All undergraduate majors are eligible and encouraged to participate in research. Research opportunities can be a part of an independent study with a faculty member, as a part of a class assignment, or participating in a funded project. All Geology faculty members are involved in undergraduate research because we believe that it significantly enhances the educational experience. Student research enhances observational and interpretative skills, develops oral and written skills, and provides a connection between the classroom and the real world. Some recently completed or ongoing undergraduate research projects are outlined below.
The Paleocene Fort Union Formation was studied at three localities in the western Bighorn Basin of western Wyoming. Detrital zircon U-Pb geochronology was used to determine the provenance of these rocks to better understand the transition between Sevier thin-skinned and Laramide thick-skinned deformation. Uppermost Fort Union strata were sampled near the WY-MT state line near Belfry, MT, just east of Cody, WY and north of Meteetse, WY. A total of 248 zircons were analyzed at the University of Arizona Laserchron Laboratory. Proterozoic zircons dominated each of the samples, ranging from 48-63% of each sample. Numerous Proterozoic orogens supplied these zircons. Mesozoic zircons were the next most abundant component in each sample, ranging in proportion from 20-23%. Archean zircons comprised 8-15% of each of the samples. Paleozoic zircons were the smallest fraction, accounting for only 2-8% of the zircons analyzed. The preponderance of Proterozoic zircons indicates that the principal source area of the Fort Union in the Big Horn Basin is the Sevier Highlands to the west. These zircons were likely recycled from Neoproterozoic metasedimentary rocks that are common throughout that area. The presence of a significant proportion of upper Cretaceous zircons suggests that areas of the Idaho Batholith were exposed as well and supplying sediment. The paucity of Archean zircons indicates that the Beartooth uplift was not as yet unroofed, and thus not a significant source area during Fort Union deposition. Archean zircons present could also have been recycled from distal westerly sources.
|Mary Ann Scroggins|
Quartzite cobble conglomerates occur within the Tertiary strata of the western Big Horn Basin. Our goal in this research is to characterize the age and provenance of these clasts using detrital zircon U/Pb Geochronology. As part of this study, we sampled three different formations (#332 zircon analysis total). The Paleocene Fort Union Formation was sampled along Grass Creek (#83). The lower Eocene Willwood Formation was sampled at two localities: along Gooseberry Creek (#84) and near Meeteetse (#96). The middle Eocene Wapiti Formation was sampled at Jim Mountain (#70). Meso- and Paleoproterozic (1300-2000 Ma) dominated each of the samples, ranging from 79-87%. Each locality also contained smaller amounts of Archean (>2500 Ma 7-17%) and Grenville (950-1200 Ma; 6-10%). The most abundant age for each sample is 1650-1700 Ma. The similarity of detrital zircon signatures indicates that these rocks were most likely derived from the same source area, which is the Sevier highlands to the west. The sandstone protolith of these quartzites were eroded from Yavapai-Mazatzal rocks and then transported north to the Neoproterozoic continental margin of Idaho and Montana. These quartzites were then uplifted during the Sevier orogeny, were weathered, and shed as clasts east into the Western Interior Basin during early Tertiary time. These quartzite clasts have similar deterital zircon spectra to the time equivalent Harebelle and Pinyon Formations to the west.
