A COMPARISON OF MULTIPLE TIDAL INLET AND BREACH FILL TRENDS ALONG ASSATEAGUE ISLAND, MD-VA: A WAVE-DOMINATED BARRIER ISLAND

Assateague Island National Seashore is a 60-km long wave-dominated barrier island located along the open-ocean coast of Maryland and Virginia. Numerous former tidal inlets and breaches have been documented along the span of the barrier island in both the historic and geomorphic record. This study focuses on three former tidal inlets (Sinepuxent Inlet, Green Run Bay Inlet, and Green Run Inlet) and one former breach (Fox Hills Breach Zone) along Assateague Island. One sediment core from each site was analyzed and textural analysis was performed on the sand portion of the core at 10 cm intervals. Sinepuxent Inlet fill deposits spanned 3.8 m in thickness. Mean grain size within the inlet fill fined upward from 0.42 to 2.84 φ. Sediment from the Fox Hills Breach exhibited an overall fining upward trend with mean grain size decreasing from 1.94 to 2.45 φ. The breach fill thickness was 2.0 m thick. Green Run Bay Inlet was represented by a fill package that spanned 2.4 m in thickness and contained sediments that fined upward from 0.44 to 1.66 φ. The inlet fill succession from Green Run Inlet fined upward from 0.51 to 1.64 φ, and spanned 2.7 m in thickness. A comparison of the infill from the three former tidal inlets revealed that while infill thickness somewhat varied (spanning a 1.4 m range), maximum mean grain size did not. The infill from all three former tidal inlets exhibited a similar maximum mean grain size (within a 0.09 φ range) in channel lag deposits, thus indicating little variation in the energy setting between tidal inlets. Infill thickness and maximum mean sediment grain size from Fox Hills Breach Zone differed from the tidal inlets. Fox Hills Breach Zone represented the thinnest fill package and the finest maximum mean grain size, signifying a lower energy setting than the three tidal inlets.