Radiocarbon Dating, Chronologic Framework, and Changes in Accumulation Rates of Holocene Estuarine Sediments from Chesapeake Bay

Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20min length and used numerous radiocarbon ages measured by accelerator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210Pb and 137Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

The Probe, Issue 210 – May/June 2000

NADCA Election in Progress Berryman Institute Announces 1999 Awards New Probe Editor to be Appointed: Larry Sullivan Ken Garner Retires Book Review: "Master Land Snaring: Canine and Coon Techniques, Effective in All Terrains." by Newt Sterling as told to Bob Noonan. 1999. 58 pages, illustrated. NPCA Gets New Name Lobster Plates: PETA (People for the Ethical Treatment of Animals) is fighting to prevent the return of the lobster to Maine's automobile license plates. Active Antis in the Northwest Animal Rights Violence on Increase Abstracts from the 6th Annual Conference of The Wildlife Society: Monitoring of Sin Nombre Hantavirus in deer mice of the Southwest, USA -- Robinson, Rhonda /., Kathryn D. Bennett, James R. Biggs, Timothy K. Haarmann, David C. Keller, and Mary E. Salisbury Predators in the classroom: A prickly paradigm for educators -- Rollins, Dale Trends in bat rabies in the U.S.: Shaping public health policy -- Rupprecht, Charles E., Sharon B. Messenger, and Jean S. Smith