Archaeological prospecting at the Double Ditch State Historic Site, North Dakota, USA

摘要

A four-year programme of remote sensing at the Double Ditch State Historic Site, a fortified earth-lodge village in the Great Plains of North Dakota, USA, demonstrates the importance of combined prospecting methods for understanding the multidimensional nature of complex settlements. Aerial survey from a powered parachute acquired high-resolution digital colour and thermal infrared imagery. The former distinguishes houses, borrow pits and ditches from middens and fill areas by changes in vegetation; the latter does the same through temperature variations that also highlight substantial village deposits and century-old excavations. Magnetic gradiometry reveals two previously unknown fortification systems that vastly increase the settlement's area and projected population to perhaps 2000 individuals. Vast numbers of food storage pits that supported that population are also indicated. Vertical soundings and area surveys of magnetic susceptibility aid in the understanding of storage pit magnetism and anthropogenic soil mounding and removal. A high-resolution digital model of topography documents surface expressions caused by ditches, houses, borrow pits and mounds; when combined with overlays of geophysical data understanding of remote sensing responses is improved and relationships between large mounds with village defenses are made clear. Ground-penetrating radar gives insights into mounded midden interior forms and yields details about house interior components, while electrical resistance results improve definition of middens, other depositional areas, houses and borrow pits. This multisensor remote sensing programme reduced excavation costs by allowing a wide variety of archaeological features of interest to be targeted accurately Excavations confirmed anomaly identifications and established a chronology that documents late fifteenth century origins to an ultimate abandonment about AD 1782.