Abstract

The Ford’s Bight Diatreme is an apparently rare feature on the Precambrian coast of Labrador. Originally described as a Jurassic-Cretaceous sedimentary breccia cut by lamprophyric dykes, an early report of marine microfossils in the strata poses an interesting sedimentary and petroleum geology problem. In revisiting the area, the succession is now viewed as a rift related diatreme with a Cretaceous (ca. 137 Ma) radiometric age. In earlier work, this rock was dated from assemblages of poorly preserved Jurassic and early Cretaceous marine microfossils. Our own lengthy search for fossils in igneous rocks and clasts and carbonate matrix was fruitless. Some apparently carbonized debris is identified in microscopy and with some oddly shaped (non-biologic) microcrystalline structures seen under SEM. With an age and origin for this feature established from basic geology and radiometric dating, this therein leaves an unresolved petroleum exploration risk - and, namely, did Jurassic marine conditions cover this part of the Labrador coast before earliest Cretaceous volcanism?

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