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Abstract: An early to mid-Holocene humid period has been inferred from a variety of geo-bio-archives of the Sahara and the Arabian Peninsula including sabkhas, palaeo-lakes, sand dunes, wadis, speleothems or marine sediments. On the Arabian Peninsula, most of these records are located in the southern and southeastern part. Studies from the northern part are rare. This paper presents the first results from palaeo-environmental and hydrological investigations on the sabkha basin of the Tayma oasis, northwestern Saudi Arabia. Sedimentary characteristics, micro- and macrofauna, a digital elevation model based on DGPS measurements, and 14C-AMS data indicate the presence of a perennial lake with a minimum depth of 13 m, a stored water volume of 1.16 × 107 m3 and a surface of 18.45 km2 between 10,000–9000 cal BP. Foraminiferal test malformations and the shape of sieve pores on ostracod valves were used to detect trends in palaeo-salinity and ecological stress conditions. The reconstructed gradual contraction of the lake at least after 8500 cal BP reflects the long-term aridisation trend on the Arabian Peninsula after the early Holocene. Based on the hydrological water balance equation, quantitative data on minimum palaeo-rainfall during the early Holocene humid period were calculated. Input parameters for the equation are the minimum lake level, lake surface, and lake volume during the peak of the early Holocene humid period as well as palaeo-evapotranspiration, groundwater infiltration, and surface runoff. Accordingly, a perennial lake in the endorheic basin of the modern sabkha with a lake level at the same elevation as the uppermost shoreline deposit would have required a minimum annual precipitation of 150 ± 25 mm. This value amounts to c. 300% of recent precipitation rates. [Copyright &y& Elsevier]

Barchan dune fields are a dominant landscape feature in SE Qatar and a key element of the peninsula’s geodiversity. The migration of barchan dunes is mainly controlled by dune size, wind patterns, vegetation cover and human impact. We investigate the variability of dune migration in Qatar over a time period of 50 years using high-resolution satellite and aerial imagery. We then explore its relation to the regional Shamal wind system, teleconnection patterns, and limitations in sand supply associated with the transgression of the Arabian Gulf. Strong size-dependent differences in migration rates of individual dunes as well as significant decadal variability on a dune-field scale are detected, which are found to correlate with the intensity of the North Atlantic Oscillation (NAO) and the Indian Summer Monsoon (ISM), in particular during years of relatively strong (weak) summer Shamals. High uncertainties associated with the extrapolation of migration rates back into the Holocene, however, do not permit further examination of the timing of the loss of sand supply and the onset of the mid-Holocene relative sea-level (RSL) highstand. For the youngest phase considered in this study (2006–2015), human impact has likely accelerated dune migration under a weakening Shamal regime through sand mining and excessive vehicle traffic upwind of the core study area. [ABSTRACT FROM AUTHOR]