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New insights into the genesis of the “Poznań clays” – upper neogene of Poland

Maciaszek Piotr, Chomiak Lilianna, Urbański Paweł, Widera Marek

Civil and Environmental Engineering Reports

2020

Vol. 30, no. 1

18--32

The present study focuses on the upper Neogene deposits, called the “Poznań Clays”, that cover more than 75,000 km2 of Poland. They are situated between the first midPolish lignite seam and the glaciogenic deposits of the Pleistocene age. Lithostratigraphically, the “Poznań Clays” belong to the uppermost portion of the lignite-bearing Grey Clays Member and the whole Wielkopolska Member (Poznań Formation). The examined fine-grained sediments include mud-rich floodplain deposits with palaeosol remnants and large sandy-muddy or muddy palaeochannel bodies. Therefore, taking into account facies analysis, cross-sectional geometry, and the planform of the palaeochannels, it can be stated that the “Poznań Clays” formed in the environment of a late Neogene anastomosing river.

Preglacial to Holocene auriferous sediments from the East Sudetic Foreland: gold grades and exploration

Wierchowiec J.

Geological Quarterly

2006

Vol. 50, No. 2

289-302

Auriferous sediments in the East Sudetic Foreland region include up to five gold-bearing horizons associated with preglacial and Quaternary fluvial sediments. The largest placer potential lies in the preglacial (Eopleistocene?) drainage system, primarily in palaeochannels of the Biała Głuchołaska River. The White Gravel series is the richest gold-bearing horizon. It contains between 0.37 g/m3 Au near the base and <0.10 g/m3 Au in its upper part.Maximumgold grade occurs in the first 1–2mabove the contact with the bedrock. Gold concentration in this area was controlled by the ability of streams to aggradation and the development of sedimentologic traps, where gold was accumulated during the preglacial valley erosion. Oblique orientation of the palaeo-Biała Głuchołaska valley and its tributaries to the regional ice-flow direction probably prevented the glaciers fromeroding deeply into the palaeochannels. From the exploration prospective, study of palaeochannel systems in the vicinity of Otmuchów–Prudnik could identify other buried placer gold occurrences. Gold-bearing sediments, correlated stratigraphically with the Biała Głuchołaska palaeochannel White Gravels occur in several other areas, including the Nysa Kłodzka, Kwisa and Kaczawa valleys.