| Abstract: | Tasmanian Darwin glass has a fusion age sensibly identical with that of Australasian tektites and it is reasonable to assume all were produced in the same event. Recently a number of new Darwin glass localities and an associated crater have been discovered. The glass stewnfield covers at least 400 km2 and there is a strong positive correlation between glass fragment size and abundance and proximity to the crater. The glass was distributed from some point near the crater, with the smallest pieces traveling furthest. This structure is apparently an impact crater of rather unusual configuration and fortuitous location. Our gravity survey reveals a closed sedimentary basin about 1000 meters in diameter. A centrally located drill hole penetrated 60 meters of lacustrine clays and 40 meters of mixed clay, sand and rock fragments. The hole was terminated at 100 meters in loose sand containing sand-sized fragments of Darwin glass and lechetelierite. The 100 meters of cored sediments accounts for only about half of the observed 3.5 milligal negative anomaly and there must be a substantial additional thickness of low density material at depth. Further drilling is essential to confirm an impact origin and to delineate the subsurface crater configuration. This information would be of great calibration value for theoretical modeling studies of explosive cratering. The Darwin strewnfield characteristics support the theory that the distribution of Australasian tektites was aided by an impact-generated, atmospheric blast wave (or waves). The stratigraphic position of glass below 100 meters of lake sediments is strong evidence that the postulated stratigraphic age of the Australian land tektites is incorrect. |
