An Outline of Lower-Middle Carboniferous Sedimentation on Svalbard: Effects of Tectonic, Climatic and Sea Level Changes in Rift Basin Sequences

Abstract

Abstract The sedimentary response to climatic change (humid to arid), to tectonic instability (rifting) and to longer term sea level rise is outlined with reference to the Lower-Middle Carboniferous successions on Bjornoya (Bear Island), southern Spitsbergen (Hornsund) and central Spitsbergen (Billef-jorden). Movements along important N-S fault lines are generally reflected by thick, very coarse clastic successions and more precisely by repeated (often cyclic) facies changes (each facies sequence 5 to 40 m thick): for example, a sudden influx of marginal marine sandstones and carbonates followed by coarsening-upward coastal plain/alluvial fan sequences. A large-scale change in sediment type from grey and black fluvial, coal-bearing elastics and monomict conglomerates to red, ephemeral fluvial and polymict alluvial fan deposits, reflects a change from a humid to a more arid climate. Long term relative sea level rise is indicated by an overall change from fluvial to marine deposits, and may be either eustatically controlled or is dependent on widespread Middle Carboniferous subsidence and relative sea level rise over much of the region, possibly due to closure of the Mid-European Ocean.