Wisconsin Geological and Natural History Survey

Mineral Point, WI, United States

Wisconsin Geological and Natural History Survey

Mineral Point, WI, United States
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Cramer B.D.,Ohio State University | Kleffner M.A.,Ohio State University | Brett C.E.,University of Cincinnati | McLaughlin P.I.,Wisconsin Geological and Natural History Survey | And 3 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

The Wenlock Epoch of the Silurian Period has become one of the chronostratigraphically best-constrained intervals of the Paleozoic. The integration of multiple chronostratigraphic tools, such as conodont and graptolite biostratigraphy, sequence stratigraphy, and δ13Ccarb chemostratigraphy, has greatly improved global chronostratigraphic correlation and portions of the Wenlock can now be correlated with precision better than ±100kyr. Additionally, such detailed and integrated chronostratigraphy provides an opportunity to evaluate the fidelity of individual chronostratigraphic tools. Here, we use conodont biostratigraphy, sequence stratigraphy and carbon isotope (δ13Ccarb) chemostratigraphy to demonstrate that the conodont Kockelella walliseri, an important guide fossil for middle and upper Sheinwoodian strata (lower stage of the Wenlock Series), first appears at least one full stratigraphic sequence lower in Laurentia than in Baltica. Rather than serving as a demonstration of the unreliability of conodont biostratigraphy, this example serves to demonstrate the promise of high-resolution Paleozoic stratigraphy. The temporal difference between the two first occurrences was likely less than 1million years, and although it is conceptually understood that speciation and colonization must have been non-instantaneous events, Paleozoic paleobiogeographic variability on such short timescales (tens to hundreds of kyr) traditionally has been ignored or considered to be of little practical importance. The expansion of high-resolution Paleozoic stratigraphy in the future will require robust biostratigraphic zonations that embrace the integration of multiple chronostratigraphic tools as well as the paleobiogeographic variability in ranges that they will inevitably demonstrate. In addition, a better understanding of the paleobiogeographic migration histories of marine organisms will provide a unique tool for future Paleozoic paleoceanography and paleobiology research. © 2010 Elsevier B.V.

McLaughlin P.I.,Wisconsin Geological and Natural History Survey | Emsbo P.,U.S. Geological Survey | Brett C.E.,University of Cincinnati
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2012

