Today, central New York and most of eastern North America is viewed as a relatively stable tectonic setting. Aside from a few ancestral faults and bedrock joints in the strata of the Mohawk and Black River Valleys, the region is considered to be relatively "quiet" in terms of tectonic activity. The Upper Ordovician rocks, however, including those of the Trenton Group, record a remarkable story of tectonic change in ancestral North America beginning approximately 460 million years ago. This tectonic change is recorded through the transition of very shallow, peritidal carbonate deposition on the "Great American Carbonate Bank" through siliciclastic dominated deep-water shales, and siltstones, and finally to shallow, marine to non-marine sandstones and mudstones of later Ordovician time. This event, referred to as the Taconic Orogeny, resulted from the collision of a series of volcanic island arcs and microterrains with the eastern flank of ancestral North America. This collision substantially modified the topography of eastern North America, and introduced siliciclastic sediments onto the once pure-carbonate shelf. Moreover, this tectonic event modified the paleoceanographic and paleoclimatic patterns, which undoubtedly had major influences on the origination, distribution, and extinction of faunas in the region.
Although the entire duration of the Taconic Orogeny was between 20-25 million years (beginning to end), the period of time critical to understanding the tectonic setting of the Trenton Group represents only a minor portion of this time. Most recent estimates, including those of Holland (2003), suggest that the transition from the stable, shallow cratonic platform of pre-Trenton time to relatively deep-water shale-dominated deposits of post-Trenton time occurred over a much shorter time interval. It is believed that the duration of deposition of the Trenton Group was approximately 4 to 5 million years. The following discussion briefly considers the record of tectonic activity in relation to Trenton Group deposits. The primary goal is to familiarize the reader with the concept of the Taconic Orogeny and the sedimentary signatures of this event as recorded within New York State and adjacent regions. The following sections will detail both regional and local patterns of tectonic influenced deposition. It is not intended that the discussion present all details of the complicated history of research on the Taconic Orogeny. For more information the reader is encouraged to use the bibliography of this site or those included in the references of cited works.