Sedimentation of the Middle Eocene of the Magura Series, Polish western Carpathians

Abstract

O sedymentacji środkowego eocenu serii magurskiej w polskich Karpatach zachodnich Methods of investigation previously employed by N. B. Vassoyevich and by A. B. Vistelius are adopted in an integrated sedimentological study of flysch rocks, known from the work of M. Książkiewicz. Comparison of time trends of sedimentation, defined by time series of layer thickness values, reveals striking differences between flysch formations, referable to differing distances of the depositional area from the edge of the basin and hence, to differing sensitivities to tectonic or climatic change, operative in the source area. Computer simulation of deposition, based on a stochastic model, supports the case for sedimentation of each individual simple bed from a single moving suspension. An independent-event model, used for comparison, is inapplicable to either proximal or distal flysch sedimentation as a whole, though such a model is to a limited extent mimicked in proximal sequences, largely made up of composite beds. These conclusions are substantiated and supplemented by limited petrographic study and by more detailed considerations of the geometries of internal sedimentary structures, as revealed by radiography, associations of interfacial structures and gross assemblages of trace fossils. Organic clasts, particularly the tests of benthonic and pelagic Foraminifera, used as tracers within individual beds, provide additional information, relating to erosion of the substratum by moving suspensions, pelagic sedimentation and also the action of bottom currents, not of turbidity-current type.