New moldavites from SW Poland

Abstract

Large impact craters are relatively rare in geological record on the Earth. All over the world only 164 crater structures are above 1 km in diameter and only 40 with with more than 20 km in diameter (Earth Impact Database). The most notable features of such big impacts are significant pressure and temperature caused by extraterrestrial body fall. In some cases, impact may lead to glass production, which is named tektite. The distribution and chemical features of impact glasses are the most diagnostic features of the cosmic body impacts. Tektites are distal ejecta type deposits, next to three other impact melt products (Osinski 2003): (1) crystalline melt bodies in the impact structure, (2) glassy clasts in melt-bearing breccias or suevite, and (3) injection dykes in the crater. These different types of glasses form during the shock melting phase of target. Impact melt glasses resemble a terrestrial volcanic glass in appearance. There are three properties, which can be used to distinguish between the impact and terrestrial types of glasses: (1) the impact glass has a chemical composition of one lithology or mixture of different rock types that are present in the source basement (Dence 1971), (2) it is characterized by the presence of lechatelierite (Stöf-fler 1984), and (3) it has inclusions of shocked minerals (Engelhardt 1972). Characteristic shapes of tektites result from three stages of processes (Baker 1963): (1) the cooling of molten terrestrial material, (2) the flight of tektites through the atmosphere (however this stage did not occur in most of the tektites) and (3) emplacement on Earth's surface, when geochemical processes, like redeposition or weathering, finally influence the morphology of tektites.Up Będzińska Str. 60, krzysztof.szopa@us.edu.pl, lukasz.karwowski@us.edu.pl. ABSTRACT:Brachaniec, T., Szopa, K. and Karwowski, Ł. 2016. New moldavites from SW Poland. Acta Geologica Polonica, 66 (1), 99-105.Warszawa.Four newly discovered moldavites from the East and West Gozdnica pits, SW Poland, are characterized. All specimens, including other four, reported earlier, are from Upper Miocene fluvial sediments of the Gozdnica Formation. Their weight varies between 0.529 and 1.196 g. The moldavites are bottle green in colour and have bubbles and inclusions of lechatelierite. Low degree of corrosion suggests short river transport, apparently eastward from Lusatia.

The most distal moldavite findings from Lower Silesia, Poland

“…The Ries crater was produced by the impact of an asteroid that was probably 1.5 km in diameter (STÖFFLER et al, 2002). European tektites originated from the melting of the uppermost sedimentary target rocks that belong to the Upper Freshwater Molasse, which overlies the Swabian-Franconian Alb plateau (MEISEL et al, 1997;TRNKA and HOUZAR, 2002;ŘANDA et al, 2008;MAGNA et al, 2011; BRACHANIEC et al, 2014bBRACHANIEC et al, , 2015BRACHANIEC et al, , 2016, and this study). B. and C. General view of the Gozdnica Formation in the western part of the Nowa Wieś Kącka sandpit.…”

“…Additionally, the small amount of gravel in deposits and paleoriver meanders of the Gozdnica Formation, along with some low- Table 2. Chemical composition (based on electron microprobe analysis) of Polish moldavites from all known localities; *data from BRACHANIEC et al (2015), ** data from BRACHANIEC et al (2016), *** this study, **** LANGE (1995). …”

“…According to BOUŠKA et al (1968), LANGE (1995LANGE ( , 1996, TRNKA and HOUZAR (2002), and to BUCHNER and SCHMIEDER (2009), the brittle character of tektite glass is thought to drastically reduce the lifetime of fluvially transported glasses, and the distance of transport. Accordingly, BRACHANIEC et al (2015BRACHANIEC et al ( , 2016 claimed that the largest Polish tektites (ranging from 0.15 to 1.196 g), found in the Gozdnica section near the German border, indicate rather short fluvial transport. Additionally, the small amount of gravel in deposits and paleoriver meanders of the Gozdnica Formation, along with some low- Table 2.…”

“…(d'après BRACHANIEC et al, 2014b(d'après BRACHANIEC et al, , 2015(d'après BRACHANIEC et al, , 2016 2012SKÁLA et al, 2016;RODOVSKÁ et al, 2016). BRACHANIEC et al (2014bBRACHANIEC et al ( , 2015BRACHANIEC et al ( , 2016 and SZOPA et al (2017a) recently described moldavite finds in SW Poland. The present communication discusses the recently discovered Polish moldavites.…”

An experimental model for the tektite fluvial transport based on the most distal Polish moldavite occurrences

“…Based on paleogeographical reconstruction and from the Polish tektite size, Brachaniec et al. (, , ) concluded that they originated from Lusatia. In order to test this suggested long‐distance moldavite transport, tumbling experiments were conducted.…”