HR: 1340h
AN: B43B-1172    [Abstracts]
TI: Foraminiferal Assemblage Zones of Oregon Salt-Marshes: Implications for Studies of Relative Sea-Level Change
AU: Horton, B
EM: bphorton@sas.upenn.edu
AF: University of Pennsylvania, Hayden Hall 240 South 33rd Street, Philadelphia, PA 19104, United States
AU: * Hawkes, A D
EM: hawkesa@sas.upenn.edu
AF: University of Pennsylvania, Hayden Hall 240 South 33rd Street, Philadelphia, PA 19104, United States
AU: Alan, N
EM: anelson@usgs.gov
AF: USGS, P.O. Box 25046 Mail Stop 966, Golden, CO 80225-0046, United States
AU: Kemp, A
EM: kempac@sas.upenn.edu
AF: University of Pennsylvania, Hayden Hall 240 South 33rd Street, Philadelphia, PA 19104, United States
AB: Salt-marsh foraminifera can be useful tools for reconstructing Holocene sea-level change. The use of fossil assemblages as a relative sea-level indicator is underpinned by (1) the relation between characteristic modern foraminiferal assemblages and the tidal frame, (2) that these modern relations can be quantified, and (3) that modern assemblages are representative of past conditions recorded in Holocene salt-marsh sedimentary sequences. Using correspondence and transfer function analysis on large data sets, the former elevation (relative to the tidal frame) of a preserved salt-marsh deposit can be determined from foraminifera therein. This measure of paleomarsh-surface elevation, when combined with other lithostratigraphic data, can be used to infer the past position of local relative sea-level. We have collected sediment samples along elevational transects across the modern surface of seven tidal salt- marshes along coastal Oregon for foraminifera and environmental variables (elevation relative to the tidal frame, loss on ignition, grain size, pH, salinity) to determine the local and regional foraminiferal assemblage zones. Dominant agglutinated taxa in salt-marshes include Balticammina pseudomacresens, Haplophragmoides wilberti, Trochammina inflata, and Miliammina fusca. We will use canonical correspondence analysis of the modern assemblage and environmental data to determine what variable(s) control foraminiferal distribution. Seasonal and temporal changes in assemblage and species infaunality can modify the assemblage zonation decreasing the precision of environmental reconstruction. Therefore we sampled our sites twice throughout the year and compared the collected faunal assemblages and assessed species infaunal migration through staining live foraminifera in 30cm short cores.
DE: 0468 Natural hazards
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting