A revised geological time-scale

摘要: The time-scale constructed in 1947 was based on certain assumptions that have recently been shown to be wrong. Appalachian pegmatites dated at 350 million years (m.y.) and thought Taconic (Ordovician) are now found Acadian (late Devonian), while others, 255 m.y. can referred the Permian. Other recent evidence consistently leads an extension of scale carries beginning Cambrian back about 600 ago. from data available up October, 1959, is as follows (in m.y.): One more significant consequences this revision many rocks Africa other “Gondwanaland” continents which were formerly ascribed late Precambrian become Cambrian. Important orogenic plutonic phases a major geological cycle, implying by analogy extensive system geosynclines, occurred close early Ordovician.