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Prosenjit Ghosh (CIT) Carmala Garzione (Rochester) John M. Eiler (CIT)

Reconstructing elevation histories using 13 C- 18 O bonds in soil carbonates. Prosenjit Ghosh (CIT) Carmala Garzione (Rochester) John M. Eiler (CIT). Pieces of the Isostatic Puzzle. Uplift. Elevation. Paleoaltimetry based on lava vesicle size (Sahagian, 2002). Botanical Paleoaltimetry

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Prosenjit Ghosh (CIT) Carmala Garzione (Rochester) John M. Eiler (CIT)

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  1. Reconstructing elevation histories using 13C-18O bonds in soil carbonates Prosenjit Ghosh (CIT) Carmala Garzione (Rochester) John M. Eiler (CIT)

  2. Pieces of the Isostatic Puzzle Uplift Elevation

  3. Paleoaltimetry based on lava vesicle size (Sahagian, 2002)

  4. Botanical Paleoaltimetry (Wolfe, 1995) Variants: • Multi-parametric correlations w/ T • Multi-parametric correlation w/ enthalpy • Physiognomic correlation w/ p(CO2)

  5. ‘Conventional’ Stable Isotope Paleoaltimetry (Drummond et al., 1993; Chamberlain et al. 1999; Garzione et al., 2002) Measure Derive ? Guess

  6. 13C-18O ‘clumping’ in calcite: Rigorous T measurement using isotopes 40Ca13C16O3 + 40Ca12C18O16O2 40Ca12C16O3 + 40Ca13C18O16O2 . ~1000 (keq-1) Harmonic, DFT-LDA-NCPP model; Schauble, pers. com.

  7. Getting the ‘clumps’ out of the carbonate CaCO3 + H3PO4 = gaseous CO2 + ‘CaO’ in dilute solution In the absence of any analytical fractionation, ∆47 of product CO2 Should equal ∆[13C18O16O2-2] in reactant carbonate

  8. Calibration using inorganic calcite and biogenic aragonite

  9. The Altiplano — a 4 km high plateau in the central Andes Km After Jordan et al., 1983

  10. Two independent ‘votes’ on altitude ±1se 6.7-5.8 Ma 7.6-7.3 Ma Today 11.4-10.3 Ma 6.7-5.8 Ma ±1se 7.6-7.3 Ma Today 11.4-10.3 Ma

  11. There must be something more we can do with two independent constraints…

  12. Combined T-d18Owater constraints on altitude of the Altiplano

  13. Integrated uplift history of the Altiplano

  14. Conclusions Geologic evolution of the Altiplano • Plateau rose at 1.03 ± 0.12 mm/yr between 10.3 to 6.7 Ma • This is 3x rate expected for crustal shortening driven by plate motions • Implies altitude rise occurred in response to de-lamination of dense lower crust and/or lithospheric mantle (?) • Timing coincident with change in Nazca—SA convergence, slowing of shortening across Altiplano, river incision, and other changes Broader problem of paleoaltimetry • ‘Clumped isotope’ approach appears capable of reconstructing altitude with precision of ±200 to 400 m for groups of several samples • Applicable to soil carbonates; should also be useful for lake sediments • Should be tried in southern Altiplano, Tibetan plateau, Colorado plateau

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