Marine Sediments and Corals (Chapter 6)

Dating Methods Biogenic: oceanic information (temp., salinity, oxygen, etc.)

Dating Methods Terrigenous: fluvial errosion, ice rafting (i.e., humidity-aridity, winds, etc.)

Special issue: Tropical SST at LGM Dating Methods Special issue: Tropical SST at LGM

Calcareous tests Planktic (0-200 m) or Benthic (bottom) “Composed of, containing, or characteristic of calcium carbonate, calcium, or limestone” Foraminifera (zooplankton) - almost macroscopic (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Calcareous tests Planktic (0-200 m) or Benthic (bottom) “Composed of, containing, or characteristic of calcium carbonate, calcium, or limestone” Foraminifera (zooplankton) - almost macroscopic Coccoliths (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Calcareous tests Planktic (0-200 m) or Benthic (bottom) “Composed of, containing, or characteristic of calcium carbonate, calcium, or limestone” Foraminifera (zooplankton) - almost macroscopic Coccoliths Dinoflagellates - cellulose tests with calcareous cysts - important for SST and sea ice (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Siliceous tests Planktic (0-200 m) or Benthic (bottom) “Containing, resembling, relating to, or consisting of silica.” Radiolaria (zooplankton) (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Siliceous tests Planktic (0-200 m) or Benthic (bottom) “Containing, resembling, relating to, or consisting of silica.” Radiolaria (zooplankton) Silicoflagellates (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Siliceous tests Planktic (0-200 m) or Benthic (bottom) “Containing, resembling, relating to, or consisting of silica.” Radiolaria (zooplankton) Silicoflagellates Diatoms (algae) (www.geol.umd.edu/~tholtz/G331/lectures/lecture2.html)

Where to look? Somewhat organism dependent Issues: Differential removal Scouring of bottom Contamination by exotics

How used? Foram oxygen isotopes in calcium carbonate Species assemblages Morphological variations due to environment

Issues: Continuous or seasonal presence? Depth vs. life stage?

O Isotopes - Calcareous Tests Urey (1947, 1948): - Calcium carbonate crystallization  18O > water concentration - 18O enhancement varies with temperature: T = 16.9 - 4.2(dc - dw) + 0.13(dc - dw)2 dc = d18O of sample dw = d18O of sample’s water Problem: What is dw ? Changes with global ice volume Can we estimate that?

Paleo dw : Deep ocean (benthic) temps. close to 0˚C http://www.utdallas.edu/~pujana/oceans/northbasin.html Deep ocean (benthic) temps. close to 0˚C Little change from glacial periods Benthic d18O due to paleoglaciation enhancement dw

O Isotopes - Calcareous Tests 18O enhancement & temperature - further complications (1) Metabolic CO2 may alter dc (generally lower) Species-dependent  use species in isotopic eq. with surrounding water

O Isotopes - Calcareous Tests 18O enhancement & temperature - further complications (2) Forams tend to live at fixed water density: what happens with temp. and salinity change?

O Isotopes - Calcareous Tests 18O enhancement & temperature - further complications (3) Calcification as foram descends: what is T(depth)?

O Isotopes - Calcareous Tests 18O enhancement & temperature - further complications (4) Salinity effects: Estimate near-surface salinity?

O Isotopes - Calcareous Tests 18O enhancement & temperature - further complications (4) Salinity effects: Estimate near-surface salinity?

Oxygen Isotope Stratigraphy Primary d18O factor: ice volume on continents Thus, a global signal  can synchronize cores Still need absolute dating

Oxygen Isotope Stratigraphy Primary d18O factor: ice volume on continents Thus, a global signal  can synchronize cores Still need absolute dating

Oxygen Isotope Stratigraphy (Kleiven and Jansen, 2003) http://www-odp.tamu.edu/publications/177_SR/chap_12/c12_.htm

Oxygen Isotope Stratigraphy (Kleiven and Jansen, 2003)

Oxygen Isotope Stratigraphy (Kleiven and Jansen, 2003) Primary d18O factor: ice volume on continents

Oxygen Isotope Stratigraphy South Atlantic North Atlantic (Kleiven and Jansen, 2003) Primary d18O factor: ice volume on continents

Oxygen Isotope Stratigraphy Primary d18O factor: ice volume on continents Thus, a global signal  can synchronize cores Also - local changes on land may not align with global changes!

