The geology of the Jabal Harûn area

Paula Kouki

(click the image to see a larger map with legend) Barrages in Wad as-Saddat (photo: P.Kouki).

Jabal Harûn is located on the fringes of the Wadi 'Arabah rift valley. The average elevation from the sea  level in the survey area is ca. 3280 feet, while the top of Jabal Harûn reaches 4330 feet asl. The difference in elevation in the Petra region is considerable: from the 328  feet asl on the bottom of the Wadi 'Arabah up to over 5250 feet in the ash-Sharah mountains to the east of Petra. The bedrock of the Jabal Harûn area in mainly formed of Cambrian to Ordovician sandstones, but to the east of the mountain there is a geosyncline where Cretaceous limestones are met. These limestones have originally sedimented in the sea bed and then been subjected to folding in the subsequent tectonic events. To the north and east of the mountain there are exposures of Proterozoic-Early Cambrian volcanic porphyry, which remains as evidence of early volcanic activity in the area. The network of dry river-beds (wadis) is very dense in the Jabal Harûn area, which is typical of mountainous semi-arid areas. The largest of these channels have been follow the fault lines in the bedrock. Numerous smaller channels running down the slopes join these main wadis. In the event of a rainstorm flows of water will rapidly fill these channels, transporting large amounts of fine-grained sediment and depositing it in the level areas. The Nabataeans utilized this phenomenon for cultivation. By the means of terraces built on the slopes and dams constructed across the channels they directed and slowed down the flow of water, to collect the fine sediment and water for irrigation on their fields.