STRATIGRAPHY AND PROVENANCE OF THE CONNECTICUT VALLEY-GASPE BASIN IN WESTERN NEW ENGLAND: EVIDENCE FOR A TOPOGRAPHIC BARRIER BETWEEN THE ACADIAN HINTERLAND AND FORELAND

The Connecticut Valley-Gaspe basin (CVGB) is one of several basins in the northern Appalachians filled by Silurian and Devonian rocks. The Shaw Mtn (VT) and Russell Mtn (MA) Fms form discontinuous lenses of quartzite along the western contact of the basin. The Northfield (VT) and Goshen (MA) Fms structurally overlie the quartzite lenses. The Waits River and Gile Mtn Fms are exposed east of the Northfield and Goshen Fms. Fossil evidence suggested a Devonian age for the Waits River and Gile Mtn Fms (Hueber et al., 1990). Recent absolute age constraints include dates from meta-rhyolites in the Meetinghouse Slate Mbr of the Gile Mtn Fm (407 ± 3 Ma; Rankin and Tucker, 2009) and the Goshen Fm. (405 ± 4 Ma; Karabinos and Aleinikoff, 2011).

New U-Pb LA-ICPMS and CA-IDTIMS zircon dates constrain the age and provenance of these units. Two detrital zircon age spectra from the Russell Mtn Fm have significant Silurian, Ordovician, Neoproterozoic, and Mesoproterozoic peaks, and show a mixed Laurentian and Gondwanan provenance. One sample of the Shaw Mtn Fm from northern VT contains abundant Ordovician zircon grains and shows a mixed Laurentian and Gondwanan provenance. In contrast, two samples of the Shaw Mtn Fm from southern VT contain exclusively Laurentian grains and no grains younger than Neoproterozoic. Detrital zircon age spectra from the Waits River, Gile Mtn, and Northfield/Goshen Fms have significant Early Devonian, Ordovician, and Proterozoic peaks, and show a mixed Laurentian and Gondwanan provenance. Airfall tephras are preserved in the Goshen Fm and one newly identified felsic bed gave a CA-IDTIMS date of 408.6 ± 0.1 Ma. The youngest grain dated from the Goshen Fm in MA, just south of the VT border and on strike with the Northfield Fm is 414.1 ± 0.3 Ma.

We suggest that 1) the western contact of the CVGB is a fault along its entire length, 2) there is a significant age gap between Russell Mtn and Shaw Mtn Fms and other CVGB units, 3) the Waits River Fm is older than the Gile Mtn and Northfield/Goshen Fms, which may be facies equivalents of each other, and 4) a significant topographic barrier separated the CVGB from the Silurian-Devonian Catskill basin, which did not receive abundant Ordovician and Silurian zircon grains until the Middle Devonian and did not receive Gondwanan detritus until the Upper Devonian (Selleck et al., 2016).