SAGE 2004 Archaeological Magnetics Survey San Marcos Pueblo, New Mexico J. Mark Hale University of Utah

San Marcos Pueblo, NM

Outline Introduction to Magnetics Archaeological Contributions Instrumentation Software and Data Analysis Archaeological implications of the magnetic data at San Marcos Pueblo Conclusions Caveats and Improvements

Possible Sources of Remnant Magnetism TRM = Thermo-Remnant Magnetism, Curie point volcanic rocks and archaeological hearths. DRM = Depositional Remnant Magnetism, sedimentary rocks and sedimentary cores. Dipole Profile is Dependent on the Orientation of the Body

G-858 Magnetometer Operating Principle: Self-oscillating split-beam Cesium Vapor with automatic hemisphere switching. Heading Error: ±1 nT Sensor Height: 0.5 m WinGLink® Data Analysis Software

Pros and Cons of Magnetic Data for Archaeological Use Benefits: - Magnetics can cover a wide area in a short amount of time. Reduction of survey area. - Easily obtained approximate depths. Detriments: - Approximate depths carry large discrepencies and are subjective in nature. - Anomaly type remains a mystery until excavation

Mission Complex Magnetic Anomalies

Mission Site Anomaly Profiles

Mission Site Anomaly Depths (Acquired using maximum slope approximation) Anomaly (name) Slope Depth Approximation (m) W-mission_12.2 W-mission_21.6 W-mission_32.2 W-mission_40.6 E-mission_13.8 E-mission_20.7 E-mission_31 E-mission_41.1 E-mission_50.9 E-mission_61.1 E-mission_70.9 rebar0.4 Maximum slope approximation

Mission Complex 1 st Horizontal Derivative (as an estimate of depth)

Midden 2 Magnetic Anomalies

Volkswagen Anomaly Strong dipole signature Dipole low trends towards magnetic north Reasonable depth estimate ~ 1.5 m Great profile!

Midden 2 Site Anomaly Profiles

Midden 2 Site Anomaly Depths Anomaly (name)Slope Depth Approximation (m) Galisteo 13 Galisteo 22.1 Galisteo 32.8 Topographic Depression Topographic Depression 21.5 (very unreliable) Midden 2 Anomaly1.5 Volkswagen1.5

Conclusions The San Marcos Pueblo has several magnetic anomalies with reasonable depths. The Galisteo “fins” contribute to the DRM of the site. The Mission site still has unearthed anomalies at reasonable depths The Volkswagen anomaly is the strongest in the Midden 2 site.

Caveats and Improvements Depth estimates are just estimates Anomalies are highly ambiguous There is no such thing as untainted data Caveats Improvements for Further Research Plotting magnetometer data using real GPS data Use forward modeling to determine size and shape of magnetic body More time to conduct a proper evaluation More computer power!