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Abstract 230Th normalization is a valuable paleoceanographic tool for reconstructing high‐resolution sediment fluxes during the late Pleistocene (last ~500,000 years). As its application has expanded to ever more diverse marine environments, the nuances of230Th systematics, with regard to particle type, particle size, lateral advective/diffusive redistribution, and other processes, have emerged. We synthesized over 1000 sedimentary records of230Th from across the global ocean at two time slices, the late Holocene (0–5,000 years ago, or 0–5 ka) and the Last Glacial Maximum (18.5–23.5 ka), and investigated the spatial structure of230Th‐normalized mass fluxes. On a global scale, sedimentary mass fluxes were significantly higher during the Last Glacial Maximum (1.79–2.17 g/cm2kyr, 95% confidence) relative to the Holocene (1.48–1.68 g/cm2kyr, 95% confidence). We then examined the potential confounding influences of boundary scavenging, nepheloid layers, hydrothermal scavenging, size‐dependent sediment fractionation, and carbonate dissolution on the efficacy of230Th as a constant flux proxy. Anomalous230Th behavior is sometimes observed proximal to hydrothermal ridges and in continental margins where high particle fluxes and steep continental slopes can lead to the combined effects of boundary scavenging and nepheloid interference. Notwithstanding these limitations, we found that230Th normalization is a robust tool for determining sediment mass accumulation rates in the majority of pelagic marine settings (>1,000 m water depth).
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School Desegregation and Resegregation in the Upper South: An Introduction and Overview
Despite strong progress toward school desegregation in the late 20thcentury, many locations in the Upper South have recently experienced school resegregation. The articles in this issue investigate similarities and differences across this region in attitudes underlying these developments. Individual papers treat factors including resident location within and across school districts, as well as the role of school choice. Papers also advocate for combining the results of case studies and opinion polls in elucidating these dynamics. The issue concludes with a look forward regarding the social and political forces that will contribute to whether or not the Supreme Court’s mandate, based on Brown v. Board of Education, will be realized by its 100thanniversary in 2054.
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- Award ID(s):
- 1528559
- PAR ID:
- 10286040
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- American Behavioral Scientist
- Volume:
- 66
- Issue:
- 6
- ISSN:
- 0002-7642
- Format(s):
- Medium: X Size: p. 671-677
- Size(s):
- p. 671-677
- Sponsoring Org:
- National Science Foundation
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