Browsing by Subject "stratigraphy"
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Item Aquifer and Stratigraphy Code Prediction Using a Random Forest Classifier: An Exploration of Minnesota’s County Well Index(2021-05) Thielsen, ChrisWe live in an era of big data, brought on by the advent of automatic large-scale data acquisition in many industries. Machine learning can be used to take advantage of large data sets, predicting otherwise unknown information from them. The Minnesota County Well Index (CWI) database contains information about wells and borings in Minnesota. While a plethora of information is recorded in CWI, some objective codes are missing. A random forest classifier is used to predict aquifer and stratigraphy codes in CWI based on the data provided in drillers’ logs; i.e., before the strata are interpreted by a geologist. We find that by learning from the information written down by the well driller, stratigraphic codes can be predicted with an accuracy of 92.15%. There are 2,600,000 strata recorded in CWI; these codes are not only useful in understanding the geologic history of Minnesota, but also directly inform groundwater models.Item Bulletin No. 38. The Stratigraphy and Structure of the Mesabi Range, Minnesota(Minnesota Geological Survey, 1954) White, David A.The later Precambrian Animikie group in northeastern Minnesota consists of three sedimentary units: the Pokegama (quartzite), Biwabik (iron-rich rock), and Virginia (argillite) formations. "Mesabi range" designates the preglacial outcrop belt, 1/4 to 3 miles wide and 120 miles long, of the Biwabik formation. Varieties of iron-rich rock ("taconite") are either granular or slaty and consist dominantly of chert, iron silicates, magnetite, and siderite. The Lower Cherty, Lower Slaty, Upper Cherty, and Upper Slaty members of the Biwabik formation, which averages 600 feet in thickness, can be further subdivided as shown on a detailed longitudinal stratigraphic section. These members are fairly uniform along most of the range, but only one cherty and one slaty member exist on the Westernmost Mesabi, where the lithic units are intertongued. The areal distribution of rock units on the Westernmost Mesabi is shown on a geologic map. The Biwabik, Pokegama, and Virginia formations are considered conformable. Mesabi rocks probably correlate with those of the Emily district 30 miles away. Chert, greenalite, minnesotaite, stilpnomelane, magnetite, some hematite, and siderite probably formed either during deposition or diagenesis. The rocks are essentially unmetamorphosed. The Pokegama and Biwabik formations were probably produced by the migration of a series of coexisting environments of deposition during an advance, a retreat, and a second advance of the Animikie sea. The deposits formed, during the retreat, in successive environments seaward from shore, were clastic material, carbonaceous-pyritic mud, chert-siderite, chert-magnetite, and iron silicate. Fine clastics of the Virginia formation, perhaps furnished by an outburst of volcanic activity, spread across the former environments of chemical sedimentation. Possible conditions of iron sedimentation were as follows: derivation of iron and silica by weathering of a low-lying land mass, perhaps under an atmosphere rich in carbon dioxide, and a seasonal climate; tectonic stability; and deposition in a shallow, quiescent epicontinental sea. The Animikie beds strike about N. 75 degrees E. and commonly dip 6-12 degrees SE. A structure contour map on the base. of the Biwabik formation shows numerous small anticlines, synclines, monoclines, and faults. Three major joint sets are present. The few rocks intrusive into the Biwabik formation include diabase sills, the Duluth gabbro, and the Aurora syenite sill. Contact metamorphism by the soda-rich Aurora sill has produced crocidolite in adjacent taconite. Minor internal folding of Animikie beds seems to be more prevalent where the underlying rocks are volcanic or sedimentary rather than granitic. The Mesabi range is covered by glacial drift which thickens southward, commonly from 20 to 200 feet, away from a ridge known as the Giants Range. Drift is as much as 500 feet thick over the Westernmost Mesabi. A map of the thickness of drift shows many drift-buried preglacial bedrock valleys that extend from notches in the Giants Range southward across the Mesabi range. Cretaceous iron-ore conglomerates, which at places overlie the Biwabik formation, occur as erosional remnants on bedrock ridges. The scattered soft iron-ore bodies in the Biwabik formation are residual concentrates of oxidized iron minerals formed by the leaching of silica from the chert and iron silicates in taconite. Conditions favoring ore concentration are thought to be as follows: accentuated fracturing at folds and faults allowing ready circulation of leaching solutions; a high iron content in taconite; reducing rather than oxidizing conditions of deposition of the original taconite; the fine size of the grains in taconite and the intimate intermixing of different minerals; a lack of metamorphism, which coarsens the grain; and the availability of large amounts of solutions. The soft ores may have been concentrated by downward-circulating ground waters.Item C-39, Geologic Atlas of Washington County, Minnesota(Minnesota Geologica Survey, 2016) Bauer, Emily J.