Episodes of instability in the global climato-oceanic system have become the hallmark of the Silurian Period. These events are marked by six large positive carbon isotope excursions associated with major extinctions. The widespread environmental consequences of these perturbations of the global carbon cycle remain poorly documented. A high-resolution chronostratigraphic reconstruction of the Appalachian foreland basin (AFB) provides a framework to evaluate environmental signatures of two of these carbon isotope excursions (Valgu and Ireviken events; Telychian-Sheinwoodian) at a regional scale. Integration of published biostratigraphic range data, mapping of sequence stratigraphic surfaces and facies, and generation of high-resolution carbon isotope profiles for several transects provides precise correlation of the basin stratigraphy yielding a high-resolution temporal framework. This chronostratigraphic reconstruction of the AFB highlights the importance of time-specific facies (TSF) during these intervals. For instance, packages of red, green, and gray marine rocks separately occupied discrete time intervals-cutting across "local" facies belts indicative of shallow to deep marine environments. Similarly, widespread iron mineralization occurred during discreet time slices as "bathtub rings" rimming the margins of the basin. Changes from one time-specific facies to the next are coincident with changes in carbon isotope values, indicating a genetic link between fractionation of the global carbon reservoir and redox changes from generally oxic to anoxic oceanic conditions in parts of the AFB. The basal part of the study interval was deposited during the Valgu Event. This first event begins with an unconformity marking global lowstand. This fall in sea level was coincident with rising carbon isotope values as recorded in adjacent basins. A slight sea level rise and flooding of the subaerial unconformity occurred near the peak in carbon isotope values. Oxidized iron minerals were deposited in a zone that extended from the lower shoreface into the basin center-pinching out into shallower parts of the basin. Thin pyrite-phosphorite-glauconite layers, associated with black shales in the basin center, were deposited over these ferruginous strata. As the event ended and carbon isotope values shifted negatively to a more stable baseline, temperatures warmed, sea level reached a Silurian high, and oxic conditions associated with very low rates of organic carbon (OC) burial were established. These conditions were relatively stable for nearly four million years. This long period of stasis was punctuated by the Ireviken Event, which displays a strikingly similar progression of TSF patterns, yet more intense and longer lived than the preceding Valgu Event. With the first positive shift in carbon isotopes at the onset of the Ireviken Event, the basin redox system changed from largely oxidizing to reducing, coincident with a rapid drop in sea level and an abrupt reappearance of iron mineralization on the basin margins. The sea level fall associated with the shift to peak values of the carbon isotope excursion is marked by the progradation of a significant body of sand well out into the basin. During this sea level drop, conditions in the basin center became highly reducing and periodically sulfidic. Widespread ironstones and ankeritic carbonates were deposited isochronously, rimming the shallow basin margins where they alternated with light gray pyritic shales, indicating fluctuating redox conditions. A large negative carbon isotope excursion of ~. 3‰ is coincident with a shift from regression to transgression, suggesting glacial melting via methane release. Continued deposition of ironstones through this time interval suggests a primary link to shallow marine redox processes rather than large-scale transgression or regression of the shoreline. The ironstones are overlain by gray to black pyritic shales deposited across all environments, revealing a final stage of redox progression into sustained sulfidic conditions as peak values of the carbon isotope excursion returned to a high stable baseline near + 4‰. The similar expression of TSFs within the AFB of these two global events demonstrates that fractionation of the global atmospheric and oceanic carbon reservoirs had a predictable, cascading impact on shallow sea floor environments. The associated redox processes reveal the dynamic regional interactions of a shallow oxic epicontinental water mass with a broader anoxic oceanic water mass, providing valuable insight into the origin of some of the largest extinctions in the Silurian Period. © 2012 Elsevier B.V.

Leaf A.T.,SoundEarth Strategies | Hart D.J.,Wisconsin Geological and Natural History Survey | Bahr J.M.,University of Wisconsin - Madison
Ground Water | Year: 2012

Subsurface heterogeneity in hydraulic properties and processes is a fundamental challenge in hydrogeology. We have developed an improved method of borehole dilution testing for hydrostratigraphic characterization, in which distributed temperature sensing (DTS) is used to monitor advective heat movement. DTS offers many advantages over conventional technologies including response times in the order of seconds rather than minutes, the ability to profile temperature synoptically in a well without disturbing the fluid column, sensitivity to a wider range of flow rates than conventional spinner and heat pulse flow meters, and the ease of interpretation. Open-well thermal dilution tests in two multiaquifer wells near Madison, Wisconsin, provided detailed information on the borehole flow regimes, including flow rates and the locations of inflows from both fractures and porous media. The results led to an enhanced understanding of flow in a hydrostratigraphic unit previously conceptualized as homogenous and isotropic. © 2012, The Author(s). Ground Water © 2012, National Ground Water Association.

Schaetzl R.J.,Michigan State University | Attig J.W.,Wisconsin Geological and Natural History Survey
Quaternary Research (United States) | Year: 2013

We present the first study of the distribution, genesis and paleoenvironmental significance of late Pleistocene loess in northeastern Wisconsin and adjacent parts of Michigan's Upper Peninsula. Loess here is commonly 25-70. cm thick. Upland areas that were deglaciated early and remained geomorphically stable preferentially accumulated loess by providing sites that were efficient at trapping and retaining eolian sediment. Data from 419 such sites indicate that the loess was mainly derived from proglacial outwash plains and, to a lesser extent, hummocky end moraines within and near the region, particularly those toward the east of the loess deposits. Most of the loess was transported on katabatic winds coming off the ice sheet, which entrained and transported both silt and fine sands. The loess fines markedly, and is better sorted, distal to these source regions. Only minimal amounts of loess were deposited in this area via westerly winds. This research (1) reinforces the observation that outwash plains and end moraines can be significant loess sources, (2) provides evidence for katabatic winds as significant eolian transport vectors, and (3) demonstrates that the loess record may be variously preserved across landscapes, depending on where and when geomorphically stable sites became available for loess accumulation. © 2012 University of Washington.

