Current research projects

Currently I am involved in two somewhat related research projects in geology. We (my collaborator Dr. Dyanna Czeck at UW-Milwaukee, and my current student Michael) are studying the anastomosing shear zone network exposed near the township of Mountain in Oconto County, Northern Wisconsin. One of these projects revolves around understanding how centimeter-scale ductile shear zones originated and interacted with each other during the Penokean Orogeny about 1.8 Billion years ago. We do geologic field work to collect samples of deformed and not-so-deformed granitic rocks, map the locations and extents of "foreign" rock bodies within the granitic rocks, collect GPS data of the sample locations and plot them on the geologic map of the area using GIS. This helps us to see how the highly deformed zones are spatially related in multiple scales. We bring the samples back to lab and compare the mineralogical make-ups and chemical compositions between sheared and unsheared parts of the same hand specimens to understand why the shear deformation localized within certain parts of the host rock body. We get to use a petrographic microscope and an XRD unit... cool toys.
Michael's project involves the "foreign" rocks, which we call "Mafic Microgranular Enclaves" or MMEs. These rocks look very different from the granitic rocks around them. They could be part of the original sedimentary or metamorphic rocks that were there before the granitic magma intruded that area, or they could be part of one or more mafic intrusion(s) that came in after the granitic rocks were deformed, or those rocks could be evidence of both of these scenarios. Michael and I are currently describing and analyzing those samples and trying to separate them in groups. Eventually we will have a clearer idea about the history of those MMEs we are studying. Michael will present his research in the upcoming 2009 Geological Society of America Annual Meeting in October.

The other part of the project involves using GIS and remote sensing technologies to characterize mineral distribution patterns on hand sample scale and quantifying shear zone networks using GIS. My former student Kristin (Graduated in May '09) worked on staining granitic rocks and using image analyses techniques to determine the distribution characteristics of K-spar and plagioclase. I am at present developing that approach to study mineral distribution characteristics under microscopes. It is exciting to try out an entirely new approach for studying rocks and minerals. I am going to present this research at the 2009 Geological Society of America Annual Meeting as well.

Every member of the research group has presented their research to different professional meetings. Here is a list of our publication and presentation abstracts updated till Fall 2009.

Besides these projects I am also working on developing innovative hands-on lab activities or classroom demonstrations for teaching, incorporating GIS-based activities in courses, getting students to do authentic research in context of a course, teaching science in the context of civic and community issues, and similar education related research. Here is a list of some of my education-related publications and conference presentations.

• Bhattacharyya, Prajukti, and Czeck, Dyanna (2008): Using network analyses within geographic information system technologies to quantify geometries of shear zone networks. Geosphere, vol. 4, No. 4, 640-656
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  Shear zones often exhibit anastomosing network geometries. Previous work has shown that the detailed geometries of shear zone networks may partially control strain localization, fluid flow, rheology, and deformation mechanisms. However, there are currently no reliable tools to quantify network geometries such as the distribution of individual small shear zones and the connectedness of the network. Geographic information systems (GIS) provide a potential method for quantifying network geometries. GIS-based networking analyses have been used to quantify many different types of other networks, and here they are applied to shear zones. Many parameters within GIS-based networking analyses are useful for quantifying shear zone network geometries, including the connectivity parameters gamma and alpha, sinuosity, and vertex distribution patterns. Sets of these parameters are useful to quantitatively distinguish geometrical patterns of shear zone networks over a variety of conditions. Further quantification of shear zone network geometries may allow us to link those geometries to shear zone mechanisms, strain accumulation, and rheology.

Professional conference presentations. * indicates student presenters/co-authors

• Bhattacharyya, Prajukti, (2009): No Scale too Small: Applying Remote Sensing and Geographic Information Systems (GIS) Based Software for Quantifying Mineral Distribution Patterns on Photomicrographs. GSA Abstracts with Programs, Annual Meeting 2009, paper 144-5, October 2009.
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  Spatial variations of mineral distribution patterns can provide important information about different geological processes, such as fabric development due to deformation, strain softening, etc. This presentation describes an approach to quantify mineral distribution patterns on microscopic as well as on hand specimen scales on suitable digital images using remote sensing and GIS based software, which are commonly used to analyze and quantify landscape patterns containing a mosaic of elements (patches) belonging to different classes. Digital images best suited for these types of analyses are those on which different mineral phases are associated with specific shades of color, and thus can be grouped into different classes containing individual mineral aggregates or patches. These software can be used to quantify the areal extent of different mineral phases within an image, the shape and size of individual mineral aggregates, their nearest neighbor distances, as well as their spatial distribution characteristics, such as dispersion or connectivity of each patch in relation to other patches within the same class.

