THE ENGINEER CANTONMENT: A SIGNIFICANT HISTORIC SITE WITHIN A BURIED, LATE HOLOCENE TERRACE-FAN COMPLEX

In the fall of 1819, members of the Stephen F. Long Expedition constructed two log and limestone structures along the west bank of the Missouri River north of modern Omaha, Nebraska, to serve as winter quarters (the Engineer Cantonment). Expedition member Titian Peale produced a watercolor of the site, which shows a cabin sitting at the base of the bluffs on a narrow, low terrace-fan complex near a prominent bend in the river channel. After abandonment in 1820, much of the cabins fell into ruins and the site was subsequently buried. The site was re-discovered in 2003 and portions excavated by archeologists from the Nebraska State Historical Society. A soils-geomorphic investigation of the site reveals a low fan at the base of the bluffs which interfingers with fluvial overbank sediments from the Missouri river. Surface soils are dark-colored Entisols. The buried soil which contains the site also shows weak morphology (A-BC-C horizonation), but is more complex as it can be traced from fine-grained fluvial overbank sediments onto fan deposits. The fan includes multiple buried soils and pre-historic cultural features. Based upon degree of soil development, I interpret the low terrace-fan complex as late Holocene in age. Channel deposits are present at the eastern margin of the site, suggesting that Peale's watercolor was an accurate portrayal of the 1819 landscape. Laboratory analyses of the soils and five radiocarbon ages obtained from cultural features and charcoal within alluvium are expected to confirm the facies relationships and late Holocene age of the fan-terrace complex. The site is significant in that it suggests strategies for reconstructing the complex fluvial history of the middle Missouri River valley. Prior to channelization, the Missouri was an actively migrating stream, and much of the wide valley bottom is underlain by a complex assemblage of recent channel and overbank deposits. However, terrace remnants and alluvial fans occur along the valley margins which preserve much of the late Wisconsin and Holocene record. Many of these fans and terrace remnants are small and rather subtle. Hence, reconstruction of the Holocene history of the middle Missouri River valley may depend upon detailed investigations along its margins, rather than traditional cross-valley transects.