KOMUNIKATY NAUKOWE Paleogleby w zapisie sedymentacyjnym formacji z Siodeł w Górach Świętokrzyskich (perm górny–trias dolny)

Abstract

Paleosols in the sedimentary record of the Siod³a Formation in the Holy Cross Mountains (Upper Permian–Lower Triassic).A b s t r a c t. The uppermost Permian in the NW Holy Cross Mountains is represented by red mudstones with sandstone and conglomerate interbeds, forming the PZt cyclothem (dated by miospores of the Lueckisporites virkkiae Bc Zone), which grade upwards into the Siodła Formation. This succession is overlain by sandstones and mudstones of the Jaworzna Formation yielding the lowermost Triassic spore-pollen assemblage of the Lundbladispora obsoleta–Protohaploxypinus pantii Zone. Mudstones of the Siodła Formation reveal mottling structure with numerous root traces, rhizobreciation, as well as nodular and bedded calcretes. The root structures are represented by calcite tubules and root moulds, the latter filled with dark red calcareous mudstones. The presence of root traces in the Siodła Formation clearly indicatesan increase of substrate moisture in contrast to the underlying PZt cyclothem. The mottled red mudstones were deposited in the playa-lacustrine depositional system and lost their primary structure due to rooting and other pedogenic processes. Carbonate nodules and thin indurated calcretes are related to periods of lower sediment accumulation rate or even non-deposition periods favouring development of continental carbonates. A relatively rapid switch to the alluvial depositional system represented by the Jaworzna Formation appears to be coeval to the increased sediment flux in terrestrial setting, postulated by Newell et al. (2010) at the Permo-Triassic boundary, driven by a devegetation event of upland catchments.