Paleokarst and Associated Mineralization at the Linwood Mine, Scott County Iowa

Operations at the Linwood Mine in Scott County, Iowa, have exposed, on two working levels, extensive pre-Pennsylvanian paleokarst and associated sediment fillings and mineralization in Middle Devonian limestones. Cavities in Davenport-Spring Grove host rocks range up to 270 meters in length and are virtually all filled with fluviatile sediment. Cavities in Cedar Rapids host rocks, on average, are smaller and some are unfilled. Limestone dissolution was controlled by high-angle fractures with a wide variety of orientations and by bedding plane and stylolitic partings. Dissolutional features on both levels of the mine provide evidence for phreatic and vadose processes. Most of the unfilled cavities in the Cedar Rapids Limestone contain abundant mineralization, which occurs as cavity linings, fracture linings and fillings, breccia cements and disseminations in sediment fillings and cavity walls. Mineralogically, calcite is dominant, marcasite, barite and pyrite are widespread and locally abundant, sphalerite is uncommon, and chalcopyrite and quartz are rare. Calcite appears in several generations involving alternations between acute and obtuse crystal forms. Barite occurs in a wide variety of habits; multictystalline barite differs from monoctystalline barite in color and distribution within cavities. Iron sulfide precipitation began early, and continued intermittently throughout the period of the mineralization. Calcite is intermediate to late and barite is late. Distinctive features of mineralization include minerals contained wholly within mudstone, boxwork, and iron sulfide which appears to be stalactitic. Vertically, most of the mineralization occurs in the well-bedded lower part of the Cedar Rapids Limestone. Presence or absence of specific minerals, mineral distribution and paragenesis suggest that conditions during karst-filling sedimentation and mineralization were alternately reducing and oxidizing, but most of the mineralization formed during reducing (phreatic) conditions. Mineralization at Linwood shows similarities and differences when compared to other paleokarst-associated deposits in eastern Iowa. Similarities with main district upper Mississippi Valley zinc-lead deposits include broadly similar paragenesis and similarities in multiple generations of calcite

Sulfide Mineralization at Mineral Creek Mines, Allamakee County, Iowa

The Mineral Creek sulfide deposits are located in Allamakee County, Iowa on the extreme northwest fringe of the upper Mississippi Valley zinc-lead district. The ores consist of extensively weathered lead, zinc, and iron sulfides which were emplaced in areas of intense solution-collapse brecciation and along bedding plane and steeply-dipping longitudinal fractures. Mineralization appears to be localized on the crest of a NE-trending anticline, related to early Ordovician tectonism which affected NE Iowa and adjacent Wisconsin. Mineralogy and paragenesis of vein and hydrothermal alteration deposits at Mineral Creek are very similar to those of other fringe deposits in Iowa and Wisconsin. Much of the silicification (jasperoid) appears to be prehydrothermal

Hydrothermal Mineralization of the Mississippi Valley Type at the Martin-Marietta Quarry, Linn County, Iowa

A hydrothermal sulfide mineral deposit is exposed at the Martin-Marietta Quarry (MMQ) near Cedar Rapids, Iowa. Mineralization occurs along solution-enlarged vertical joints in host rocks of the Silurian Scotch Grove and Gower formations. The hydrothermal minerals in general order of deposition are: marcasite, pyrite, sphalerite, calcite. Wall rock alteration is not extensive, and consists of solution enlargement of joints and dissemination of microscopic marcasite in the host rock. Fluid inclusion homogenization temperatures for sphalerite and calcite range from 69° to 99°C. The physical mineralogical similarities between the MMQ deposit and main-district Upper Mississippi Valley hydrothermal deposits evidence cogenesis. The origin of the MMQ deposit is considered in light of the East Central Iowa Basin model of Ludvigson, et al (1983a)

Policy Paper: The Need to Enhance Victims’ Rights in the Florida Constitution to Fully Protect Crime Victims’ Rights

Given the emerging consensus concerning victims\u27 rights as reflected in many state constitutions as well as in federal law, Florida should not simply rest on the nearly thirty-year-old provison currently in its constitution. Instead, Florida should, through its established and recognized procedures, expand the protections contained in its provision to cover the rights reflected in provisions enacted across the country and reflected in Marsy\u27s Law