The Eocene volcanic rocks at Hominy Peak represent a southwestern outlier of the Absaroka Volcanic Supergroup. As part of this study, we used U-Pb dating methods to determine the zircon age spectrum on an ash fall tuff (#32), a polymict agglomerate matrix (#85) and a quartzite cobble conglomerate matrix (#77) from the Hominy Peak Formation. The quartzite cobble conglomerate has a zircon spectrum that is 41% Archean, 30% Proterozoic, 20% Eocene, and 8% Mesozoic. Age of the 10th youngest grain is 50.44 +0.96 -0.68 Ma. The polymict agglomerate had a surprisingly diverse zircon suite that includes 48% Proterozoic, 25% Eocene, 13% Archean, 4% Paleozoic, and 3% Mesozoic ages. The age of the 10th youngest grain for this unit is 49.25 +0.91 -1.20 Ma. The ash fall tuff spectrum consisted of 63% Eocene zircon, with a variety of Paleozoic and Precambrian zircons also present. The weighted mean age of this unit is 50.3 +/- 1 Ma. The zircon provenance of the Hominy Peak Formation is diverse. These rocks contain a surprisingly high proportion of non-Eocene zircons in what has been interpreted to be a primary volcanic unit. During Hominy Peak time, the source areas included the uplifted Laramide Teton Range to the south that produced the Archean ages, the active Absaroka volcanic rocks to the north that yielded the Eocene ages, and the underlying Pinyon and Harbelle Formations that yielded that Proterozoic and and Mesozoic Zircons. The age of 50.3 +/- Ma would make these rocks correlative to other Bridgerian rocks to the east, which would include the Wapiti Formation.
The Cloverly Formation of Wyoming represents the first synorogenic strata shed from the Sevier highlands of ID and MT. Detrital zircon U-Pb geochronology was used to determine the provenance of these rocks to better understand the early stages of unroofing of the Sevier highlands. Lowermost Cloverly Formation Sandstones were sampled at three localities in the Big Horn Basin (#283 zircon total) and two localities in the western Powder River Basin (#185 zircon total). The Big Horn Basin detrital zircon spectra are dominated by Proterozoic ages (78-83%), which are mainly Grenville age zircons. Paleozoic zircons represent 10-15% of the spectra of each sample. Lesser amounts of Mesozoic (1-3%) and Archean (2-6%) also were present. The Powder River zircon spectra also were dominated by Proterozoic zircons, but the proportion was smaller (55-69%) and the age distribution was much more diverse. Mesozoic zircons were more prominent (12-23%), Paleozoic (11-13%), and Archean (9-10%) were more abundant as well. The Proterozoic and Archean zircons were likely recycled from cratonic Mesozoic and Paleozoic strata that was eroded as the Highlands were unroofed. The Mesozoic zircons were derived from the underlying Idaho Batholith and related plutonic rocks in the region. It is curious that the more distal Powder River Basin Cloverly localities are more enriched in younger zircons. This may indicate that distal Cloverly sandstones are comprised of sediment derived from more deeply eroded areas of the Sevier Highlands.
Quartzite conglomerates Late Cretaceous to Eocene in age outcrop in deposits up to 1-4 km thick in areas of Sublette and Teton Counties. Our goal in this research is to characterize the age and provenance of these clasts using detrital zircon U/Pb geochronology. As part of this study, we sampled three different formations (#475; zircon analysis total) at six localities. The Harebell Formation was sampled at along Buffalo Fork (#85) and Pacific Creek (#83). The Pinyon Formation was sampled along Pacific Creek (#=43), in the Gros Ventre Mountains (#=98) and at Hominy Peak (#=82). The Hominy Peak Formation was sampled just south of Hominy Peak (#=84). Meso- and Paleoproteroic zircons dominated these spectra, ranging from 71-91%. Grenville and Archean zircon populations also are present, ranging from 1-15% and 5-18%, respectively. The overlap and similarity indices ranged from 0.62-0.82 and 0.68-0.84, respectively. These data indicate that the protolith sediment of these quartzites were generated in the Yavapai-Mazatzal orogenic belt to the south and east. This sediment was transported to the Neoproterozic continental margin of ID and MT and then metamorphosed. These quartzites were then uplifted during the Sevier Orogeny, were eroded and the clasts were transported eastward into the Western Interior Basin. It is likely that much of this sediment could have been reworked and recycled into younger conglomeratic units. The quartzite clasts studied here have identical detrital zircon spectra to quartzite bearing conglomerates of the Fort Union, Willwood and Wapiti Formations to the east.