Global Climate Change Effects on the Mid-Continent
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A Stable Isotopic Record for the Badlands National Park was obtained across the Eocene-Oligocene Transition (Greenhouse to Icehouse global climate change). The isotopic record indicates changes in temperature and aridity and allows for direct comparision of a local continental climate response to a global climate change event. Effect on regional biota are also described. This presentation was given at the GSA North-Central/South-Central Combined Meeting 2010.
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Global Climate Change Effects on the Mid-Continent
- 1. STABLE ISOTOPE RECORD OF SOIL CARBONATES FROM THE EOCENE-OLIGOCENE TRANSITION, BADLANDS NATIONAL PARK, SOUTH DAKOTA, USA Michelle R.D. Mullin, MS Candidate Richard H. Fluegeman, PhD Ball State University Department of Geological Sciences
- 2. Eocene-Oligocene Tectonics Drake Passage Tasman Passage Tethys Sea 38 Myr = pole of rotation changes, affecting global tectonics
- 3. Eocene-Oligocene Climate Global Mean Annual Temperature Dropped 5 0 C Atmospheric CO 2 decreased substantially Marine extinctions Development of large ice sheet on Antarctica
- 6. Zachos et al., 2001
- 7. Current Research Aims to answer question 1: Does North American terrestrial climate exhibit the same pattern as the global record?
- 9. Results
- 10. Comparison to Global Climate
Editor's Notes
- Marine pelagic diversity was at a maximumin the Eocene- now there are mass extinctions Marine invertebrate extinctions included genera disappearances of foraminifera, dinoflagellates and nannoplankton. Warm and deep water taxa epsecially hit hard, experiencing diversity decreases if not extinct. Benthic forams however show gradual, stepped decreases from mid E to O with no clear turnover event at Oi-1, indicating not a huge change in temperature. Upwelling in tethys region limited oxygen in bathyal environment, benthic forams died Temperature drop associated with increased seasonality Thermohaline circulation begins (cold bottom water currents) Sea Level Drop/ Mid-Latitude albedo increase/ more weathering CCD drops 2,000 meters
- Terrestrial sequences are given Land Mammal Ages to define their place in time. The only way to directly correlate to a marine record is through magnetostratigraphy. Age errors on magneto layers are 100,000 to 200,000 years, much less than previous k-Ar dates. Using 40Ar/39Ar now
- The oxygen isotopic composition of modern soil carbonate is well correlated with the isotopic composition of local meteoric water (Cerling, 1984). δ 18 O is typically interpreted as recording changes in paleoclimatic variables, while δ 13 C responds to more general paleoenvironmental shifts (Bowen et al., 2001). Screening for kinetic effects, alteration and pre-infiltration evaporative enrichment of 18 O in meteoric waters is accomplished by the existence of identical values and trends in multiple coeval samples (Denniston, et al., 2007). isotopes of the infiltrating water should reflect the oxygen isotopic composition of infiltrating water and the temperature at which the calcite precipitates from the water (Denniston et al., 2007). Carbon in soil carbonate is derived from soil CO 2 , which is a mixture of carbon dioxide from the atmosphere and organic decomposition, and soil-respired CO 2 , derived from root respiration (Bowen et al., 2001). δ 13 C value for soil carbonate, but the most important are depth in the soil profile, the fraction of C 3 biomass, and P(CO 2 ,) of the atmosphere (Cerling, 1991). C3 plants are expected to have a carbonate signature of -5 to -15 permil after fractionation and enrichment through the infilatration and ppt process-this is the amount we see- shifts are then related to plant productivity which is dependent on precipitation. Errors:d18O- Sample errors span the range of 0.06‰ to 0.93‰, where 0.2‰ represents a 1-sigma of standard deviation. The majority of errors are near a 1-sigma deviation d13C -0.01‰ to 0.46‰, where 0.1‰ represents a 1-sigma of standard deviation. The majority of errors are near a 1-sigma deviation If diagenesis had occurred, d13C would remain about the same, but the δ 18 O values are generally depleted in the sparite by up to 10‰, - not suspected generally in these samples, though possibly in the Chamberlain Pass Trends in the record discussed are primary, and reflect syndepositional changes in the δ 18 O value of temperature.
- D18O and d13C lag behind marine record= Terrestrial temperature and aridity changes did not happen at the E-O boundary, but after. Terrestrial temperature may be more strongly influenced by local tectonic activity and topography which are strong influencers on atmospheric circulation Large fluctuation in the d18O does indicate a significant drop in temperature Supports large drop in atmospheric CO2 Variability in the d18O indicates that decreasing atmospheric CO2 was not the only Influencing factor on terrestrial climate Paleotopography may have had a significant role. Ice volume increases probably led to increasing aridity Badlands National Park Paleosol carbonates appear to bridge the gap between stable isotopic data from the Gulf Coast and fossil teeth of the Badlands It is difficult to draw any conclusions from the δ 13 C record obtained from paleosol carbonates. More positive values support the notion of increased aridity- as plant stress would have affected d13C. ). δ 13 C of Eocene-Oligocene records also reflects C 3 water stress, plant productivity and canopy structure, all increasing with increasing aridity
- Notably lacking is the variability in the late Eocene or increased aridity
- Wooded forest and herbaceous vegetation (open woodland) indicated by large root traces and thin paleosols with fine root traces Limestone fossils show high abundance and low diversity with fish kill horizons and death horizons of ostracodes - evidence of environmental stress Asian immigrants adapted to woody scrub-land immigrated in Eocene – including lophodont rodents, pig-like enteledonts, several families of artiodactyls, and several groups of perissodactyls, including tapiroids and rhiocertoids . This pic is actually the Subhyracodon sculpted by Allen. Belongs to the family Hyracodontidae (like rhino’s, but extinct) brontotheres Brule formation vegetation was largely the same- just thining trees and more open grassland and less streams
- Floral change across the Eocene-Oligocene in the Badlands region appears to have been subtle, but characterized by increased aridity. Trees became scattered with grasses and bushes between them Mammals extinction likely due to disruption in water supply and temperature drop New appearances of mammals had high-crowned teeth for eating tough vegetation
- The two existing isotopic studies of the Badlands are in agreement regarding temperature change, but are not resolved in terms of aridity FINAL POINT: Hence the terrestrial response to climate appears to be decoupled from the marine response. Though a definate global climate signature was impressed upon the mid-continent- it appears clear that the relationship is not direct, and is poorly understood.
- The two existing isotopic studies of the Badlands are in agreement regarding temperature change, but are not resolved in terms of aridity FINAL POINT: Hence the terrestrial response to climate appears to be decoupled from the marine response. Though a definate global climate signature was impressed upon the mid-continent- it appears clear that the relationship is not direct, and is poorly understood.