Geoscience Colloquia for Spring 2011 Semester

DanielHolm_sm_cropThursday February 24, 2011 4 PM
Dr. Daniel Holm
Professor Kent State University
Title: Proterozoic Formation, Growth, and Evolution of Laurentia, Upper Great Lakes Region: A NICE Perspective

The Upper Great Lakes region of the North American mid-continent has served as a pioneering area for Precambrian research and as a natural laboratory for countless students of geology throughout the past century. Lying along the southern margin of the Canadian Shield, this area preserves a uniquely important record of construction and stabilization of a continent during the Proterozoic. In the recent decade, an abundant amount of new data have resulted in refinement of, and even significant reinterpretation of, the region's Proterozoic tectonic and crustal evolution. The rich and complex geologic history chronicles an important progression of southward tectonic growth and crustal stabilization following breakup of the Neoarchean Superior Province at ca. 2.2-2.1 Ga. A compilation of aeromagnetic and isotopic data, interpreted in conjunction with geologic bedrock 'ground-truth' reveals fundamental tectonic, structural, and thermochronologic boundaries that reflect important differences between Archean and newly accreted Proterozoic lithospheric rheologies. Additionally, the breakup architecture had an important influence on the subsequent accretionary history. The protracted accretionary history broadly mimic that for Proterozoic growth of the southwest U.S. The diminishing influence of subsequent metamorphic and plutonic events in the continental interior likely reflects the southward migration of the supercontinent's active margin during Laurentia's construction. The northern interior continental evolution (NICE) suggests that within a few hundred million years of its formation and growth, the characteristics of a cratonized lithosphere appear to have been firmly established.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

ELG_Argentina_cropThursday March 3, 2011 4 PM
Dr. Erik Gulbranson
Post-doctoral Researcher, UWM
Title: Paleo-Isotope Ecology: understanding polar ecosystems in deep time

Climate predictions for the next century suggest that forested ecosystems of the northern hemisphere will expand poleward as thresholds for these ecosystems are reached at higher latitudes, potentially resulting in radiative forcings of up to 1.5 W m-2 K-1 from positive feedbacks between the biosphere and atmosphere.

The possibility of forests in polar regions raises questions on how photosynthesis operates in an environment with months of continuous light and months of continuous darkness? Will polar soils continue to sequester the same amount of carbon under a vibrant forested ecosystem? We have no modern analogue to study these problems. And the climate scenario for the next century is so different from much of the Neogene that it necessitates investigations into deep time archives of climate and ecology to understand how polar forests interact with and influence climate and how these ecosystems participate in the terrestrial cycle carbon.

In this talk I present a methodology to study ancient polar forests from an Earth systems approach that explicitly links soils, plants, and climate through biogeochemical and paleobotanical techniques. I will explore two time intervals that maintained forests at polar latitudes: the Permian and Triassic of Antarctica, and the Eocene of the Canadian Arctic. These case studies will address (1) how the application of isotope geochemistry and paleobotanical techniques can reveal new insights into ancient terrestrial ecosystems, (2) the nature of the carbon cycle and hydrologic cycle at polar latitudes, and (3) the potential impact that polar ecosystems have on climate.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

dan_peplinski_1_cropThursday March 10, 2011 4 PM
Dan Peplinski, P.E., P.G.
Layne Hydro - a division of Layne Christensen Company
Title: Using geologic reconnaissance and geophysical methods to identify productive bedrock fracture zones

This is a case study of an exploration program in a fractured bedrock aquifer that was performed for a community in Northeastern Illinois. High capacity supply wells utilizing the regional Silurian Dolomite aquifer typically produce between 300 to 500 gpm. However, an exploration program was performed that resulted in the development of two wells with a combined sustainable capacity of more than 2,500 gpm.

