Environmental evolution of peat in the Sacramento – San Joaquin Delta (California) during the Middle and Late Holocene as deduced from pollen, diatoms and magnetism

Quaternary International
By: , and 

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Abstract

We studied the sequence of climatic and hydrological events associated with the formation of peat during the Holocene, using pollen, diatoms and environmental magnetism from peat cores at three locations in the Sacramento-San Joaquin Delta of California: Browns Island, Franks Wetland and Webb Track Levee. Our data show that peat first formed under relatively dry conditions in a freshwater environment before 6.5 ka BP. Subsequently, pollen accumulation rates were highest prior to intervals with high peat accretion rates but are inversely correlated with organic accumulation rate. Intervals of high peat accretion were preceded by pulses of terrigenous material. During intensive drainage episodes, high flows delivered abundant, coarser-grained sediment to the marshes, which inundated the existing vegetation and decreased the rate of biochemical decay. The build-up of undecomposed organic material led to the acceleration of peat accretion. Our data support the rarely discussed hypothesis that most of the peat in the Sacramento-San Joaquin Delta formed in freshwater marshes that were fed by rivers draining from the Sierra Nevada, rather than in saltwater wetlands resulting from sea level rise and estuarine submergence. This result has important implications for current attempts to remediate and restore the Delta ecosystem.

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Publication type Article
Publication Subtype Journal Article
Title Environmental evolution of peat in the Sacramento – San Joaquin Delta (California) during the Middle and Late Holocene as deduced from pollen, diatoms and magnetism
Series title Quaternary International
DOI 10.1016/j.quaint.2020.05.012
Volume 621
Year Published 2022
Language English
Publisher Elsevier
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 12 p.
First page 50
Last page 61
Country United States
State California
City Sacramento
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