Were they engraved? Cave art taphonomy in the Lesser Antilles - Working hypotheses

Here we present the working hypotheses of a project dedicated to the taphonomy of cave rock art in the Lesser Antilles, based on results provided by the preliminary study of two Amerindian-occupied caves in Marie-Galante, FWI. In the caves of Guadeloupe, it is sometimes possible to observe wall morphologies that resemble pre-Columbian petroglyphs, but without engraved lines. The question arises then whether these morphologies are engraved pictures. Blanchard Cave (S coast of Marie-Galante), contains such wall morphologies that can be thought to represent weathered petroglyphs, especially when considering the pre-Columbian burials preserved in the cave entrance. The study of physical processes acting in the site provides an understanding of mechanisms that could have caused the engravings' disappearance. Site microclimatology, assessed by hygrometric and thermic measurements, reveals an unstable regime due to air currents that bring cold air deep into the cave. The result is a limited hygrometry and, above all, a transport of sea spray. The marine aerosol inputs highlight the occurrence of salt and gypsum minerals on the walls that trigger salt weathering of the rock. The resulting sediment is typically loose, very light tan silt that accumulates on the cave floor. Test pits were used to characterize and to date sediments deposited in the cave. Taking into account the rate of accumulation of sediments produced by weathering allows estimates of mean wall weathering of up to 0.6 cm/century. Such a rate would explain the alteration and even the disappearance of Amerindian carvings that are several centuries old. The questionable morphologies observed in Blanchard Cave have been compared to the Pre-Columbian petroglyphs preserved in the nearby cave of Morne Rita through photogrammetric recording. This comparison shows that the wall morphologies observed in the first site have a size and shape that fall into the variability of Pre-Columbian artworks, although they are characterized by a blurred surface and an enlargement of the outline and the cupules ascribable to the wall alteration by salt weathering. Based on these observations, it can be hypothesized that the Blanchard cave is a degraded petroglyph site. These preliminary results also help to identify the factors leading to certain types of degradation (size, morphology, nature of the rock and location). Considering that such factors are common in Lesser Antilles caves, a more general theory can be proposed that a number of engraved caves of the Lesser Antilles have not been identified as such. These hypotheses, if proven true, have two important implications for the interpretation of the pre-Columbian decorated caves distribution: 1) an under-representation of the number of known sites and 2) a bias, in the preserved sites, favoring "wet" caves where salt weathering of the cave walls does not occur.