Schaetzl R.J.,Michigan State University | Forman S.L.,University of Illinois at Chicago | Attig J.W.,Wisconsin Geological and Natural History Survey
Quaternary Research (United States) | Year: 2014

We present textural and thickness data on loess from 125 upland sites in west-central Wisconsin, which confirm that most of this loess was derived from the sandy outwash surfaces of the Chippewa River and its tributaries, which drained the Chippewa Lobe of the Laurentide front during the Wisconsin glaciation (MIS 2). On bedrock uplands southeast of the widest outwash surfaces in the Chippewa River valley, this loess attains thicknesses >. 5. m. OSL ages on this loess constrain the advance of the Laurentide ice from the Lake Superior basin and into west-central Wisconsin, at which time its meltwater started flowing down the Chippewa drainage. The oldest MAR OSL age, 23.8. ka, from basal loess on bedrock, agrees with the established, but otherwise weakly constrained, regional glacial chronology. Basal ages from four other sites range from 13.2 to 18.5. ka, pointing to the likelihood that these sites remained geomorphically unstable and did not accumulate loess until considerably later in the loess depositional interval. Other OSL ages from this loess, taken higher in the stratigraphic column but below the depth of pedoturbation, range to nearly 13. ka, suggesting that the Chippewa River valley may have remained a loess source for several millennia. © 2013 University of Washington.

Brett C.E.,University of Cincinnati | McLaughlin P.I.,Wisconsin Geological and Natural History Survey | Histon K.,University of Modena and Reggio Emilia | Schindler E.,Senckenberg Forschungsinstitut und Naturmuseum Frankfurt | Ferretti A.,University of Modena and Reggio Emilia
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2012

The term "time-specific facies" (TSF) was introduced to the scientific community by the late Otto H. Walliser to refer to unique facies typical of particular narrow intervals, some of which were related to bioevents. In some senses, however, the concept was recognized much earlier and is even engrained in the very names of some geologic periods. The concept of time-specific facies is expanded slightly herein to include distinctive or unique regional to global characteristics of the sedimentary record that characterize particular intervals of geologic time. The recognition of time-specific and widespread processes in the sedimentary record is a critical step in unraveling the interplay between processes of differing scale. These range from very short-term, but widespread facies that overlap with event deposits, to general facies types that may persist for intervals up to 10s of millions of years in duration. This paper briefly summarizes the history of development of the TSF concept, provides examples to illustrate a few of the key aspects of time-specific facies and offers a few tentative explanations for this phenomenon. Among the factors that control TSFs, abrupt changes in redox conditions and early diagenetic mineralization, sedimentary condensation, often associated with abrupt sea level change, altered climate and paleoceanography, and biotic evolution and extinction seem to be most critical and permit a preliminary genetic classification of TSFs. Inevitably, however, many TSFs reflect multiple effects and some remain largely unexplained. © 2012 Elsevier B.V.

In many regions of the world, crystalline bedrock aquifers are the only choice for groundwater supply. This is the case in northern Wisconsin, located in the upper Midwest of the continental United States. Here, groundwater flow to wells occurs only through fractures in the granitic basement. Although hydrofracturing of these wells is common and generally increases well yield, the precise mechanism for the increased yields remained unknown. Stressed and ambient flow logs were obtained in two 305-m-deep granitic boreholes in northern Wisconsin prior to hydrofracturing. From those logs, it was determined that nearly all of the groundwater flow to the boreholes occurred in less than 10 fractures in the upper 80 m, with no measureable contribution below that depth. Following hydrofracturing of the boreholes, stressed and ambient flow logs were again obtained. The transmissivity of the two boreholes increased by factors of 8.6 and 63 times. It was found that (1) the fractures that had contributed flow to the boreholes increased in transmissivity, (2) although the applied pressures were large enough in some instances to create new fractures, those new fractures did not increase the borehole transmissivities significantly, and (3) fractures without measureable flow before hydrofracturing remained without measureable flow. Hydrofracturing increases yield in granitic boreholes; however, that increase seems to only occur in fractures where flow was pre-existing and in the upper 80 m of the boreholes. These observations suggest that efforts to enhance yield in granitic aquifers should be focused on the upper part of the borehole. © 2015, Springer-Verlag Berlin Heidelberg.

