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IODP Expedition 347 (Baltic Sea): a high resolution test of the pyrite trace element seawater proxy

Citation

Johnson, SC and Jensen, J-B and McGoldrick, PJ and Large, RR and Meffre, S and Danyushevsky, L and Halpin, JA and Noble, T, IODP Expedition 347 (Baltic Sea): a high resolution test of the pyrite trace element seawater proxy, Abstracts of the 22nd Australian Earth Sciences Convention 2014, 7-10 July 2014, Newcastle, Australia, pp. 256. ISSN 0729-011X (2014) [Conference Extract]

Abstract

With ever-increasing emphasis placed on environmental change, shelf areas and enclosed basins are the most prone to the impacts of climatic variations. Effects such as oxygen depletion, water column stratification and temperature variations are focused in these geographical settings, and can be recorded by the behaviour of trace elements in this changing depositional environment. The Baltic Sea Basin is in a unique position to have experienced and recorded a multitude of environmental changes on a large scale. Over 1.6 km of sediment was drilled and logged as part of the IODP Expedition 347 (completed in November 2013), with the Onshore Science Party phase completed in late February 2014. Presented here is a summary of the sedimentology and preliminary geochemistry from sites across the Baltic Sea, one of the world’s largest modern intercontinental basins. This Mission Specific Platform focussed on the extreme climatic variations experienced by the Baltic Sea Basin over the Pleistocene and Holocene, exploring not only the fluxes between freshwater and marine conditions during the past glacial periods but also between anoxic, hypoxic and oxic conditions, driven by salinity and temperature gradients and periods of increased stratification.

During Expedition 347, a unique and continuous sequence of sediment was recovered which spanned the last glacial cycles and into the overlying Holocene freshwater and marine sequences. Several sites (i.e. Little Belt (BSB-3), Bornholm Basin (BSB-7) and Landsort Deep (BSB-9)) contain abundant organic-rich muds and record many of the key transitions in the development of the Baltic Sea Basin. Each of these shifts can be accompanied by variations in salinity, oxygen content and, importantly, fluxes in trace metal. Black mud horizons in these cores are conducive to the degradation of organic matter and production of pyrite and Fe-monosulfide precursors. Work by Large et al. (2014), utilising LA-ICP-MS, has shown that sedimentary pyrite from marine black shales may have the ability to record first-order changes in seawater chemistry through geological time, thereby providing a new potential proxy.

The preliminary data presented here uses the above method to understand trace element content of pyrites collected from the Baltic Sea Basin. The unique archive in these cores has allowed for the first high-resolution test of this seawater proxy and its ability to capture trends in the context of geologically short timescales. In this project, the ability of pyrite to record trace element changes on varying timescales will be tested, with particular reference to that of the general residence times of elements in seawater. In addition, our initial interpretations of Baltic Sea Basin evolution over this time period will be discussed. The Baltic Sea also provides a new and suitable analogue for ancient restricted seas. Understanding how redox sensitive metals behave in such environments has implications for ore deposit modelling and wider understanding of periods of oxygen stagnation and depletion in the geological record.

Item Details

Item Type:Conference Extract
Keywords:pyrite, palaeo-oceanography, seawater proxy
Research Division:Earth Sciences
Research Group:Geology
Research Field:Tectonics
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Johnson, SC (Mr Sean Johnson)
Author:McGoldrick, PJ (Dr Peter McGoldrick)
Author:Large, RR (Professor Ross Large)
Author:Meffre, S (Dr Sebastien Meffre)
Author:Danyushevsky, L (Professor Leonid Danyushevsky)
Author:Halpin, JA (Dr Jacqueline Halpin)
Author:Noble, T (Dr Taryn Noble)
ID Code:100953
Year Published:2014
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2015-06-03
Last Modified:2015-06-04
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