Luminescence Dating of Samples Collected from the Lumbini World Heritage Site, Nepal, January 2012

Cresswell, A. , Kinnaird, T., Sanderson, D. and Simpson, I. (2012) Luminescence Dating of Samples Collected from the Lumbini World Heritage Site, Nepal, January 2012. Technical Report. Scottish Universities Environmental Research Centre.

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Abstract

Optically stimulated luminescence (OSL) investigations have been undertaken on sediment collected from several stratigraphies at the Lumbini World Heritage Site (Rupandehi District, Western Terai, Nepal) to provide a chronology to interpret the early alluvial history and cultural activity at the site. These investigations are one part of a larger project, funded by UNESCO/Japanese Funds-in-Trust for the Preservation of the World Cultural Heritage, and initiated in 2011, to identify, evaluate and interpret the archaeological signature of the Lumbini World Heritage Site. The project is under the directorship of Robin Conningham. Archaeological investigations at Lumbini in January 2011, 2012 and 2013 have provided the opportunity to undertake geoarchaeological investigations of the soils and sediment in a number of stratigraphies through the Maya Devi Temple and the Lumbini Village Mound. Following the excavations in 2011, sediment samples were submitted to the luminescence laboratories at SUERC, to obtain chronologies for three sediment stratigraphies, including two within the Maya Devi Temple, and one through the Lumbini Village Mound (see Kinnaird et al., 2011). The dates obtained indicated a significant degree of antiquity within the Maya Devi Temple, with the earliest occupational layers identified at the site of the temple dated at 990 ± 290BC and 1080 ± 245 BC dates, some 600 years before the visit of Asoka. Additionally, the results indicated two distinct phases of occupation on the Village Mound, an early phase dated at 670 ± 160 BC, and a later phase, AD 260 ± 170 to 640 ± 110. A further fifteen samples were submitted for dating following fieldwork in 2012 (see Cresswell et al., 2012); OSL age determinations provide the chronology to interpret the natural and cultural processes that led to the formation of the sedimentary sequences in a further section from the Maya Devi Temple (C13), a second section through the Lumbini Village Mound (Trench LVM-12), and a section through an accumulation of natural/cultural material in a palaeo-channel (LPC-12). X samples were submitted following fieldwork in 2013. The dating questions associated with the samples taken from the stratigraphy within the Temple, relate to the early phases of cultural activity on the site, with a particular focus on pre- Mauryan levels. The questions associated with the material obtained from the stratigraphies through the Village Mound and palaeo-channel are related to their depositional sequences, which encompass the natural/cultural transition, the early human-environment interactions. Furthermore, the samples provide a means of appraing the multiple phases suggested during the first OSL study. Sample preparation and analysis was undertaken at the Scottish Universities Environmental Research Centre (SUERC). OSL SAR dating utilises extracted quartz from the samples to determine the radiation dose experienced by the sediments since their last zeroing event, assumed to be by exposure to light prior to final deposition. This is combined with dose rate analysis based on field and laboratory measurements of environmental radioactivity. The age is determined as the ratio of dose divided by dose rate. In this work, dose rates for the bulk sediment were quantified using high resolution gamma spectrometry and thick source beta counting in the laboratory, coupled with water content analysis and in-situ gamma dose rate measurements. Quartz was extracted using standard laboratory procedures, and purity checked with scanning electron microscopy. Equivalent doses were determined, initially, on 16 aliquots of quartz per sample using the quartz single-aliquot regenerative (SAR) procedure. The material exhibited good OSL sensitivity and produced acceptable SAR internal quality control performance. Radial plotting methods were used to appraise sample homogeneity, and robust statistics were used, for aliquots satisfying SAR acceptance criteria, to estimate equivalent doses. OSL dating has provided a chronology to aid in the interpretation of the early alluvial history and cultural activity at the Lumbini World Heritage Site.

Item Type:Research Reports or Papers (Technical Report)
Status:Published
Glasgow Author(s) Enlighten ID:Kinnaird, Dr Timothy and Sanderson, Professor David and Cresswell, Dr Alan
Authors: Cresswell, A., Kinnaird, T., Sanderson, D., and Simpson, I.
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
College of Arts > School of Humanities > Archaeology
Publisher:Scottish Universities Environmental Research Centre

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