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Aseismic ridge subduction as a driver for the Ordovician Taconic orogeny and Utica foreland basin in New England and New York State

Robert D. Jacobi
Robert D. Jacobi
EQT Production, EQT Plaza, 625 Liberty Avenue, Suite 1700, Pittsburgh, Pennsylvania 15222, USA
Department of Geology, University at Buffalo, SUNY, 126 Cooke Hall, Buffalo, New York 14260, USA
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Charles Mitchell
Charles Mitchell
Department of Geology, University at Buffalo, SUNY, 126 Cooke Hall, Buffalo, New York 14260, USA
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Publication history
13 February 201819 November 2018


Aseismic ridge subduction is common along modern convergent margins. We enumerate six criteria that can be used to recognize aseismic ridge subduction in orogens, including a magmatic gap with uplift followed by bimodal volcanism, which commonly includes explosive, voluminous rhyodacitic volcanism that erupts far from the trench. Features temporally linked with the explosive volcanism include retroarc thrusts and consequent thrust-loaded retroarc foreland basin development.

Using these criteria to examine features of the Taconic orogen, together with new stratigraphic and structural data from the Utica basin that constrain the basin subsidence architecture and thrust timing, we propose that at least the older units of the 456–435 Ma Oliverian Plutonic Suite in New England were generated during steepening of the downgoing slab after passage of a subducting aseismic ridge. Weakened crust from delamination and decompression melting promoted westerly directed thrusts (present-day coordinates) that loaded the Taconic retroarc foreland. The resulting Utica basin subsided rapidly and nearly synchronously over an ~150-km-wide region and contains interbedded 453–451 Ma ash layers from the Oliverian Plutonic Suite or coeval plutons to the south.

This history of basin subsidence indicates that the major thrust loads that drove development of the Utica basin were emplaced over a similarly brief interval beginning ca. 455 Ma. Thus, the Taconic thrusts, the Utica basin, the volcanic ashes, and the early Oliverian felsic magmatic units could all be related to an aseismic ridge subduction event. Because of the ubiquity of seamount chains, we expect that aseismic ridge subduction affected other segments of the Taconic orogen.

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GSA Special Papers

Tectonics, Sedimentary Basins, and Provenance: A Celebration of the Career of William R. Dickinson

Geological Society of America
ISBN electronic:




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