Thermally assisted hydrolysis and methylation of the black deposit coatingthe ceiling and walls of Cueva del Encajero, Quesada, Spain

The black deposit coating the ceiling and walls of Cueva del Encajero, a ca vity with rock art was investigated. Thermally assisted hydrolysis and meth ylation revealed that the material is mainly composed of methylated fatty a cids, aliphatic dicarboxylic acids, benzene-carboxylic acids and phenolic a cids. Their comparison with humic acid-like fractions from fresh olive mill waste waters and aged sludge obtained from an evaporation pond indicates t hat this material is totally compatible with a plant origin. It is suggeste d that the black deposit derives from the decomposition of olives from non harvested olive trees growing on the surface, above the cave. (C) 1999 Else vier Science B.V. All rights reserved.