NH21E-01
Morphology and Age of the Southern New England Landslide Zone
Tuesday, 15 December 2015: 08:00
309 (Moscone South)
Jason D Chaytor1, Uri S Ten Brink1, Christopher D. P. Baxter2, Daniel S Brothers3 and T David Hallam2, (1)US Geological Survey, Woods Hole, MA, United States, (2)University of Rhode Island, Department of Ocean Engineering, Narragansett, RI, United States, (3)USGS Pacific Coastal and Marine Science Center Santa Cruz, Santa Cruz, CA, United States
Abstract:
The southern New England continental slope between Hudson and Veatch canyons, here referred to as the Southern New England Landslide Zone (SNELZ), has undergone intense modification by submarine landslide and other mass transport processes. The SNELZ is a morphologically complex region developed through multiple phases of failure covering more than 32,000 km2 from the uppermost headwalls at water depths of 500 m to the toes of the coalesced mass transport deposits (MTDs) at depths of about 4500 m. Using a suite of existing and newly acquired geophysical, geological, and observational data, we investigated the style, timing, and controls on the most recent phase of landslide activity across the most intensely failed segment of the SNELZ - Block Canyon to Alvin Canyon (BCAC). Within the BCAC segment, crosscutting translational evacuation zones spanning a > 1000 m vertical section of the slope have removed several hundred meters of the seaward dipping Quaternary stratigraphy. This removed material appears to have largely disintegrated during failure. While the step-bench morphology of the region suggested retrogressive processes, it is not clear that these processes acted contemporaneously across the region. Small-scale debris lobes linked to scalloped scarp morphologies show that episodic retrogressive degradation of the scarps that bound these evacuations zones has continued into the Holocene. Within the SNELZ-BCAC MTD accumulation zone where seafloor gradients are on the order of 0.5o, rotational failure and earthflow-like transport have remobilized pre-existing surficial MTDs. Radiocarbon dating, an age-constrained Globorotalia menardii first-appearance biostratigraphic datum, and oxygen isotope records from hemipelagic units overlying incompletely evacuated or transported MTDs within the BCAC evacuation and accumulation zones reveal that large landslide and other mass transport processes occurred prior to 7.4 ka with several occurring between 20-14 ka.
