Great Falls to Wolf Creek part of MT Field Guides
Great Falls is underlain by the Lower Cretaceous Kootenai Formation (Aptian), a series of red sandstones and shales which is considered to have been deposited in a "mostly" nonmarine environment. The city is on a crest of a broad northwest-plunging anticline called the South Arch, which lies just east of the Montana Thrust Belt. As we drive southwestward towards the Montanta Thrust Belt today, we will travel off the northwest flank of the South Arch. This will take us gradually from Lower Cretaceous to Upper Cretaceous outcrops until we reach the edge of the mountain front.

Rhyolite-basalt volcanism of the Yellowstone Plateau and hydrothermal activity of Yellowstone National Park, Wyoming part of MT Field Guides
This field guide provides an overview of the major geologic and hydrothermal features along the park roads through the western and northern parts of Yellowstone National Park. A number of sites from Old Faithful to Mammoth Hot Springs are described in the context of the geologic history of the Yellowstone region. Areas receiving special emphasis are the Firehole River and Upper Geyser Basin (including the Old Faithful area), Midway and Lower Geyser Basins, Firehole Canyon, Madison Junction, Norris Geyser Basin, the Norris-Mammoth Corridor, and Mammoth Hot Springs.

Geology and Evolution of the Grand Canyon of the Yellowstone, Yellowstone National Park, Wyoming part of MT Field Guides
This field guide concerns that part of the Grand Canyon of the Yellowstone seen by most visitors between Chittenden Bridge and Sevenmile Hole. The focus of the field guide is the stratigraphy and erosional history of the volcanic and sedimentary rocks (all younger than 610 Ka) that are observed in the canyon walls at 11 locations within or adjacent to the canyon: Inspiration Point, Red Rock, Lower and Upper Falls, Cascade Creek, Uncle Toms Trail, Uncle Toms Rest Area, Artist Point, and a location near Chittenden Bridge. The volcanic and sedimentary features observed at the various stops are discussed in terms of a sequential geologic framework.

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.

The Hebgen Lake Earthquake Area, Montana and Wyoming part of MT Field Guides
Several high-angle normal faults bounding the west front of the Madison Range north of Hebgen Lake, recurrently active during much of Neogene time, reactivated catastrophically on August 7, 1959. Faulting was accompanied by largest historic earthquake within the Intermountain Seismic Belt. Unusual geologic features were formed--spectacular fault scarps, a large landslide, a deformed lake basin (Hebgen Lake), and a new lake (Earthquake Lake)--each of which demonstrates the destructive power of a large eathquake. These features are described in the context of the bedrock geology in this field guide.

Stratigraphy and sedimentology of the Paleocene Fort Union Formation along the Powder River, Montana and Wyoming part of MT Field Guides
The Paleocene Fort Union Formation in the Powder River Basin in Montana and Wyoming and adjoining areas contains a large number of very thick, closely spaced coal beds that make up some of the largest coal reserves in the United States. The main purpose of this field guide is to provide a knowledge of the stratigraphy, fluvial facies sequences, and depositional environments of portions of this coal resource at three main localities along the Powder River. Field data from measured sections and outcrop descriptions are synthesized into a depositional model for the origin of the Tongue River Member of the Powder River Formation.

Depositional Surfaces in the Eagle Sandstone at Billings, Montana part of MT Field Guides
Marine shelf sandstones and barrier bars are commonly formed by lateral accretion of sand bodies with time lines inclined to the formation boundaries. Shelton (1965) described low-angle inclined bedding in the lowermost sandstone unit of the Eagle Sandstone at Billings, Montana. He recognized these beds as shoreface accretion surfaces of a barrier bar and likened them to those found on present-day Galveston Island, Texas. The Billings location provides an excellent opportunity to examine an important hydrocarbon reservoir rock of the Northern Rocky Mountain region.

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.

Geology of the Butte Mining District, Montana part of MT Field Guides
The Butte mining district is one of the major mining districts of the world with continuous production from both underground and open pit mines for 119 years, from 1864 to 1983. During this time, mining activites at Butte have introduced many firsts in mining methods, techniques of mine mapping, and the detailed recording of geologic data. This field guide describes the geology of the mineral deposits, provides a geologic map of the district, and concludes with a tour of eight locations of interest, including Alice pit, Syndicate pit, Berkeley pit, the Emma and Orphan Boy veins of the Anaconda system, the World Museum of Mining, and the Montana Tech Mineral Museum.