THE RESILIENCE AND RECOVERY OF THE DELAWARE BAY SALT MARSHES TO SEA-LEVEL RISE AND STORMS

The salt-marsh sediments preserved beneath coastal wetlands along the Delaware Bay provide a 2,500 year long history of wetlands development and response to land-falling storms and other environmental changes.

Stratigraphic investigation of salt marshes in the southern New Jersey documented seven depositional sequences of peat-mud couplets representing dramatic changes in sedimentation regime. These abrupt contacts suggest erosion of salt-marsh peat followed by rapid infilling of accommodation space by tidal mud and salt-marsh sediment. At Sea Breeze, New Jersey, the depth of the erosional surfaces were correlated well across a 2.5 km area, which suggests a common mechanism of erosion attributed to storms/hurricanes. Younger sequences correspond with historical land-falling hurricanes, providing further support for this mechanism. At Fortescue, New Jersey, located ~ 20 km south from Sea Breeze, three peat-mud couplets were identified. The radiocarbon dates of salt marsh sediments above tidal mud deposits suggest correlation with three sequences identified at Sea Breeze and with overwash deposits documented along the New Jersey coast.

We estimated wetland recovery time from storm-induced erosion using radiocarbon dates that bracket the erosive event in the sedimentary record. Following erosion and lowering of the marsh surface into the tidal frame a low-marsh ecosystem recolonizes the site, followed by recovery to a high salt-marsh environment. We estimate that this ecological and sedimentary succession can take up to 150-200 years.