Shape analysis of moldavites and their impact origin

Abstract

SUMMARY. I666 moldavites from 19 localities in Bohemia and 617 moldavites from IO localities in Moravia were measured to yield parameters L (length), B (breadth), and T (thickness). A digital computer was programmed to calculate values T/L, (L--B)/(L--T), andThe data obtained permit an interpretation that localities of moldavites with low average sphericity contain less heated material. Less heated and thus more viscous glass could have flown along shorter trajectories (Bohemia). More heated glass was ejected to geographically more distant places (Moravia) or travelled along reIatively long steeper trajectories (several localities in Bohemia).MOLDAVITES from localities in Bohemia are mostly drop-like, flat or elongate, whereas moldavites from localities in Moravia are frequently massive to spheroidal. Among the moldavites in Bohemia, complete forms are rare, which can be explained by an easier breakage of flat or rod-like forms with a relatively low sphericity. Massive torspheroidal moldavites from Moravia yield more complete forms. Most fragments, irrespective of their present shape, indicate sphericity of the original forms, so that average values of a large number of measurements characterize individual localities.Shape, colour, weight, and surface features of several thousand moldavites were described qualitatively by Bou~ka, Faul, and Naeser (I968). They concluded that 'Shapes of moldavites show significant differences among localities, but no trends appear, it is possible to state only that the moldavites from Moravia have mainly round shapes. Moldavites could not have been transported more than a few km by water, and the original strewn fields must have been very small.' Konta and Mr~tz (1969) studied the relationship between chemical composition, bulk density, and sphericity and hypothesized a relationship between sphericity of moldavites and viscosity of the hot glass and the magnitude of thermal energy liberated in different impact areas.This study was aimed at exploiting the shape analysis of moldavites to verify the assumed mutual position of the source area (Ries Crater) and the strewn fields. Shape parameters of tektites such as sphericity, which have not been explored yet, were analysed quantitatively. The shape parameters of moldavites were expressed analogously to those of fragments used in petrology of coarse clastic sediments (Sneed and Folk, I958; Zingg, 1935). In the course of a secondary relatively short transport by 9

The formation of the Ries Crater, West Germany; Evidence of atmospheric interactions during a larger cratering event

“…The extremely localized occurrence of moldavites in only one direction from the crater may point to an oblique impact from the west (Schultz and Gault, 1982). Konta (1971) has suggested that the variations between the Moravian and Bohemian Moldavites could be explained by different ejection angles from the Ries crater resulting in different atmospheric heating histories, with the lesser heated material landing in Bohemia (a range of 260 km) and the more heated glass landing in Moravia (a range of 400 km).…”

“…Moldavites found in different localities have systematic differences in shape and in contents of lechatelierite and bubbles that may represent different degrees of heating (Konta, 1971). Bohemian moldavites at a range of approximately 300 km from the Ries crater, consist mainly of drop-like, flat, or elongated fragments with an average weight of 4.5 gm (Konta, 1971).…”

“…Bohemian moldavites at a range of approximately 300 km from the Ries crater, consist mainly of drop-like, flat, or elongated fragments with an average weight of 4.5 gm (Konta, 1971). These moldavites have lechatelierite inclusions (0.45 mm average diameter) and evacuated bubbles (0.48 mm average diameter; Barnes, 1964).…”

“…These moldavites have lechatelierite inclusions (0.45 mm average diameter) and evacuated bubbles (0.48 mm average diameter; Barnes, 1964). Moldavites from Moravia, however, at a range of 400 km, consist of massive to spheroidal forms with average weight of 15.4 gm (Konta, 1971). The lechatelierite inclusions and bubbles are smaller and less abundant (0.12 mm and 0.29 mm average diameters, respectively; Barnes, 1964).…”

The first polish tektites: preliminary sem investigation

“…The amount of lechatelierite depends on the temperature conditions of origin. Higher temperature caused a lower abundance of lechatelierite in Czech and German moldavites (Barnes 1969;Konta 1971a;Lange 1995). Lechatelierite in moldavites is represented by very pure silica (Fig.…”