THE pXRF MEASUREMENTS OF NEAR-SURFACE MANGANESE FOR THE RELATIVE PHASING OF THE LONGMENKA PETROGLYPHS, RUTOG COUNTY, XIZANG: AN EXPLORATORY ASSESSMENT

Establishing relative chronologies for open-air petroglyphs remains difficult where direct dating is unavailable. This study evaluates pXRF-derived near-surface manganese signals as complementary evidence for the Longmenka petroglyphs in Rutog County, Xizang. A total of 371 measurements were obtained from petroglyph and adjacent un-pounded sandstone surfaces, from which 113 image-level observations were retained after screening and aggregation. Because pXRF integrates signals from both rock varnish and underlying weathered sandstone, normalised Mn (NMn) is treated as a local composite index rather than a direct measure of age. NMn showed only a weak negative association with elevation; regression residuals (NMncor) were therefore used cautiously as an exploratory ordering variable. All nine independently observed superposition and cross-cutting relationships followed the expected stratigraphic direction in the NMncor sequence. Combined with production traces, motif comparison, inscriptions, and regional archaeological evidence, the results support a provisional four-phase model extending from the early first millennium BCE to a latest phase beginning no earlier than the 7th century CE.