Northeastern Section - 49th Annual Meeting (2325 March)

Paper No. 58-9
Presentation Time: 1:30 PM-5:35 PM


GRAHAM, Brandon L., CLIFT, Andrew D., KOZLOWSKI, Andrew L., and BIRD, Brian, New York State Geologic Survey, New York State Museum, 3140 Cultural Education Center, Albany, NY 12230,
The Keene Valley Surficial Geologic Mapping project was initiated by the activation of New York State’s largest natural slope failure; an 82-acre rotational slump on Adrian’s Acres Road located along the eastern slope of Porter Mountain in the Keene Valley Quadrangle of Essex County, New York. The landslide’s crown, previously mapped as glacial till over bedrock, was observed to be upwards of 20 meters (65 feet) in thickness and composed of laminated sands, silts and clay without encountering bedrock. This anomaly regarding thickness of the surficial materials present necessitated the production of an improved surficial map and documentation of slope failures throughout the Keene Valley quadrangle. Traditional mapping techniques at the scale of 1:24,000 were implemented during field work, resulting in a surficial map that was digitized using geographic information software (GIS). Surface and subsurface sampling was conducted using a hand auger and shovels, stream exposures, Shelby tubes, soil samples via Geoprobe coring and ground penetrating radar (GPR), and were coupled with digital elevation models (DEM) and water well data.

Information compiled from the data provides insight into Keene Valley’s slope failure susceptibility. Further, additional field reconnaissance revealed 23 noticeably large slope failures of various mechanisms were identified through field observation or aerial/satellite photographs. 91% of failures are considered rock slides found on the steep slopes of mountains. They are easily identifiable via photographs and can be over 1km long. The Adrian’s Acres Road slope failure is a deep rooted, multi-lobate toe, rotational slump. The third significant type of failure is located on Putnam Brook on the eastern edge of the quadrangle, and is classified as a translational slide. The Putnam Brook slide is active from 600-650 m above mean sea level (AMSL) and consists of compact diamicton and stratified sand, gravel and boulder.

The resulting new map provides a better understanding of sediment distribution and landslides in relation to the complex depositional setting that once existed in a glacial and proglacial lacustrine environment. New maps and information serve as a blue print for wise use in planning and development.