Two geochemical techniques from soil mineralogy were used with lake sediment to reconstruct soil development in the catchments of two lakes-one on outwash and the other on till-in the Great Lakes region. A sodium pyrophosphate extraction provides information about leaching of exchangeable and organically complexed cations from terrestrial sources, while an acidified ammonium oxalate extraction removes mineral materials without well-developed crystalline structure that are indicative of podzolization. More evidence of pedogenesis is preserved in sediment of the lake on outwash- likely a result of greater retention of material within the soil profile in the catchment on till. This difference between the record suggests that excessively well-drained (leaky) catchments may provide better records of soil development than those with higher water-holding capacity. Evidence of acidification and podzolization appeared first at the lake on till and 4500 years later at the lake on outwash. Both records reveal a late Holocene intensification of weathering that coincided with a regional climatic change to greater moisture availability. The variability in weathering rates observed presents a more complex picture of weathering than the simple exponential functions often assumed in chronosequence studies. Use of lake sediment records provides better temporal resolution of significant events in soil formation than could be achieved using a chronosequence approach.
Bibliographical noteFunding Information:
We Thank A. Bernstein, R. Calcote, S. Cronlund, M. Davis, G. Fuller, S. Hotchkiss, and S. Sugita for help coring. R. Knurr did the acid dilution and ICP analyses. Earlier versions of this paper were improved by comments from R. Calcote, M. Davis, C. Douglas, J. Ford, P. Groffman, S. Halpern, S. Hobbie, S. Hotchkiss, K. Weathers, and three anonymous reviewers. Support came from the Geological Society of America, the Dayton and Wilkie Funds, NSF/BIR-9413239, University of Wisconsin’s Trout Lake Station, NSF/ATM-9709633, NSF/ATM-9809285, and a NASA Earth System Science Fellowship.
- Acidified ammonium oxalate
- Ecosystem leakiness
- Sodium pyrophosphate
- Soil development