Browsing by Author "Jirsa, Mark J"

Now showing 1 - 8 of 8
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    Bedrock Geologic Map of Ogishkemuncie Lake, Boundary Waters Canoe Area, Lake County, Northeastern Minnesota
    (2010-08) Birkemeier, R; Boley, T; Brannan, B; Doucette, R; Jirsa, Mark J; Lee, A
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    Bedrock Geologic Map of the Central Part of Knife Lake, Boundary Waters Canoe Area Wilderness, Northern Minnesota
    (2014-08) Krogmeier, Ben; McKevitt, Dylan; Roepke, Liz; Sara, Michael; Szkilnyk, Paul; Jirsa, Mark J
    This map of the central Knife Lake area in the Boundary Waters Canoe Area Wilderness (BWCAW, Fig. 1) is the result of six days of bedrock mapping in August, 2014 by PRC Field Camp students under the guidance of Mark Jirsa, Minnesota Geological Survey, along with information gathered from Jirsa and Miller (2004), Gruner (1941), and Mulcahy and others (2013). The geology in this area has not been mapped in detail due to its remote location. The authors conducted extensive canoe shoreline mapping and inland traverses in an attempt to better define geologic contacts, structural features, and depositional facies for an improved understanding of the region. The relationships between mafic metavolcanic rocks, diverse metasedimentary units, and various intrusions were better characterized. Mineralized shear zones and locally intense sulfide mineralization may be indicators of economic significance within this complex Neoarchean terrane. Field mapping was conducted using 1:24,000 scale maps, and digitally compiled at 1:12,000 scale.
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    Bedrock Geologic Map of the Paulsen Lake Area, Northeastern Minnesota
    (2008-08) Kowalik, Jacqueline; Niedermiller, John; Cowan, Hugh; Jirsa, Mark J
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    Bedrock Geology Map of the Knife Lake Group and Related Intrusions near Kekekabic Lake: Lake County, Minnesota
    (2015-08) Christenson, Jaron; Kent, Morgan; Puzel, Ryan; Spreitzer, Steven; Upton, Margaret; Jirsa, Mark J
    This map was created by undergraduate students attending the Precambrian Research Center Field Camp in the summer of 2015 under the guidance of Mark Jirsa, Minnesota Geological Survey. Reconnaissance mapping at a scale of 1:24,000 was conducted by the authors in the Boundary Waters Canoe Area Wilderness (BWCAW) in the vicinity of Kekekabic Lake. The goal of this endeavor was to uncover the regional geologic history of Neoarchean rocks of the Knife Lake Group that have been influenced by volcanism and intruded by igneous bodies. An additional goal was to acquire an understanding of the contact between the Mesoproterozoic Duluth Complex and other Proterozoic intrusions, and the Knife Lake Group. Nearly 220 outcrops were examined in the course of 8 days by traveling approximately 130 miles by canoe and land traverses to con rm the internal lithologic variability, contact relationships, stratigraphic facing, and structure. The area primarily contains etasedimentary, metavolcanic, and intrusive rocks of the Neoarchean Knife Lake Group. Metasedimentary rocks including graywacke, slate, sandstone and conglomerate that were deposited in alluvial fan, fluvial, and subaqueous environments. Metavolcanic rocks include largely porphyritic, mafic and intermediate flows that shed detritus to the sedimentary units. The metasedimentary and metavolcanic units are intruded by polyphase intrusions, which also contributed detritus to some sedimentary rocks. The Neoarchean rocks were intruded by Proterozoic diabase dikes and the Duluth Complex.
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    Bedrock Geology of Bingshick Lake Area, Boundary Waters, MN
    (2009-08) Jirsa, Mark J; Jaret, Steven; Watson, Tabitha; Totenhagen, Michael; Fahrenkrosg, Brooke
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    Bedrock Geology of the Hanson Lake Mapping Area
    (2013-08) Mucahy, Connor; Romanelli, Daniel; May, Mitchell; Schulz, Roger; Moorhead, Steven; Jirsa, Mark J
    This map was created by PRC Field Camp students under the guidance of Mark Jirsa, M.Sc., Senior Geologist, Minnesota Geological Survey. The purpose of this map is to further understand the geology of the Hanson Lake area, with special focus on the sedimentary and structural history of Archean and Proterozoic bedrock. This map is the product of seven days of field mapping by the authors in August 2013. Outcrops were mapped by canoe along shorelines and by foot along inland traverses within the Dutton Lake, Ester Lake, Kekekabic Lake, and Ogishkemuncie Lake quadrangles. Although the field mapping was carried out on 1:24,000 scale maps, the digitization of data allowed this map to be produced at a 1:12,000 scale. It is the first detailed geologic map of the area to be produced at this scale.
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    Bedrock Map of the Ester Lake Quadrangle, Lake and Cook County, The Boundary Waters Canoe Area Wilderness, Northeastern Minnesota
    (2012-08) Craddock, S; Doyle, M; Korman, K; Walter, J; Lee, A; Jirsa, Mark J
    This map portrays detailed bedrock geology of an 8 mile2 area adjacent to the US-Canadian border in the Ester Lake 7.5 minute quadrangle. The area was incorporated in previous regional scale-mapping by Leith (1910) and Gruner (1941), and parts were mapped in the 1970’s and 1980’s by graduate students of the University of Minnesota Duluth. Historically, mapping was focused on lakeshores and waterways. A wind storm in 1999 and subsequent Cavity Lake forest re of 2006 generated impressive exposure of bedrock and easier access to inland areas. A preliminary geologic map of the fire area was generated by Jirsa and Starns (2008), based on previous work and some localized traverses. Subsequent mapping by Jirsa and students of the Precambrian Research Center during the 2008- 2012 field seasons will allow publication of a final map of the Cavity Lake fire area in 2012. This map depicts diverse geological structure and lithology representing crustal evolution spanning the Archean to Proterozoic Eons. The Archean rocks represent a granite-greenstone terrane within the Wawa subprovince of the Superior Province of the Canadian Shield. The Ester Lake 7.5-minute quadrangle consists of metabasaltic rocks of unknown age, but possibly equivalent to the Ely Greenstone (ca. 2722), the 2690 Ma Saganaga Tonalite (Driese and others, 2011), and arkose, conglomerate, greywacke, slate, and iron-formation of the Knife Lake Group. Field evidence indicates that the Saganaga Tonalite was uplifted and subaerially eroded, generating tonalitic detritus to nearby basins, now manifest as Knife Lake Group strata. All rock types on the map sheet appear to have been metamorphosed to low greenschist facies.
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    Reconnaissance Geologic Map of the Central Boundary Waters Canoe Area Wilderness
    (2011-08) Baggetto, Louis; Eliason, Garret; Hansen, Darren; Hoxie, Erin; Kilpatrick, Kayla; Jirsa, Mark J
    This map was created by PRC students under the guidance of Mark Jirsa, Minnesota Geological Survey, over an eight day period between August 7-14, 2011. The purpose of the map was to build upon and improve previous geologic mapping (e.g., Jirsa and Miller, 2004; Jirsa et. al. 2011). It was also done to re ne contact locations and locate sheer and fault zones amongst the Knife Lake Group, the Newton Lake Formation, Basswood Lake granodiorite and associated sheared rocks. Reconnaissance-style shoreline mapping was completed by students along a 44 mile traverse through 22 lakes and includes 240 outcrops in the central Boundary Waters Canoe Area Wilderness.