Development, distribution and palaeoenvironmental significance of terrestrial carbonates in the Petra region, southern Jordan

Abstract Terrestrial carbonate deposits are common in both natural and human-modified landscapes in Petra and its surroundings. Three broad genetic categories are recognized: cementations of pre-existing clastics (veins, crusts, cemented cobbles); free-water deposits (Massive Laminated Deposits (MLD), rhizoliths, carbonate blisters, coatings on archaeological water delivery systems), and pedogenic deposits (nodules, calcrete). The oxygen isotopic composition of carbonates suggests mainly precipitation from stored water that reflects the weighted isotopic average of rainfall in the area. Oxygen and carbon isotope data indicate that a combination of evaporation and CO2 degassing are the mechanisms for precipitation, depending on the setting and climate at the time of deposition. Strontium isotopes of carbonates point to an aeolian source (from adjacent sources) for the calcium. The cementations of pre-existing clasts are both markers of previous base levels in the case of cemented cobbles, and the presence of soil above impermeable bedrock in the case of crusts and veins. These types of deposits help to discover previously terraced sites. The open water deposits reflect humid Pleistocene conditions, and their presence inform on the extent and distribution of water resources that may have been available in the Late Pleistocene and early Holocene.