A•flisch/littoral succession in the Sudetic Upper Cretaceous

Abstract

The Coniacian marine sediments of the·Nysa graben (Idzików Beds) are divided into the lower member consisting of altering claystone and sandstone layers, and the upper member comprising sandstones and conglomerates. Sedimentary features of the lower member, especially the type of bedding planes, sole markings, trace fossils, succession of structures and textures indicate that the principal agents controlling the sedimentation were subaqueous mass movements and turbidity currents. The upper member·shows the features of shallow water sediments, including medium- and large-scale cross-bedded units and numerous fossils, i.a. shallow water lamellibranchs, gastropods and decapods The sequence and distribution of facies within the Idzików Beds point to a consistent development of the sedimentary basin in which were laid down in succession: distal turbidites, proximal turbidites, shallow water and high-energy littoral deposits. Such .a development was closely related and synchronous to the uprising movements in the fore-Sudetic land and in the Śnieżnik and Kłodzko massifs. The tectonic uprising movements which embraced parts of these massifs were coming closer and closer to the Nysa graben, and caused migration of the fades and finally led to the regression of the sea.