Wyniki wyszukiwania - BazTech

1

Tubular tempestites from Jurassic mudstones of southern Poland

Leonowicz P. M.

Geological Quarterly

|

2016

|

Vol. 60, No. 2

385--394

EN

This paper presents tubular tempestites from southern Poland and their application for environmental and sequence stratigraphy interpretation. Tubular tempestites are present in muddy successions of the Lower Jurassic Ciechocinek Formation and in the Middle Jurassic Częstochowa Ore-Bearing Clay Formation in the Silesian-Kraków region. They occur as sand-filled tubes of Spongeliomorpha and Thalassinoides entrenched in the mudstone, which form two characteristic horizons. Tubes were emplaced in semi-consolidated substrate and filled with sand brought by storm-generated bottom currents. The trace fossils reveal features typical of Glossifungites ichnofacies associated firmgrounds, which record discontinuities in the stratigraphical record, linked with a depositional hiatus or condensation and erosion of the sea-floor. The coincidence of these horizons with early phases of regional transgressions suggests that they represent transgressive surfaces of erosion. Their limited spatial extent probably resulted from varying intensity of erosion, which locally scoured deeply down to already consolidated substrate, whereas in other places erosion was weaker or even absent, and thus it is not marked in the sedimentary record there.

2

Storm-influenced deposition and cyclicity in a shallow-marine mudstone succession - example from the Middle Jurassic ore-bearing clays of the Polish Jura (southern Poland)

Leonowicz P. M.

Geological Quarterly

|

2015

|

Vol. 59, No. 2

325--344

EN

Sedimentological analysis of bioturbated mudstones from the Middle Jurassic ore-bearing Częstochowa Clay Formation has revealed common relics of sedimentary structures, such as thin silt/sand laminae, bedding-plane accumulations of shell debris, small and medium silt-sand lenses, as well as silt-, sand- and shell-debris-rich levels, accompanied by erosion surfaces and minor scours. These features document periodical high-energy conditions of mud deposition, including storm stirring, event sedimentation and the activity of storm-generated bottom currents, which were responsible for seafloor erosion and sediment supply from shallower parts of the basin. The sea bottom was prevalently below the storm wave base, but it rose above it during exceptionally strong storms and in the Early Bathonian zigzag chron when the basin experienced considerable shallowing. The shallowest and highest energy conditions occurred in the late macrescens subchron, when the bottom was close to, or above the fair-weather wave base. The estimated depth of the sea did not exceed several tens of metres, but in some periods it could be even less than 20 m. Based on the vertical variation of the sand, silt and clay contents, seven transgressive-regressive cycles have been distinguished in the approximately 75-m thick succession spanning the Upper Bajocian - Upper Bathonian. Cycles TR1, TR2+3, TR5 and TR6+7 correlate with those distinguished in the coeval succession from central Poland, although the stratigraphic position of cycle boundaries is slightly shifted. These cycles record relative sea-level changes that affected the entire Polish Basin. Regressions R2 and R6 were smaller-scale-events, generated in response to a local tectonic activity and autocyclic shoreline progradation.

3

Strefowość wzrostu kryształów galeny z kopalni Bolesław koło Olkusza (region śląsko-krakowski)

Natkaniec-Nowak L., Pawlikowski M., Sikora M., Tarkowski J.

Przegląd Geologiczny

|

2007

|

Vol. 55, nr 6

498-502

EN

Idiomorphic galena crystals occurring within Triassic dolomites from the Bolesław mine near Olkusz were the subject of the study. The samples were collected from vein-pocket-like aggregates of galena, where two stages of mineralization were distinguished. Polished samples were etched with HCl (1:3). Etching revealed the growth zones of PbS crystals. Subsequently, decrepitation, chemical and X-ray analyses were applied. Two decrepitation effects, recorded at the maximum at 150-180°C and 250-300°C, are related to decrepitation of the two inclusion types. The chemical composition and unit cell size vary within the individual growth zones of the crystals. It can be concluded that during growth of the galena crystals the physico-chemical conditions were not stable.