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Isotope geochemical applications in paleooceanography, environmental sciences, paleoanthropology and paleoclimatology

English title Isotope geochemical applications in paleooceanography, environmental sciences, paleoanthropology and paleoclimatology
Applicant Nägler Thomas
Number 113658
Funding scheme Project funding (Div. I-III)
Research institution Institut für Geologie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Geochemistry
Start/End 01.10.2006 - 30.09.2009
Approved amount 555'724.00
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Keywords (11)

Environmental geochemistry; Nuclear waste disposal; Quaternary dating; Paleoclimate; Human evolution; Molybdenum isotopes; atmospheric oxygen; U-series nuclides; speleothem dating; Hominid evolution; Palaeoclimatology.

Lay Summary (English)

Lead
Lay summary
This project comprises three parts. (1): Molybdenum and zinc isotopefractionation: applications in paleoceanography and environmental geochemistry; (2): Studies of 230Th/234U/238U systematics in Opalinus Clay; (3): U-Pb and 234U/238U systematics for dating cave deposits older than 500 ka: applications in Palaeanthropology and Palaeoclimatology.
In Part (1) a detailed Mo isotope study of black shales through the entire stratigraphy of the early Proterozoic Transvaal Supergroup (2.67 - 2.1 Ga), will be completed, and a study of Mo and Zn isotope fractionation in rivers will be carried out. Mo solubility is dependent on its redox state, and Mo isotope fractionation occurs only if some Mo is in solution.Therefore isotope fractionation is a proxy for oxygenated conditions in the ocean, and we have shown that oxygenation of the oceans progressed gradually through the above period, although the record shows oscillation rather than a simple rise. Work on rivers is essential to provide a baseline for more detailed palaeoceanographic modeling of the Mo system, and Zn functions as a control, as its solubility is not redox-dependent.Further, groundwork is carried out for the use of Mo and Zn isotope fractionation in environmental geochemistry.
The theme of Part (2) is a detailed study of 230Th-234U-238U systematics in two natural laboratories of rock-water interaction: (a) rock samples and groundwater of borehole Benken, Zürich Weinland (quasi-steady-state rock-water interaction with old, reducing groundwater), (b) similar samples from the section of Mont Terri, Jura (quasi-steady-state, but modern, oxidising groundwater). 234U, an intermediate natural radioisotope in the 238U decay chain, is a proxy for highly mobile actinide species that occur in radioactive waste. 234U/238U and 230Th/234U activity ratio data on bulk Opalinus Clay samples and differential leaches help to predict the effective diffusivity of mobile actinides. The study combines analytical work and transport modeling.
In Part (3) the U-Pb method is applied to absolute dating of stalagmites and flowstones that are older than 500’000 years, and thus too old to be dated by the 230Th/234U dating method. Specific areas of study are: (a) Sterkfontein cave in Gauteng, South Africa, which is a world-renowned site of early hominid fossils possibly spanning an age range of 4 to 1.5 Ma, and (b) Saudi Arabia and Yemen, where stalagmite samples collected by D.Fleitmann and A. Matter may yield a terrestrial palaeoclimatic record extending back millions of years.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
105505 Isotope geochemistry and questions of the early atmosphere, nuclear waste disposal, paleoclimate and hominin evolution 01.10.2004 Project funding (Div. I-III)
126759 Investigation on the control of the Mo isotope signature of river water: approaching a refined global Mo model for paleredox reconstructions 01.10.2009 Project funding (Div. I-III)

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