The Sebree Trough: Probable Origin and Control by Intraplate Paleotectonic Structures and the Taconian Orogeny

Abstract

The Sebree Trough is a mid-Late Ordovician (Chatfieldian) trough-like thickening of sediments that extends from western Tennessee and Kentucky, through southern Indiana and into northeastern Ohio, where it joins the Taconian foreland basin. Much of the sediment thickening coincides with Keweenawan, Grenvillian and Iapetan basement structures, suggesting that Ordovician reactivation of the structures through extensional down-drop created the extra accommodation space that characterizes the trough. Southwestward beyond Tennessee, the trough apparently opened into the much deeper Ouachita Sea, which facilitated entry of deep, nutrient-rich waters into the trough and generated conditions ideal for the accumulation of dark organic-rich shales, like the Maquoketa, Point Pleasant and Utica, therein. The opening of the trough was coeval with initial Chatfieldian stages of the Taconic tectophase of the Taconian Orogeny when convergence was focused at the New York promontory through east-verging subduction below an island arc. East-verging subduction at this time apparently set up an extensional cratonic regime as far away as western Kentucky during which the trough and many connected structural basins were generated and successively filled with dark shales. Near the Chatfieldian-Edenian transition, however, east-verging subduction was abruptly replaced by west-verging subduction. The resulting compressional regime inverted many structures and generated a regional, westward-dipping paleoslope that resulted in filling the trough and inundating nearby platform areas with a flood of lighter-colored, finer-grained clastic sediments. The facts that the trough opened during one regime and was effectively buried at the initiation of another suggest control by larger Taconian tectonic regimes. In fact, major orogenic events like the Taconian Orogeny generate far-field forces, both extensional and compressional, that may extend more than 1600 km from the orogenic event and exert their influence through the reactivation of paleotectonic basement structures. The coincidence of the Sebree Trough with paleotectonic basement structures, as well as the timing of its origin and demise, all point to large-scale control by Taconic tectonism, even though it was more than 1000 km distant.

AAPG Datapages/Search and Discovery Article #90218 © 2015 Eastern Section Meeting, Indianapolis, Indiana, September 20-22, 2015