Sedimentology of the Lower Cambrian sediments at Ena, Nordre Osen, Southern Norway.

Abstract

The Lower Cambrian sedimentary rocks at Ena river comprise quartzitic and wellsorted sandstones, shale beds and some thin conglomerates. The sandstones display several sedimentary structures, such as horizontal and vertical burrows (Monocraterion), ripple marks, load casts, diapiric structures and ball-and-pillow structures, besides some others of uncertain origin. Black, phosphatic fossil fragments occur scattered throughout the sandstones, but art especially enriched in two conglomerate beds. The pebbles of these are dominated by dolomite rocks with relicts of o\u00CElites and microfossils. The dolomite has a Lower Cambrian age, as indicated by Lower Cambrian phosphatic fossils. The formation of the dolomite rocks and their erosional products as wellas the sandstones and shales are discussed on the basis of temporary eustatic changes in sea lever during the transgressive phase in Lower Cambrian. The paragenesis of mineral formed during diagenesis is quartz-chlorite\/sericite-calcite. Galena, pyrite and calcite poikiloblasts are epigenetic.