Tectonic history of the northern Appalachian orogen

点击翻译按钮获取中文摘要

Remnants of ancient mountain belts of various ages form most of the Earth's continents, including Canada. These remnants provide an opportunity to investigate mountain-building processes by exposing the internal architecture of the former mountains. My research proposal focuses on understanding the originally separate components (or "terranes") that came together between about 650 and 320 million years ago to form the Appalachian mountain belt. I hope to figure out more accurately when the pieces came together within that time span, whether they came as numerous separate blocks or as a single large composite block, and from where they came - possible source areas are now located in other continents, such as South America, Africa, and Europe, or they could have been pieces of ancestral North America that broke away and then came back again. My students and I will examine rocks in the field and map their distribution. We will collect representative samples and then in collaboration with colleagues who have the necessary equipment and expertise, we will find out the precise ages of the rocks and determine their mineral and chemical (including isotopic) compositions. We are planning to measure their ancient magnetic field directions, which can help us to estimate where they were located relative to the Earth's poles when they formed. Fossils present in the rocks will help us to know their ages relative to one another. All of these different types of information will be utilized to make interpretations about what was happening (and where) at the various times when each kind of rock was forming. Some features of the rocks, such as their isotopic compositions, may help us to know what kinds of rocks underlie those that we see at the surface, information that will help us to interpret from where the various terranes were derived. It is important to understand events and processes that happened even so long ago because they shaped the environment in which we now live, and provided the natural resources that enable us to not only survive but thrive on the Earth.