Sediment-filled karst depressions and <i>riyad</i> – key archaeological environments of south Qatar

Abstract

Abstract. Systematic archaeological exploration of southern Qatar started in the 1950s. However, detailed local and regional data on climatic fluctuations and landscape changes during the Holocene, pivotal for understanding and reconstructing human–environment interactions, are still lacking. This contribution provides an overview on the variability of geomorphic environments of southern Qatar with a focus on depression landforms, which reveal a rich archaeological heritage ranging from Palaeolithic(?) and Early Neolithic times to the Modern era. Based on a detailed geomorphic mapping campaign, sediment cores and optically stimulated luminescence data, the dynamics of riyad (singular rawdha; shallow, small-scale, sediment-filled karst depressions clustering in the central southern peninsula) and the larger-scale Asaila depression near the western coast are studied in order to put archaeological discoveries into a wider environmental context. Geomorphic mapping of the Asaila basin shows a much greater geomorphic variability than documented in literature so far with relict signs of surface runoff. An 8 m long sediment core taken in the sabkha-type sand flats of the western basin reveals a continuous dominance of aeolian morphodynamics during the early to mid-Holocene. Mounds preserved by evaporite horizons representing capillarites originally grown in the vadose zone are a clear sign of groundwater-level drop after the sea-level highstand ca. 6000–4500 years ago. Deflation followed the lowering of the Stokes surface, leaving mounds where the relict capillarites were able to fixate and preserve the palaeo-surface. Abundant archaeological evidence of Early and Middle Neolithic occupation – the latter with a clear focus inside the central Asaila basin – indicate more favourable living conditions than today. In contrast, the sediment record of the investigated riyad in the south is very shallow, younger and controlled by surface discharge, deflation and the constantly diminishing barchan dune cover in Qatar over the Middle and Late Holocene. The young age of the infill (ca. 1500 to 2000 years) explains the absence of findings older than the Late Islamic period. Indicators of current net deflation may relate to a decrease in surface runoff and sediment supply only in recent decades to centuries. In the future, geophysical prospection of the riyad may help to locate thicker sedimentary archives and the analysis of grain size distribution, micromorphology, phytoliths or even pollen spectra may enhance our understanding of the interplay of regional environmental changes and cultural history.

High‐resolution facies analysis of a coastal sabkha in the eastern Gulf of Salwa (Qatar): A spatio‐temporal reconstruction

“…The moderately to well‐rounded quartz grains of Facies E2 underlie the transgressive wedge of the sabkha and represent the aeolian dunes of the dry, late Pleistocene Gulf of Salwa. Its characteristic unimodal grain‐size distribution corresponds to modern aeolian sands of barchan dunes and surface depressions found in Qatar today (Embabi & Ashour, 1993; Engel et al ., 2018, 2020) and is directly related to the drowned barchan dunes, which have been identified inside the Gulf of Salwa (Kassler, 1973; Al‐Hinai et al ., 1987).…”

“…In the Asaila Basin, central‐eastern Qatar, deflation is also dominant and controlled in a similar way by a lowering groundwater level and Stokes surface after the mid‐Holocene RSL highstand. Ground surface lowering has been estimated to a minimum of 1.5 m, inferred from the elevation of remnant yardang‐type mounds (Engel et al ., 2020).…”

“…Miocene sedimentary rocks are mainly found in southern Qatar, represented by the shallow marine Dam and continental Hofuf formations. Quaternary deposits and landforms mainly comprise aeolian sand as sheets or barchan dunes (Embabi & Ashour, 1993; Engel et al ., 2018), silt to coarser‐grained alluvium covering inland karst depressions ( riyad ) (Engel et al ., 2020), mixed siliciclastic–carbonate inland and coastal sabkhas (e.g. Al‐Yousef, 2003; Billeaud et al ., 2014; Whitaker et al ., 2014; Strohmenger & Jameson, 2015, 2018), as well as skeletal beach sands (Shinn, 1973a; Strohmenger & Jameson, 2015; Rivers et al ., 2020).…”

Preface: Special Issue “Geoarchaeology and past human–environment interactions”

“…The study of Engel et al (2020) reports the results of a joint German-Qatari study that was carried out in the southern Qatari peninsula and was led by scientists from the University of Cologne. The authors investigated the current geomorphic setting and palaeoenvironmental changes recorded in karstic depressions that were centers of prehistoric settlement activity at least since the Neolithic period, focusing on the former availability of water resources.…”

“…In Germany, for example, most excavations are advance archaeological excavations in the context of construction works that are carried out by state departments of archaeology either on their own or by authorized private excavation companies in agreement with the authorities. The comprehensive and systematic application of geoarchaeological approaches is now slowly being realized at archaeological excavations, which also holds true for its use in the context of other applied archaeological questions such as creating databases for monument preservation (Gerlach et al, 2012;Tinapp, 2013;Beilharz and Krausse, 2015;Nadler, 2019). In addition to the development and integration of innovative methods and the further development of existing geoarchaeological concepts, the application of comprehensive and systematic geoarchaeological approaches in the daily practice of archaeological excavations and monument conservation is therefore a current challenge that must be addressed in the coming years in order to prevent further research gaps and an irreversible loss of potential knowledge.…”