ARCHAEOLOGICAL SITE BURIAL: A MODEL FOR SITE FORMATION WITHIN MIDDLE-TO-LATE HOLOCENE ALLUVIAL SETTINGS OF THE GREAT LAKES AND MID-ATLANTIC REGIONS, USA

Data collected from alluvial settings in Great Lakes and Mid-Atlantic regions reveal that distinct flood intervals, separated by quiescent periods, mark the past 5000 years. Increased flooding occurred during the intervals 3500-4000 BP, 2000-1500 BP, and 700-400 BP. This cyclical deposition pattern relates to long-term fluctuations in regional climate. Temporal correspondence of the 700-400 BP flood interval with the "Little Ice Age” and the preceding low-flood period with the “Medieval Warm” implies that increased flooding resulted from a cooler, wetter climate that followed relatively warmer, dryer quiescent conditions. This pattern has important implications for discovery and preservation of buried archaeological sites. For example, because the most recent flood interval (700-400 BP) spans the protohistoric in the region, much of the prehistoric record of human flood plain occupation and the Holocene fluvial and climatic history lies buried in alluvium and can only be revealed by coring or excavation in flood plains.

Specifically, variations in stream hydraulics affected archaeological site formation by controlling near-surface residence time. Longer near-surface residence time allowed greater natural and human context disturbances while rapid, deep burial preserved context. During periods of relative fluvial stability, limited flood plain accretion allowed comparatively extensive surface weathering. Additionally, limited alluviation and regular human reoccupation of the flood plain formed a distinctive "midden-like" surface deposit. Though such sites are artifact-rich, long near-surface residence time allowed extensive context and temporal mixing. Accelerated alluviation, related to cooler, wetter climate episodes, however, limited both sediment weathering and artifact accumulation and progressively buried short-term, ephemeral occupation surfaces that formed between major floods. Because of limited soil formation within ephemeral buried surfaces, associated artifacts today commonly appear scattered within less distinctive subsoil horizons, unrelated to distinct paleosols. Although content-poor, the rapid burial and short near-surface residence of these horizons offer great potential for preservation of single-component, single-use sites.