Middle Proterozoic Belt Supergroup, Western Montana part of MT Field Guides
From Great Falls, to Butte, Helena Glacier National Park and Spokane, this field trip crosses onto the leading edge of the Rocky Mountain thrust belt and proceeds to the stratiform copper-silver deposits in the Revett Formation of the Troy Mine in the main part of the Belt basin. The road log includes sections on the paleontology of the Middle Proterozoic Belt Supergroup, stromatolites of the Belt Supergroup (specific to Glacier National Park), Middle Proterozoic Tectonics of the Belt basin, and a sedimentologic and tectonic interpretation of the Belt Supergroup.

Heart Mountain Detachment Fault and Clastic Dikes of Fault Breccia, and Heart Mountain Break-Away Fault, Wyoming and Montana part of MT Field Guides
This field guide describes the geology of two sites near Silver Gate, MT (near Cooke City) where different features related to the Heart Mountain detachment are displayed. At the first site, several features pertaining to the origin of the Heart Mountain detachment fault can be examined, including: (1) severely deformed upper plate rocks in contact with undeformed lower plate rocks; (2) the character and composition of the fault breccia; (3) contacts of volcanic rocks with upper plate blocks and the Heart Mountain fault; and (4) dikes of carbonate fault-breccia injected into both upper plate blocks and overlying volcanic rocks. The second site is an exposure of the Heart Mountain break-away fault.

Geology of the Highwood Mountains, Montana: A Survey of Magma Types and Sources part of MT Field Guides
The Highwood Mountains represent a dissected Eocene volcanic and intrusive complex composed of latites and highly potassic, mafic to felsic igneous rocks. Along with the Bearpaw Mountains and Eagle Buttes, they form a northeast-trending belt within the Montana Alkalic Province, and were all emplaced between 54 and 50 Ma. In the Highwoods an older suite of quartz-normative latites is overlain and intruded by a younger suite composed mostly of mafic phonolite flows and dikes, minette and trachyte dikes, and shonkinite-mafic syenite stocks. This trip examines a variety of dikes, sills, and stocks composed of these unusual rock types.

Shonkin Sag and Square Butte Laccoliths, Montana part of MT Field Guides
Shonkin Sag and Square Butte laccoliths are at the eastern edge of the Highwood Mountains as part of the Central Montana Alkalic Province. Rocks in the Highwood Mountains date to 50-53 Ma. Both laccoliths are internally differentiated and contain a variety of rock types, including shonkinite, syenite, and pegmatite.

Geology Along Going-To-The-Sun Road, Glacier National Park, Montana part of MT Field Guides
This guide to the geology along Going-to-the-Sun Road in Glacier National Park describes many of the major geologic features of the Park. It is directed toward the Park visitor with little no no background in geology. The guide begins with a short introduction to the science of geology and the geologic time scale, followed by a simplified geologic cross section through the Park from SW to NE. The bulk of the field guide is a 21-stop road log, keyed to numered octagonal signs along the road, which describes the geology along the road. A glossary of geologic terms and an appendix is included which contains a brief geologic history of Glacier National Park, explanations of rock colors and fossil algae (stromatolites), and descriptions of the Proterozoic rock formations that can be seen along the Going-to-the-Sun Road. An extremely useful resource included at the back of the book is a fold-out geologic map, plotted on an oblique shaded-relief diagram, that depicts the landscape and the distribution of rock formations and faults in the vicinity of Going-to-the-Sun Road.

A Study in Contrasts: Archean and Quaternary Geology of the Beartooth Highway, Montana and Wyoming part of MT Field Guides
Nowhere in the U.S. are the oldest and the most recent aspects of geology as spectacularly displayed as along the Beartooth Highway. The Beartooth Mountains are a block of largely Archean bedrock uplifted along high-angle reverse faults of Laramide age. The Precambrian rocks (3400-700 Ma) contain one of the best records of the early history of the igneous and metamorphic basement of the middle Rocky Mountains. These rocks include granulite-facies supracrustal rocks proposed as products of continental collision, calc-alkaline volcanic and plutonic rocks generated along an Archean continental margin, and mafic dikes some of which were emplaced during continental rifting. This Precambrian record encompasses at least two extensive periods of crustal evolution and records more geologic history at one location than any other place in the Wyoming Province. Descriptions of two key areas showing the fundamental relations between the Precambrian rocks are included: the Quad Creek area and the Long Lake area. The Beartooth Plateau has been extensively sculpted by glacial processes during the Pleistocene. The highway crosses a classic locality of "biscuit-board topography"--plateau remnants partially dissected by cirques--as well as deposits left by glaciers that etched the plateau. Features to be seen include glacio-fluvial terraces showing downstream effects of the glacial system and extensive areas of periglacial features that postdate glaciation. Glacial features are described from the Red Lodge area, Rock Creek Canyon, the hairpin turns, the Beartooth Plateau, and the Clark Fork basin.

The Stillwater Complex, Southern Montana; A Layered Mafic Intrusion part of MT Field Guides
Layered complexes provide the most visible evidence of processes of magmatic differentiation; thus, they occupy a central place in the study of igneous petrology. Such complexes are not only scientifically rewarding, they are host to several types of mineral deposits, including copper-nickel, chromium, and platinum-group elements. The Stillwater Complex is one of the world's great layered mafic intrusions, distinguished not so much by its size as by the fact that it is tilted on its side, and erosion has exposed the layering to ready access. This fieldguide presents a summary of the geology of the complex in the Benbow and Mountain View areas. The Benbow area offers easy access to a variety of rocks from the ultramafic series and chromite deposits but only limited exposures of features from the banded series. The Mountain View area offers easy access to most of the banded series and the platinum deposits.

Yellowstone and Grand Teton National Parks and the Middle Rocky Mountains part of MT Field Guides
This trip is designed to show participants the granite-cored Laramide (Late Cretaceous-earliest Eocene) mountain ranges in the middle Rocky Mountains, and their various stages of burial by Cenozoic deposits and subsequent Quaternary exhumation. Mountain-flank structures involving Precambrian, Paleozoic, and Mesozoic rocks, the classic Heart Mountain detachment fault complex, and the rootless overthrust mountain ranges of the Wyoming-Utah-Idaho thrust belt are traversed.

Road Log to the Picket Pin Mountain, Chrome Mountain and Contact Mountain Areas part of MT Field Guides
This road log describes the geologic features along the access roads for three additional traverses: Guide to the Picket Pin Mountain Area, Guide to the Chrome Mountain Area, and A Traverse Through the Banded Series in the Contact Mountain Area. "This trip requires nearly 2 hours without stops. Beyond 12.5 miles, the road is rough and steep in places; a four-wheel-drive vehicle is recommended.

A Traverse Through the Banded Series in the Contact Mountain Area part of MT Field Guides
This traverse through the Banded Series of the Stillwater Complex follows the section described in detail by McCallum and others (1980)....Unusual or particularly interesting features are highlighted by the 22 localities along the traverse. In view of the nearly continuous outcrop, however, there is much of interest to see between localities, and full appreciation of the entire section would require several days. Nonetheless, most of the important rock types can be seen on a 1-day trip.