Analyses of pollen, plant macrofossils (seeds, fruits, wood and mosses), molluscs, diatoms and vertebrate (mainly fish) remains allowed a detailed reconstruction of a middle-Holocene alluvial forest and its associated hydrological conditions. The use of multiple proxies resulted in a taxonomically more detailed and environmentally more comprehensive understanding of terrestrial as well as aquatic habitats. The results demonstrate possible biases in palaeoecological reconstructions of alluvial and estuarine environments drawn from single proxies. Many locally occurring woody taxa were underrepresented or remained undetected by pollen analyses. Seeds and fruits also proved to be inadequate to detect several locally important taxa, such as Ulmus and Hedera helix. Apparently brackish conditions inferred from diatoms, pollen and other microfossils conflicted strikingly with the evidence from molluscs, fish bones and botanical macroremains which suggest a freshwater environment. Brackish sediment (and the microfossil indicators) is likely to have been deposited during spring tides or storm surges, when estuarine waters penetrated more inland than usual. Despite the reworking and deposition of estuarine and saltmarsh sediment well above the tidal node at such events, local salinity levels largely remained unaffected.
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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.
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RBINS Staff Publications 2018
