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2 2019

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Środowisko sedymentacji i domniemane źródło materiału detrytycznego w górnokredowej formacji red-bed Ashua (Peru)

Paulo Andrzej, Ciesielczuk Justyna, Racki Grzegorz, Żaba Jerzy, Gaidzik Krzysztof

Przegląd Geologiczny

2019

Vol. 67, nr 3

189--191

Ashua Formation was deposited in Coniacian-Early Santonian time near shore of a shallow sea and in a plethora of continental arid environments. Its main component is fine-grained siliciclastic materialforming lithic and subordinate arkosic graywackes. Limestones are frequent in the lower member, and in the upper one gypsum and halite are present. Based on sedimentary textures and detailed petrographic studies, nine general microfacies were identified: shallow sea, beach, brackisch and mud flats, lagoon, sabkha and playa, deltaic, alluvial, mud flows, dunes at shoreline of an agitated water basin. The present authors suggest that the main source of detritus was pyroclastic deposits. They probably belong to the heavily eroded Lower Cretaceous Matalaque Formation.

In situ gamma-ray measurements of 40K, 232Th and 238U in high-grade metamorphic rocks from the Sowie Mountains (Sudetes, SW Poland)

Malczewski Dariusz, Żaba Jerzy

Geological Quarterly

2019

Vol. 63, No. 3

493--504

This paper reports on the abundance of primordial radionuclides (40K,232K and 238U) in characteristic lithologies from the Sowie Mountains (SW Poland). In situ gamma-ray measurements were conducted at 12 localities hosting exposed augen gneiss, flaser gneiss, granulite, homophanized gneiss, hornblendite, layered gneiss, layered migmatite, migmatic gneiss, mylonitic gneiss and mylonitic granulite. The activity concentration of 40K varied from 180 Bq kg-1 (mylonitic granulite) to 845 Bq kg-1 (layered gneiss). The activity concentrations associated with 228Ac (232Th) varied from 10 Bq kg-1 (mylonitic granulite) to 53 Bq kg-1 (homophanized gneiss), while activity associated with 226Ra (238 U) varied from 9 Bq kg-1 (mylonitic granulite) to 43 Bq kg-1 (layered gneiss). An augen gneiss adjacent to the Intra-Sudetic Fault showed the highest combined Th + U activity (89 Bq kg-1). The average Th/U ratio (3.6) calculated for gneiss outcrops of the Sowie Mountains falls within the range reported for biotite gneiss (3.5-4). Subsurface outcrops from the Walim-Rzeczka underground complex did not give noticeably higher 238U activities. The results obtained forthe Sowie lithologies are compared with those obtained by similar methods for similar rocks as reported in literature sources.