| Popis: |
The Australasian (AA) tektite strewn field covers more than 10% of the Earth’s surface [1]. This areal distribution, together with the size of individual tektites (up to ~25 kg) and total recovered mass, indicates that the AA “strewn field–forming event” produced several orders of magnitude more tektites than other tektite-forming events (i.e., Bosumtwi, Ries, Chesapeake Bay). Despite indications for the location of the impact site near the Indochina peninsula [2], the young age of ~0.8 Ma [3], and an estimated crater size between 20 and 100 km Ø [4,5], no AA tektite related impact structure has been identified so far. Therefore, other scenarios, such as a low-altitude airburst of an intercepting comet, were suggested to have formed the AA tektites to explain the missing impact structure [6]. Wasson [6] referred to the absence of a projectile-related signature in the AA tektites as strong support for his scenario. In contrast to an impact cratering event, a low-altitude airburst does not involve direct contact between the projectile and the solid surface and does not provide the conditions to efficiently mix projectile and target materials. So far, a projectile-related signature in tektites has only been unambiguously identified in few Ivory Coast specimens ejected from the Bosumtwi crater by rhenium- osmium and Cr isotope systematics [7,8]. We report the identification of a projectile-induced signature in AA tektites. |
