Geoarchaeology of Holocene oasis formation, hydro-agricultural management and climate change in Masafi, southeast Arabia (UAE)

Abstract

Oases are subject to decreasing resources and changing human activities. Fully aware of their rich heritage, the United Arab Emirates (UAE) have undertaken work to preserve and revitalize these oases. However, there is a clear lack of understanding of the dynamic links between climate change, hydraulic and agricultural management, and socioeconomic activities. To clarify these links, our team conducted a systematic geoarchaeological, geophysical, spatial, and chronological study of the Masafi oasis, UAE. Results indicate the existence of a natural humid area as early as the late Pleistocene (~18 cal ka BP). These conditions persist during the early-mid Holocene with drainage activation and soil development (~12–6.3 ka). During the late Holocene, after the emergence of the “artificial” oasis around ~3250 cal yr BP, cycles of intense management suggesting water availability (~3250–2380 cal yr BP; 550 cal yr BP) alternate with episodes of fluvial detritism (~2380–1870 cal yr BP; >550 cal yr BP) and scattered evidence of farming activities with complex hydroclimatic signatures (~2300–550 cal yr BP). These results, together with regional environmental data, indicate that water and soil resources were available and exploited strategically throughout the Holocene despite adverse climatic conditions, and the oasis of Masafi could have acted as a desert refugium.

Exploitation of groundwater in the oasis of Masāfī (UAE): A diachronic perspective

“…The lower part of the gallery’s fill was made of compact brown clays in which two complete ceramic vessels were found and dated from the fifteenth–sixteenth century AD. This is coherent with data from the geoarchaeological test pits that indicate important hydraulic activity around the fifteenth–seventeenth century AD in Masāfī, in particular the digging of irrigation channels in the western part of the oasis (Purdue et al, 2019: 122). This suggests that the underground gallery was dug during the Late Islamic period, perhaps even before the fort.…”

“…A layer of dark brown to dark reddish‐brown fine silts was radiocarbon‐dated to the end of Iron Age II (796–542 cal. BC; Purdue et al, 2019: 119), thus providing a terminus ante quem for the digging of W. We can therefore suggest that the latter was in use during the Iron Age II.…”

“…Fifty hydraulic structures were identified in the southern part of the oasis (Figure 2), dated from the mid‐second millennium BC up to today (Charbonnier et al, 2017a: 59–60; Purdue et al, 2019: 125). Forty‐five of them were detected on the surface during the field surveys, while five ancient wells were identified in stratigraphy, geoarchaeological Test pits A, B and C).…”

“…Third, survey in the oasis itself has also shown the trace of an ancient perched aquifer formed at the contact between Early Holocene/Late Pleistocene fine sediments and cemented Pleistocene fan deposits (Purdue et al, 2019: 128). This perched aquifer was probably fed by increased local rainfall and/or higher levels of the harzburgite aquifer.…”

“…BC by radiocarbon. This Iron Age layer corresponds to a past agricultural soil that shows traces of in situ burning, probably related to a cultivation technique (Purdue et al, 2019: 119).…”