Carter J.T.,Currently at Barr Engineering Company | Gotkowitz M.B.,Wisconsin Geological and Natural History Survey | Anderson M.P.,University of Wisconsin - Madison
Ground Water | Year: 2011

Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale-and-dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30-m-thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4-year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water-table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi-aquifer wells and groundwater withdrawal in perched systems can further alter such pathways. © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

Hart D.J.,Wisconsin Geological and Natural History Survey | Wang H.F.,University of Wisconsin - Madison
Geophysics | Year: 2010

Gassmann's original equation provides a means to relate bulk elastic parameters of a porous material with the compressibility of the pore fluid. The original analysis assumed microhomogeneity and isotropy, which assumed that pore compressibility was equal to grain compressibility. Although subsequent theoretical arguments have shown that Gassmann's original assumption is violated for most rocks and that pore compressibility need not equal grain compressibility, few experimental studies have compared the two compressibilities; the assumption that pore compressibility equals grain compressibility is still commonly made. We measured hydrostatic poroelastic constants of Berea sandstone and Indiana limestone under drained, undrained, and unjacketed conditions over a range of confining and pore pressures to test the assumption that pore compressibility equals grain compressibility. These two rocks were chosen because they havesimilar values of porosity but different elastic behaviors: Berea sandstone is nonlinearly elastic, especially at low effective stresses, but Indiana limestone is linearly elastic at nearly all stresses. At low effective stresses below MPa, the pore compressibility for Berea sandstone does not equal grain compressibility but approaches fluid compressibility. Even at higher effective stresses, pore compressibility for Berea sandstone does not equal bulk grain compressibility but approaches a value approximately two to three times the bulk grain compressibility. In contrast, pore compressibility for Indiana limestone does seem to be equal to grain compressibility except perhaps at low effective stresses below MPa. The difference between pore compressibilities of these two rocks is likely from the presence of more compliant clay minerals mixed with quartz grains with more microcracks in the Berea sandstone as compared to the well-cemented Indiana limestone. © 2010 Society of Exploration Geophysicists.

Rayne T.W.,Hamilton College | Bradbury K.R.,Wisconsin Geological and Natural History Survey
Journal of Environmental Planning and Management | Year: 2011

Using simple numerical groundwater flow models, we tested the impacts of suburban developments on groundwater levels and discharge to streams. We used lot sizes of 1, 3 and 5 acres (4000, 12,000 and 20,000 m2) with one domestic well per lot that pumped water from shallow aquifers. Our modelling showed that pumping had little impact on water levels and groundwater discharge to streams if the developed area is of a moderate size. However, domestic wells had the potential to impact local groundwater levels and baseflows in large developments. In township-wide development scenarios of 1-acre (4000 m2) lots, simulated drawdowns beneath developed areas ranged from 1 to 18 ft (0.3 to 5.5 m), and baseflow reductions ranged from 20 to 40%. Impacts generally were inversely proportional to lot size, recharge rate and hydraulic conductivity of the aquifer materials. Developments using individual domestic wells have the potential to impact local groundwater levels and surface water features. The impacts can range from negligible to severe, depending on local hydrogeologic conditions and on whether wastewater is recharged onsite or is removed from the basin. An assessment of groundwater impacts should be a part of the planning process for all suburban developments. © 2011 University of Newcastle upon Tyne.

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