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.Item C-41, Geologic Atlas of Hubbard County, Minnesota(Minnesota Geological Survey, 2018) Lusardi, Barbara AA 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.Item C-45, Geologic Atlas of Hennepin County, Minnesota(Minnesota Geological Survey, 2018-12) Steenberg, Julia R.; Bauer, Emily J; Chandler, V.W.; Retzler, Andrew J; Berthold, Angela J; Lively, Richard SA 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. Note: Bedrock surfaces rasters and the Atlas Users guide were updated (updated_files.zip) 04/01/19.Item C-50, Geologic Atlas of Dodge County, Minnesota(Minnesota Geological Survey, 2019) Steenberg, Julia, RA 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.Item Guidebook 13. Field Trip Guidebook for the Archean and Proterozoic Stratigraphy of the Great Lakes Area, United States and Canada(Minnesota Geological Survey, 1979) Morey, G.B.This guidebook is prepared for the field excursion accompanying the Fifth Meeting of the International Union of Geological Sciences Subcommission on Precambrian Stratigraphy, to be held September 4-19, 1979, in the Great Lakes area, United states and Canada. Separate segments of the guidebook were prepared by the various field trip leaders and assembled by G. B. Morey, editor. M. J. Frarey coordinated the separate contributions for the Canadian part of the field excursion. The main purpose of the field excursion is to examine classic Precambrian sequences in the Lake Huron and Lake Superior regions, as a background for discussions on possible subdivision of the Archean and Proterozoic. The field excursion will be followed by technical sessions held in the Duluth, Minnesota, area.Item Guidebook 22. Field Trip Guidebook Landforms, Stratigraphy, and Lithologic Characteristics of Glacial Deposits in Central Minnesota(Minnesota Geological Survey, 2006) Knaeble, A.R.This guidebook was prepared for the 50th Midwest Friends of the Pleistocene Field Conference, sponsored by the Minnesota Geological Survey and held at St. John's University on June 4-6, 2004. The purpose of this guidebook is to provide conference participants with an up-to-date general summary of the glacial geology of central Minnesota and a comprehensive reference list of previous research completed in the area. There are a number of reasons why we were motivated to host the Friends of the Pleistocene in central Minnesota. First, over the last 10 years the Minnesota Geological Survey has completed numerous mapping projects in the central Minnesota area (Steams, Pope, and Crow Wing County atlases; the Otter Tail regional hydrogeological assessment; and the USGS Statemap St. Cloud, Baxter, Brainerd, and Gull Lake quadrangle maps), and is in the process of completing mapping projects in Todd, Traverse, and Grant Counties. The large volume of data (samples and descriptions from outcrops and drill holes) collected from these projects has allowed us to evaluate the work done by previous researchers and contribute new insights and interpretations. Second, in 1954 Herb Wright, AI Schneider, and Harold Ameman led the 5th Midwest Friends of the Pleistocene field trip in central Minnesota. We will revisit the area, on this 50th anniversary of that trip, to examine how interpretations have changed and evolved. The guidebook will use a simple, direct approach to summarize the region's glacial geology, similar to that used in 1954. It is our intention to pay tribute to the accomplishments of Herb and AI during the field trip and banquet. We will also acknowledge other researchers who, over the last 50 years, have made contributions to the glacial geology of central Minnesota. Third, we would like to discuss how mapping techniques and technology have changed in the last 50 years. We will examine which techniques have been most effective in understanding the complex stratigraphy of central Minnesota. Finally, field exposures were selected to stimulate interest and discussion about the following glacial topics: erosion, transport, and deposition of source-area materials; processes involved in drumlin formation; the relationship between ice dynamics and glacial landforms; processes important in the formation of the St. Croix moraine; and the challenges of interpreting thick, complex drift stratigraphy. These stops highlight geomorphic features, stratigraphic relationships, and specific unit characteristics (lithology, color, etc.) in an attempt to provide an overview of the glacial geology of this region.Item Guidebook 7. Field Trip Guide Book for Geomorphology and Quaternary Stratigraphy of Western Minnesota and Eastern South Dakota(Minnesota Geological Survey, 1972) Matsch, C.L.; Tipton, Merlin; Steece, F.; Rutford, R.H.; Parham, W.E.The land surface of eastern South Dakota and southwestern Minnesota is underlain mainly by sediments of Quaternary age, and most of the land forms themselves are the result of erosional and depositional events that were closely controlled by climatic fluctuations during the Pleistocene Epoch. As a result of climatic changes, glacier ice advanced and retreated across the region, leaving a complicated stratigraphy of glacier-derived sediments. So recently did the last glacier deteriorate that the present landscape still retains the forms impressed by that complicated process. Even though geologists have been studying the Quaternary sediments of the region for almost 100 years, their interpretations are still controversial. Fundamental questions still incompletely answered are (1) how many drift sheets are present?; (2) where do the drifts fit into the mid-continent Quaternary time scale?; and (3) what is the surface distribution of each of the major drift units? During the last two decades the availability of aerial photography