Karstic surface in the Lower Permian sabkha sequence of the Gipshuken Formation, central Spitsbergen, Svalbard

Abstract

Some unusual karst structures occur in the upper part of the evaporite-dominated sequence of the Gipshuken Formation. This Lower Permian unit is characterized by interbedded anhydrite and dolomites, and is now interpreted in terms of superimposed sabkha cycles. The karst structures are found in the inner part of Skansdalen in Dickson Land, and have not yet been observed elsewhere in corresponding horizons in Svalbard. These structures, often seen as linked hemispheroids. consist of almost pure anhydrite and are here interpreted as representing the remnants of consolidated sabkhas; the original sabkha plain was flooded and partly dissolved, and abandoned channels between the hemispheroidal structures were then filled with sediments of later sabkha cycle. The younger sediments which fill the relief between and above the structures contain small enterolithic folds which indicate primary formed anhydrite. Anhydrite is still the most common subsurface mineral in these sulphatic deposits. an3 there is no evidence of gravitational or tectonic movements within these beds.