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Title: Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA

Abstract

Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma March over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10--35{per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5{per_thousand} between 500 yr BP and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3--4{per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100--300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600--700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}Cmore » {approximately} {minus}12{per_thousand}) to CAM ({delta}{sup 13}C = {minus}26{per_thousand})-type vegetation over time.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Geology
  2. Australian National Univ., Canberra (Australia). Dept. of Geology
  3. Univ. of Wollongong, New South Wales (Australia). School of Geoscience
  4. Lawrence Berkeley National Lab., CA (United States). Center for Isotope Geochemistry
  5. Univ. of California, Berkeley, CA (United States). Dept. of Geography
Publication Date:
OSTI Identifier:
338611
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 62; Journal Issue: 19-20; Other Information: PBD: Oct 1998
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; CALIFORNIA; MARSHES; ISOTOPE RATIO; AQUATIC ORGANISMS; PALEOCLIMATOLOGY; SEA LEVEL; CLIMATIC CHANGE

Citation Formats

Ingram, B.L., Deckker, P. de, Chivas, A.R., Conrad, M.E., and Byrne, A.R. Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA. United States: N. p., 1998. Web. doi:10.1016/S0016-7037(98)00240-3.
Ingram, B.L., Deckker, P. de, Chivas, A.R., Conrad, M.E., & Byrne, A.R. Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA. United States. doi:10.1016/S0016-7037(98)00240-3.
Ingram, B.L., Deckker, P. de, Chivas, A.R., Conrad, M.E., and Byrne, A.R. Thu . "Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA". United States. doi:10.1016/S0016-7037(98)00240-3.
@article{osti_338611,
title = {Stable isotopes, Sr/Ca, and Mg/Ca in biogenic carbonates from Petaluma Marsh, northern California, USA},
author = {Ingram, B.L. and Deckker, P. de and Chivas, A.R. and Conrad, M.E. and Byrne, A.R.},
abstractNote = {Stable isotope ({sup 18}O/{sup 16}O and {sup 13}C/{sup 12}C) and minor-element compositions (Sr/Ca and Mg/Ca ratios) of ostracodes and gastropods separated from marsh sediments from San Francisco Bay, Northern California, were used to reconstruct paleoenvironmental changes in Petaluma March over the past 700 yr. The value of {delta}{sup 18}O in the marsh carbonates reflects changes in freshwater inflow, evaporation, and temperature. Mg/Ca and Sr/Ca in ostracode calcite reflect changes in both freshwater inflow and temperature, although primarily reflect temperature changes in the salinity range of about 10--35{per_thousand}. Ostracode {delta}{sup 18}O values show a gradual increase by 5{per_thousand} between 500 yr BP and the present, probably reflecting rising sea level and increased evaporation in the marsh. Superimposed on this trend are higher frequency Mg/Ca and {delta}{sup 18}O variations (3--4{per_thousand}), probably reflecting changes in freshwater inflow and evaporation. A period of low Mg/Ca occurred between about 100--300 cal yr BP, suggesting wetter and cooler conditions during the Little Ice Age. Higher Mg/Ca ratios occurred 600--700 cal yr BP, indicating drier and warmer conditions during the end of the Medieval Warm Period. Both ostracode and gastropod {delta}{sup 13}C values decrease up-core, reflecting decomposition of marsh vegetation, which changes from C{sub 4} ({delta}{sup 13}C {approximately} {minus}12{per_thousand}) to CAM ({delta}{sup 13}C = {minus}26{per_thousand})-type vegetation over time.},
doi = {10.1016/S0016-7037(98)00240-3},
journal = {Geochimica et Cosmochimica Acta},
number = 19-20,
volume = 62,
place = {United States},
year = {1998},
month = {10}
}