BACKGROUND INFORMATION ON THE BEARTOOTH MOUNTAINS

The rocks of the Beartooth Mountains of Montana and Wyoming span 4 billion years of earth history. The geologic features range from the more recent spectacular glaciation of the Beartooth Plateau and the volcanism and thermal activity of the Yellowstone area (south of the Beartooth Mountains) to the ancient crust containing constituents that are over 4 billion years old.

Most of recent research has concentrated on the well-exposed metamorphosed supracrustal rocks that are part of a large tectonic melange caught up in the areally extensive, 2.8 billion year old granitoid plutons of the eastern Beartooth Mountains. One reason that these rocks are particularly significant is that some of the detrital zircons in the quartzites are 4 billion years old. The metamorphosed supracrustal rocks have at least two high grade metamorphic events superimposed on them: (1) an initial   granulite facies event accompanied by deformation that was probably no older than 3.2 billion years old and (2) a second upper amphibolite/granulite facies overprint with no deformation that was associated with the thermal effects of the massive granitoid intrusions at 2.8 billion years.  These rocks are part of one of oldest pieces of crust in North America and provide many insights into early crustal formation on the Earth.

Summary of the geologic history of the eastern Beartooth Mountains

Other plots useful to project

COMPARISON OF BIOTITE AND AMPHIBOLE CHEMISTRY

Amphibole classification diagram for calcic amphiboles with low A-site occupancy
Amphibole classification diagram for calcic amphiboles with high A-site occupancy
Biotite Al vs. Mg/(Mg+Fe) relations
Biotite Ti vs. Mg/(Mg+Fe) relations

IMAGES OF LOCATIONS OF SAMPLES USED FOR THE PET ROCK PROJECT

BEARTOOTH RECONNAISSANCE SAMPLES AND FIELD VIEWS

Sample location map for the BTR samples. Map modified from Fig. 2 of Wooden et al. (1982). Click on the thumbnail map on the left for a full scale image of the map.
Sample locations for BTR-13 and BTR-14 on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
Sample locations for BTR-23, BTR-29 and BTR-38 on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
   

 

HELLROARING PLATEAU

Sample locations for HR02-44 and QC81-72 on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
Sample locations for HR02-44 and QC02 samples on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
Picture of  Hellroaring Plateau to the west of Rock Creek. This image is shot from the Beartooth Pass. HR02-44 locality is in yellow. Click on the thumbnail image on the left for a full scale image.
Picture of  Hellroaring Plateau Road outcrop from Andrew Maas MS thesis (2004) to the west of Rock Creek. Multiple sample locations are given. Click on the thumbnail image on the left for a full scale image.

 

QUAD CREEK AND ROCK CREEK

Sample locations for HR02-44 and QC81-72 on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
Sample locations for HR02-44 and QC02 samples on Google Earth map. Click on the thumbnail map on the left for a full scale image of the map.
Roadcut of lower Quad Creek section. Lower Quad Creek locality with interlayered granitic gneisses, quartzites and amphibolites with a crosscutting mafic dike. Pet rock sample locations are in yellow. Click on the thumbnail map on the left for a full scale image of the map.
Roadcut of lower Quad Creek section. Lower Quad Creek locality with interlayered granitic gneisses, quartzites and amphibolites. This is from Andrew Maas' MS thesis (2004). Pet rock sample locations are in white. Click on the thumbnail map on the left for a full scale image of the map.
Roadcut of lower Quad Creek section. Lower Quad Creek locality with interlayered granitic gneisses, quartzites and amphibolites with a crosscutting mafic dike.  Pet rock sample locations are in yellow. Click on the thumbnail map on the left for a full scale image of the map.