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Hurricanes play an important role in shaping the coast of Louisiana. Although the sedimentary signatures of hurricane deposits have been documented in several different coastal environments along the northern Gulf coast, no studies have as yet documented the signatures in wetlands adjacent to large, inland brackish water bodies. In this paper we present results of a case study documenting the distribution and characteristics of storm surge deposits related to Hurricane Isaac (2012) in a wetland on the western shore of Lake Pontchartrain, Louisiana. Hurricane Isaac, a category1 storm, made landfall near the mouth of the Mississippi River on August 28, 2012. Due to its large size and slow movement, Isaac generated strong easterly winds across Lake Pontchartrain, producing a large storm surge along the west shore of the lake and unprecedented flooding in the surrounding lowlands. Loss-on-ignition, XRF, radioisotopic, and grain-size analyses conducted on sediment cores and surface samples from the area identify two distinct sedimentary signatures for the Hurricane Isaac deposits. Near the lake shore the signature is characterized by a laminated silty sand with a geochemical profile closely resembling that of lake bed material. Storm deposits located in a brackish swamp ~ 1km inland consist of a dark, low-organic mud with low concentrations of terrestrial metals and elevated concentrations of Br, S, and Cl. Differences in the storm signal are explained by the differing effect of topographical features on the depositional and transportation processes occurring at the two sites. Utilizing the geochemical/compositional signatures as a hurricane-generated storm surge proxy indicates the possible occurrence of a similar event predating the historical record. [ABSTRACT FROM AUTHOR]

Sedimentary paleotempestological studies have documented that tropical cyclone activity levels in the North Atlantic have been characterized by significant fluctuations since at least the mid Holocene, with activity regimes typically lasting from several centuries to > 2000 years. These activity-level estimates are based on site-specific hurricane strike histories derived from proxy records of overwash events attributed to landfalling major hurricanes. Here we present a 7000 year composite record from two adjacent wetland sites in coastal Belize, Central America that records both tropical cyclone-generated storm surges and large precipitation events. Although overall sensitivity appears to decrease over time, this record displays clear evidence of continuous oscillation between distinctly different activity regimes, with active and quiet periods each covering ~ 50% of the record. Active periods occur during ~200–600 BP, 1450–2600 BP, 3200–4200 BP, 4750–5450 BP, 5750–6050 BP, and 6700–6900 BP. This activity pattern does not match regional records from the northern Gulf of Mexico, the northern Caribbean or the Atlantic coast of the USA, thereby supporting the view that activity patterns are temporally variable throughout the North Atlantic, and that hyperactivity does not occur simultaneously across the entire basin. [ABSTRACT FROM AUTHOR]