FIELD RECOVERY OF LAYERED TEKTITES IN NORTHEAST THAILAND

We recovered Australasian tektites in place throughout a 40X130 km reg ion in northeast Thailand extending from the Laotian border westward t o a line connecting Na Pho Klang in the northeast through Det Udom to Nam Yun in the south. With two exceptions, in sites near the western e dge of this region, all fragments are layered (muong-Nong-type) tektit es, It appears that large layered tektites are mainly found by rice fa rmers in fields that were forested until the recent past. The presence of layered tektites in this 40X130 km area implies that impact melt t hat fell in these areas was hot enough to flow if it was deposited on a sloping surface. The absence of splash-form tektites from the region indicates that the layer was still molten when masses having shapes ( teardrops, dumbbells, etc.) produced by spinning reached the ground. T o account for this and to allow time for the melt to flow a few tens o f centimeters requires that the atmosphere remained hot (>2300 K) for a few minutes. Tektites that are in place are almost always associated with a widespread IO-cm to meter-thick layer of laterite. In two case s (one involving layered, one involving splash-form tektites), where a ccurate stratigraphic control demonstrated that the tektites were stil l in section, they were sited on top of the laterite layer just below a layer of aeolian sand.