Composition of Modern Dust and Holocene Aeolian Sediments in Archaeological Structures of the Southern Levant

Abstract

Archaeological structures are often filled with sediments and may serve as effective dust traps. The physical parameters and chemical composition of archaeological soils in hilltop ruins, ancient runoff-collecting terraces, and cleanout spoils of cisterns were determined in the Petra region in southern Jordan and the Northern Negev in Israel. Different types of ruins are characterized by certain soil structures, but could not be distinguished with regard to substrate composition. This reflects a predominance of aeolian processes for primary sedimentation, while fluvial processes seem to only re-distribute aeolian material. In the Petra region, the physical and chemical properties of all archaeological soils show a significant local contribution from associated weathered rocks. Compared to modern settled dust, archaeological soils in Southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This seems connected with preferential fixation of silt and clay by surface crusts, and a role of moisture in sedimentation processes as calcareous silt was found to be deposited in greater amounts when associated with precipitation. In contrast, the contribution of rocks is negligible in the Negev due to greater rock hardness and abundant biological crusts that seal surfaces. Archaeological soils in the Negev are chemically similar to current settled dust, which consists of complex mixtures of local and remote sources, including significant portions of recycled material from paleosols. Archaeological soils are archives of Holocene dust sources and aeolian sedimentation processes, with accretion rates exceeding those of Pleistocene hilltop loess in the Negev. Comparison with Pleistocene paleosols suggests that dust sources did not change significantly, but disappearance of snow could have reduced dust accumulation during the Holocene.

Holocene dust dynamics archives in archaeological ruins in arid and semi-arid environments in the Southern Levant

“…However, some structures are characterized by wall remains still higher than their sediment fill: the circular hilltop ruin (central wadi) in the northern Negev and the Jabal Farasha and Monastery garden hilltop ruins near Petra. Based on the ages available from these sites, it was possible to estimate mean annual sedimentation rates: ~ 0.14 mm were found in the circular hilltop ruin (central wadi) in the northern Negev and in the Jabal Farasha hilltop ruin in the Petra region, which are located on isolated hilltops (Lucke et al 2019b). These rates are in good agreement with values from current dust collection in standard dry marble collectors (Lucke et al 2019b;Kidron et al 2014).…”

“…Based on the ages available from these sites, it was possible to estimate mean annual sedimentation rates: ~ 0.14 mm were found in the circular hilltop ruin (central wadi) in the northern Negev and in the Jabal Farasha hilltop ruin in the Petra region, which are located on isolated hilltops (Lucke et al 2019b). These rates are in good agreement with values from current dust collection in standard dry marble collectors (Lucke et al 2019b;Kidron et al 2014). However, proximity to rock cliffs hosting active tafoni in the Petra region, given at the monastery garden and a close collector of current dust, is connected with doubled deposition rates of ~ 0.29 mm per year (Lucke et al 2019a, b).…”

“…However, the cleanout mound next to the open cistern in the Negev proved more promising for dating. Although it was partly affected by bioturbation of large mammals (probably porcupines), sediments could be dated and represent aeolian-fluvial deposition during the period of cistern use in the Byzantine and early Islamic periods (Lucke et al 2019b).…”

“…Deposition amounts in archaeological hilltop ruin soils thus exceed Pleistocene sedimentation rates in natural hilltop soils in the southern Negev, which were calculated as 0.02-0.058 mm per year (Crouvi et al 2009). In terraces, sedimentation rates vary strongly, but are not connected to catchment size or bedrock (Lucke et al 2019b). They probably depend on the situation and functioning of the runoff irrigation system.…”

Quaternary influx of proximal coarse-grained dust altered circum-Mediterranean soil productivity and impacted early human culture: COMMENT

“…Crete is also not devoid of terrace remains (Orengo and Knappett, 2018) and they are abundant in nearby islands (Bevan et al, 2013). Ancient terrace construction did not depend on sufficiently deep hilltop soils: research at Petra in Jordan demonstrated that Nabatean runoff-irrigated terraces harvested not only water, but also aeolian sediments, thus creating fertile soils on previously barren rocks (Lucke et al, 2019). Moreover, agriculture has been practiced on various soils of the southern Levant, favorably on colluvial soils of local depressions (Singer, 2007).…”