Midwestern Geology and Cornell College: The First 125 Years

The history of geology at Cornell College can be traced back almost to the college\u27s beginnings. Though not the first to reach geology at Cornell, William Harmon Norton, more than any other person, shaped the Department of Geology and set it on its course of excellence. Born in 1856, the son of a Methodist minister, Norton developed an ardent interest in geology in his boyhood. A graduate of Cornell in Classics, Norton was hired by his alma mater in 1876 to reach Greek, bur his avocation was geology. He spent most of his spare time on weekends and during summers studying the rocks and fossils of eastern Iowa. Norton\u27s avocation became his vocation in 1881 when he began reaching geology along with Greek. Nine years later he gave up classics and continued with geology. His skills as a keen observer, mapper, and writer were recognized by Samuel Calvin, director of the new Iowa Geological Survey, and he was hired in 1893 under the ride Special Geology\u27\u27. Norton authored several publications on the geology of eastern Iowa, including reports on the geology of Linn, Scott, Cedar and Bremer Countries. During the course of his research he recognized and described several new Silurian and Devonian formations, the names of which are currently in use. He is best known for his studies on the character and distribution of Iowa\u27s underground water resources, with publications totaling nearly 2,000 pages. His service to the Iowa Geological Survey spanned 40 years and his tenure as a teacher at Cornell 67 years. Norton\u27s legacy includes a college textbook, Elements of Geology , written in collaboration with William Morris Davis, and 6,000 lantern slides

Strippable Coal Reserves in Twelve Southern Iowa Counties

Estimates of strippable coal reserves were made for 12 counties in south-central Iowa, for the purpose of updating information regarding Iowa\u27s coal reserve base. Strippable coal here is defined as that coal occurring in seams no less than 28 inches (71 cm) thick and beneath no more than 150 feet (46 m) of overburden. Data concerning location, depth, and thickness of coal were obtained from county reports, and coal mine and water well records on file at the Iowa Geological Survey, supplemented by information from the survey\u27s coal drilling program. Extension of information outside known data points was made in accordance with procedures established by the United States Geological Survey. The all-too-frequent lack of good information about the character of Iowa coal, plus the geological complexity of the coal-bearing rock, make coal bed correlation extremely difficult and adversely affect the reliability of the estimates. About two billion tons (1.8 billion metric tons) of strippable coal are contained within the 12 counties investigated. Coal distribution maps prepared in conjunction with this study may be of value to future coal exploration in Iowa

Cathodoluminescence as a Means for Distinguishing Hydrothermal from Pre-hydrothermal Quartz in Sulfide-Bearing Mineral Deposits on the Northern Fringe of the Upper Mississippi Valley Zinc-Lead District, NE Iowa and SW Wisconsin

Sulfide-bearing mineral deposits, located on the northern fringe of the Upper Mississippi Valley Zinc-Lead District, are contained in early Ordovician carbonate rocks that are extensively silicified and dolomitized. Some silica and dolomite appear to be products of the hydrothermal processes that also formed fracture-filling and cavity-lining sulfides and other cogenetic minerals; other silica and dolomite appear to result from low-temperature, pre-hydrothermal regional diagenesis. Distinguishing hydrothermal quartz (jasperoid) from pre-hydrothermal quartz (chert) solely by hand specimen and thin section petrography is difficult because these two types of mineralization are often intimately associated with each other. Polished slabs from several of these deposits were studied using cathodoluminescence (CL). Demonstrable chert exhibits light to dark blue CL, while demonstrable jasperoid exhibits red-brown to tan CL. It appears that intimately-associated jasperoid and chert can be distinguished with CL. A result is that much of what was previously described as jasperoid in the Upper Mississippi Valley Zn-Pb District is very likely non-hydrothermal chert

Silicification of Corals, Stromatoporids, and Brachiopods at the Weathered Surface Within the Devonian-Age Little Cedar Formation (Solon and Rapid Members) in Eastern Iowa

Diagenesis of fossils contained in middle-Devonian limestones was studied at the Troy Mills and Robins quarries in Linn County, Iowa and at the Four County and Ernst quarries in Johnson County, Iowa. Fossils located at weathered bedrock surfaces were preferentially silicified, and the silicification affected corals, stromatoporids and, to a limited extent, brachiopods, but not other fossils or the host rock. The siliceous horizon extends no more than a few centimeters below the weathered surfaces, suggesting that silicification was constrained by them. Silica for silicification might have come from a variety of sources, including sponge spicules or radiolarian tests, insoluble residues (fine-grained quartz and clay minerals) contained within the host carbonate rock, sediment deposited over the area that was subsequently eroded, or from weathering and alteration of clay minerals contained in paleokarst-hosted Pennsylvanian fluviatile sediment. A change in pH or other chemical variable(s) in upward- or downward-moving fluids, at the interface between Devonian carbonate rock and adjacent Pennsylvanian fluviatile sediment, could have created an environment favorable for silica precipitation. The extent of silicification of different fossils was likely controlled by variations in permeability of skeletal material. Mineral diagenesis began with precipitation of euhedral microcrystalline calcite, followed by three types of quartz (megacrystalline quartz, chalcedony and microcrystalline quartz), and ended with anhedral coarse-grained calcite. The position in the paragenetic sequence of rare chert and dolomite could not be determined