THERMAL AND BURIAL HISTORY OF THE CRACOW-SILESIA REGION (SOUTHERN POLAND) ASSESSED BY CONODONT CAL ANALYSIS

Conodont colour alteration (CAI) data have been applied in the reconst ruction of palaeothermal conditions in the Cracow-Silesia region, sout hern Poland. The analysis of conodont CAI values supplemented by elect ron spin resonance (ESR) data provided a complex maturity pattern whic h coincides well with the tectonostratigraphical divisions of this reg ion during the Variscan and Alpine diastrophic cycles. The Palaeozoic rocks in the Upper Silesian Coal Basin attained the observed thermal m aturity during Late Carboniferous or Permian time just after the tecto nic inversion of the basin. Vertical maturity trends suggest that pala eo-geothermal gradients were significantly higher than the present val ues. The irregular maturity pattern recognized in the Cracow-Myszkow Z one is related to the thermal overprint of intrusive igneous rocks on the maturity field resulting from the relatively shallow burial. This pattern has not been modified by Mesozoic hydrothermal events. The low maturity level of Devonian and Early Carboniferous rocks in the subst rate of the Carpathian Foredeep is a product of the subsidence during Miocene time. The implications for hydrocarbon generation and further exploration are discussed. The CAI data are consistent with other indi cators of organic metamorphism previously used in this region. The stu dy highlights also features about the conodont colour alteration, such as the influence of silica mobilization on conodont colour, which lim it the application of the CAI method.