Sevan Wonders: Building the geochronological framework for the Lake Sevan (Armenia) sedimentary archives

Overview

Lake Sevan, eastern Armenia, lies at a proverbial “crossroads” for human migration between Africa, Europe and Asia. Evidence of nearby prehistoric human occupation has been discovered just over the Georgian border at Dmanisi, dating to circa 1.8 Ma (Gabunia & Vekua 1995), as well as more modern Palaeolithic sites (circa 300 ka) in Armenia (Adler et al. 2014).
In order to provide palaeoenvironmental context for this lengthy archaeological record, appropriate archives must be sought and, to this end, the sediments of Lake Sevan offer huge potential. A preliminary field season retrieved two short sediment cores (likely representing the last few thousand years) from the North and South basins of the lake, as well as obtaining material from multiple exposures around the lake. Two further field seasons (in the first and second years of the proposed project, respectively) will centre upon deeper drilling of the lake, aiming for at least complete coverage of the Holocene.
The advertised PhD studentship will focus on building the geochronology of these sedimentary archives, which will involve the combination of multiple complementary techniques. A second associated PhD studentship (to be based at the University of Newcastle under the primary supervision of Prof Andrew Henderson) will focus on developing the palaeoenvironmental history at the site.

Methodology

Radiocarbon (14C) dating will be central, but not straightforward. Freshwater reservoir effects produce inbuilt age in “bulk” sediment compared to the authentic timing of sediment deposition, but preferred terrestrially-originating plant macrofossils are likely to be sparse. Under the supervision of Dr Richard Staff, the successful applicant will develop an optimised 14C dating strategy involving different sedimentary fractions (alkali-insoluble “humin”, alkali-soluble humic acids, and potentially black carbon, BC, and other Compound-Specific Radiocarbon Analysis, CSRA). Radiocarbon dating will be integrated with tephrostratigraphy (potentially providing linkages to terrestrial sequences for more robust 14C dating), and tephrochronology (40Ar/39Ar, under the supervision of Prof Darren Mark), cosmogenic nuclide dating (10Be/9Be, under the supervision of Dr Derek Fabel), and the shorter-lived isotopes 210Pb and 137Cs for the uppermost sediment sections. Knitting together the data from these complementary techniques will require robust Bayesian chronological modelling, which will be supervised by Staff. In addition, co-supervisor Dr Andrew Henderson will work with the student to ensure that the geochronological focus of the PhD complements the multi-proxy palaeoenvironmental data being generated as part of the broader Lake Sevan project team.

Project Timeline

Year 1

Reviewing of existing literature in order to refine key research direction; training in core geochronological skills; initial processing of samples from existing short cores and sedimentary exposures for geochronological analysis; attendance of short course in ‘Radiocarbon Dating and Bayesian Chronological Analysis’ (Mar 2023); PhD progression presentation (~May 2023); initial field season at Lake Sevan.

Year 2

Majority of sample processing for geochronological analysis to be undertaken; on-going data analysis and statistical modelling; presentation at international conference (e.g. QRA ADM, Jan 2024); second field season at Lake Sevan to retrieve deeper lake sediment core(s).

Year 3

Completion of sample processing; completion of data analysis and statistical modelling; presentation at international conference (e.g. EGU, Apr 2025); thesis write-up and drafting of manuscripts for publication in high impact international peer-reviewed journals.

Year 3.5

Completion of write-up of PhD thesis; presentation at international conference (e.g. AGU, Dec 2025); finalise manuscripts for publication.

Training
& Skills

The student will be trained in a broad range of geochronological and palaeolimnological techniques, including bespoke training in field skills (e.g. sediment coring and stratigraphic logging) and laboratory skills (principally, focussed on the multiple geochronological techniques outlined above). The student will also have the opportunity to attend the NERC-recognised short courses on radiocarbon dating and Bayesian chronological analysis, stable isotope analysis, and statistics for geoscientists.

References & further reading

Regional setting:

Adler et al., (2014) “Early Levallois technology and the Lower to Middle Paleolithic transition in the Southern Caucasus”. Science, 345, 1609-1613
Gabunia & Vekua (1995) “A Plio-Pleistocene hominid from Dmanisi, East Georgia, Caucasus”. Nature, 373, 509-512

Cromartie et al., (2020) The vegetation, climate, and fire history of a mountain steppe: A Holocene reconstruction from the South Caucasus, Shenkani, Armenia. Quaternary Science Reviews, 246, 106485.

Joannin et al., (2014) Vegetation, fire and climate history of the Lesser Caucasus: a new Holocene record from Zarishat fen (Armenia). J. Quat. Sci., 29: 70-82.

Leroyer (2016) Mid Holocene vegetation reconstruction from Vanevan peat (south-eastern shore of Lake Sevan, Armenia). Quaternary International 385, 5-18

Palumbi, G (2016) The Early Bronze Age of the Southern Caucasus. Oxford Handbooks Online. DOI: 10.1093/oxfordhb/9780199935413.013.14

von Suchodoletz et al. (2018) North Atlantic influence on Holocene flooding in the southern Greater Caucasus. The Holocene, 28: 609-620.

Methods:

Ascough, P.L. et al. (2010) “Hydropyrolysis: Implications for radiocarbon pretreatment and Characterization of Black Carbon”. Radiocarbon 52, 1336-1350

Brock, F. et al. (2010) “Low temperature (LT) combustion of sediments does not necessarily provide accurate radiocarbon ages for site chronology”. Quaternary Geochronology 5, 625-630

Bronk Ramsey (2008) “Deposition models for chronological records”. Quaternary Science Reviews 27 (2008) 42–60

Mark et al., (2017) “High-precision 40Ar/39Ar dating of Pleistocene tuffs and temporal anchoring of the Matuyama-Brunhes boundary”. Quaternary Geochronology, 39, 1-23

Further Information

For further information or questions relating to this project proposal contact Dr Richard Staff at: richard.staff@glasgow.ac.uk

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