The exploration program consisted of fracture trace analysis, evaluation of specific capacity trends and surface geophysical techniques including electromagnetic induction (EM), azimuthal electrical resistivity and earth temperature profiling. Commonly, the cone of depression surrounding pumping wells that utilize these fracture systems is elongated along the identified fracture system. In this presentation, we discuss the application and results of this exploration process and present the results from similar investigations and aquifer performance tests in this type aquifer.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

me and Feldspar_cropThursday March 17, 2011 4 PM
Dr. Stephen Allard
Professor Winona State University
Title: 1.8-1.7 Ga assembling of North America as exposed in the Southeastern Wyoming Province: New thoughts on an old problem

The Black Hills of South Dakota contain the only exposure of the Southern Trans Hudson Orogen in the US. Additionally, the Black Hills lie near the truncation of the Trans Hudson by the Central Plains (Yavapai?) Orogen. This presentation will discuss how these suturing events are expressed in the Black Hills and the wider SE Wyoming Province, will expose contradictions in the data, and will suggest possible solutions.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

Kaj_JohnsonThursday April 7, 2011 4 PM
Dr. Kaj Johnson
Professor University of Indiana
Earthscope Speaker Series
Title: Potential for Earthquakes On and Off Major Faults in California

The quantity and quality of GPS measurements of surface motions in the Western U. S. has been significantly enhanced through the Earthscope Program of the National Science Foundation. A fundamental question we wish to answer with these observations is: “where is stress accumulating in the crust, and will it be released in future large earthquakes?” Answering this question is not straightforward because it requires an understanding of how observed strain accumulation at Earth’s surface relates to accumulation of stress on faults at depth. Furthermore, the current GPS surface velocity field provides only a time snapshot of surface deformation rates that vary over decadal to millennial time scales due to time-variable crustal and mantle deformation processes. Therefore, inferring potential for earthquakes on faults requires models that implement what we know about the behavior of faults in the lower crust and deformation processes in the mantle. In this talk I will show how we are using deformation models and GPS data from California to: 1) obtain estimates of long-term slip rates on major faults; 2) infer where faults are locked and accumulating stress and where faults are creeping and not accumulating stress; and 3) estimate the potential size and frequency of large earthquakes on and off major faults.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

juk_cropThursday April 14, 2011 4 PM
Dr. Prajukti (juk) Bhattacharyya
University of Wisconsin-Whitewater
Title: Unconventional uses of Remote sensing and GIS-based Software in geology

Remotely sensed images and GIS based software have been used for analyzing and quantifying landscape patterns containing a mosaic of elements (patches) belonging to different classes. These software can be used to calculate a variety of patch level, class level and landscape level metrics to quantify the areal extent of each patch type within the landscape, the shape and size of individual patches, nearest neighbor distances, as well as the spatial distribution characteristics, such as dispersion or connectivity of each patch in relation to other patches within the same class. This presentation will discuss various ways those software can potentially be used for fabric analyses at different scales.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

jichaThursday April 28, 2011 4 PM
Brian Jicha
Brian's CV (pdf; 117kb)
University of Wisconsin-Madison
Title: Deep and shallow evolution of magma beneath Volcán Santa Maria, Guatemala

The Plinian eruption in October, 1902 of 8.5 km3 of dacitic pumice and minor basaltic andesitic scoria and ash at Volcán Santa Maria in NE Guatemala violently interrupted a 25 kyr period of repose that had followed ~78 kyrs of cone-growth. To provide context for processes that ultimately led to and occurred during the 1902 eruption, geochemical, isotopic (Sr, Nd, Pb, U-series), mineralogic, and melt inclusion data from the composite cone and 1902 eruption products will be presented. The temporal pattern in trace element, Sr-Nd-Pb, and U-Th isotope data indicate that cone-forming basaltic andesite lavas record processes operating in the deep crust. Wallrock heating sufficient to induce partial melting and assimilation involved several pulses of recharging mantle-derived basalt over at least 50 kyr. U-series isotope data also provides insight into magma genesis including the nature of crustal components involved. A fundamental shift in process coincides with the termination of cone-building at 25 ka: the 1902 dacite reflects fractional crystallization of 20 km3 of basaltic andesite magma left-over following cone-building that cooled slowly without assimilating a significant amount of additional crust.

