IAWA JOURNAL, vol.33, no.3, pp.319-326, 2012 (SCI-Expanded)
Oltustone is a semi-precious gemstone found only in the Late Cretaceous (Upper Maastrichtian) Dutlu Formation of Turkey. Microscopic examination of oltustone reveals that it consists of fossilized Agathoxylon wood (Araucariaceae). This represents one of the latest occurrences of the Araucariaceae in southern Eurasia and is also the southernmost recorded for the Laurasian continent.