | OpenAIRE |
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