Minerały ilaste miocenu morskiego z profilu Kobylniki (zapadlisko przedkarpackie)

Ryszard Wyrwicki, Andrzej Wiewióra




In the Kobylniki borehole (Carpathian Fore-Deep) marine clay sediments have been encountered underneath the Quaternary (4 m). At the depth of 4.0-67.0 m they are represented by the Krakowiec clays (Sarmatian), from 67.0 to 102.8 m - by Pecten clays (Tortonian) and below - by the Chodenice beds (Tortonian). The Krakowiec and Pecten clays are similar in appearance. These are grey clays and silts frequently with sand laminae and with macroscopically visible carbonified plant detritus, mica scales, and with pyrite either dispersed or in the form of concentrations. Additionally - in the Pecten clays - calcite shells detritus has been noticed. Five samples of the Krakowiec clays and two of the Pecten clays have been examined. The depth of the samples and their granulometric composition is given in Table 1. All the samples and their grades have been subject to DTA. Examples of DTA curves of two samples (Figs. 1 and 2) reveal a considerable differentiation of the mineral composition of the individual grades. Clay minerals have been examined in grades below 2 μm; the DTA curves are presented in Fig. 3, the diffraction patterns in Figs. 4-6. The results of the present studies are reviewed below. The clay minerals assemblage in the Krakowiec and the Pecten clays is much the same. Beidellite is the main constituent and it is accompanied by illite, chlorite, kaolinite, and an illite-beidellite mixed-layer phase. Samples 1 and 2 contain the smallest proportion of beidellite of poorly developed structure. Structurally best developed and most abundant beidellite is reported from the lower portion of the Krakowiec clays (samples 4 and 5). The biggest illite content has been found in samples 1, 2, 6 and 7, while samples 4 and 5 show the lowest amounts of this mineral. Pecten clays contain the smallest amounts of kaollinite (samples 6 and 7), whereas the biggest kaolinite content has been found in the lower portion of the Krakowiec clays. The present results have confirmed the smectitic character of the clay deposits of the marine Miocene from the Carpathian Fore-Deep.


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