Comparative sequence stratigraphy of two classic Upper Ordovician successions, Trenton Shelf (New York–Ontario) and Lexington Platform (Kentucky–Ohio): implications for eustasy and local tectonism in eastern Laurentia

Late Ordovician (Chatfieldian) catastrophic volcanism and abrupt carbonate platform-interior subsidence: A tectonic link across a Taconian foreland basin (Quebec Embayment) due to inherited crustal weakness

“…A prominent structural event influenced the Upper Ordovician platform margin peripheral to the Québec Embayment a few million years prior to its regional collapse (Joy et al, 2000;Prave et al, 2000;Brett and Baird, 2002;Jacobi and Mitchell, 2002;Mitchell et al, 2004;Brett et al, 2004). We present evidence that a contemporaneous event created a high-order (<30 m) stratigraphic unit extending ~300 km west of the platform margin, within the platform interior now preserved in the Ottawa Embayment (Fig.…”

“…First, the tectonosedimentary record documented from the Ottawa Embayment is of similar thickness to stratigraphic patterns elsewhere in the Taconian foreland interior that have been linked to possible eustatic origin (Brett et al, 2004). Second, abrupt subsidence within the Ottawa Embayment, which lies well inboard of the Appalachian (and Taconian) structural front, is unexpected and may be linked to the response of inherited crustal weakness of the underlying Precambrian fault system to regional tectonic processes.…”

“…2), this succession contains depositional sequences, each of which (e.g., M5a; Fig. 2) defines a relatively short-term transgressive (shallow to deep) facies succession Brett et al, 2004). A similar stratigraphy occurs <900 km to the southwest in Ohio and Kentucky, and is interpreted to represent a highorder (eustatic?)…”

“…A similar stratigraphy occurs <900 km to the southwest in Ohio and Kentucky, and is interpreted to represent a highorder (eustatic?) allocyclic control on platform sedimentation superimposed on regional tectonic influences (Brett et al, 2004).…”

“…But the platform succession also contains a higherorder allostratigraphic framework that has been traced along the Taconian foreland interior in the eastern United States (Brett et al, 2004). Regional distribution of contemporaneous (within the available biostratigraphic resolution), shortterm depositional sequences that correspond to stratal accumulation of meters to <10-15 m within a platform interior is usually considered to represent eustatic control, a critical parameter superimposed on regional subsidence within the Late Ordovician Taconian foreland basin (Ross and Ross, 1995;Brett et al, 2004). The potential significance of short-lived structural influence within the platform interior is much less understood (Dorobek, 1995).…”