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Non-marine paleoclimatic evidence

Non-marine paleoclimatic evidence. Speleothems. Speleothems. Commonly known as stalagmites and stalactites. Like trees, speleothems form growth rings that develop over hundreds or thousands of years. Growth rate depends on amount and rate of precipitation and on cave temperature and humidity.

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Non-marine paleoclimatic evidence

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  1. Non-marine paleoclimatic evidence Speleothems

  2. Speleothems • Commonly known as stalagmites and stalactites. • Like trees, speleothems form growth rings that develop over hundreds or thousands of years. • Growth rate depends on amount and rate of precipitation and on cave temperature and humidity.

  3. Speleothem • Dating of speleothems is based on U-Th series. • Theoretical precision: <1‰ (10 yr in 10 kyr). Realistically, precision is better than 1% (100 yr in 10 kyr).

  4. Lachniet et al., 2004. Costa Rican speleothem.

  5. Speleothem-Paleoclimatic proxies • Carbon and oxygen isotopes of calcite reflect vegetation and climate, respectively. • Growth rate appears to reflect precipitation. • Recent techniques: Mg/Ca, radiocarbon.

  6. Speleothem-oxygen isotopes • Oxygen isotopes in speleothem calcite ultimately come from rainwater. • Some researchers argue that oxygen isotope ratios in rainwater depend on temperature. • Others argue that the isotope ratios depend on rainfall amount, particularly in tropical regions. • Also, some argue that the isotope ratios depend on evaporation taking place in soils or in the cave.

  7. Coldest Warmest Speleothem-oxygen isotopes • Colder climate = lower d18O values. • Speleothem d18O-MAT relationship is ~0.35 per mil/°C. ~4oC Dorale et al., 1998.

  8. Speleothem-oxygen isotopes • Site-specific calibrations are the best approach. • Rainfall amount, rain d18O values, and surface and cave temperatures are measured over some time. Simultaneously, d18O values of cave drips and newly formed calcite are measured. • A transfer function can then be developed for the cave.

  9. Isotopic composition of rain water in Israel (Bar-Matthews et al., 2003)

  10. Relationship between oxygen isotope ratios of rain water and rainfall in Israel (Bar-Matthews et al., 2003).

  11. Bar-Matthews et al., 2003).

  12. Speleothem-carbon isotopes • It appears that speleothem carbon isotopes primarily come from plants above the cave. • Based on photosynthetic pathways, there are two major groups of land plants: C3 and C4 plants. • C4 plants: warm season grasses adapted to high temperatures and relatively drier climates. • C3 plants: Trees, shrubs, and cool season grasses.

  13. Speleothem-carbon isotopes • C4 grasses show high d13C values. • C3 plants show low d13C values. • Speleothem high d13C values are then interpreted to indicate more C4 grasses.

  14. Crevice Cave, MO (Dorale et al., 1998)

  15. Crevice Cave, MO (Dorale et al., 1998)

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