The removal of exchangeable oxygen from diatom opal prior to δ18Odiatomanalysis is a crucial first step before analyzing frustule oxygen isotopes for paleoceanographic applications. We present the results of experiments that quantify the temperature‐dependent reactivity of biogenic silica with water under laboratory conditions. We demonstrate that controlled exchange between rinse water and diatom opal at room temperature results in predictable alteration of δ18Odiatom, after vacuum dehydroxylation. Diatom samples equilibrated with an18O‐enriched δ18Oequil. watersolution of +94.4‰ at ~21 °C for 70 hr prior to dehydroxylation yield δ18Odiatomdata that can be directly interpreted with existing empirical δ18Odiatomversus temperature relationships. We compare sediment trap‐based δ18Odiatomtemperature data with modern δ18Oforamtemperatures. Finally, we present an ~220 year record of δ18Odiatomdata from an eastern Pacific Guaymas Basin boxcore, analyzed using the microfluorination technique, that indicates diatom chlorophyll maximum (Chlmax) temperatures have shifted from a period during the late eighteenth and nineteenth centuries that was 8 °C cooler during the fall bloom relative to mean annual alkenone
Centuries‐long intensive land‐use change in the north‐eastern United States provides the opportunity to study the timescale of geomorphic response to anthropogenic disturbances. In this region, forest‐clearing and agricultural practices following EuroAmerican settlement led to deposition of legacy sediment along valley bottoms, including behind mill dams. The South River in western Massachusetts experienced two generations of damming, beginning with mill dams up to 6‐m high in the eighteenth–nineteenth century, and followed by construction of the Conway Electric Dam (CED), a 17‐m‐tall hydroelectric dam near the watershed outlet in 1906. We use the mercury (Hg) concentration in upstream deposits along the South River to constrain the magnitude, source, and timing of inputs to the CED impoundment. Based on cesium‐137 (137Cs) chronology and results from a sediment mixing model, remobilized legacy sediment comprised
- Award ID(s):
- 1654462
- NSF-PAR ID:
- 10456178
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Earth Surface Processes and Landforms
- Volume:
- 45
- Issue:
- 10
- ISSN:
- 0197-9337
- Page Range / eLocation ID:
- p. 2380-2393
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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