Early Proterozoic Geology of the Highland Mountains, Southwestern Montana, and Field Guide to the Basement Rocks that Compose the Highland Mountain Gneiss Dome part of MT Field Guides
The Highland Mountains are underlain by the largest of the northwesternmost exposures of basement crystalline rocks in southwestern Montana....Metasedimentary rocks in the Highland Mountains are in part lithologically similar to the Late Archean multilithologic sequence (in the Tobacco Root, Ruby, and the northern Madison and Gravelly Ranges), but are considerably thinner. In the Highland Mountains the individual beds of aluminous schist, marble, quartzite, and iron-formation extend for only short distances, but the assemblage as a whole is mappable. It nowhere exceeds 300 ft (100 m) in thickness and appears to pinch out to the north....these rocks in the Highlands, unlike those to the southeast, are overlain by more than 10,000 ft (3000 m) of aluminous biotite gneiss that may have been deposited as muds basinward from the Late Archean shelf edge.

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 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.

Multiple Catastrophic Drainage of Glacial Lake Missoula, Montana part of MT Field Guides
This field guide describes two localities related to the history and drainage of Glacial Lake Missoula northwest of Missoula, Montana. The first site highlights spectacular erosional and depositional features that illustrate the effects of extremely large discharge related to the drainage of the lake. In a sense, the area is the world's most extravagant natural flume experiment. Features include bedrock basins (scoured by flood waters), large deltaic bars, and megaripples as large as 35 feet from crest to trough. The second site, a large roadcut along I-90, contains a record of at least 36 fillings of the lake, presumably during Pinedale(?) time, suggesting that drainage occurred many times. Another roadcut exposes a similar, but unstudied record of deposition in a higher terrace that probably formed during Bull Lake(?) time and may indicate an older history of lake formation and drainage.

Missouri Breaks Diatremes, Montana part of MT Field Guides
The Missouri Breaks diatremes are some of the best exposed diatremes in the United States, and display remarkable subsidence features. The diatremes and associated intrusions are important in showing (1) genetic connections of alnoitic, kimberlitic, and carbonatitic magmas, (2) xenolith suites representing the upper mantle and lower, middle, and upper crust of the Eocene lithosphere, and (3) mechanisms of eruption and emplacement of volatile-rich magmas. Some of the diatremes are fairly accessible in good weather. However, the Missouri Breaks is a remote area in which most of the roads are unimproved tracks across clay-rich sedimentary rocks, and even a small amount of rain may immobile four-wheel drive vehicles and make steep grades terminally hazardous.

Geology of the Butte Mining District 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.

Crazy Mountains, Montana part of MT Field Guides
This trip examines a variety of mid-Eocene alkalic (feldspathoidal) stocks, laccoliths, sills, and dikes emplaced into Cretaceous and Paleozoic sedimentary strata. These rocks include mafic and felsic varieties, and are both texturally and compositionally variable. Most of the mafic alkalic rocks are unique in the Montana Alkalic Province in having Na2O > K2O. They are unusual even among feldspathoidal rocks because they are stongly enriched in incompatible elements, and have Sr, Nd, and Pb isotopic compositions which reflect an ancient source having low Rb/Sr, Sm/Nd, and U/Pb.

Guide to the Picket Pin Mountain Area part of MT Field Guides
This traverse through part of the Banded series provides relatively easy access to the upper half of the exposed part of the Stillwater Complex. The percentage of outcrops is high, and even in areas of soil or tundra cover, the float appears to be sufficiently immobile and concentrated to give an accurate picture of the underlying bedrock geology....The traverse begins in the Middle gabbro zone and terminates where Paleozoic limestone unconformably overlies the Upper anorthosite zone. Above the Middle anorthosite zone, it follows the Picket Pin section described by McCallum and others (1980) and Raedeke (1982b)....An optional traverse through some lithologically complex and intriguing rocks in the Upper anorthosite zone north of the Castle Creek fault is also described. Total traverse time, including the drive from Carter's Camp and return, is 8-10 hours. Elevations range from 9,300 to 10,000 feet.

A Traverse Across the Central Belt Basin From Bowmans Corner, Montana to East Hope, Idaho part of MT Field Guides
This road log highlights a variety of sedimentary rock types and structures along a transect of the Rocky Mountain Fold and Thrust Belt. The log follows Montana Highway 200, which crosses the central part of the Middle Proterozoic Belt basin from the Montana disturbed belt to Missoula, where it turns northwesterly into northern Idaho, traversing rocks of the western and northwestern Belt basin. The road log begins east of the Rocky Mountain front in the disturbed belt underlain by soft, Cretaceous shale and somewhat more resistant sandstone units. Next, the road log passes into the eastern thrust belt where thrust faults bring Belt rocks first over Cretaceous, then over Paleozoic rocks, and finally over Proterozoic rocks farther to the west. At Rogers Pass, the route crosses the Continental Divide and into the Ovando block where Cenozoic listric normal faults form the major structures. The leading edge of the western thrust belt is encountered at Bonner, MT. From Missoula, Highway 200 trends northwestward to northern Idaho and diagonally crosses the western part of the Belt basin. Changes in grain-size and sediment type observable from outcrops along this road log illustrate the evolution of sedimentary transport and facies tracts within the central part of the Belt basin.