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Clumped isotopes: potentials and challenges 11/1/12 Artist’s rendition of Mammuthus primigenius, whose body temp was measured at 38.4 +/- 1.8°C by clumped.

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Presentation on theme: "Clumped isotopes: potentials and challenges 11/1/12 Artist’s rendition of Mammuthus primigenius, whose body temp was measured at 38.4 +/- 1.8°C by clumped."— Presentation transcript:

1 Clumped isotopes: potentials and challenges 11/1/12 Artist’s rendition of Mammuthus primigenius, whose body temp was measured at /- 1.8°C by clumped isotopes (Eagle et al., PNAS, 2010)

2 The Idea Consider the isotope exchange rxn: we would expect an equilibrium constant of 0.25, given random distribution of isotopes BUT… there is a slight preference for D 2, b/c of heavy isotope “clumping” AND… this preference is greater at low temperatures and less at high temperatures THEREFORE, we have established the basis for a paleo-thermometer that is based on the ordering of heavy isotopes in carbonate only (single phase equilbrium) NO dependence on fluid composition Eiler, 2007

3 Elements CO 3 2- Relevant Reaction and Isotopologues Ghosh et al, 2006 Eiler and Schauble, 2004 Definition of Δ 47 (where 47= )

4 How do you establish a new paleo-thermometer? 1)develop a way to reliably and repeatably measure the quantity of interest - choose to dissolve carbonate in H 3 PO 4, measure evolved CO 2 Ghosh et al, 2006 nominal precision = +/- 0.03‰ reducible to +/ ‰ for repeat measurements

5 2)test the temperature sensitivity of Δ 47 in inorganic and biogenic carbonates Ghosh et al, observe a fractionation of of Δ 47 from statistical model. Assuming it’s also T-dependent, must control for it when doing measurement

6 2)test the temperature sensitivity of Δ 47 in inorganic and biogenic carbonates Ghosh et al, aragonite samples fall on calcite curve -some “vital” effects, as observed for these samples δ 18 O and δ 13 C

7 3)go after real signals in real geologic records -eg: Red Sea coral Ghosh et al, 2006

8 3)go after real signals in real geologic records -sense of Δ 47 signal matches that of Sr/Ca-based temperatures, but amplitude far exceeds that predicted from observed SST variations and calibrations of Δ 47 (cause unknown “vital effect”?) expected Δ 47 signal Ghosh et al, 2006

9 2)test the temperature sensitivity of Δ 47 in inorganic and biogenic carbonates WOW: this really seems to work! Tripati et al, 2010

10 Vital effects and Δ 47 Tripati et al, 2010

11 δ 18 O and δ 13 C of forams contain obvious “vital effects” Tripati et al, 2010

12 planktonic thermocline benthic Data look pretty good, especially considering how the temperature is unknown for some forams’ habitats Tripati et al, 2010

13 Δ 47 of forams does not contain obvious “vital effects”

14 Δ 47 (‰) D47 speleothem results D47 Δ 47 in Soreq cave speleothems Modern speleothem: Δ 47 =0.642±0.006‰, 26±1ºC. Modern bedrock temperature: 18 ºC. Kinetic isotope effect?  18 O reflects equilibrium within the range of observed cave water. Assumption: kinetic effect must be small.  18 O from Matthews et al., 2000 Affek et al, 2008

15 KIE3 Combining kinetic and equilibrium effects drip water  18 O = -5.32±0.76‰ - if you know the fluid composition, and you know the temperature, then you can predict a certain relationship between Δ 47 and δ 18 O Affek et al, 2008

16 KIE4 Combining kinetic and equilibrium effects drip water  18 O = -5.32±0.76‰ Affek et al, 2008

17 KIE5 Million dollar question: Is the offset constant through time? Both  18 O and Δ 47 are consistent with KIE offset at ~19°C. The offset in  18 O is lost in the natural variability of cave water  18 O. Affek et al, 2008

18 Temperature (°C) Yes? Clumped isotope T estimates agree with paleo-T estimates from other techniques Affek et al, 2008

19 Ghosh et al, 2008 Question: How fast did the Bolivian Altiplano uplift? Approach: Measure Δ 47 and δ 18 O water in carbonate nodules in paleosol Answer: it uplifted FAST!

20 Ghosh et al, 2008 Implications of fast uplift: - removal of dense lower crust and/or mantle lithosphere, replacement by less dense, hot aesthenosphere caused isostatic rise in Altiplano?

21 Huntington et al, 2010 Question: How fast did the Colorado Plateau uplift? Approach: Measure Δ 47 and δ 18 O water in modern and ancient carbonates along an elevation gradient modern = calibration ancient = reconstruction Modern carbonates show that δ 18 O water is not a good proxy for elevation, but Δ 47 is

22 -little change in lapse rate inferred, so no change in elevation post-20Ma -large 8°C temperature change inferred (consistent with paleo-T from sediments off California?) Huntington et al, 2010

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24 Eagle et al, 2010 Modern Δ 47 calibration of teeth bio-apatite Lesson: use enamel! So you can see the difference in old teeth from warm- and cold-blooded animals…

25 Eagle et al, 2011 Large dinosaurs: warm- or cold-blooded?


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