Taconic orogeny Taconic orogeny The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the United States. As the mountain chain eroded in the Silurian and Devonian periods, sediments from the mountain chain spread throughout the present-day Appalachians and midcontinental North America. Beginning in Cambrian time, about 550 million years ago, the Iapetus Ocean began to close. The weight of accumulating sediments, in addition to compressional forces in the crust, forced
Eburnean orogeny Eburnean orogeny The Eburnean orogeny, or Eburnean cycle was a series of tectonic, metamorphic and plutonic events in what is now West Africa during the Paleoproterozoic era about 2200–2000 million years ago. During this period the Birimian domain in West Africa was established and structured. Eburnian faults are found in the Eglab shield to the north of the West African craton and in the Man Shield to the south of the craton. There is evidence of three major Eburnean magmatic events in the Eglab shield. Between 2210 and 2180 Ma, a metamorphosed batholith was formed in the Lower Reguibat Complex