Date of Graduation

5-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Dynamics (PhD)

Degree Level

Graduate

Department

Environmental Dynamics

Advisor/Mentor

Kay, Marvin

Committee Member

Stoner, Wesley D.

Second Committee Member

Hays, Phillip D.

Keywords

Early Agriculture; Lithics; Sickle; Sickle Gloss; Use-Wear

Abstract

This series of experiments is designed to understand the development and chemistry of sickle gloss. Sickles are common in the archaeological record and have long been studied for their eponymous “sickle gloss”. There is debate as to how this gloss is formed. Five experimental sickles containing flint and novaculite blades were used to harvest high and low moisture content rye and common fescue and associated field weeds. The differences in the development of sickle gloss were examined. High moisture content plants create thick, smooth fields of polish with undulating, billowing margins at a higher developmental speed. Low moisture content plants generate thin, scratch fields of polish with flat, tapering margins at a lower developmental speed. The speed of development and appearance of the polish is also linked to the type of stone. Flint blades generate polish at a faster rate with a thicker appearance than do novaculite blades on the same sickle. There is a statistically significant difference in the width of striations when comparing type of plant and moisture content of the plant. Three steel blades were polished to three levels of grit: a rough file, 220 grit, and 1000 grit. They were used to cut high moisture content plants for 3 hours. Each blade was found to have sickle polish layers. The surface variance changes the location of initial polish development and the appearance of nascent polish. Initial development occurs on peaks of the microtopography a few microns away from the cutting edge. Surfaces with higher variance exhibit polish with a mounding characteristic while surfaces with lower variance exhibit thin fields of polish. Cross sectioning the stone blades for analysis with LA-ICP MS shows a clear spatial distribution in ions associated with plant metabolism in instances of high moisture content contact. The spatial distribution is less clear in instances of low moisture content contact. Mechanical removal of material near the edge of the blade showed no meaningful oxygen isotopic signal. Use of a more refined sampling method is recommended. For raw LA-ICP MS data of the cross sectioned blades and the plant samples please see the supplemental documents.

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