The core of North America consists of old (Archean-Proterozoic) metamorphosed rock including supracrustals (sediments and volcanics) and orthogneisses (intrusive igneous rocks). These rocks are often referred to as 'basement' because they are unconformably overlain in most areas by younger rock. They are diverse but mostly covered, only exposed where blocks of crust have been tectonically uplifted so that the cover eroded away. Much argument is devoted to matching these rocks to other continents to understand the linkages across earlier supercontinental cycles.

From the late Proterozoic until near the end of the Paleozoic, the western margin of North America was a wide shallow continental shelf with little or no tectonic activity (passive margin). Steady sedimentation (clastic and carbonate) built up a thick sequence of sediments containing fossils which record the Cambrian Explosion!

Tectonic activity began in the late Paleozoic and a series of collisions brought new terranes to the North American margin and resulted in shortening of the platform sediments. Subduction initiated in the middle Mesozoic. Western North America rose above sea level and sedimentation changed from marine to subaerial. Arc-related and plate-reorganization-related magmatic activity produced the 148 Ma Independence Dike Swarm and lots of small plutons which contributed to ore deposit formation in the eastern Sierra. The Keystone-Muddy Mountain Thrust system developed during the late Cretaceous Sevier Orogeny and shallowly thrust older marine rocks inland (eastward) over the Mesozoic continental sediments. Steeper reverse faults took over from low angle thrusts in some areas, indicating a change in orogenic style called the Laramide Orogeny. Laramide uplifts revealed Proterozoic crystalline rocks in some of the mountain ranges. The early part of the Cenozoic was not well recorded in the rocks of the region.

Geologic map of southern California, grabbed from the California Geological Survey. Light yellow = recent sediments. Red = recent volcanics. Pink = Mesozoic granites. Bright green and light blues = metamorphic basement.

During the Miocene, extension started up and produced both steep normal faults and shallowly dipping detachments. The geometry of these fault systems usually result in older faults rotating out of favorable orientation and new faults developing, so the current landscape includes many active and dormant normal faults. Uplifting continental blocks become mountain ranges and shed sediments into the basins between them, giving the region of extension the characteristic "Basin and Range" landforms. During recent colder and wetter times (Plio-Pleistocene), many of these valleys were filled with lakes and big glaciers in the High Sierras fed major outflowing rivers whose sediments still blanket the landscape. At the present time, the right- lateral strike-slip motion of the Pacific-North America plate boundary, which is mostly taken up on the San Andreas Fault system near the coast, has partitioned some of the motion inland producing oblique and even strike slip motion in the Eastern California Shear Zone / Walker Lane (a zone of faults along the eastern side of the Sierra Nevada). Many of these normal and strike slip faults are "leaky" - occasionally erupting small cones and flows.

You need a lot of things with you in the field every day. You will be taking measurements with a compass and recording them in your notebook and on the map using a protractor. You will shade in geologic units as you walk around. You will be using different pens and pencils for each purpose. Most of these items are pretty generic. The mapboard you will build yourself. It should be a stiff clipboard you can carry around all day and write on, and needs a cover that will protect your map from dust and rain and spills, which won't blow around. I will show you in informational meetings how to make one from two pieces of perspex, some duct time and binder clips. You can also use a normal clip board and a piece of perspex. The top should be transparent so that you can see the map for navigating and locating yourself without exposing the map to the elements (wind being the worst).

This course is designed to take your classroom and field trip experience and bring it to life in some of the most beautiful geological sites on the planet. Southern Nevada and eastern California are traditional stomping grounds for geologist training courses from all over the world, due to the variety of rock types and structural features which are well-exposed in strikingly beautiful landscapes.

This course is designed to develop your spatial perception and understanding of maps, give some hands-on experience, and increase your literacy in the methods practiced by geologists working in academia, government, and the resource industries.

The southwest US has experienced a continual evolution from passive margin deposition to continental shortening to extension to the present-day transition to transform motion. Complex histories require exceptional supporting observations. In this course students will enjoy a skim of the literature of field observations which have led to the development of this protracted tectonic history, and identify a particular event or geologic feature for deeper study and presentation. Students will them visit field examples of the deformation structures and learn to map these structures and extract kinematic and relative chronological data from these structures.

This course is designed to develop and reinforce field geological mapping skills at graduate level with emphasis on interpreting the observations in the tectonic context. Specific assignments will be tailored to the skill level and interests of enrolled students.