Preliminary Results: Deep Drill Core (U-Th)/He Thermochronology, Southeastern Connecticut

The topography of passive margins should, according to conventional models, decay monotonically over time due to the absence of compressional stresses associated with active margins. By such models, the persistence of high... [ view full abstract ]

The topography of passive margins should, according to conventional models, decay monotonically over time due to the absence of compressional stresses associated with active margins. By such models, the persistence of high relief in New England is confounding because over 250 million years have passed since the last major orogenic event. This study attempts to constrain the exhumational history of southeast Connecticut through a combination of (U-Th)/He and apatite fission track (AFT) thermochronology over a vertical transect of the Moodus Deep Core, a ~1450 m deep drill core in southeast Connecticut. An abrupt shift towards younger (U-Th)/He ages near 1200 m in the core hints at a period of more rapid exhumation beginning ~50 Myr ago. However, the presence of a fracture zone associated with the Eastford lineament bisects the core at ~1070 m depth and raises the possibility that the younger samples have been structurally displaced from the overlying samples. Ongoing work will combine drill core data with nearby surface AFT ages in a thermal model to better constrain the timing and pattern of post-rift exhumation in southeast Connecticut.