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

Abstract

Reworking and redeposition of tektites is a highly complex and multistage geological process including many factors. A tumbling experiment was therefore undertaken with the aim of estimating a distance of transport that such moldavites can withstand. Though the experiment probably did not accurately mimic natural conditions, our results proved that moldavites can withstand considerable transport only over a distance of a few kilometers. Observed abrasion of tektites was significant in the early stage of experimental transport; the rate of abrasion decreased correlatively with increasing distance of transport as usual. Overall, given the results obtained from this experimental study and their state of preservation described in the literature, it is very likely that Polish tektites were reworked and redeposited by rivers from the Sudetes Mountains. Based on the paleoreconstruction of river flows, it can be assumed that the Polish tektites originated from two independent sediment supply areas.

Modavite finds in Middle Miocene (Langhian Stage) deposits of southwestern Poland

“…510 km from the Ries crater (BRACHANIEC, 2017), but fluvial transport made it challenging to reliably estimate the original ex-tent of the dispersal area of all redeposited tektites. Generally, tektites could survive hundreds of km by fluvial transport (HURTIG, 2019), not as previously thought, a dozen or so at most (VAM-BEROVÁ and ŠEVČÍK, 1990;BRACHANIEC, 2018aBRACHANIEC, , 2018bBRACHANIEC, , 2019aBRACHANIEC, , 2019b. The discovery of moldavites in the Middle Miocene deposits in SW Poland is consistent with modeling (STÖFFLER et al, 2002;ARTEMIEVA et al, 2013).…”

Variations in fluvial reworking of Polish moldavites induced by hydrogeological change

“…Initial results of experimental reworking of moldavites showed that their abrasion progresses very quickly (mainly during the early phase of cycles) and their transport is only possible on relatively short distances (BRACHANIEC, 2018). For the purpose of experiment tumbling cycles carried out by BRACHANIEC (2018) are provided as "cycles no.…”

“…This explains why the age of moldavite-bearing deposits differs so drastically from the age of these tektites' formation. The preliminary results of the experimental tumbling of moldavites confirmed their high susceptibility to fluvial abrasion (BRACHANIEC, 2018). However, the generally accepted river-flow velocities in SW Poland and sedimentary deposition variability did not allow for the precise determination of the relationship between river flow velocity, sedimentary type, and distance of fluvial transport of tektites at hand (BRACHANIEC, 2018).…”

“…The preliminary results of the experimental tumbling of moldavites confirmed their high susceptibility to fluvial abrasion (BRACHANIEC, 2018). However, the generally accepted river-flow velocities in SW Poland and sedimentary deposition variability did not allow for the precise determination of the relationship between river flow velocity, sedimentary type, and distance of fluvial transport of tektites at hand (BRACHANIEC, 2018). An important factor determining the distance of glass transport in river environments seems to be the amount of gravel: in the case of moldavitebearing sediments of SW Poland, the percentage of gravel in these deposits increases from the West to the South-East (fieldwork observations).…”

A scheme for moldavite fluvial abrasion based on observations from a natural river stream

“…1). Initial results of experimental barrel observations (Brachaniec 2018a(Brachaniec , 2018b(Brachaniec , 2019a(Brachaniec , 2019b and compiled literature data ( Zebera 1972;Bou ska et al 1999) indicate that moldavites display low resistance to water abrasion, and subsequently can only withstand reworking over a short distance (up to a dozen km). However, such a process is so poorly known and so complex that such an issue requires baseline analyses and detailed research aimed at re-creating the process of water transport of impact glass.…”