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Jacqueline Sigmon

1999 Research

Abstract: Garnet-bearing orthopyroxene±cordierite hornfels from the contact aureole of the Stillwater Intrusive Complex, Montana: A preliminary report
Mentor: Dr. Jennifer Thomson, Department of Geology


The Stillwater Complex, located along the northern boundary of the Beartooth Mountains in Montana is a 48 km long layered mafic and ultramafic igneous intrusion of Precambrian age (Figure 1). Of great economic interest, the complex was projected in 1987 to supply 3% of the United States total annual need for platinum and 8% of the total need for palladium (Foose, 1991). The complex also contains significant quantities of chromium, copper, and nickel. Due to its economic and scientific importance, the Stillwater Complex has undergone decades of inquiry by a host of workers (Howland et al., 1936; Wager and Brown, 1967; Page, 1979; Todd et al., 1982; Irvine et al., 1983; Turner et al., 1985; Boudreau and McCallum, 1985; Page and Zientek, 1985a ; Foose, 1991). As a result, a plethora of information exists concerning the stratigraphy, structure and petrogensis of the intrusive. In contrast to the intrusive itself, the contact metamorphosed rocks exposed at the base of the complex have received relatively little attention until fairly recently (Papike and Vaniman, 1977; Vaniman et al., 1980; Beltrame, 1982; Labotka et al., 1982; Mueller et al., 1984; Labotka, 1985; Page and Zientek, 1985b, Kath and Labotka, 1986). The contact aureole, exposed only along the southern margin of the complex, is comprised of metasedimentary rocks including diamictite, iron formation, blue metaquartzite, and layered and massive hornfels (Beltrame, 1982).

1998 Research

Abstract: Clarification of Hexagonella ramosa from the Kalabagh member in the Wargal Limestone Formation of the Zaluch Group, the Salt Range, north-central Pakistan

Mentor: Dr. Ernest Gilmour, Geology

The Hexagonella genus was first identified by Waagen and Wentzel in 1886. An eye for detail and a few crude scientific instruments were all the two had to describe the cystoporate bryozoans. Drawing were done as close to scale as possible, and the magnification was very low.

Throughout the years, others have redefined some species of Hexagonella described by Waagen and Wentzel (1886). For example, Crockford (1944) recharacterized Hexagonella plana and Sakagami (1971) redefined Hexagonella robusta. The purpose of my study was to determine if the Hexagonella ramosa specimens from the Waagen and Wentzel localities needed to be redefined using modern technology.

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