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Abstract Detail

Paleobotanical Section

Hsiung, Shih-Yi [1], Byrne, Roger [2], Looy, Cindy V [1].

A signal of climate change during the last interglacial period from Clear Lake, California.

Pollen analysis is a well-established method to study Quaternary vegetational and climatic changes in North America. Well-preserved fossil pollen assemblages that show shifts in floral composition, provide insight in local environmental changes. During the start of the last interglacial, around 130,000 year ago, California experienced a warming event believed to be an analogy to a future warmer condition in California. Therefore, the last interglacial period was chosen for a high resolution pollen study. Based on marine oxygen isotopes from Pacific core V28-238, the warmest average temperature in the last interglacial period was 1.5 degrees centigrade higher than today. Prior palynological studies at Clear Lake have provided low resolution records, but results hardly allow precise inference of vegetation shifts due to the lack of detail. The purpose of this research is to use 140 m cores from Clear Lake, California to establish pollen assemblages through the last glacial-interglacial period and to infer vegetation shifts in northern California during this period of time. Clear Lake has rapid sedimentation rates around 0.8 and 1.0 mm/yr beginning about 140 ka to the present. Rare high sedimentation rates have provided high opportunities to develop a high resolution pollen record. These factors make Clear Lake a unique lake for vegetation and climate reconstruction in California. Two 140-m lake cores, CLDP-CLCA12, were drilled by DOSECC in May, 2012. Based on earlier age assessments the cores represent ~150,000 years. Pilot samples were taken every 50 centimeters, each over a 5cm interval (0 to 5cm, 50 to 55cm, 100 to 105 cm, etc) to make correlations with the earlier USGS studies possible. Based on these prior studies the previous interglacial period covers the 110-120 m depth intervals. The first 8 samples from 105-140 m depth were processed in the palynology acid lab at UC Berkeley. Pollen slides showed well-preserved pollen grains. The deepest and therefore oldest sample showed a high proportion of conifer pollen related to a glacial environment. Samples from higher up in the core contain a higher proportion of oak pollen and a higher total diversity of pollen types. These are the first results of an ongoing study. Over a hundred more samples will be processed and analyzed and will provide a high-resolution record for changes in vegetation and climate change in California during the previous interglacial.

Broader Impacts:

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Related Links:
Drilling Clear Lake
Dispatches from Clear Lake, part 1
Dispatches from Clear Lake, part 2

1 - University of California, Berkeley, Department of Integrative Biology and Museum of Paleontology, 3060 Valley Life Sciences Building #3140, Berkeley, CA, 94720, USA
2 - University of California, Berkeley, Department of Geography, 507 McCone Hall, Berkeley, CA, 94720, USA

Clear Lake
Climate Change

Presentation Type: Poster:Posters for Sections
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PPB008
Abstract ID:837
Candidate for Awards:None

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