- 1. Hells Canyon to the Bitterroot Front: Transect from the Accretionary Margin Eastward across the Idaho Batholith.
Thurs.–Sun., 15–18 May. US$245. Max: 32.
Reed Lewis, Idaho Geological Survey; Keegan Schmidt, Lewis-Clark State College, ; Richard Gaschnig, Univ. of Maryland; Todd LaMaskin, Univ. of North Carolina–Wilmington; Basil Tikoff, Univ. of Wisconsin; Tor Stetson-Lee, Univ. of Wisconsin; Karen Lund, USGS; Keith Gray, Washington State University.
This field trip is associated with Theme Session 8.
Vans depart from Bozeman on Thursday, 15 May.
- This trip will start in the Blue Mountains island-arc complex in Hells Canyon, traverse the complex boundary with continental North America eastward, and finish by crossing the Bitterroot lobe of the Idaho batholith.
- 2. Sedimentary Record of Glacial Lake Missoula Deposition and Draining, Clark Fork River Corridor from St. Regis to near Drummond, Montana.
Sat.–Sun., 17–18 May. US$195. Max: 20.
Larry N. Smith, Montana Tech of The Univ. of Montana; Michelle A. Hanson, Saskatchewan Geological Survey.
- We will examine the sedimentary and geomorphic record of sedimentation, lake-level lowering events, and evidence for lake floor/exposure in deposits of glacial Lake Missoula. Field-trip stops will concentrate on sections of gravel deposited during outburst floods and glacial-lake silts that have been described in recent publications. Discussions will center on the character of draining events and reconstruction of a lake-level history. The sites will be along road, rail, and stream cuts that will require walks of less than one mile and some scrambling across loose-sediment overlooks and quarries.
- 3. Tracking a Big Miocene River across Southwest Montana.
Sat.–Sun., 17–18 May. US$275. Max: 32.
James W. Sears, Univ. of Montana.
- The trip will investigate Miocene fluvial deposits that show that a major river with headwaters in Utah and Nevada may have flowed through a rift system across Montana and Idaho before being cut off by Yellowstone hotspot tectonics after 6 Ma.
- 4. A Slice through Time: Fifty Years of Field Trips to Hyalite.
Sun., 18 May. US$65. Max: 24.
Anthony Hartshorn, Montana State Univ.; Stephanie Ewing, Montana State Univ.; Jean Dixon, Montana State Univ.
- For more than two generations, Montana State students have explored the influence of Hyalite’s gneiss, Flathead sandstone, Wolsey shale, Meagher limestone, Absaroka volcanics, as well as organic material on soil development—an amazing lithosequence. This field trip will recap the historical development of these field explorations through the leadership of John Montagne, Cliff Montagne, and Gerry Nielson, and then explore how a new generation is using this lithosequence to quantify the influences of moraines and dust on these “backyard” soils.
- 5. Neotectonics and Geomorphic Evolution of the Northwestern Arm of the Yellowstone Tectonic Parabola: Controls on Intra-Cratonic Extensional Regimes, Southwest Montana.
Sun., 18 May. US$75. Max: 40.
Cal A. Ruleman, USGS; Mort Larsen, Wyoming State Geological Survey; Michael C. Stickney, Montana Bureau of Mines and Geology.
- Since the catastrophic Hebgen Lake Earthquake of 18 August 1959 (MW 7.3), many geoscientists have worked to develop new methods to better understand active tectonics in extensional tectonic regimes that address seismic hazards. The Madison Range fault system (MRFS) and adjacent Hebgen Lake–Red Canyon fault zone (HRFZ) provide an exceptional intermountain-active tectonic analog for regional analyses of extensional crustal deformation. The MRFS is a system of fault zones (~100 km) that have multiple salients and embayments marked by preexisting structures exposed in the footwall. The MRFZ has differing Quaternary tectonic activity rates along its length, with less displacement to the north. Within the Hebgen Lake basin, the 1959 earthquake is the latest slip event in the HRFZ, since the geomorphology and paleoseismicity clearly indicate previous faulting events on the HRFZ. Geomorphic mapping and contemporary seismicity support a structural linkage between the MRFS and the HRFZ. This trip will look at the preexisting structural controls on Quaternary surface rupture patterns and characteristic prehistoric earthquake magnitudes, supported by historic seismicity. The one-day field trip begins and ends in Bozeman, and includes an overview of the active tectonics within the Madison Valley and Hebgen Lake basin, southwest Montana. Participants will witness a range of tectonomorphic landforms along the eastern portion of the Madison Valley and within the Hebgen Lake basin. We will also review abundant geological evidence, which includes a new generation of geologic maps, surficial mapping, and geomorphic analyses, that demonstrates preexisting structural controls on surface rupture patterns along the Madison and Hebgen Lake fault systems.
- 6. Regional Setting and Deposit Geology of the Golden Sunlight Mine: An Example of Responsible Resource Extraction.
Sun., 18 May. US$75. Max: 35.
Nancy Oyer, Barrick Gold Corp.; John Childs, Childs and Associates.
