Prompt transgression and gradual salinisation of the Black Sea during the early Holocene constrained by amino acid racemization and radiocarbon dating |
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| Authors: | William Anthony Nicholas Allan R. Chivas Colin V. Murray-Wallace David Fink |
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| Affiliation: | 1. GeoQuEST Research Centre, School of Earth & Environmental Sciences, University of Wollongong, NSW 2522, Australia;2. Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia;1. Department of Physical Geography, Stockholm University, SE-106 91, Stockholm, Sweden;2. Department of Geomorphology & Palaeogeography, Lomonosov Moscow State University, Leninskie gory, GSP-1, Moscow, 119991, Russian Federation;3. School of Earth & Environmental Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW, 2522, Australia;4. Institute for Environmental Research, Australian Nuclear Science & Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia;5. Department of Geography, Durham University, Lower Mountjoy, South Road, Durham, DH1 3LE, UK;1. Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia;2. Antarctic Climate & Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, TAS, Australia;3. Desert Research Institute, Reno, NV, USA;4. Australian Antarctic Division, Kingston, TAS, Australia;5. Australian Nuclear Science and Technology Organisation, Menai, NSW, Australia;6. Woods Hole Oceanographic Institution, Woods Hole, MA, USA;1. College of Science and Engineering, James Cook University, Townsville, Qld 4811, Australia;2. School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa;3. Australian Nuclear Science and Technology Organization, PMB1, Menai, NSW 2234, Australia;4. School of Earth and Environmental Science, University of Wollongong, Wollongong, NSW 2522, Australia;1. 15 Summerleas Road, Fern Tree, Tasmania 7054, Australia;2. Australian Nuclear Science and Technology Organisation, Menai 2234, NSW, Australia;1. Wollongong Isotope Geochronology Laboratory, GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, Australia;2. Department of Earth and Environmental Sciences, Korea Basic Science Institute, Ochang Centre, Chungbuk, 28119, South Korea;3. Australian Nuclear Science and Technology Organization, Lucas Heights, NSW, Australia;4. Institute of Earth and Environmental Sciences, University of Potsdam, Potsdam, Germany;5. Department of Geography, Macquarie University, North Ryde, NSW, Australia;6. CSIR Center for Mathematical Modelling and Computer Simulation, Bangalore, Karnataka, India;7. Wadia Institute of Himalayan Geology, Dehradun, Uttarakhand, India;1. School of Environment, The University of Auckland, Auckland 1142, New Zealand;2. ANTARES-AMS, Australian Nuclear Science and Technology Organisation, Sydney 2234, Australia;3. Geography, The University of Melbourne, Parkville 3000, Melbourne, Australia |
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| Abstract: | The restricted environment of the Black Sea is particularly sensitive to climatic and oceanographic fluctuations, owing to its connection with the Mediterranean Sea via the narrow Bosphorus Strait. The exact mechanism and timing of the most recent connection between these water bodies is controversial with debate on the post-glacial history of the Black Sea being dependent on radiocarbon dating for numerical ages. Here we present new 23 accelerator mass spectrometer (AMS) radiocarbon ages on peat and bivalve molluscs, supported by the first amino acid racemization (AAR) dating of bivalve molluscs (n = 66) in the Black Sea. These data indicate infilling of the Black Sea during the early Holocene from an initial depth 107 m below sea-level, and 72 m below that of the Bosphorus Sill. These data combined with a review of previous radiocarbon ages has enabled a unique perspective on the post-glacial Black Sea. A sea-level curve based on conventional and AMS radiocarbon ages on peat and AMS-based ages on Dreissena sp. shells indicate the water-level in the earlier lake phase continued, until the early Holocene, to be lower than the Bosphorus Sill after the Younger Dryas ended. However, the absence of AMS-dated mollusc ages from the shelves of this basin older than the Younger Dryas is suggestive of sub-aerial exposure of the shelves, and comparatively lower water-levels when the Younger Dryas began. Thus post-glacial outflow from the Black Sea occurred through a lowered or open Bosphorus seaway. Basin-wide radiocarbon ages on peat indicate a prompt increase in water-level from that of the pre-existing and unconnected palaeo-lake during the earliest Holocene (9600–9200 cal a BP). Mass colonisation of the Black Sea by Mediterranean taxa did not occur until salinity had risen sufficiently, a process which took 1000 a or more from the initial transgressive event. This gradual change in salinity contrasts with the prompt transgression which would have taken ～400 a to occur. |
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