Dean, W. E.. US Geological Survey, dean@usgs.gov
Brachfeld, S. E.. Department of Geology and Geophysics, brac0009@umn.edu

 
A HOLOCENE RECORD OF MAJOR AND TRACE COMPONENTS IN THE SEDIMENTS OF AN URBAN IMPOUNDMENT ON THE MISSISSIPPI RIVER: LAKE PEPIN, MINNESOTA
 
Lake Pepin is a natural pool formed by damming of the Mississippi by an alluvial fan of a tributary, the Chippewa River, that enters the Mississippi from Wisconsin. Lake Pepin is, therefore, somewhat unique among impoundments in that it has preserved a 9500-year record of materials that have been transported down the Misisissippi . This natural record can then be compared to changes that have occurred since European settlement (ca. AD 1830). The most immediate response in the sediments of Lake Pepin to settlement was an increase in bulk-sediment accumulation rate. This was accompanied by increases in concentrations of phosphorus (P), organic carbon (OC) (Almendinger and Engstrom, this session). The increase in P was far greater than any of the minor fluctuations in P that occurred throughout the Holocene, but the increase in OC was comparable to an increase in OC that occurred in the early Holocene. The concentrations of several metals (e.g. cadmium and lead) also are elevated in recent sediments, although higher concentrations of some metals (e.g. iron and manganese) occur in mid-Holocene sediments, perhaps due to changes in redox conditions.
 
Day: Tuesday, Feb. 2
Time: 09:00 - 09:15am
Location: Sweeney Center
 
Code: SS19TU0900S