The Precambrian–Cambrian boundary in parts of Scandinavia and Greenland

Abstract

The discovery of Ediacara type faunas and later the Tommotian fauna at levels below the supposed first appearance of trilobites has brought new life to the discussion of the formal position of the Precambrian–Cambrian boundary. The oldest shelly faunas are apparently restricted to a few favoured areas, whereas transition beds developed as quartz sandstones, mostly unfossiliferous apart from trace fossils, seem to have a much larger regional distribution. The sequences of quartz sandstones overlie a Precambrian crystalline basement of a much greater age or clastic sediments, in part tillites, and are in turn overlain by a variety of rocks containing olenellacean trilobites.