34 D1. Geomorphic Processes and Landscape Evolution Across Diverse Systems

Friday, 21 March 2025
10:30 AM - 12:00 PM
Alleghany A

HIGH ELEVATION QUARTZ MYLONITE QUARRIES DEVELOPED WITHIN BOUDINAGE OF THE ASHE METAMORPHIC SUITE, SENIARD MOUNTAIN, PISGAH NATIONAL FOREST, NORTH CAROLINA

Paper number: 34-3
Program: Technical Sessions
Time: 11:00 AM – 11:15 AM

Authors

Abstract

Geologic mapping (1:2000) at Seniard Creek, North Carolina, has revealed quartz mylonite boudinage in the Ashe Metamorphic schist (AMS). Cross-cutting relationships infer that quartz was emplaced along a fault as hydrothermal vein fillings. Taconic deformation folded the AMS and fault, resulting in boudinage of competent quartz within the ductile schist. Hand sample and petrographic observations indicate that the quartz is mylonitized. Deformation mapping shows boudinage are oriented 240° to 270° within folds in the AMS. Lineations have been measured along the surfaces of boudins. Recrystallization fabric, or pressure solution halos are sub-parallel to S1.

Section 106 investigations identified preContact quarries at Seniard Creek. Excavations of 50 x 50 cm units yielded archaeological implements unlike those traditionally discovered at preContact quarries. Instead of the typical bifaces, bifacial cores, and taxonomic flakes; excavations yielded elongate and tapered adzes, polyhedral cores, and flaked/ground picks. Projectile points include a Guilford (4000-6000 BP) and a side notched Palmer (8000-10000 BP). The Guilford is fashioned from a pressure solution phase of silica inherent within the S1 of the boudins. The Palmer is from a coarsely crystallized phase of pressure-solution quartz. Laboratory analysis revealed that stone tools are preferentially oriented parallel to S1 of the boudins, suggesting that flaking was parallel to S1. Large block and polyhedral cores are defined on their proximal and distal faces by S2 and S3 joints. Bifacially flaked objects bear L1 lineations parallel to the long direction of either their dorsal and ventral face.

Taxonomic flake scars are scarce at this site, and traditional flake scars are less common. The Seniard quartz mylonite quarry may have produced wood working adzes, as well as picks. Ophiolite outcrops are present along the base of Seniard Mountain. Distal fragments of quartz mylonite picks located in creek beds at the foot of Seniard Mountain bear L1 on their dorsal and lateral surfaces. These observations indicate that quartz mylonites may have served as sources of picks for the construction of soapstone vessels. Evidence suggests that there may be a cultural relationship between quartz mylonite quarries in high elevations and soapstone quarries in lowlands.

Geological Society of America Abstracts with Programs. Vol. 57, No. 2

doi: 10.1130/abs/2025SE-408932

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