Browsing by Author "Jirsa, Mark A."

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C-42, Geologic Atlas of Becker County, Minnesota
(Minnesota Geological Survey, 2016) Bauer, Emily J.; Chandler, V.W.; Jirsa, Mark A.; Marshall, Katherine J.; Gowan, Angela S.; Hamilton, Jacqueline D.; Radakovich, Amy L.;
A County Geologic Atlas project is a study of a county's geology, and its mineral and ground-water resources. The information collected during the project is used to develop maps, data-base files, and reports. This same information is also produced as digital files for use with computers. The map information is formatted as geographic information system (GIS) files with associated data bases. The maps and reports are also reproduced as portable document files (PDFs) that can be opened on virtually any computer using the free Acrobat Reader from Adobe.com.
C-59, Geologic Atlas of Pipestone County, Minnesota
(Minnesota Geological Survey, 2024) Retzler, Andrew J.; Mayer, Jordan A.; Bradley, Margeurite C.; Chandler, Val W.; Severson, Allison R.; Jirsa, Mark A.; Conrad, Daniel R.; Gowan, Angela S.; Van Berkel, Jordan T.; Francis, Sarah W.
A County Geologic Atlas project is a study of a county's geology and its mineral and groundwater resources. The information collected during the project is digitized and used to develop maps and database files. The map information is formatted as geographic information system (GIS) files with associated databases. The maps and reports are also reproduced as portable document files (PDFs).
Information Circular 20. Aggregate Resources Inventory, Twin Cities Metropolitan Area, Minnesota
(Minnesota Geological Survey, 1984) Meyer, Gary N.; Jirsa, Mark A.
Aggregate is derived from two major sources in the seven-county area. Surficial deposits of sand and gravel, or "natural" aggregate, are the primary source. These are deposits of rock detritus broken down and sorted by the actions of glacial ice and running water. A second and increasingly important source is carbonate (limestone and dolomite) bedrock, which is converted to aggregate by blasting and crushing. Because ongoing urban development both restricts access to sources of aggregate and requires more aggregate for construction, a report was published by the Metropolitan Council of the Twin Cities area as an aid for industrial and governmental planners dealing with the problems of aggregate supply and demand. The plates and Appendix A of that report summarized the data in this information circular.
Information Circular 22. Analytical Results of the Public Geologic Sample Program, 1983-1985 Biennium
(Minnesota Geological Survey, 1985) Morey, G.B.; McSwiggen, Peter L.; Kuhns, Mary Jo P.; Jirsa, Mark A.
In 1983 the Minnesota Geological Survey, in conjunction with the Minnesota Department of Natural Resources, Division of Minerals, began a geologic sample program whereby the general public was encouraged to submit samples of geologic material for identification and possible analysis. The program was roughly patterned after a similar program in Finland. The Finnish program has resulted in a heightened public interest in the mineral potential of that country and has resulted in the discovery of several ore deposits. It was for those reasons, as well as the potential increase in geologic knowledge that could result, that a similar program was initiated in Minnesota. As originally conceived, the geologic sample program was to focus on samples submitted to the Minnesota Geological Survey by the general public. As part of its public service function, the Survey was to identify and classify rock or mineral samples that were collected in the state. If any of the samples were thought to have potential scientific or economic interest, they were to be submitted for chemical analyses or other appropriate tests. A copy of a brochure that was prepared to advertise the program is shown in Figure 1, and the sample submittal form that sets forth the operating conditions for the program is shown in Figure 2. The brochure and other publicity about the program led to requests for 238 submittal forms and to approximately 500 walk-in and telephone requests for additional information. Unfortunately, of the more than 700 inquiries, only 9 samples were ultimately judged suitable for additional chemical analysis (Table 1). The "suitability" rate of only slightly more than 1 percent was due to a number of factors. Many people only became aware of the program very late in the biennium. Other people who had samples of scientific or economic interest were unwilling to submit those samples to the Geological Survey for several reasons, including (a) the expense of mailing samples, (b) an unwillingness to part with a "prized" specimen, or (c) a lack of knowledge about mineral rights (i.e., a fear of jeopardizing their rights by revealing the location of a sample). However the great majority of samples were submitted by individuals who simply wanted them identified without concern as to possible scientific or economic value. Because of the sluggish public response, the program was modified in early 1985 to include samples of scientific or economic interest that were submitted by personnel of the Minnesota Department of Natural Resources, Division of Minerals, or the Minnesota Geological Survey. This programmatic change led to the additional analysis of 304 samples from various components of the Early Proterozoic Animikie basin on the Mesabi and Cuyuna ranges and in east-central Minnesota (Tables 2, 3, 4, and 7) and from various poorly known rock units in southwestern (Tables 5 and 8) and southeastern Minnesota (Tables 6 and 9).
Information Circular 26. Scientific Core Drilling in Parts of Koochiching, Itasca, and Beltrami Counties, North-Central Minnesota, 1987-1989: Summary of Lithological, Geochemical, and Geophysical Results
(Minnesota Geological Survey, 1989) Boerboom, Terrence J.; Jirsa, Mark A.; Southwick, D.L.; Meints, Joyce P.; Campbell, Frederick K.
