Carbonate crusts of Petra: Typologies, genesis and implications

Autor

• Nizar Abu-Jaber
  • nizar.abujaber [at] gju.edu.jo
  • website
  • reasearchgate.net
  • academia.edu

Institution

Center for the Study of Natural and Cultural Heritage, German Jordanian University, Amman, Jordan, Amman Madaba Street, 11180 Amman/Jordan

Abstract

Surficial carbonate deposits are ubiquitous in Petra and in the surrounding areas. These deposits take the forms of veins, cemented alluvium, pans, nodules, tufa, dust deposits, spring deposits, and encrustations within hydrological instillations such as pipes, dams, and cisterns among others. While these typologies seem to be distinct, there is often a clear continuum between some of them in certain places, strongly suggesting similar genesis.

These deposits are clearly related to the movement of water, both on the surface and within surficial soil/alluvium. Field observations, microtextures, geochemical and isotopic investigations give answers to questions on the conditions giving rise to the formation these deposits. These include information on the sources of calcium and carbonate, temperature conditions and hydrological conditions at the time of deposition.

The timing of deposition, on the other hand, remains elusive. Some of the depositional typologies are closely related to man-made structures and objects from the Nabatean period (water installation and storage systems such as pipes, cisterns, dams and wells to other more complex structures such as terraces). This relationship places an upper limit on these cases of about 2000 years. On the other hand, some of the crusts formed before the Nabatean period have not re-formed after removal caused by quarrying. Overall, the evidence suggests that the deposits are mostly relatively young.

Mapping the carbonates can help elucidate surface conditions at the time of formation as well as changing conditions in this tectonically active area. Some of them record some of the very active tectonic movements. Trapped clues of environmental change (such as pollens, spores and phytoliths) have yet to be explored. Some of these crusts have been associated with early human settlement abandonment such as prehistoric Sabra 3 and the Natufian Beidah. Archaeologist used these crusts to date the site abandonment, claim climatic catastrophic events and tectonic movements, yet these remain to be studied and cross checked. Thus, the study of these deposits promises to reveal important aspects of recent environmental history of the Petra region.