Geology & Astronomy Seminar:Wednesday, Nov. 18 at 4:15 PM in SSN 191. Refreshments served at 4.
Sediment Accumulation and Marsh Accretion in Tidal Wetlands of the Delaware River Estuary
Chris Sommerfield, College of Marine Studies, University of Delaware
The tidal Delaware River and Bay system is fringed by one of the largest, most continuous tidal wetland coasts in the U.S. Mid-Atlantic region. This ecosystem provides immeasurable environmental and economic benefits despite having been impacted by centuries of human intervention. In recognition of historical disturbances in the natural supply of river sediment to the estuary, there is concern over the fate of wetland marshes. To establish baseline conditions of marsh sediment supply and accretion, we core sampled sites along the full length of the wetland coast, from tidal freshwater marsh to salt marsh near the bay mouth, and dated the sediments by radionuclide geochronology. Results indicate that marsh accretion rates are highest in the tidal freshwater segment of the estuary (>6 mm/yr), decreasing to rates of 4-6 mm/yr in the brackish estuary where organogenic material comprises a large component of the sediment column. Salt marshes near the mouth of Delaware Bay, far removed from turbid waters of the middle estuary, exhibit the lowest accretion rates (<4 mm/yr) and quantity of buried mineral matter. This along-estuary pattern suggests that the external influx and accumulation of minerogenic sediment, in addition to vegetative growth and organic accumulation, is a key factor in the overall rate of marsh accretion.
Dr. Sommerfield graduated from WCU with B.S., Geology in 1986. He earned an M.S. in Marine Environmental Science from SUNY, Stony Brook in 1993 and a Ph.D. in Coastal Oceanography from SUNY Stony Brook in 1997.
