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Please join us for a guest presentation by Marguerite Toscano on Wednesday, July 10th. 

Sea Level Reconstructions from Mangrove Peat Deposits in Florida, Belize and Panama

Marguerite A. Toscano
Smithsonian Environmental Research Center, Edgewater, MD
National Science Foundation, Directorate for Geosciences, Alexandria, VA

"Mangrove peat deposits have documented ~9 kyrs of accumulation in response to Holocene sea level rise (SLR) from Florida to South America.  Radiocarbon-dated core records from oceanic R. mangle peat sequences in Florida (6 m), Belize (12 m) and Panama (3.5 m) indicate rates of SLR that mangroves in open ocean settings have survived and accumulated through belowground biotic processes with minimal sediment inputs. Computed Tomography (CT) and peat LOI analysis demonstrate the lack of compaction in oceanic peat systems and highlight the key role of water in maintaining peat elevations over time. Comparison of depth-correlative basal and continuous peat dates show large lag times of basal peat formation after sea level rise, indicating that basal peats alone give a “too-late and too-low” sea level record.  Using the full peat stratigraphy in each area reveals other issues affecting the fidelity of fossil peat as a tide-range limited sea-level indicator, including the ubiquitous problem of 14C age inconsistencies and reversals due to pervasive mixing of living and fossil roots and peat. Both legacy (1980s-1990s) and new (2012 and later) peat data suggest a rise in peat elevations during the mid-Holocene, not seen in the contemporaneous Acropora palmata coral data in Belize and Florida.  When plotted with independently modeled ICE-6G relative sea level (RSL) curves, a mid-Holocene highstand in the RSL models mimics the rise in the peat data, but with large misfits (not reduced through tectonic correction). This suggests hypotheses specific to peat systems, including paleoclimatic influences (temperature, hydroclimate) resulting in the possibility of syn- or post-depositional peat expansion in warmer or wetter conditions. Accurate paleo sealevels and rates during deglaciation and climate changes are predictors of the sustainability of peat forming ecosystems into the next 50-100 yr of accelerating rates of SLR." 

Date: 11:00 AM ET, Wednesday, July 10, 2019

GS Talk:

Phone: 703-648-4848 Code:52829583