This report summarizes the results of scientific core drilling undertaken primarily to gain a better understanding of the bedrock geology in north-central Minnesota. The drilling and concomitant mapping were supported by the Minerals Diversification Program of the state legislature. The study area lies in southern Koochiching, northern Itasca and east-central Beltrami Counties. This region was selected because data are suggestive of mineral resource potential, but existing geologic maps were too generalized to guide private minerals exploration efforts. The thick cover of glacial deposits in this region requires bedrock geologic mapping to be based largely on the interpretation of geophysical maps. Core drilling and outcrop mapping identify the rock types responsible for the geophysical patterns. It is hoped that geologic mapping by this method will encourage private minerals exploration. In addition, this mapping is an acceleration of on-going efforts by the Minnesota Geological Survey to produce accurate geologic maps of the state to meet existing and future societal, academic and economic needs. The resulting bedrock geologic map at 1:250,000 scale has been released as Minnesota Geological Survey Open-File Report 89-1 which is being reviewed before formal publication. In the course of the drilling program much information was acquired regarding the thickness and lithology of Quaternary surficial deposits and the locally thick weathered bedrock materials (regolith). No formal plans exist at this time to publish an interpretation of these data, but the data are presented here on the geologic logs.
Information Circular 37. Scientific Core Drilling in Parts of Itasca, St. Louis, and Lake Counties, Northeastern Minnesota, 1989-1991
(Minnesota Geological Survey, 1993) Meints, Joyce P.; Jirsa, Mark A.; Chandler, V.W.; Miller, James D., Jr.
This information circular is the fifth since 1980 to report on the basic results of test drilling (Fig. 1) by the Minnesota Geological Survey (MGS). As with the previous projects, this test drilling was conducted primarily to provide a better understanding of the Precambrian geology in areas of Minnesota where bedrock is covered by variable thicknesses of glaciogenic sediment, and thus could not be thoroughly mapped by standard outcrop mapping and sampling procedures. The drilling summarized here was conducted during 1989-1991 in areas where the bedrock is locally well exposed, but where exposures are separated by covered terrane. Thus, the selection of drill targets was constrained largely by the interpretation of geophysical surveys (Chandler, 1983a, b). Our procedure is to formulate a regional geologic interpretation based on geophysical maps, new and existing outcrop data and the archived records of previous drilling, and then to constrain and test the interpretation by selective drilling. The results have been incorporated into new geologic maps of the region including Jirsa and others (1991) and Southwick (in prep.). An important secondary objective of this project is to describe the Quaternary deposits that overlie bedrock, though no systematic regional interpretation of those deposits has been undertaken to date. This report summarizes the results of studies in two areas of vastly different geology: 1) Archean and Early Proterozoic rocks of the Cook area in west-central St. Louis and eastern Itasca Counties, and 2) Middle Proterozoic rocks of the central Duluth Complex in parts of St. Louis and Lake Counties. The geology of each area is summarized in the "results" section of this report.
Information Circular 40. Scientific and Exploration Drilling in Northwestern Minnesota
(Minnesota Geological Survey, 1993) Jirsa, Mark A.; Boerboom, Terrence J.
Scientific test drilling in northwestern Minnesota was undertaken by the Minnesota Geological Survey (MGS) primarily to elucidate the geology of Precambrian and Phanerozoic bedrock in this area where the bedrock is buried beneath several hundred feet of Quaternary glacial sediment. The results of this drilling of 23 holes, and of selected logging, and analyses of the approximately 80 archived records and core from previous drilling, are presented in this report. These data, in conjunction with various geophysical maps, were utilized by the authors and others to construct a series of new geologic maps of northwestern Minnesota that are part of MGS Open-File Report 93- lA (Jirsa and others, 1993). Parts of that report will soon be published in the MGS Miscellaneous Map Series. An important secondary objective of this project is to describe the Quaternary deposits that overlie bedrock, though no systematic regional interpretation of those deposits has been undertaken to date. This is the seventh information circular since 1980 to report the results of test drilling by the Minnesota Geological Survey. Figure 1 shows the areas covered by those earlier studies in relation to this study area in northwestern Minnesota.
Information Circular 42. Scientific Test Drilling and Mapping in East-Central Minnesota, 1994-1995: Summary of Lithologic Results
(Minnesota Geological Survey, 1997) Jirsa, Mark A.; Chandler, V.W.
This report summarizes the results of test drilling, outcrop mapping, and geophysical analyses conducted by the Minnesota Geological Survey (MGS) in east-central Minnesota (Fig. 1). It is a companion to MGS Open-File Report 95-1 Jirsa, and others, 1995a). The results reported here, along with information from water-well records; exploration, engineering, and scientific test drilling; and existing geophysical maps, were used to construct the open-file map and the geological description in the following section. The western part of the map relies heavily on the interpretations of Boerboom and others (1995). Because geophysical data and interpretations played an essential role in targeting drill-hole locations and creating the geologic map, they are presented in a separate publication (Chandler and Jirsa, in preparation). This study focused on the Archean and Early Proterozoic geology of east-central Minnesota, which was some of the least understood in Minnesota. Previous interpretations depicted the area as largely Penokean granitoid intrusions. This work indicates that much of the area is indeed granitic; however, gravity and aeromagnetic data, and results given here, provide new insight about diverse rock types and complex structures that are also present. In addition, the study provided valuable stratigraphic information about the Middle Proterozoic (Keweenawan), Paleozoic, and Cretaceous bedrock, Quaternary glacial sediments, and the nature of boundaries between these strata.