Two oxide and pyroxene thermometry reveal an oxidized (Ni-NiO+2 log units) and thermally-zoned magma body existed prior to 1902 in which basaltic andesite with 54 wt.% SiO2 at 1020 °C and dacite with 65 wt.% SiO2 at 870 °C coexisted. Plagioclase in the dacite pumice and basaltic andesite scoria shows remarkably similar zoning characterized by repeated excursions toward high anorthite and increases in Mg, Fe, and Sr associated with resorption surfaces along which dacitic to rhyolitic melt inclusions are trapped. The melt inclusions increase slightly in K2O as SiO2 increases from 69 to 77 wt.%, whereas H2O contents between 5.2 to 1.4 wt.% drop with increasing K2O. These observations suggest that crystallization of the plagioclase, and evolution of a high-silica rhyolitic residual melt, occurred mainly in the conduit as the compositionally-zoned magma body decompressed and degassed from >180 MPa, or >5 km depth, toward the surface. The similarity of plagioclase composition, zoning, and melt inclusion compositions in pumice and scoria suggest that crystals which grew initially in the cooler dacite, were exchanged between dacitic and basaltic andesitic magma as the two magmas mingled and partially mixed en route to the surface. Small contrasts in Sr-Nd-Pb ratios, and a larger difference in the (238U/230Th) activity ratio between the 1902 scoria and dacite indicate that these two magmas are not strictly cogenetic, rather this basaltic andesite is likely a recent arrival in the system. Since 1922 >1 km3 of dacitic magma similar to the 1902 pumice has erupted effusively to form the Santiaguito dome complex in the 1902 eruption crater. A 238U-230Th isochron of 9.5±2.5 ka for a 1972 Santiaguito dacite lava suggests that deeper, occluded portions of the silicic magma body not erupted in 1902 incubated in the crust for >10 kyr prior to the 1902 eruption.

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.

Pomes1_cropThursday May 5, 2011 4 PM
Mike Pomes , Ph.D., L.G.
Environmental Protection Agency
Title: From the U.S. Geological Survey to the U.S. Environmental Protection Agency, via the Kansas Department of Health and Environment: An Organic Geochemist finds a Career in Underground Storage Tanks

Efforts to step up enforcement of the requirement that owners and operators of underground storage tanks (USTs) in Kansas check the rectifiers of their impressed current cathodic protection systems started with a fire. During the early morning hours of April 30, 2006, fire consumed a five unit apartment house in Lawrence, Kan. without any loss of life. According to Lawrence Journal World press reports, occupants of the apartment building smelled gasoline before the fire broke out. Subsequent investigation determined that fumes emanating from a plume of gasoline leaking from the UST system at a nearby gas station had ignited to cause the fire. Despite being protected by an impressed current cathodic protection system, corrosion holes were found in one of the USTs following its removal. Additionally, staff at the Kansas Department of Health and Environment (KDHE) reviewed the hour meter readings on the rectifier and determined that the number of hours only accounted for five of the eight years since the installation. . . .


Changes in the delta 13-C of Humic Substances from Soils, Soil Water, Ground, and Surface Water from a Tall-Grass Prairie Watershed, Konza Prairie Research Natural Area, near Manhattan, KS

Aquatic humic substances (AHS) derived from woody vegetation and warm season prairie grass yield distinct delta 13C signatures that change as water flows off vegetation, passes through soils, and reaches ground and surface water in a prairie watershed. AHS are generally yellow-colored, high molecular weight, polyelectrolytic organic acids extractable from water using XAD resins or comparable procedures. AHS and soil HS are composed of humic acids (HA) that precipitate when the pH of a sample is lowered to 1.0, whereas, fulvic acids (FA) remain soluble. The delta 13C values for vegetation leachates and through fall for FA and HA derived from woody vegetation (-25.76 to -28.33 o/oo relative to the Peedee Belemnite) differed from that derived mainly from warm season grasses (-15.06 to -16.77 o/oo).

Lapham Hall 262
Refreshments served prior to the colloquium at 3:30 in Lapham 380.