1. 05/11/2012
Experimental Leaching of Bedrock and Fluvial Sediments: Implications for Continental Runoff
K.M. Deuerling, E.E. Martin, J.B. Martin, G.D. Kamenov
University of Florida, Department of Geological Sciences
Geological Society of America Fall Meeting, 5 November 2012

2. Motivation: Oceanic Sediments
05/11/2012
Motivation: Oceanic Sediments
Modified from Kurzweil et al. 2010
warmer
colder
Radiogenic Pb and Weathering
238U  206Pb
235U  207Pb
232Th  208Pb
Radiogenic Pb isotopes normalized to 204Pb (nonradiogenic)
Elevated 206,207,208Pb/204Pb indicates weathering of “fresh” material
Continental weathering  seawater Pb signature
Radiogenic Pb
18O data is ice core data
Squiggles have been attributed to changes in chemical and physical weathering regimes
Have never been compared to land-based records

3. Motivation: Land-based Chronosequences
05/11/2012
Motivation: Land-based Chronosequences
Harlavan et al. 1998
Leached fraction more radiogenic than bulk soil values
Leached fraction approaches bulk values over time

4. Question Significance
05/11/2012
Question
How do radiogenic isotope ratios vary between different weathering environments in glacial forelands?
Significance
Initial evaluation of the importance of fluvial weathering environment on continental runoff signature
Identification of distinct isotopic signatures in proglacial and deglaciated weathering environments

5. Glacial Foreland Stream Morphology
Proglacial Streams
Predominantly glacial melt
Deglaciated Streams
Predominantly local precipitation
↑ discharge
↑ suspended sediment load
↓ discharge
↓ suspended sediment load

6. Glacial Foreland Stream Morphology
(Mernild et al. 2010)
~50% of melt near Kangerlussuaq is derived from deglaciated watersheds

7. Rock/Sediment Sample Collection Sites
05/11/2012
Rock/Sediment Sample Collection Sites
~20 km from coast
2 rock types (granite, gneiss)
2 proglacial, 1 deglaciated sediment samples
Google Earth

8. Experiment I: 24-Hour HCl Leach
05/11/2012
Experiment I: 24-Hour HCl Leach

9. Water Sample Collection Sites
05/11/2012
Water Sample Collection Sites
(PG 1-1)
(PG 1-2)
(DG 1-2)
(DG 1-1)
(PG 2-2)
Five water samples taken for radiogenic isotope analysis
3 proglacial, 2 deglaciated
Google Earth

10. Initial Data: Ilulissat Water Samples
05/11/2012
Initial Data: Ilulissat Water Samples

11. Initial Data: Ilulissat Water Samples
05/11/2012
Initial Data: Ilulissat Water Samples
(PG 1-1)
(DG 1-1)
(DG 1-2)
(PG 1-2)
(PG 2-2)
(PG 1-1)
(PG 1-2)
(DG 1-2)
(DG 1-1)
(PG 2-2)
Anthropogenic Pb input to deglaciated watersheds?
Downstream input of deglaciated water into proglacial watershed  mixed source signal

12. 05/11/2012
Conclusions
Proglacial and deglaciated leaching experiments indicate that sediments in the field area are relatively “new” and unweathered
Water samples demonstrate disparate isotope fields for proglacial and deglaciated streams
Proglacial headwaters  subglacial signal?
Mixing/integrated signal over path length
Once scaled up, should be able to use the information to validate the marine records, or to look at more pertinent fjord cores

13. 05/11/2012
Future Work
Analyze leachates, residuals, and bulk rock/sediment for radiogenic Sr and Nd
Widespread sampling expedition from Kangerlussuaq to Sisimiut, West Greenland scheduled for Summer 2012
Google Earth

14. Questions? Acknowledgments
This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE
Funding also provided by the University of Florida Faculty Enhancement Opportunity awarded to J. Martin

15. Experiment I: 24-Hour HCl Leach
05/11/2012
Experiment I: 24-Hour HCl Leach

16. Experiment II: 5-Day HCl Leach
05/11/2012
Experiment II: 5-Day HCl Leach

17. Experiment II: 5-Day HCl Leach
05/11/2012
Experiment II: 5-Day HCl Leach