Early Precambrian Plate Tectonics

Abstract

The Precambrian comprises geologic time before 540 Ma, the time before the Cambrian. The term Precambrian has been used by geologists for a long time and although it is no longer recognized as a formal term in the most recent timescales, it is still a useful term and used accordingly herein. The Precambrian consists of the Archean Eon (4000–2500 Ma; archaios, Greek very old) and the Proterozoic Eon (2500–540 Ma; proteros, zoon, Greek earlier [than] animals). Proterozoic plate tectonic events are widely documented in many places including the Wopmay orogen of NW Canada and the Yavapai and Mazatzal orogens of Arizona. Although there is some debate on the rates at which Proterozoic plate tectonics occurred, there is little question that plate tectonics, as we know it today, has been around for over 2 billion years. What remains uncertain is the existence and nature of Archean plate tectonics; this and a discussion of the oldest rocks on Earth are the subjects of this chapter.