Geoscience Reference
In-Depth Information
figure 23. Stratigraphy of the sediment core from Rush Ranch,
Suisun Marsh, in the northern San Francisco Bay. From let to right
are the calibrated radiocarbon ages, the sediment types in the core, the
diatom index, the percentage of Chenopodiaceae pollen, and carbon
isotope values. h e diatom index refers to the percentage of diatoms
that live in higher salinity waters versus fresher waters. Values ranging
between 0.00 and 0.30 are dominated by marine taxa, 0.31 to 0.70 are
dominated by a mixture of taxa, and 0.71 to 1.00 are dominated by fresh-
water taxa. h e Chenopodiaceae pollen (from marsh plants that grow
in higher salinity waters, such as
Salicornia
and
Atriplex
) represents the
percentage of that pollen relative to the total marsh pollen. h e d13C
value δ
13
(plotted on the right) of fresher marsh plants is closer to -25 per
mil, with those growing in higher salinity waters being closer to -15 per
mil. h e data show a higher salinity interval from 1750 to 750 years ago,
encompassing the Medieval Climate Anomaly. (Graph modii ed using
data from Byrne et al. 2001.)
