I gather that the sign on her office door says "PEGMATITES RULE."Enuf said!
- Benjamin Grosser (University of North Carolina, Wilmington. B.S. Geology 2001)
Thesis Title: Petrology and geochemistry of the Wildcat Gulch syenite: Comparison with the Tolvar Peak granite and the Powderhorn carbonatite complex
Near Gunnison, Colorado in the area known as Wildcat Gulch there are several outcrops of syenites which intrude the Proterozoic (1.8 - 1.7 Ga) Dubois greenstone succession. In the Wildcat Gulch region these syenites have only been examined as part of a more extensive survey of the relationship between thorium resources and the Lower Paleozoic alkalic and mafic rocks in south central Colorado (Olson et al. 1977). This study examined three syenites from the study area and reported the mineralogy, whole rock major element composition and provided K-Ar ages of 1.33 to 1.39 (± 0.4) Ga (Olson et al. 1977). Nevertheless, these syenites are still lumped into the lithological description of the Dubois greenstone without regard to their origin or potential for constraining the geological framework of this region.
Preliminary fieldwork (as a result of a mapping project for the 2001 North Carolina geology field course) indicates that the syenites are not deformed and show a variety of intrusive contact relationships from black wall (biotite mica selvages) mineralization to irregular, blocky assimilation contacts with the mafic component of the Dubois greenstone in this area. Since the Dubois greenstone has been metamorphosed to upper greenschist facies and highly deformed, the lack of deformation (as well as the contact relationships observed) suggest the syenites are much younger, as indicated by Olson et al (1977). However, preliminary petrographic analysis indicates that there is some deformation of the syenites at the microscale. This could mean that the analyzed syenites intruded prior to the 1.7-1.8 Ga metamorphism of the Dubois greenstone and their age determination is incorrect, or that there are multiple syenite intrusions in the area of differing ages. Olson et al (1977) defines two separate periods of intrusion in the region one between 1.35-1.4 Ga and the other at 570 Ma. Both of these periods of intrusion contain syenite bodies. The question is do the syenites in the Wildcat Gulch region fit into the scheme of Olson et al (1977), or are they part of another intrusive event.
Two potential sources for the syenite are the Tolvar Peak granite and the Powderhorn Carbonatite complex, both outcropping south of the field area. The Tolvar Peak granite is found in contact with the mafic component of the Dubois greenstone, and has been metamorphosed and deformed to the same degree as the Dubois greenstone (Nelson, 1981).
Trachyte dikes and carbonatite from the alkalic stock of the Powderhorn Carbonatite complex are found within the Dubois greenstone, but no correlation with the syenites in the study area has been investigated, even though many of the intrusive bodies near Powderhorn are either pyroxene or nepheline syenites. Lastly, the undeformed nature of the syenites found in the field area is puzzling. If the K-Ar ages of the syenites as reported by Olson et al (1977) are correct, the deformation of the Dubois greenstone is prior to this event. However, the Dubois greenstone and the Tolvar Peak granite are both deformed, and the metamorphism of the Tolvar Peak granite was placed at 1.35 to 1.4 Ga by Hedlund and Olson (1981). This suggests that either the age determined for the syenite is incorrect or that there are different syenites found in the study area that postdate the metamorphism of the Tolvar Peak granite or are related to the Cambrian Powderhorn Carbonatite complex. This study will attempt to answer this question. To do this a more detailed investigation, via mapping, examining contact relationships, and petrological and geochemical study, is proposed that will provide more insight into the geologic framework of this economically important region.
Bickford, M.E., Shuster, R. D., and Boardman, S. J., 1989, U-Pb geochronology of the Proterozoic volcano plutonic terrane in the Gunnison and Salida areas, Colorado, Geological Society of America Special Paper 235, pp. 33-48.
Condie, Kent C., and Nuter, Janet A., 1981, Geochemistry of the Dubois Greenstone Succession: An early Proterozoic bimodal volcanic association in West-Central Colorado, Precambrian Research, v. 15, pp. 131-155.
Hedlund, D.C., and Olson, J.C.,1981, Precambrian geology along parts of the Gunnison Uplift of Southwestern Colorado, New Mexico Geological Society Guidebook, 32nd Field Conference, Western Slope Colorado, pp. 267- 272.
Nelson, Craig J., and Riesmeyer, Duncan W., 1983, Geology of the Anaconda-Gunnison mine area Gunnison County, Colorado, In Robert C. Handfield (ed.) Gunnison Gold Belt and Powderhorn Carbonatite Field Trip Guidebook, Denver Region Exploration Geologists Society, pp. 8-18 with 6 figures.
Olson, Jerry C., Marvin, Richard F., Parker, Raymond L. and Mehnert, Harald H., 1977, Age and tectonic setting of lower Paleozoic alkalic and mafic rocks, carbonatites, and thorium veins in South-Central Colorado, Jour.Research U.S. Geol. Survey, v. 5 no. 6, pp.673-687.
Ben has an abstract addressing the petrological and geochemical comparisons of these syenites that was presented at the March 2004 NE/SE GSA regional meeting in Tyson's Corner, Virgina.
Grosser, Benjamin and Smith, Michael S. (2004) The Petrology And Geochemistry Of The Wildcat Gulch Syenite, Gunnison County, Colorado. Geol. Soc. America Abstr. with Programs, v. 36, no. 2., 70-71.
The introduction and use of ballast stones in the Cape Fear Region: An underutilized tool for archaeologist and historians.
Kemp Magnus Burdette (University of North Carolina, Wilmington. B.A. History and B. A. Geology, May 2003).
Kemp was a Fulbright Scholar at Memorial University, Newfoundland in Maritime History (2003-2004), was a Peace Corps volunteer (along with his wife - Jenn) in Nicaragua, and is currently undertaking a master program at UNCW. A manuscript for a special edition of the Society of Historical Archaeologists (Historical Archaeology) ha been submitted on these ballast stones.