and topographic maps has facilitated detailed surface mapping projects. Absolute age determinations have been helpful in establishing a chronology for events during the last 40,000 years. The recognition, definition and tracing of lithostratigraphic units, begun several years ago, have added new dimensions to Quaternary studies in the region.Item Guidebook 9. Field Trip Guidebook for Stratigraphy, Structure and Mineral Resources of East-Central Minnesota(Minnesota Geological Survey, 1979) Morey, G.B.; Davidson, D.M. JrEarly in the 20th century, east-central Minnesota became the source of appreciable quantities of iron and ferromanganese, and even earlier, the source of a variety of granite products (Morey, 1977). Because of the obvious economic importance of the commodities to the state, most of the geologic work in east-central Minnesota focused on the Cuyuna iron-mining district or on the St. Cloud area where there are numerous granite quarries. Less attention was given to the geology of other parts of east-central Minnesota and to the possible presence of other mineral resources. This was true mainly because a fairly ubiquitous mantle of Quaternary materials made it difficult, time consuming and expensive for a company to establish the basic geologic information necessary to a successful exploration program. However, recent geologic work (Morey, 1978) has led to the recognition of several geologic environments that are similar to mineral-producing districts elsewhere in the world (Morey, 1977). Although these studies have shown that a variety of mineral occurrences may exist, most attention to date has focused on environments that may contain uranium. This road log starts at the Minnesota-Wisconsin border along the st. Louis River near Fond du Lac, the westernmost suburb of Duluth, Minnesota, and terminates near Sturgeon Lake on U.S. Interstate Highway 35 some 50 miles southwest of Duluth. Note that the mileages in this road log are approximate.Item OFR15-01, HYDRAULIC CONDUCTIVITY AND HYDROSTRATIGRAPHY OF THE PLATTEVILLE FORMATION, TWIN CITIES METROPOLITAN AREA, MINNESOTA(Minnesota Geological Survey, 2015) Runkel, Anthony C.; Steenberg, Julia R.; Tipping, Robert G.; Jansen, Steve; Retzler, Andrew J.This report synthesizes a large body of data that provide a better understanding of the hydrogeologic characteristics of the Ordovician Platteville Formation in the Twin Cities Metropolitan Area (TCMA). The carbonate-dominated Platteville Formation plays an important role in the TCMA hydrogeologic system by limiting vertical infiltration of relatively recent water to the more commonly utilized aquifers beneath it. Furthermore, it has been impacted by numerous contaminant plumes, which threaten the water quality in domestic wells and the large number (dozens) of springs along the Mississippi River and its tributaries. Hydraulic conductivity data are synthesized and interpreted across a range of scales, with the recognition of variable user needs. For example, generalized bulk hydraulic conductivity for parts of the Platteville Formation may be useful for modeling water budgets through relatively large areas. In contrast, more site-specific needs such as development of remediation strategies and prediction of flow paths may be facilitated by considering the large range in hydraulic conductivity, measured at a number of scales, and by recognizing the location of fast-flow secondary pore networks as well as key aquitards.Item OFR18-02, Stratigraphic Positions of Springs in Southeast Minnesota(Minnesota Geological Survey, 2018) Steenberg, Julia R; Runkel, Anthony CSprings are places where groundwater is returned naturally to the surface and are a place to study the state of the groundwater in the aquifer system. In southeast Minnesota, springs are outlets in a conduit flow system in both carbonate and siliciclastic bedrock formations. They provide baseflow for streams and are a critical source of cold, relatively constant temperature water for trout. This report and associated database summarizes the results of various projects, inquiries, and studies over the years during which MGS staff investigated the location and stratigraphic position of southeastern Minnesota springs. It was produced as part of a contract between MDNR and MGS. The primary contract deliverable is a GIS feature class that contains the essential data from our hydrostratigraphic work. We have also placed notes associated with many of our interpretations into Appendix A of this report.Item OFR19-02, Geochemical Analysis of Till From Minnesota Drill Cores(Minnesota Geological Survey, 2019) Thorleifson, L.H.; Conrad, D.R.; Staley, A.E.Compositional analysis of texture and very coarse sand lithology have been used to support characterization of till properties, and interpretation of correlation, process, and provenance. In 2007, results were released for more thorough compositional analyses of near-surface till samples collected statewide. Quaternary stratigraphic efforts are now focused on information needed to support regional groundwater management. To support that effort, till from selected rotasonic cores extending to tens of meters depth were submitted in 2018 and 2019 for geochemical analysis following the method used for part of the 2007 study - four-acid leach of air dry <63 micron fraction followed by ICP. Examples of elements that correlated to provenance are As in shale-rich till, Ca in carbonate-rich till, Na in shield-derived till, and Fe in Lake Superior-derived till. All data are here provided as a reference.