ABSTRACT Castagno, K.A.; Donnelly, J.P., and Woodruff, J.D., 2021. Grain-size analysis of hurricane-induced event beds in a New England salt marsh, Massachusetts, USA. Journal of Coastal Research, 37(2), 326–335. Coconut Creek (Florida), ISSN 0749-0208. Tropical cyclones pose a growing threat to coastal infrastructure and livelihood. Because instrumental and historic records are too short to help us understand interactions between tropical cyclones and climate on a longer scale, proxy records are the only means for reconstructing millennia of tropical cyclone impacts. This study determines grain-size trends in storm-induced overwash deposits along a transect of sediment cores from a salt marsh in Mattapoisett, Massachusetts, to characterize sorting trends and compare deposits associated with individual storms. The overwash deposits preserved within the high-marsh peat provide a record spanning the last two millennia. Building on a 2010 study, a different approach was used to accurately determine the grain-size distribution of overwash deposits from cores in a transect running perpendicular to the adjacent sandy/gravely barrier. Although maximum grain-size values are expected to decrease as distance from the barrier increases, not all event deposits that were studied follow this trend within uncertainty. Analysis of the storm event beds reveal a significant difference in settling trends between historic and prehistoric deposits, with historic deposits largely displaying landward-fining trends and prehistoric deposits largely displaying landward-coarsening trends. This suggests changes in the hydrodynamic or that geomorphic regime may have altered the way in which storm beds were deposited at this site. This new in-depth, transect-based approach has utility for improving the accuracy of future storm reconstructions, particularly for events for which no historic record exists.

ABSTRACT Maio, C.V.; Gontz, A.M.; Sullivan, R.M.; Madsen, S.M.; Weidman, C.R., and Donnelly, J.P., 2016. Subsurface evidence of storm-driven breaching along a transgressing barrier system, Cape Cod, U.S.A. Relict and historic tidal channels buried within coastal barriers provide a geologic signature of environmental change, thus enhancing our understanding of how barrier systems respond to extreme storm events. Earliest maps from 1846 depict three inlets along the Waquoit Bay barrier system located on Cape Cod, Massachusetts. These channels were not depicted on maps after 1846, and we lack any information pertaining to them before 1846. The principle objective of this study was to identify the location and map the internal geometry and channel-fill configuration of the buried inlet structures using geophysical and sedimentological data acquisition methods. This was done by collecting 6.2 km of shore-parallel ground-penetrating radar data and five sediment cores ranging in depth from 4 to 5 m. The sediment cores allowed for the ground truthing of the ground-penetrating radar data and provided six samples for radiocarbon dating. The 13 paleochannels identified ranged in depths from 1.3 to 3.7 m below the present beach surface. These appeared in the radar imagery as broad U-shaped cut-and-fill features incised into adjacent barrier facies. The 13 paleochannels composed 24% of the barrier lithosome totaling 704 m in length. Individual channels were primarily less than 65 m in length and between 2.5 and 1.3 m in depth, although an additional 275-m-wide, 3.7-m-deep channel sequence was imaged and likely represents a major and long-lived paleochannel. The results will contribute toward deciphering the evolution of the Waquoit system and identify areas vulnerable to storm-driven coastal change.

Accelerator mass spectrometry (AMS) radiocarbon dating of basal high-marsh sediments from Romney Marsh, Revere, Massachusetts, provides a revised reconstruction of the late Holocene relative sea-level history of the region. After correction for changes in tidal amplitude, the sea-level change envelope reconstructed from five AMS radiocarbon dates of basal marsh sediments at Romney Marsh in Revere, Massachusetts, indicates a rise in mean sea level (MSL) of close to 2.6 m in the past 3300 years. The data indicate a possible decrease in the average rate of rise from 0.80 ± 0.25 mm/y between 3300 to 1000 YBP to a rate of 0.52 ± 0.62 mm/y between 1000 YBP and the past 150 to 500 years. An increase in the rate of sea-level rise is evident over the past few hundred years. A slowing of the rate of sea-level rise between 1000 YBP and historic times and the increase in the rate of rise to modern values is also evident in other sea-level records from Maine and Connecticut. The coherence between these sea-level records and concomitant climate changes in and around the North Atlantic indicates that regional-scale sea-level fluctuations in the region may be driven by climate forcing. However, earlier sea-level fluctuations correlated to sea-surface temperature variability are not well-resolved by this record or other records in the region and may indicate that changes in sea level are not tightly coupled with sea-surface temperature changes.