ABSTRACT

The 1755 Cape Ann earthquake, the most damaging historic earthquake in New England, caused strong ground motion of modified Mercalli intensities (MMIs) VI–VII in eastern Massachusetts, most likely affecting lake sediments in the area. We present multiproxy data of a well‐dated sedimentary record from Sluice Pond in Lynn, Massachusetts, that contains a mass wasting deposit of possible seismic origin. Sediment cores retrieved from the deepest basin in nearly 20 m water depth were interpreted using a combination of geophysical, sedimentological, geochemical, and palynological proxies. Age–depth relationships calculated using radioisotopes, onset of industrial contaminants, and pollen stratigraphy indicate that the upper 40 cm of the sedimentary record were deposited since 1600. The lake sediments are composed of dark brown to black organic‐rich silts that appear homogeneous in the lower part but show some faint laminations above 29 cm core depth. A distinct light brown layer that occurs in 31–29 cm core depth is normally graded and composed of sediment and microfossils typically found in near‐shore aquatic environments. We interpret this unit, deposited between 1740 and 1810, as a turbidite generated by underwater mass wasting along the steep basin slopes during intense ground shaking in 1755. These results suggest that strong earthquakes in New England leave a record in the organic‐rich sediments of small ponds. Such lakes are abundant in this formerly glaciated terrain and can be used to establish paleoseismic records for a region where the recurrence interval of large, potentially damaging earthquakes is mostly unknown.

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