What can be learned from the K-Ar ages of illite from Rotliegend sandstones of the Fore-Sudetic Monocline, SW Poland?

Authors:

• Julita Biernacka

Abstract

The available K-Ar ages of authigenic illite from Rotliegend aeolian sandstones of the Fore-Sudetic Monocline, SW Poland, including those from six samples examined in the present study, are critically reviewed in terms of their geological meaning and compared with the K-Ar ages of illite from the remaining part of the Southern Permian Basin in Europe. The majority of ages fall in the range between 195 and 150 Ma, i.e. they correspond to Jurassic times. The results may be grouped in several time intervals, which are almost identical to those identified for Rotliegend sandstones of Central and Western Europe, and which are tentatively interpreted as pulses of intense illite growth. Short-lasting illitisation is recorded only at places. More of- ten, illitisation proceeded as a multi-stage process, which in the northern part of the Fore-Sudetic Monocline might have lasted until the Cretaceous. The K-Ar ages of authigenic illite generally coincide with the modelled time of gas generation from Carboniferous rocks and the filling of reservoirs in the area of the Fore-Sudetic Monocline. Possibly, the same underlying processes triggered illitisation and hydrocarbon expulsion, or hydrocarbon migrations triggered fluid flows and illite crystallisation