Complementary data on the palynostratigraphy of the Carboniferous succession of SW Poland

Abstract

New palynostratigraphical data concerning the Carboniferous sedimentary succession of SW Poland has been obtained from the Czerńczyce IG 1 borehole and the Brońsko boreholes on the northern slope of the Wolsztyn-Leszno High, where the oldest rocks were expected. The miospore assemblages recovered from the Czerńczyce IG 1 borehole allowed assignment of the interval studied to the Marsdenian (Namurian B) and Yeadonian (Namurian C). These results, supplemented with previous palynostratigraphical data, refute the existence of a stratigraphic gap between the early Namurian and Duckmantian (Westphalian B). The reinterpretation of the unpublished miospore results of Górecka et al. (2000b, 2001a) from the Carboniferous rocks from the Brońsko boreholes, also indicate that they should actually be assigned to the upper Marsdenian and Yeadonian. All analysed miospore assemblages are mixed and contain abundant reworked specimens. The results above complement previous opinions and permit a re-evaluation of the stratigraphy of the Carboniferous siliciclastic succession of SW Poland. Its sedimentation was certainly initiated in the earliest Namurian or earlier and probably lasted without long gaps until the Stephanian. The abundance and common occurence of reworked miospores indicate the age of rocks eroded during Carboniferous deposition. The lithological and palynofacial features of the late Namurian rocks from the Czerńczyce IG 1 borehole may be interpreted as a record of the shallowing of the sedimentary basin, including the possibility that some of the sedimentation occured in continental conditions. This means that the transition from the deep marine environment to shallow-water or even continental habitats likely had already taken place by the late Namurian. This suggestion, together with the tectonic deformation dated as post-Bolsovian, corresponds to the timing of the deposition and deformation in the German part of the Variscan Foreland Basin.