Undergraduate Honors Research
Ballast is material loaded into a vessel to regulate its position in the water, thereby maximizing the sailing efficiency of the vessel. Prior to the advent of steel-hulled ships, where water is used as ballast, wooden-hulled vessels frequently used rocks as ballast. These ballast stones were on/off-loaded regularly in port cities, and were commonly kept in areas accessible to, but not in the way of mariners. Today, these materials are represented by a significant number of exotic rocks found in and around port cities used by commercial sailing vessels.
Studies of ballast stones as a maritime tool are rare among historians, archaeologist, and geologists, and until now none have been attempted for the Cape Fear region. This study examines ballast stones collected in the Cape Fear Region to augment information about shipping trends and ports of origin for this area from 1650 to 1850. Ballast stones for this study were collected during the exploration of Campbell Island, at the mouth of Town Creek on the Cape Fear River seven miles south of Wilmington. Hand sample petrology was utilized as well as thin-section analysis to determine the mineral assemblage and to further characterize the ballast.
Using petrologic methods and microfossil identification, this study suggests that significant amounts of commonly observed chert and flint ballast stones in the region appear to have Caribbean origins in addition to English or French origins as previously reported.
Burdette, Kemp M. and Smith, Michael S. (2003). The introduction and use of ballast stones in the Cape Fear Region: An underutilized tool for archaeologist and historians. North Carolina Academy of Science, Abstracts.
Burdette, Kemp Magnus Wilkes and Smith, Michael S. The Mineralogy, Petrology, and Provenance of Ballast Stones From The Cape Fear, North Carolina: 1725 - 1825. In review Journal of Historical Archaeology.
Mineralogical and petrological investigation of Historic St. Mary's city, Maryland, orange micaceous ceramics.
M. Rhonda Cranfill (University of North Carolina, Wilmington. B.A. Anthropology and Minor in Geology, May 2004)
Rhonda has recently (May 2006) attained her Master degree in the geoarcheology program at the University of Georgia - Athens where she continued her investigation of the Merida wares.
Undergraduate Honors Research
Seventeenth century utilitarian orange micaeous ceramics from the site of Historic St. Marys City, Maryland were investigated using optical mineralogical techniques and archaeological attribute analysis. Two groups of sherds were separated by decoration and typology. No glazes were found, although a slip may have been applied. The paste has been fired to greater that 550ºC and reflects complete oxidation. The aplastic components (temper) were identified as minerals (quartz, muscovite, biotite and feldspar), rock fragments and grog. The abundance of the individual temper components varied among the sherds, however the components were all represented. Quartz is found as subangular to subrouned monocrystalline mineral grains and polycrystalline rock fragments. Some of the monocrystalline quartz contained rutile needle inclusions. Muscovite is much more abundant than biotite and feldspar. Grog is rounded, reddish black to black and represents refired ceramic material. Although these sherds have been tentatively assigned as Spanish Merida in origin, these results suggest that these wares could have been manufactured at or near the site of Historic St. Marys City.
Cranfill, M. Rhonda and Smith, Michael S. (2004) Mineralogical And Petrological Investigation Of Historic St. Mary's City Orange Micaeous Ceramics. Middle Atlantic Archaeological Conference. Rehoboth Beach, Delaware, March 12-14.
Cranfill, M. Rhonda and Smith, Michael S. (2004) Mineralogical And Petrological Investigation Of Historic St. Mary's City Orange Micaeous Ceramics. Geol. Soc. America Abstr. with Programs, v. 33, no. 2, 65.
Cranfill, M. Rhonda (2006) Three Colonial ceramic wares: A comparison based on mineralogical, petrographical and compositional data. Geol. Soc. America Abstr. with Programs, v. 38, no. 3, 30.
Mineralogical and petrological investigation of prehistoric ceramic sherds from the island of Anguilla in the northern Lesser Antilles Island chain of the Caribbean
Brianne L. Caitlin (University of North Carolina, Wilmington. B.S. Geology, August 2005)
Brianne has been accepted to the Masters program in Geology at the University of California - Santa Barbara and will be continuing to work in the field of geoarchaeology on Mayan Classic Period wares.
Undergraduate Honors Research
Pottery found on the islands of the Lesser Antilles island chain is composed of local clay/sand material and volcanic rock and carbonate (rock or shell) fragments. Each island has a unique geologic composition that varies from eastern volcanic island chain to the western carbonate island platforms. This study used petrographic microscope techniques to identify the mineralogical components of 45 pottery sherds from the carbonate platform island of Anguilla in the northern Lesser Antilles island chain. The Late Ceramic Age (post - Saladoid) sherds were separated into four groups using carbonate fragments, volcanic to shallow intrusive igneous rock fragments, rare sedimentary rock fragments, and grog. The carbonate material within the pottery is mostly shell material, however it has been highly altered by the firing process. The igneous rock fragments vary mineralogically and may allow correlation with specific volcanic islands in the chain. Abundant minerals within the sherds are feldspars (plagioclase and K-spar), quartz, biotite, epidote, and amphibole. A small number of sherds contained igneous rock fragments with small tourmaline crystals. The grog appears as red to red-black subrounded clasts with quartz, plagioclase, and amphibole mineral fragments. This petrologic analysis will allow for further interpretation of the material culture of the post-Saladoid people.
Catlin, Brianne L., Smith, Michael S., and Petersen, James A. (2005). Mineralogical and petrological investigation of prehistoric ceramic sherds from the island of Anguilla in the Lesser Antilles Island chain of the Caribbean. Geol. Soc. America Abstr. with Programs, v. 37, no. 7, 276.