164-10 Quartz Formation at Montpelier Plantation, VA: A Geologic Mystery with Anthropologic Connections

Session: Advances and Applications of Geochemistry in Archaeology

Presenting Author:

Marina Ashurkoff

Authors:

Ashurkoff, Marina Christina¹, Hamelin, Clementine², Bailey, Christopher M.³, Reeves, Matthew⁴, McCague, Liz⁵, Anglin, Henry⁶

(1) Dept. of Geology, William & Mary, Williamsburg, VA, USA, (2) Dept. of Geology, William & Mary, Williamsburg, VA, USA, (3) Dept. of Geology, William & Mary, Williamsburg, VA, USA, (4) James Madison's Montpelier, Montpelier Archeology Department, Montpelier Station, Virginia, USA, (5) James Madison's Montpelier, Montpelier Archeology Department, Montpelier Station, VA, USA, (6) Montpelier Descendants Community Committee, Montpelier Station, VA, USA,

Abstract:

Quartz crystal artifacts discovered at James Madison’s Montpelier in north-central Virginia provide an opportunity to improve the regional geologic understanding of Virginia’s Blue Ridge and provide context for an ongoing anthropologic story. These artifacts were discovered within the topsoil down to the subsoil of the Burial Ground of the Enslaved. They appear as clusters of singly terminated quartz crystals with the crystals in most clusters growing in a variety of directions. The Montpelier plantation is located on the southeastern limb of the Blue Ridge Anticlinorium, a major regional structure in the central Appalachians. Two major geologic units underlie Montpelier, the Catoctin Formation (an Ediacaran flood basalt that was metamorphosed and deformed in the Neoacadian) and sedimentary rocks in the Mesozoic Barboursville basin. We hypothesize that these quartz crystals formed in dilatational fractures in the Catoctin Formation due to fluid-driven metamorphism. Vein quartz in samples from both the Catoctin greenstone and Barboursville Basin were analyzed and compared to the quartz crystal artifacts using cathodoluminescence (CL) imaging and oxygen isotope analysis. Panchromatic CL imaging was done on representative artifact, Catoctin, and Barboursville Basin quartz vein samples using the JEOL JXA-iHP200F Microprobe at Virginia Tech. No major zoning of quartz veins was found in any of the samples. One Barboursville Basin sample yielded recrystallized quartz in apparent fractures that crosscut through the sandstone with similar luminescence to the vein above it.

Oxygen isotope analysis will be done in the High Temp Stable Isotope Lab at UT Austin. δ¹⁸O values of quartz from the three investigated materials will be interpreted in the context of water sources (magmatic, meteoric, seawater infiltration) and potential protoliths (basaltic, sedimentary). During examination of samples in thin section, fluid inclusions were discovered within the quartz crystal artifacts and will be an additional avenue of study. Together, these datasets contribute insights to the provenance of the quartz crystal artifacts. Determining the process through which the quartz crystal artifacts formed has implications for understanding regional geologic conditions.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8682

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