NJG83-3-04
2003
New insights into the geology of high-grade Caledonian marbles based on isotope chemostratigraphy
83
3
pp. 209-242
82-92394-09-5

A first attempt to employ carbon and strontium isotope stratigraphy together with 1.20,000 scale mapping for chronstratigraphic subdivision and geological correlation of non-fossiliferous sedimentary successions in the polydeformed, high-grade, marble-dominated terrane has been successful. The isotope stratigraphy was based on 315 analyses of major and trace elements, as well as on 231 ?13Ccarb and ?18O, and 104 87Sr/86Sr wholerock analyses of calcite and dolomite marbles, representing all major marble units of the Narvik, Evenes and Niingen nappe complexes, and the Bogen Group in the north-central Norwegian Caledonides. A thick succession of calcite and dolomite marbles in the Ofoten Synform, previously considered to be stratigraphically homogeneous and of Late Ordovician-Early Silurian age, is shown to be a complex assemblage of Neoproterozoic, Cambrian and Early Silurian carbonate formations which were tectonically imbricated and emplaced in a non-chronostratigraphic order. The real breakthrough with the new geological mapping has been the establishment and use of the Cambrian and Early Silurian chemo/chronostratigraphic markers that reveal stratigraphic heterogeneity and tectonic repetition, provide a reliable stratigraphic subdivision, and facilitate the compilation of a chronologically-based geological map.

029-196X
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