Evaluating possible prehistoric cave art in the central Mediterranean : analyses of pigment traces and identification of taphonomic processes at Għar Ħasan, Malta

Abstract

The archaeology of the Maltese Islands, particularly the megalithic ‘temple’ structures and underground mass burial sites (hypogea) of the ‘Temple Period’ (ca. 3800 – 2300 BCE), has been the subject of considerable interest. Less is known about the prehistoric use of caves. In particular reports of prehistoric cave art at Għar Ħasan (Hasan’s Cave) have remained controversial, and have been argued to reflect an otherwise unknown pre- Neolithic occupation on the islands. Here, we report a reinvestigation of Għar Ħasan. To distinguish graffiti that have accumulated over the last century and possible older rock art, a range of non-invasive methods were used to determine the chemical properties and colour spectrum of the pigment traces: portable energy-dispersive X-ray fluorescence spectrometry (p-ED-XRF) and visible (VIS) and near-infrared (NIR) spectroscopy. In addition, pigment traces were analyzed with digital microscopy and image enhancement techniques (DStretch). Most of the previously reported cave paintings were shown to have been produced in the last century. One key panel may be older, but vandalism and other destructive processes make a definitive assessment challenging. While we therefore consider the evidence for ‘Palaeolithic’ cave art at Għar Ħasan to be inconclusive, our study also identified complex taphonomic processes that pose severe limitations on the identification of pigment via p- ED-XRF and spectroscopy and can inform and guide future initiatives for rock art conservation.