RADIOCARBON DATING OF CAVE PICTOGRAPHIC ROCK ART IN PUERTO RICO

Puerto Rico has the highest densities of rupestrian rock art of the Caribbean but the absolute chronology of more than 500 context are not well known. Many studies have been carried out to understand the chronology of various manifestations of rupestrian rock art of Puerto Rico but to refine the temporal resolution of rock art on the island, its antiquity has been approximated indirectly based on its spatial proximity to absolutely dated archaeological contexts. For this study, we dated 61 pigment samples from 11 caves using accepted geoarcheological techniques of radiocarbon dating. This is the first study to date cave rock art in Puerto Rico main island. To obtain the pigment samples of the pictographs to be dated, the protocols established by Rowe (2005) were used and only pigment samples of approximately 1 to 2 mg of circumscribed spaces that did not erase any specific element of the image or alter its general configuration were collected. Samples then were processed by the Center for Applied Isotope Studies (AIS) at the University of Georgia. Carbon-14 radiometric dating uses the AIS particle accelerator mass spectrometry (AMS) for micro-samples in archaeological studies. Carbon-14 radiometric dating is used for its range (~400 - 50,000 years) but in Puerto Rico pigments were expected less than 10,000 years. Rupestrian rock art consisted in petroglyphs (carving), pictoglyphs (organic pigment) and pyroglyphs (fire). The rock art images types were abstract, anthropomorphic, zoomorphic, geometrical shapes and modern. As a result, for this study, we found the first manifestations (740-400 b.C), abstract or geometrical elements, coincide with the described Archaic Age. Then, pictographs register again between 200 - 400 a.C. using anthropomorphic faces and three centuries later, now 700 - 800 a.C., anthropomorphic bodies and rounded faces. After 1100 a.C., natural elements are incorporated as zoomorphic images and the combination of anthropomorphic and zoomorphic images started to be used 1300 a.C. and continued to the European invasion. This study pretends to start the absolute temporality of cave pictographic rock art in Puerto Rico, only 11 caves were studied out of more than 300 documented caves and shelters with rock art.