Lake Superior-Born of Fire and Ice
(Minnesota Geological Survey, 2000) Miller, James D., Jr.; Jirsa, Mark A.; Leversedge, Phillip
Set of panels designed as an explanation of the geology along Shovel Point Trail in Tettegouche State Park.
M-191 Bedrock Geology of the Western Gunflint Trail Area, Northeastern Minnesota
(Minnesota Geological Survey, 2011) Jirsa, Mark A.
M-192 Bedrock Geology of the Crane Lake and Brule Narrows 30' X 60' Quadrangles, Northern Minnesota
(Minnesota Geological Survey, 2011) Jirsa, Mark A.
M-197 Bedrock Geology of the International Falls and LittleFork 30' x 60' Quadrangles, northern Minnesota
(Minnesota Geological Survey, 2014-09-25) Jirsa, Mark A.; Boerboom, Terrence J.; Chandler, V.W.
The map depicts a complex history of volcanism, sedimentation, intrusion, multiple events of migmatization involving partial melting and melt dispersion, and several periods of deformation and metamorphism. It lies within the southern exposed extent of the Archean Superior Province. In northern Minnesota, the province is divided into three major tectonomagmatic terranes known as the Wabigoon, Quetico, and Wawa subprovinces. The publication shows the locations of mapped bedrock outcrops, structural measurements, interpreted bedrock geology in both map and cross-section views, and associated explanations. Ancillary imagery includes maps of regional geologic setting, index of archived mapping incorporated into this interpretation, and schematic depiction of geologic history.
RI-30 Interflow Sedimentary Rocks in the Keweenawan North Shore Volcanic Group, Northeastern Minnesota
(Minnesota Geological Survey, 1984) Jirsa, Mark A.
Interflow sedimentary rocks occur as lenticular units and crevice fillings between and within lavas of the North Shore Volcanic Group (Keweenawan Supergroup, middle Proterozoic age) of northern Minnesota. Individual sedimentary units range in thickness from a few centimeters to 75 m. They consist of reddish, fine-grained, well-sorted sandstone, and lesser amounts of conglomerate, breccia, shale, and tuff. Much of the sandstone is either lithic arkose or feldspathic lithic arenite. Major framework constituents include calcic plagioclase, mafic to felsic volcanic rock fragments and pyroxene. Fragments of agate, chert, and shale are present in minor amounts. Heavy minerals include magnetite, pyroxene, apatite, altered olivine, zircon, and sphene. The major cement and replacement minerals are zeolites, calcite, quartz, chlorite, epidote, prehnite, and hematite. The distribution of secondary minerals is zonal and presumably related to burial metamorphic processes. Although the predominant source for the sedimentary rocks was the intercalated lava flows themselves, some Archean, lower Proterozoic, and older Keweenawan rocks contributed minor amounts of detritus. Detritus derived from pre-Keweenawan rocks is most abundant in the lower interflow units near the present extremities of Keweenawan exposures. This implies that the volcanic rocks may not have extended very far past the present outcrop limits during the early part of sedimentary deposition. Sedimentary structures and paleocurrent measurements indicate that most units were deposited by streams that flowed generally toward the present Lake Superior basin. Paleocontours and stratigraphic and areal variations in rock type imply that some of the deposition occurred in two northeast trending sub-basins, probably separated by a basement high.
S-21 Geologic Map of Minnesota-Bedrock Geology
(Minnesota Geological Survey, 2011) Jirsa, Mark A.; Boerboom, Terrence J.; Chandler, V.W.; Mossler, John H.; Runkel, Anthony C.; Setterholm, Dale R.
This map is a new construct that incorporates existing geologic maps where prior mappers had adequate ground control, and new interpretations based on drill hole, geophysical, and unpublished data where they did not. The interpretation differs significantly from previous maps to reflect new data and accommodate scale. It portrays our current geologic understanding of the temporal and geographic distribution of units within major Precambrian terranes and of the Phanerozoic strata. The western part of the mapped Precambrian terrane is inferred largely from geophysical maps, anchored locally by drilling. In many places, contacts are drawn between units of the same or similar apparent rock type (and same unit label); these are recognized as geometrically distinct, though geophysically or lithologically similar. Digital files corresponding to this map allow removal of Cretaceous, Paleozoic, and some parts of Mesoproterozoic strata to reveal an interpretation of the underlying Precambrian bedrock. For additional data see: (http://hdl.handle.net/11299/98043 [select, copy and paste into browser]) which contains files associated with Bedrock Topography, Depth to Bedrock, and locations of Outcrop and Geochronologic analyses.

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