Luminescence Dating of Back-Dune Sedimentary Sequences from Dunnet Bay, Caithness

Burbidge, C., McIlveny, J. and Sanderson, D., (2007) Luminescence Dating of Back-Dune Sedimentary Sequences from Dunnet Bay, Caithness. Technical Report. Scottish Universities Environmental Research Centre.

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This study supports a new investigation into the climatic influence of Holocene sedimentary deposition in Dunnet Bay, Caithness (section 2). Optically stimulated luminescence (OSL) profiling and age determinations have been made for two sequences of back-dune sediments ~1 km apart and each around 50 m inland from the dune field (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). A total of 31 profiling (section 5.1) and 7 age (section 5.4) determinations were made. Dose rate determinations were made using thick source beta counting, high-resolution gamma spectrometry, field gamma spectrometry, measured water contents and calculated cosmic dose rates (sections 4.2.1 and 5.2). Equivalent dose determinations were made (sections 4.2.2, 5.3) using the OSL signals from sand sized grains of quartz separated from each sample. Profiling measurements were made using simplified equivalent dose determination procedures on polymineral coarse and hydrofluoric etched sand-sized mineral grains (sections 4.2.2, 5.1). Dose rates ranged from 0.9 to 1.5 mGy/a, De values from the dating samples rangedfrom 0.2 to 7.2 Gy. Age estimates ranged from 0.21 to 4.9 ka (section 5.4). Uncertainties on the age estimates were c. 5 % for older samples, and c. 25% for the younger samples, due to low dose rates and low luminescence sensitivity. Luminescence profiling indicated c. zero OSL signal at zero depth, geological signals at the base of section 2, a discontinuity in De values at a stratigraphic unconformity in both sections, and detailed patterns of sedimentation through the sequences. Expected correlations between the sedimentary layers were confirmed in the upper section but contradicted in the lower sections (sections 6.5, 7). Sediments from above an unconformity identified in the stratigraphy were shown to have accumulated since c. 1800 AD. Sediments below the erosional horizon dated to between 0 BC and 2900 BC. OSL dates from the sediments below the unconformity in Section 2 indicated that they were all older than those in Section 1, and that the two sequences may be sequential. This was corroborated by the presence of carbonates in Section 1 but not in Section 2.

Item Type:Research Reports or Papers (Technical Report)
Glasgow Author(s) Enlighten ID:Sanderson, Professor David and Burbidge, Dr Chris
Authors: Burbidge, C., McIlveny, J., and Sanderson, D.,
Subjects:G Geography. Anthropology. Recreation > GB Physical geography
G Geography. Anthropology. Recreation > GE Environmental Sciences
College/School:College of Arts > School of Humanities > Archaeology
College of Science and Engineering > Scottish Universities Environmental Research Centre
Publisher:Scottish Universities Environmental Research Centre

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