Luminescence Dating of Dune Sand, Wadi, Sabkha and Playa Sediments, Saudi Arabia

Burbidge, C., Sanderson, D. and Fulop, R.-H. (2007) Luminescence Dating of Dune Sand, Wadi, Sabkha and Playa Sediments, Saudi Arabia. Technical Report. Scottish Universities Environmental Research Centre.

Abstract

This study supports a new investigation into the timing and rates of clay formation in mid-Arabia as a function of climatic and geomorphological context. Optically stimulated luminescence (OSL) age determinations have been made for a range of dune, wadi, sabkha and playa deposits across mid-Arabia (section 3). The geomorphological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6). 36 sets of dose rate determinations were made (sections 4.2.1, 5.1) using thick source beta counting, high resolution gamma spectrometry, measured water contents and calculated cosmic dose rates, including separate measurements on bulk and sieved (<1 mm) material from one inhomogeneous sample. 39 sets of equivalent dose determinations were made (sections 4.2.2, 5.2) using the OSL signals from sand sized grains of quartz separated from each sample, including a travel dosimeter, two modern surface samples, and one repeat. A total of 35 age determinations were made (section 5.3), including two each from the middle and bottom parts of two vertically cored samples. Dose rates ranged from 0.42 to 2.4 mGy/a, and with the exceptions of the travel dosimeter and one sample with its OSL signal in saturation, De values ranged from 0.01 to 24 Gy. Age estimates for these samples ranged from 0.01 to 15 ka, the average being 5 ka ± 5 (section 5.3). Uncertainties on the age estimates were commonly 10 – 20 % at one standard deviation, though percentage uncertainty was higher for age estimates close to zero. Overall the data indicated that a variety of geomorphological features have ages spread through the late glacial period and early-mid Holocene (~15 to ~4 ka). Few features date to between ~4 ka and ~0.2 ka, but many date to within the last ~200 years (section 6.3). Most of the youngest features were active dune slipfaces and thin sand sheets, they also included a thicker structureless sand, relict foresets, and playa deposits, but no sabkha. The older features were mainly aggraded sabkha deposits (horizontal bedding), relict foresets (including those in which sabkha has formed), and thick structureless sands. Of these older features, the foresets and sands all dated to before ~7 ka. This period includes both wetter and dryer climatic phases, but is notable for dramatic sea level rise in the Arabian Gulf. The coastal aggraded sabkhas, and one inland sabkha, have ages ranging from 3.3 ka ± 0.5 to 5.9 ka ± 1. These correspond to a period of fluctuating wet and dry climatic conditions, and sea level fluctuating about its present day level. The results indicate major sand emplacement in the study region during late glacial and early Holocene sea level rise (16 – 7 ka), followed by mid-Holocene (6 – 3.5 ka) sabkha formation as sea levels stabilised. A lack of samples dating from the late Holocene, followed by a number dating to the last ~ 2 centuries, indicates that either there was a hiatus in landform formation until relatively recent times, or that features formed since the mid Holocene have been reworked, possibly on a bicentennial timescale.

• Item Type: Research Reports or Papers (Technical Report)
• Status: Published
• Glasgow Author(s) Enlighten ID: Fulop, Miss Reka-Hajnalka and Sanderson, Professor David and Burbidge, Dr Chris
• Authors: Burbidge, C., Sanderson, D., and Fulop, R.-H.
• Subjects: G Geography. Anthropology. Recreation > GB Physical geography; G Geography. Anthropology. Recreation > GE Environmental Sciences; G Geography. Anthropology. Recreation > GF Human ecology. Anthropogeography
• College/School: College of Arts & Humanities > School of Humanities > Archaeology; College of Science and Engineering > Scottish Universities Environmental Research Centre
• Publisher: Scottish Universities Environmental Research Centre