A 4700 YR RECORD OF CLIMATE FROM CHINA CAMP, SAN FRANCISCO BAY, CA

Tidal salt marsh deposits represent an under utilized resource for studying climate change within the coastal zone of California, where relatively few lacustrine sites exist, as they preserve a potentially valuable longterm stratigraphic archive. Most importantly, because tidal salt marshes lie at the interface between the terrestrial and oceanic realms they are sensitive to changes and perturbations in both. Thus the impacts of climate perturbations caused by ENSO and the PDO should be recorded in the stratigraphy of tidal marshes.

In order to test this hypothesis a variety of proxy data (loss-on-ignition, seeds, pollen, grain size, carbon isotopes, and trace metals) for establishing changes in climate and sea level were collected from sediment cores from China Camp State Park, San Francisco Bay, CA. China Camp is a large relatively pristine tidal salt marsh located on the west side of San Pablo Bay. Mean water salinity at China Camp is 24.6‰, with a maximum of 33.3‰ and a minimum of less than 1‰. Marsh vegetation is clearly zonal and is largely controlled by tidal inundation and salinity. The low marsh zone is dominated by Spartina foliosa and the high marsh with Salicornia virginica.

The stratigraphic data from China Camp reveals a complex history of salinity changes reflecting conditions within San Pablo Bay. Fresher water conditions than modern prevailed between 3400-2000 cal yr B.P. Following this until about 700 cal yr B.P., conditions within the Bay were overall more saline but variable. The four hundred year period between 850-450 cal yr B.P. (coeval with the Medieval Warm Period) is distinguished from later and earlier periods by evidence for high precipitation events, which may correlate with estuary wide floods, possibly related to El Niño. Geochemical evidence (e.g. Cd and possibly Ca:Mg ratio) indicates the likelihood of pronounced salinity intrusions and droughts reflecting La Niña conditions.