Ancient Ponds, Marl Deposits, and Native American Archaeology in the Ridge and Valley Province of Maryland and Pennsylvania

Abstract

Ponds of early to middle Holocene age are identified in the Ridge and Valley Province of Maryland and Pennsylvania through the occurrence of marl deposits associated with the floodplains of low order streams. A 2-sigma calibrated radiocarbon date indicates that marl formation began no later than 7812–7326 BC. The ponds and associated wetlands are one focus of native settlement movements in the region. Excavations and borings into marl, marl-related sediments and adjacent deposits reveal sequences of marl, produced during periods of ponded and still water, alternating with strata of organic, alluvial silts. These profiles represent the shrinking, swelling, and periodic disappearance of ponds. Changes in stream dynamics and climate are explored as explanations for these physical changes. Archaeological data is useful for understanding the timing of these paleo environmental changes. In turn, an understanding of the nature of the pond environments enhances reconstructions of Indian settlement and subsistence strategies.