Abstract

Lower Paleozoic strata are well exposed and only weakly metamorphosed at the northern end of the Appalachian volcanic belt in northeastern Newfoundland. The region has been segmented by major faults into structural-stratigraphic blocks which reflect differing sedimentary and tectonic histories. Faulting probably commenced in the Ordovician, contemporaneous with widespread outpourings of submarine volcanics.

The stratified sedimentary and volcanic rocks of the region compose an eugeosynclinal assemblage of deposits over 2300 m thick ranging in age from earliest Ordovician through early Silurian. The typical succession represents a coarsening flysch pattern of deposition. Early deposits interfinger with mafic lavas and are richly volcanogenic in provenance. Later strata, although not devoid of the effects of volcanism, reflect increasing introduction of felsic detritus, probably from plutonic sources. Latest deposits are quite coarse clastics, representing both cannibalization of earlier deposits raised by internal tectonic lands and the influx of plutonic debris from proximal sources.

The most interesting aspect of the succession is lateral variability. Faunal age control establishes complex relationships between volcanic and sedimentary facies throughout the Ordovician. Characteristic lithic units, such as lava flows or conglomerate lentils, are spatially restricted, but may be found at any stratigraphic level. Stratigraphic complexities in this region may also pertain in unfossiliferous or highly metamorphosed terranes throughout the Appalachian Magog Belt.

The stratigraphic record of the region reflects a tectonic history that is probably analogous with other parts of the Appalachian orogenic belt. The evidence supports a model for the evolution of that orogen which is in accord with recent hypotheses on global tectonics and sea-floor spreading.

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