Title

Radiocarbon Dating of Bioapatite from Calcine Bone: Western Washington

Presenter Information

James Brown

Document Type

Oral Presentation

Location

SURC Ballroom C/D

Start Date

16-5-2013

End Date

16-5-2013

Abstract

Only highly burned (calcine) bone survives well in archaeological sites with acidic soils (pH 4.5 to 5.5). Calcine bone may provide accurate radiocarbon age estimates, if intact bio-apatite can be extracted, processed, and assayed. Samples of calcine bone need to be thin sectioned before and after acetic acid baths. A petrographic microscope (w/polarized light) will be used in a pilot study of samples from the Bray Archaeological Site (Pierce County, Washington) to compare amounts of intact bioapatite and intrusive calcite before and after acid treatment. A general radiocarbon database is constructed for shell, charcoal and bone samples for sites in western Washington. This database shows the need for improving radiocarbon dating in western Washington and the significance of these data for building an understanding of the ecological and economic factors that drive the development of the Pacific Northwest village pattern. Along the northwest coast, mass food processing and storage were well established by 2,500 Radiocarbon Years Before Present (RCYBP), especially where marine resources were abundant. Radiocarbon dating of features at the Bray Site may provide the earliest evidence for intensification of plant resource use along the White River (3,000 RCYBP). Charcoal already dated from the ovens can be contaminated by humic acids leached from topsoil. Burned (calcine) bone may provide more accurate age estimates, if intact bio-apatite can be extracted, processed, and accelerator mass spectrometry dated.

Poster Number

8

Faculty Mentor(s)

Steve Hackenberger

Additional Mentoring Department

Anthropology

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Radiocarbon Dating of Bioapatite from Calcine Bone: Western Washington

SURC Ballroom C/D

Only highly burned (calcine) bone survives well in archaeological sites with acidic soils (pH 4.5 to 5.5). Calcine bone may provide accurate radiocarbon age estimates, if intact bio-apatite can be extracted, processed, and assayed. Samples of calcine bone need to be thin sectioned before and after acetic acid baths. A petrographic microscope (w/polarized light) will be used in a pilot study of samples from the Bray Archaeological Site (Pierce County, Washington) to compare amounts of intact bioapatite and intrusive calcite before and after acid treatment. A general radiocarbon database is constructed for shell, charcoal and bone samples for sites in western Washington. This database shows the need for improving radiocarbon dating in western Washington and the significance of these data for building an understanding of the ecological and economic factors that drive the development of the Pacific Northwest village pattern. Along the northwest coast, mass food processing and storage were well established by 2,500 Radiocarbon Years Before Present (RCYBP), especially where marine resources were abundant. Radiocarbon dating of features at the Bray Site may provide the earliest evidence for intensification of plant resource use along the White River (3,000 RCYBP). Charcoal already dated from the ovens can be contaminated by humic acids leached from topsoil. Burned (calcine) bone may provide more accurate age estimates, if intact bio-apatite can be extracted, processed, and accelerator mass spectrometry dated.