Stratygrafia warstw chodenickich i grobowieckich w Chełmie nad Rabą

Abstract

STRATIGRAPHY OF CHODENICE AND GRABOWIEC BEDS AT CHEŁM ON THE RABA RIVERThe section of the Miocene in the region of Chełm (approx. 30 km. east of Cracow) comprises the following sediments (enumerating them in ascending order):1."Sub-salt" clays and sands of 100-500 m. thickness, containing characteristic foraminifer assemblages marked by symbols IIA, IIB, IIC and IID (according to the scheme applied to the Silesia-Cracow region - S. Alexandrowicz, 1958).2. Chemical deposits developed as salts, gypsum and anhydrite forms, inter-bedded with grey clays, claystones and argillaceous shales.3. The Chodenice beds, represented by grey clays with intercalations of dolomitic or siliceous marls. In the top part of these·beds two tuffite layers appear. The lower horizon of these beds is marked by a scantinesss of microfauna (Plate I, Series 1-3), the upper horizon contains an assemblage of plankton organisms: Globigerinae, Radiolaria and Spirialis (Plate l, SampIes 4-8).4. The Grabowiec beds, comprising sands and sandstones with day and marl intercalations, northwards passing into a monotonous complex of grey clays with intercalations of fine grained sands. The foraminifer assemblage is plentiful and characteristic (Plate II). The ample participation of benthonic forminifers distinguishes this assemblage from that of the Chodenice beds (Figs. 2 and 3).Our conclusions as to age and stratigraphical position of the Chodenice and the Grabowiec beds may be summarized in the following items:1. As to, their age, the chemical deposits of the Chełm region correspond to the gypsum deposits of the region of Cracow, Pińczów and Gliwice, as component part of the index horizon of the chemical deposits.2. The clays and sands underlying the chemical deposits constitute a complex thoroughly different from the Chodenice beds.3. The Chodenice beds represent a characteristic stratigraphical index horizon, appearing directly on top of the chemical deposits. They extend with these sediments from Opava (Moravia) to Ukraine.4. The boundary between the Chodenice and the Grabowiec beds is distinctly marked, characterized. by an abrupt change in microfauna composition. The Grabowiec beds represent a wide spread horizon of stratigraphical significance.5. Both the Chodenice and the Grabowiec beds, being supra-gypsum (supra-anhydrite) deposits, should be assigned to the Upper Tortonian.