12-8 Ediacaran-Early Cambrian Crustal Cycling in the Laurentian Interior: Ithaca Basin, New York

Session: New advances in geological and geophysical research on the Appalachian orogen. (II)

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Abstract:

New geochronologic and fluid-inclusion data from the Cayuta Formation recovered at the base of the Cornell University ESH-1 geothermal exploration well demonstrate that strata in the recently identified Ithaca Basin underwent a full tectonothermal cycle of deposition, deep burial, metamorphism, penetrative deformation, uplift, and erosion through at least 15 km of vertical motion, between ca. 559 and 503 Ma. Twelve zircon U–Pb analyses from drill cuttings yield a tightly constrained age of 559 ± 6 Ma, interpreted to date bimodal volcanism or synsedimentary volcanic inputs within the Cayuta Formation. Interlayered metapelite and metabasalt record middle-greenschist facies assemblages consistent with burial pressures of ~0.2–0.4 GPa. Fluid inclusions in quartz document exhumation from ~252°C at >0.3 GPa to ~150°C at >0.2 GPa.  Additional evidence, including crystal-plastic deformation in quartz and K-feldspar approaching its plastic transition, and the occurrence of pyrophyllite indicates peak temperature >350°C and pressure estimate >0.4 GPa. The Cayuta rocks are strongly deformed, and this tectonism predates the deposition of the overlying, undeformed <503 Ma Potsdam Group sandstone.

This (≤56 Myr) sequence of deposition and volcanism, deep burial, greenschist-facies metamorphism, ductile deformation, uplift, and substantial erosion is incompatible with a typical rift-basin evolution.  We propose that the Cayuta Formation preserves a previously unrecognized Ediacaran–Early Cambrian tectonothermal event involving tectonic inversion of the Ithaca Basin.  Due to proximity, the evolution of the Rome trough and Scranton rift basin are most likely related to the Ithaca Basin.  Additionally, movement on the New York–Alabama lineament (transcurrent fault system) within the Pennsylvania reentrant may have produced transpression, driving local crustal shortening and burial of the Ithaca Basin to greenschist facies conditions, accompanied by ductile deformation.  This was followed by denudation prior to Cambrian passive margin onlap. Recognition of this event may challenge long-standing assumptions of tectonic quiescence within the interior of Laurentia during the Ediacaran–Early Cambrian, and it highlights the dynamic nature of early Paleozoic crustal processes in eastern North America. 

Geological Society of America Abstracts with Programs. Vol. 58, No. 2, 2026

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