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Part 3 Historical Synthesis |
Treatment in this chapter of the Silurian episode in the history of Svalbard must be different from that of the preceding and succeeding chapters because the stratal record is quite minimal - a fact that corresponds to the widespread Caledonian tectogenesis (Fig. 15.1). Indeed, Svalbard was subjected to mid-Paleozoic orogeny which has often obscured the earlier history. This chapter, therefore, concentrates on the tectonic story even where it overlaps earlier and later history and in turn the preceding and succeeding chapters overlap to some extent with the sedimentary record.
Historically the metamorphic rocks were first regarded as Archean. Holtedahl (1914) demonstrated their Caledonian nature first in northwestern Spitsbergen and later regionally (Bailey & Holtedahl 1938). It was, however, then a paradigm of tectonic thinking, perhaps by analogy with Wales, that the Caledonian Orogeny was conceived as deforming an Early Paleozoic geosyn-cline (Cambrian through Silurian). This was evident in early interpretations of Scandinavian, Greenland and North American mapping as well as in Svalbard. It was commonly thought that those geosynclines would begin with an initial Cambrian unconformity. Gradually, however, it became clear that the 'Caledonian' geosynclines were more complex and in each of the areas referred to above the major part of the sedimentary pile was found to be Precambrian, often with no great sedimentational break to herald the Phanerozoic Era.
Latterly interest has focused on distinguishing, within the Caledonized Precambrian successions, relicts of earlier pre-Cale-donian mainly Proterozoic orogenies referred to here as proto-basement. In contrast to the 80 million years
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