A GEOARCHEOLOGICAL ANALYSIS OF FORT CLATSOP, LEWIS AND CLARK NATIONAL HISTORICAL PARK

Fort Clatsop, built and occupied by the Lewis and Clark expedition, served as the expedition’s winter encampment in 1805-1806, following their long cross-country journey. Upon the group’s departure in March, 1806, the fort rapidly decayed in the wet coastal forest of western Oregon. The National Park Service maintains a replica fort within the Lewis and Clark National Historical Park that is believed to sit on or near the site of the original fort. The original fort, however, has not been seen since the mid-19th century and, despite efforts, remains of the fort continue to elude archaeologists. Archaeologists working at the site over the past six decades have described myriad subsurface “pit” and “lens” features, variously interpreted as fire hearths and trash or privy pits, and sometimes interpreted as evidence of Lewis and Clark. The ubiquity of such features on the landscape and the absence of corroborative artifactual evidence call into question their anthropogenic origin, and archaeologists have often failed to consider the full range of site formation processes acting on the site. In this geoarchaeological study, several methods of investigation were employed to examine subsurface profiles and purported features, and to test the various hypotheses for the origins of the pits at Fort Clatsop. Geoarchaeological investigations consisted of controlled excavations, including re-examinations of units dug by previous researchers in hopes of observing identified features. One excavation unit was placed at distance from the fort reconstruction and served as a control; the location of this unit was chosen in an attempt to reveal relatively undisturbed litho-and pedo-stratigraphic sequences (in other words, sediments that had not been disturbed by farming, road construction, brick making, or other activities). Soil descriptions, granulometry, loss-on-ignition tests, and micromorphological analyses were done to characterize and compare “pits” with surrounding deposits. Phosphorous analysis was conducted to test the hypothesis that features were trash or privy pits. Polished sections were created to characterize one of the red lenses so common in excavation profiles. These investigations, informed by principles of forest ecology, document natural and cultural disturbances to the landform, and suggest several alternative explanations for the formation of subsurface features. There is no data to suggest an early 19th-century Lewis and Clark origin for any of these features.