Orbital Tuning d18O driven by orbital variations, as mediated by terrestrial ice sheets

Orbital Tuning Thus tune d18O time series by orbital signal

Orbital Tuning Thus tune d18O time series by orbital signal

Relative Abundances Estimate T by mix of organisms? Schott (1935) Cores not available until 1960s. Figure shows quasi-periodic behavior

Relative Abundances Figure shows quasi-periodic behavior

Calibration Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Calibration Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Calibration Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

N. pachyderma (left coiling) G. bulloides Figure shows quasi-periodic behavior G. ruber (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Calibration G. bulloides G. ruber Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Calibration N. pachyderma (left/right coiling) Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Calibration N. pachyderma (left coiling) Figure shows quasi-periodic behavior (http://oceanusmag.whoi.edu/v40n2/ostermann.html)

Relative Abundances More sophisticated: use multiple species and principle patterns of species variations (principal components) Major assemblages: Polar Subpolar Transitional Subtropical Gyre Figure shows quasi-periodic behavior

Relative Abundances Calibration outcome (contemporary): Figure shows quasi-periodic behavior Calibration outcome (contemporary): Tw = 23.6 A + 10.4 B + 2.7 C +3.7 D + 2.0 K

Relative Abundances 18O from same core Figure shows quasi-periodic behavior 18O from same core Apply calibration formula to core abundances: Tw = 23.6 A + 10.4 B + 2.7 C +3.7 D + 2.0 K

Controversy: Tropical SST Were tropical sea-surface temperatures colder or like present at last glacial maximum (max 18O in Stage 2)?

Controversy: Tropical SST colder or like present ? Tropical snow lines lower: lapse rate ? GCMs need SST  5-6˚C for lowered snow line. Corals in Pacfic (16˚S) and Barbados: SST  ~ 5˚C Noble gases in Brazil groundwater: T~ 5˚C Peruvian glacier: 18O  ~ 8 o/oo Central Australia (Emu eggshells): T~ 9˚C Assemblages: SST  ~ 1 - 2˚C Alkenones: SST  ~ 1 - 2˚C Careful reassessments: No significant cooling Broecker (1986) Thunell et al. (1994) Stott & Tang (1996)

Controversy: Tropical SST colder or like present ? Missing cold-intolerant forams: T > 7 - 8˚C ? Contamination of “modern” core tops (used for calibration) by early Holocene faunas? Short cold episodes?

DSST: Present - 18k BP Note locations of cores! August Figure shows quasi-periodic behavior Note locations of cores! August

DSST: Present - 18k BP Note locations of cores! February Figure shows quasi-periodic behavior Note locations of cores! February

Corals Hermatypic Corals: Build reefs Symbiotic relationship with algae Depth limited by sunlight (0 - 20 m) Limited also by temperature (~ 20˚C) and nutrient flow Clipperton Atoll (10 N, 109 W) (http://calspace.ucsd.edu/virtualmuseum/climatechange2/05_2.shtml)

Corals Growth rate varies: Yellow bands = El Niño years (http://calspace.ucsd.edu/virtualmuseum/climatechange2/05_2.shtml)

Corals Growth rate can also indicate annual cycle: Revealed under UV light From Great Barrier Reef, Australia (http://www.onlineopinion.com.au/view.asp?article=1131)

Corals Potential utility

Corals Potential utility: SST from paleo-reefs? Possibly indicate sea-level changes?

Fossil Pollen in Marine Sediments A record of wind and desert changes (H. Hooghiemstra, 2004)

Fossil Pollen in Marine Sediments (H. Hooghiemstra, 2004)

Fossil Pollen in Marine Sediments (H. Hooghiemstra, 2004)

Fossil Pollen in Marine Sediments (H. Hooghiemstra, 2004)

Fossil Pollen in Marine Sediments (H. Hooghiemstra, 2004)

Thermohaline Circulation

Thermohaline Circulation

Thermohaline Circulation

Heinrich Events

Heinrich Events

Heinrich Events

Heinrich Events

Heinrich Events

Heinrich Events Model tidal amplitudes @ 45k BP [m] (Arbic et al., 2004)

Heinrich Events Tidal amplitude @ Hudson Strait (sea level )+ marine-based ice (sea level ) only contemporary (Arbic et al., 2004)

Heinrich Events Did the European Ice Sheet Surges Trigger the North Atlantic Heinrich Events? (Grousset et al., 1999) Use Sr-Nd isotopic compositions on the bulk lithic fraction of Heinrich layers (ice rafted debris): Dominant Laurentide signal H1, H2, H4, H5 European signal H3 BUT… Early H4 European dominant Late H4 Laurentide dominant  European trigger?

End of Last Glaciation

End of Last Glaciation

End of Last Glaciation

End of Last Glaciation

Changes in CO2: Ocean Role

Changes in CO2: Ocean Role

Marine Sediments and Corals (Chapter 6) END