Petrographic, mineralogical, and climatic analyses, and risk maps for conservation strategies

Wojciech Bartz, Jacek Kościuk, Maria Gąsior, Teresa Dziedzic



El Fuerte de Samaipata is a pre-Hispanic archaeological site in Bolivia that has been on the UNESCO World Heritage List. Its main part – the rock – is densely covered with a complex arrangement of terraces, platforms, water reservoirs, channels, and petroglyphs. The rapidly progressing erosion of the rock is making the petroglyphs less and less clear, and some are no longer recognisable. The main topic of this study is to indicate all risk factors conducive to erosion and to create risk maps identifying the most vulnerable areas that require immediate conservation intervention. Parallel mineralogical and petrographic studies show that the Samaipata rock is a quartz-rich, porous, well-sorted sandstone, classified as quartz arenite or subarcosic arenite. The cement of the rock is composed of quartz overgrowth and ubiquitous, pore-filling hematite-clay aggregates containing non-expanding kaolinite, illite, and expanding smectite. The rock exhibits different stages of weathering, from relatively fresh to strongly altered and heavily cracked. In comparison to fresh rock, the latter has cement enriched in clay minerals and is depleted in hematite due to weathering and the dissolution of the iron-bearing phase.

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