6 Applied Geological Investigations at State Geological Surveys in the Northeastern Section of GSA (Posters)

This technical session will highlight the high-level, applied work done by state geological surveys to address diverse environmental issues including geologic hazards, groundwater and surface water, and economic mineral deposits in the Northeast Section region.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Ballroom C

Investigating Killick Pond and its Connection to the Largest Landslide in the State of Maine

Paper number: 6-3
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

Abstract

Killick Pond was formed by a landslide related to the Presumpscot Formation, which is a geotechnically sensitive glaciomarine mud present in southern Maine. The pond is located in Hollis Center, Maine, has a maximum depth of 3.7 meters, and contains several partially-submerged trees from a drowned forest. We collected five sediment gravity cores of 43 cm to 59 cm length as well as five wood samples from four partially-submerged trees. Plant fragments from two sediment cores and wood from one of the partially submerged trees were sent for radiocarbon analysis. We measured magnetic susceptibility at 1 cm intervals along two gravity cores, KIL25-GC4 and KIL25-GC5. Core GC4 is 59 cm long and displays a distinct horizon at 37 cm core depth where the sediment changes from mottled brown, very fine to medium grained sand to water-saturated organic-rich dark brown mud with abundant plant fragments at the contact, likely resembling the flooded forest floor. GC5 is 51 cm long and likely preserves the sediment-water interface at its top. The bottom of the core is composed of black organic-rich sandy soil and a distinct boundary at 41 cm depth contains a large tree bark fragment that separates the soil from water-saturated dark brown organic-rich mud above. Calibrated dates of radiocarbon samples date the uppermost soils to 657–552 cal BP, 645–531 cal BP, and the drowning of trees to 672–559 cal BP, which agree with previously obtained dates from landslide-buried surfaces. Killick Pond was thus formed shortly after 645-531 cal BP when a large landslide dammed a paleoriver channel, which led to the flooding of the surrounding forest. The post-landslide lake sediments record mostly negative to very-low magnetic suceptibility κ for both cores, consistent with diamagnetic materials such as water and organic matter that are commonly deposited in lake environments. GC4 records an increase in κ to positive values below the boundary of sand that could represent an increase in Fe-containing minerals possibly related to the former channel. GC5 records a less distinct shift in κ values at the boundary, and κ remains negative throughout the core. Further analysis of the sediment cores and the drowned trees can provide additional insight into environmental changes in southern Maine during the latest Holocene.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411342

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