- The open-pit Golden Sunlight Mine in Whitehall, Montana, is an industry leader in responsible resource extraction. With a global resource of more than three million ounces of gold, and current proven and probable reserves at 318,000 ounces of gold, the deposit is one of the richest in the region. The gold-silver deposit is largely localized in a hydrothermal breccia pipe related to Late Cretaceous latite porphyry magmatism and influenced by younger cross-cutting faults and fracture systems. The milling operations contribute to efficient and environmentally friendly resource recovery by processing historical tailings and dumps from other sites around the state. The trip will explore the complex geologic and tectonic controls on mineralization and review the technical challenges of mining, milling, and reclaiming at this unique site.
- 7. Polyphase Collapse of the Cordilleran Hinterland: Bitterroot and Anaconda Metamorphic Core Complexes of Western Montana—Snoke Symposium Field Trip.
Thurs., 22 May. US$95. Max: 18.
Thomas J. Kalakay, Rocky Mountain College; David Foster, Univ. of Florida; Jeff Lonn, Montana Bureau of Mines and Geology.
This field trip is associated with Theme Session 1.
- The Anaconda and Bitterroot metamorphic core complexes are located in western Montana, along the eastern edge of the Cordilleran hinterland. This multi-tiered extensional terrain contains exceptional exposures that collectively exhibit a crustal cross section through orogenic continental crust (i.e., middle through upper crust). The core complex footwall rocks consist of Late Cretaceous arc–related plutons and Eocene granitic plutons intruded into deformed and metamorphosed Mid-Proterozoic Belt Supergroup and Paleozoic to Cretaceous shelf-platform strata. Late Cretaceous shear zones, folds, and significant thinning of the stratigraphic section dominate footwall structure. Eocene detachments, mylonites, and plutonic suites distinctly overprint the Late Cretaceous structures. A stark example of this Eocene overprint is the detachment that resulted in eastward translation of the Late Cretaceous, arc-related Boulder Batholith. This field trip will cover a transect through the core complexes from the Bitterroot valley to Butte, Montana. Field trip participants will examine key locations that allow the distinction between the timing and structural style of Late Cretaceous crustal thickening/collapse features versus those related to Eocene core complex development.
- 8. Mesoproterozoic Tectonics and Sedimentation along the Southern Margin of the Belt Basin: In Honor of Don Winston.
Thurs., 22 May. US$95. Max: 25.
David Mogk, Montana State Univ.; Jim Schmitt, Montana State Univ.; Zach Adam, Montana State Univ.; Paul Mueller, Univ. of Florida. This field trip is associated with Theme Session 4.
- This field trip will explore the southern margin of the Belt Basin. Starting from Bozeman, the trip will head north past the Bridger Range (rolling stop for the Pass Fault) to the town of Niehart, with stops at the Paleoproterozoic basement (1.86 Ga calc-alkaline arc), the basal Niehart quartzite, and the overlying Chamberlain Shale. The trip will continue south to White Sulphur Springs, with stops at the Sheep Creek Cu-Co deposit and Volcano Valley Fault and exposures of Newland Shale at Newland Reservoir. The trip will continue west over Deep Creek Pass with stops to see the Newland and Grayson Formations, and will end in Jefferson Canyon to see the basal coarse conglomerates of the LaHood formation.
- 9. The World-Class Talc Deposits of Southwestern Montana.
Thurs., 22 May. US$95. Max: 35.
John Childs, Childs and Associates; Erika Bartlett, Imerys Talc; Michael T. Cerino, Barretts Minerals Inc.; Helen B. Lynn, Childs Geoscience Inc.; Sandra Underwood, Childs Geoscience Inc.; Chad P. Walby, Childs Geoscience Inc.; Zackary S. Wall, Childs Geoscience Inc.
- This trip will include visits to world-class deposits of high purity talc east of Dillon, Montana, operated by Barretts Minerals Inc. (Minerals Technology Inc.) and south of Ennis, Montana, operated by Imerys Talc. The talc is hosted by Archean dolomitic marbles in the Ruby Range and Gravelly Range, respectively.
- 10. Geology and Paleontology of the Two Medicine–Judith River Clastic Wedge: Field Trip to The Rocky Mountain Front and North-Central Montana, Including Type Sections of The Two Medicine and Judith River Formations.
Thurs.–Sat., 22–24 May. US$375. Max: 19.
Jack Horner, Museum of the Rockies and Montana State Univ.; Ray Rogers, Macalester College; David Lageson, Montana State Univ.
This field trip is associated with Theme Session 13.
- In conjunction with the Two Medicine–Judith River Theme Session, there will be a three-day field trip to important localities in the Two Medicine and Judith River Formations. The plan is to visit sites of both paleontological and geological interest. Featured stops include the famous Egg Mountain locality near Choteau, the type area of the Two Medicine Formation along the Two Medicine River, and the type area of the Judith River Formation in the Upper Missouri River Breaks National Monument.
- 11. Glacial and Quaternary Geology of the Northern Yellowstone Area, Wyoming and Montana.
Thurs., 22 May. US$75. Max: 30.
Kenneth L. Pierce, USGS; Joseph M. Licciardi, Univ. of New Hampshire; Teresa R. Krause, Montana State Univ.; Cathy Whitlock, Montana State Univ.
This field trip is associated with Theme Session 5.
- This field trip focuses on the Paradise Valley and the northern part of Yellowstone and includes: moraines and outwash of the northern Yellowstone outlet glacier, post-glacial vegetation and fire history, Quaternary faulting and volcanism, glacially and landslide-generated flood deposits, Pinedale recessional glacial deposits, and the relationship of glacial deposits to Yellowstone’s Northern Range.