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Innovative Cultural Resources Technique Used At Luminant’s Bremond Mine

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Innovative Cultural Resources Technique Used At Luminant’s Bremond Mine

By Meg Cruse, Blanton & Associates, Inc.

Under contract with Luminant Mining Company LLC, Blanton & Associates is preparing to conduct a magnetometer (MAG) survey as part of data recovery investigations for a cultural resources site at Bremond Mine in Robertson County, Texas. Studies indicate that the site was first occupied by prehistoric hunter/gatherers around AD 200. The site was most intensively used during the Late Prehistoric Period, roughly between AD 1250 and AD 1400.

Past studies at prehistoric sites have demonstrated the effectiveness of using MAG surveys to locate burned rock. The technique constitutes an efficient, nondestructive method of locating buried rock hearth features, as the rock types composing these features are often highly magnetic. The efficiency of this innovative technique is associated with substantially reduced labor costs and time savings compared to use of excavation to locate buried rock features.

The magnetometer survey will be conducted within a control grid. The survey will be performed using a Geometrics G-858 MAG mounted on a wheeled cart. A sub-meter accurate GPS antenna will be mounted near the front of the cart and GPS positions will be logged once per second. The cart will be pulled behind the operator along parallel transects spaced 1 meter apart.

The orientation of a magnetic dipole, relative to magnetic north, can provide a clue regarding its source. Complex features, including hearths, comprised of randomly oriented magnetic constituents, produce dipolar anomalies aligned with magnetic north. In the latitude of the survey area, such anomalies will have their negative pole located on the north side of the positive pole. On the other hand, a discrete ferromagnetic source, such as a single piece of iron, may produce a dipole aligned in any direction, depending on how the object’s permanent magnetic field is oriented with respect to earth’s field direction.


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