The collision of the Alleghenian orogeny exerted massive stress on what is today the Eastern Seaboard of North America, resulting in a large-scale uplift of the entire region. The Appalachians could have risen as high or perhaps even higher than the present-day Himalaya. It should be noted that the Appalachian Orogeny is responsible for the creation of the mountains themselves and is not responsible for the topography that now typifies the Piedmont and coastal plain regions east of the mountain chain. Evidence for the Appalachian orogeny stretches for many hundreds of miles on the surface from Alabama to New Jersey and can be traced further subsurface to the southwest. The Applachian deformation extends northeast to Newfoundland. Sediments that were carried eastward form part of the continental shelf. Sediments that were carried westward form the Allegheny and Cumberland Plateau, which in some areas are popularly called mountains, but are actually simply uplifted and eroded. Carbonates and fine sediments from these mountains were carried farther to form limey rocks in a shallow sea that was later uplifted and forms the bulk of Tennessee, Kentucky, Ohio, and Indiana.

During the middle Ordovician Period (about 440-480 million years ago), a change in plate motions set the stage for the first Paleozoic mountain building event (Taconic orogeny) in North America. The once quiet, Appalachian passive margin changed to a very active plate boundary when a neighboring oceanic plate, the Iapetus, collided with and began sinking beneath the North American craton. With the birth of this new subduction zone, the early Appalachians were born. The Taconic orogeny was a great mountain building period that perhaps had the greatest overall effect on the geologic structure of basement rocks within the New York Bight region. The effects of this orogeny are most apparent throughout New England, but the sediments derived from mountainous areas formed in the northeast can be traced throughout the Appalachians and midcontinental North America. By the Late Ordovician, the Taconic island arc had collided with the North American continent, beginning in Cambrian time, about 550 million years ago, the Iapetus Ocean began to grow progressively narrower. When the Taconic Orogeny subsided in the New York Bight region during Late Ordovician time (about 440 million years ago), subduction ended. The mountain building period esulted in the formation of a great mountain range throughout New England and eastern Canada, and perhaps to a lesser degree, southward along the region that is now the Piedmont of eastern North America. newly expanded continental margin gradually stabilized. Erosion continued to strip away sediments from upland areas.

Inland seas covering the Midcontinent gradually expanded eastward into the New York Bight region and became the site of shallow clastic and carbonate deposition. This tectonically-quiet period persisted until the Late Devonian time (about 360 million years ago) when the next period of mountain-building began, the Acadian orogeny. The Acadian orogeny is a middle Paleozoic deformation, especially in the northern Appalachians, between New York and Newfoundland. It appears to have been contemporaneous with the Bretonic phase of the Variscan orogeny of Europe, with metamorphic events in southwestern Texas and northern Mexico, and with the Antler orogeny of the Great Basin.

The Iapetus Ocean was an ocean that existed in the Southern Hemisphere between what are now Scotland, England and Scandinavia between 400 and 600 million years ago. The Taconic orogeny was a great mountain building period that perhaps had the greatest overall effect on the geologic structure of basement rocks within the New York Bight region. The effects of this orogeny are most apparent throughout New England, but the sediments derived from mountainous areas formed in the northeast can be traced throughout the Appalachian and Midcontinent regions of North America. The following discussion provides a summary of events leading to the culmination of this orogeny.