A PROPOSED FACIES MODEL FOR A MULTI-GENERATION BEAVER POND COMPLEX IN A PIEDMONT STREAM INTERMITTENTLY OCCUPIED BY BEAVER

The beaver (Castor canadensis) was widespread after the last glacial maximum and may have intermittently occupied many North American lower order streams. During periods of beaver occupation deposition of sediment in beaver ponds can be one of the primary mechanisms of valley floor aggradation in affected reaches. Ives (1942) presented a simple facies model of beaver pond sedimentation that has long been accepted. That model, however, only describes a single-generation beaver pond and does not accurately represent the complex stratigraphy produced in beaver pond complexes that have experienced multiple episodes of sedimentation and erosion caused by floods (i.e. multi-generation beaver pond complexes). Nor does the Ives facies model describe the subsurface characteristics of beaver pond deposits that were formed during earlier intervals of beaver occupation.

A revised facies model for a multi-generation beaver pond complex has been constructed based on physical data collected at Mill Creek, Cabarrus County, North Carolina. Seventy-five cores were collected throughout a 65,000 m² active beaver pond complex. The cores were composed of eleven lithofacies that have been grouped into four lithofacies assemblages. Cross-sections with 14C age dates are used to constrain the distribution of lithofacies in the facies model. This multi-generation facies model differs from previous models in that it portrays the effects of multiple episodes of flood-driven erosion caused by dam breaching and sedimentation resulting from dam reconstruction. The model also portrays the stratigraphy produced by intermittent beaver occupation, separated by intervals of abandonment, during an interval of net aggradation in a Piedmont stream system.