Jahren, A. Georgia Tech, jahren@eas.gatech.edu
Arens, N. University of California, nanarens@socrates.berkeley.edu
Cabena, L. Georgia Tech, gt0050c@prism.gatech.edu

 
VASCULAR LAND PLANT ISOLATES FROM NEAR-SHORE SEDIMENTS: IMPLICATIONS FOR DELTA-13-C DETERMINATION OF THE PALEOATMOSPHERE
 
Recent methods allow interpretation of paleoatmospheric delta-13-C from either C3 or C4 bulk terrestrial plant tissue. However, many organic sediments result from near-shore deposition, and contain both marine and terrestrial inputs. Also, many Neogene and Quaternary organic sediments result from mixed C3/C4 communities. Here, we describe efforts to isolate vascular land plant tissues, identified under the microscope and separated from accumulating near-shore sediment, as indicators of paleoatmospheric delta-13-C. We describe our work along two transects: 1.) a terrestrial-marine transect from the Black River region of southwestern Jamaica. Modern forming-sediment was collected at 13 sites along a gradient of environmental salinity ranging from well up-river (0.5 g/L NaCl) to the river's mouth (5.0 g/L NaCl), encompassing several types of depositional environments associated with the strictly C3 plant community. delta-13-C value was determined and compared between bulk organic matter, land-plant stem isolates, and land-plant cuticle isolates. 2.) a 450-mile latitudinal transect from N. Florida to S. Virginia of 7 coastal wetland sites in an attempt to isolate C3 and C4 contributions to the bulk sediment. delta-13-C value was determined and compared among bulk sediments, living plant samples, and microscopic plant tissue isolates. Preliminary results show constant delta-13-C value in plant isolates across all sites within each transect suggesting that despite highly variable depositional environment, the land plant contribution can be isolated and analyzed with confidence.
 
Day: Wednesday, Feb. 3
Time: 12:15 - 12:30pm
Location: Eldorado Hotel
 
Code: SS32WE1215E