Instructor: R. Wintsch

Introduction to Petrology is the class that links the lower and upper division classes in the geological sciences that are intended for physical science majors. This 4 cr. spring semester class focuses on the recognition and origins rocks. We examine the textures and structures all common rocks with the goal of reconstructing the geological processes that produced these rocks. We learn that:

Igneous rocks associated with ancient and modern magmatic intrusions and volcanic extrusions (like Mt. St. Helens ) are mostly associated with the boundaries of tectonic plates.

Sediments are deposited at the surface, and sedimentary rocks form by the natural cementation of these sediments a few kilometers below the surface, where petroleum is also generated.

Metamorphism modifies both igneous and sedimentary rocks, especially at the edges of tectonic plates, where pervasive motion causes ubiquitous faulting and folding and drives mineral reactions.

Lectures that emphasize the scientific method are offered 3 times per week, during which we analyze and evaluate the relative significance of the processes that produce these rocks.

Laboratories for this class focus on the study of rock specimens as products of earth processes, and meet once a week. In addition to classifying rocks, we explore the significance of their textures and structures in reconstructing of the processes that produced them.

Field trips allow us to emphasize that the close associations of different kinds of rocks lead to a deeper understanding of their collective origins. In a Saturday trip in March, we take advantage of nearby sedimentary rocks on the eastern margin of the Illinois basin to investigate the sedimentary and tectonic environments of the Carboniferous times (~325 million years ago). In a weekend trip in April we travel to the St. François Mountains of Missouri to examine the fascinating relationships between and within igneous and sedimentary rock assemblages separated in age by 1 billion years of time. We also examine several interesting mineral deposits and explore their origins in the context of the origin of the rocks that contain them.

Prerequisites: A 100 level geology course is strongly advisable (especially G111 if you are a science major), and a course in mineralogy (either G221 or G225 ) is a requirement, unless waived by the instructor. College level chemistry is also strongly recommended, through C102 (or C118 for science majors).

Moving On: This class provides strong background for continuing students going on with a concentration in Earth Sciences. Three courses are typically taken as follow-up classes:

G323 Structural Geology ,

G334 Principles of Sedimentology and Stratigraphy ,

G420 Regional Geology field trip .