Date:12/21/2012

ents, dated to the end of the last glacial period, contain material deposited from icebergs (Ice Rafted Detritus, IRD) that came from surrounding ice sheets. Establishing which ice sheets were responsible for depositing this material at any particular time allows inferences to be made regarding the behavior of said ice sheets. This paper presents the first study to use the well-established uranium-lead dating technique to investigate the sources of IRD by establishing the age of individual minerals and comparing these to the ages of potential source rocks that would have been eroded by ice sheets. The results of this study show that IRD found within an ocean core near to the former ice sheet that covered Scotland cannot have come from Scotland alone and that other, distant, ice sheets (Greenland or North America) must have contributed. This conclusion provides insights into how quickly IRD is deposited around the ocean and supports previous suggestions that such dispersal is rapid.

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Direct dating of gold by radiogenic helium: Testing the method on gold from Diamantina, Minas Gerais, Brazil

Alexandre Raphael Cabral et al., Mineral Deposits, Technische Universitt Clausthal, Adolph-Roemer-Strasse 2A, D-38678 Clausthal-Zellerfeld, Germany. Posted online 28 Nov. 2012; http://dx.doi.org/10.1130/G33751.1.

Natural gold, which formed in the geological past (at a million-year scale), retains the noble gas helium produced by radiogenic decay of uranium and thorium, elements that are incorporated in trace amounts in gold. New analytical advances make it feasible to measure within the same gold sample of as little as two milligrams (0.002 g) the contents of uranium, thorium and radiogenic helium. The amounts of these elements are then used to calculate the age of gold formation. This method of direct dating of gold has been applied to a historically important gold deposit in
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Contact: Kea Giles kgiles@geosociety.org Geological Society of America Source:Eurekalert

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