Integrated Remote Sensing and Excavation at Double Ditch State Historic Site, North Dakota

Abstract

A four-year program of remote sensing at the Double Ditch State Historic Site (32BL8) demonstrates the utility of combined prospecting methods for understanding complex settlements when combined with traditional excavation methods. Magnetic gradiometry revealed countless subterranean storage pits, hearths, and two previously unknown fortification systems that vastly increase the settlement's area and projected population to perhaps 2,000 individuals. Electrical resistance surveys helped define middens, other depositional areas, houses, and earth-borrowing pits. Ground-penetrating radar yielded details about ditch, house, and mounded midden interior forms. Aerial survey from a powered parachute acquired high-resolution digital color and thermal infrared imagery. The former distinguished houses, borrow pits, and ditches from middens and fill areas by changes in vegetation; the latter did the same through temperature variations that also highlighted historic excavations. High-resolution topographic survey allowed documentation of topographic expressions caused by ditches, houses, borrow pits, and mounds. The remote sensing program reduced excavation costs by targeting features. Excavations confirmed anomaly identifications and established a chronology that documents late-fifteenth-century origins to an ultimate contraction in the eighteenth century, with abandonment after a smallpox outbreak about A.D. 1785. Evidence suggests that large mounds formed integral components of the village"s defenses. Excavations also reveal extensive earth moving for mound building, earthlodge coverings, and other reasons still unclear. This practice caused the truncation or obliteration of many earlier archaeological features and forces realization that long-occupied settlements were fluid through time with continual reworking of deposits, and complex depositional, use, and formation histories.