  For this work, digital photomicrographs captured under plane polarized light were used where the mineral phases could be broadly classified into a “dark” class where aggregates of hornblende grains made up more than 95% of the patches, and a “light” class including aggregates of quartz, feldspar and other colorless minerals. The images were classified using ERDAS Imagine 9.3® software, commonly used for analyzing remotely sensed images. The classified photomicrographs were analyzed using Fragstats 3.3®, which is a public domain spatial pattern analysis software program for quantifying landscape structures. Patch level metrics describing the shape, size and distribution characteristics of individual patches, and class level metrics including fragmentation, connectivity and dispersion of patches belonging to each class were calculated. A patch level attribute table was created for each analyzed image using ArcMap 9.3® software. Metrics thus obtained from photomicrographs from different parts of the same rock sample were compared to determine variations in mineral spatial patterns.

• *Siegner, Michael, and Bhattacharyya, Prajukti, (2009):Mafic Microgranular Enclaves Within Sheared Granitic Rocks in Mountain, WI. GSA Abstracts with Programs, Annual Meeting 2009, paper 258-44, October 2009.
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  Granitic plutons are commonly associated with enclaves either in the form of xenoliths or as mafic inclusions. Such enclaves can provide significant clues about the intrusive history of the granitic pluton. Abundant mafic microgranular enclaves (or MMEs) are present within a granitic body exposed in and around the Mountain Shear Zone near the township of Mountain, Oconto County, Northern Wisconsin. Previous researchers concluded that these rocks belong to the eastern part of the Pembine-Wausau Terrane which was accreted to the Superior craton during the Penokean Orogeny about 1,860-1,889 Ma ago. It has been claimed that the enclaves resulted when the studied granitic plutonic body intruded nearby mafic and felsic volcanic rocks. Both the mafic lava flow and the granitic pluton were later deformed by ductile shearing, forming amphibole schist and granitic gneiss respectively. We have observed MMEs within both the undeformed granitic protolith and its deformed counterpart.

  We have samples that are part of relatively undeformed large (10-100 meter scale) mafic enclaves within outcrops of highly deformed granitic rocks, which at times cuts across small scale ductile shear zones within granitic rock. Such field relationship might indicate that at least some of those mafic bodies might have intruded the region after the shearing event.

  In the Poster we will be present the location map of the field area from where we collected the MME samples and describe their mineralogical, chemical and grain size characteristics based upon petrographic and X-Ray diffraction(XRD) analyses. Future work will involve preparing a detailed map of the larger mafic enclaves in a few of the outcrops within deformed and undeformed granitic rocks and attempt to determine their spatial distribution characteristics with respect to the Mountain Shear Zone using GIS and GPS technologies. We will also conduct further detailed mineralogical analyses using petrographic microscopes and XRD, and chemical analyses using X-ray fluorescence (XRF) to compare different MME samples.

• *Adams, Kristin M., and Bhattacharyya, Prajukti, (2008): Spatial Distribution Characteristics of Minerals across Small Scale Ductile Shear Zones Using ERDAS Imagine and ArcMap 9.2 Software. GSA Abstracts with Programs, Annual Meeting 2008, paper 147-20, October 2008.
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  Image analyses techniques are frequently used for studying progressive changes in shapes and/or sizes of passive strain markers with deformation. However the distribution patterns of mineral phases cannot be determined using such techniques. Spatial distribution characteristics of stronger (e.g. potassium feldspar) or weaker (e.g. mica or amphibole) mineral phases may provide important information regarding deformation localization.
  In this poster we describe our attempts to combine image analyses with spatial pattern analyses of different mineral phases across centimeter scale ductile shear zones. We used ERDAS Imagine software, commonly used for analyzing remotely sensed images, in conjunction with ArcMap 9.2 software, used for geographical information systems (or GIS) analyses. Samples for this study were collected across the Mountain Shear zone, a ductile shear zone exposed near the township of Mountain, WI, which formed approximately 1.8 billion years ago. Polished slabs were cut from selected samples of sheared granitic rocks containing quartz, plagioclase, potassium feldspar, biotite, and amphiboles. Those slabs were stained with sodium cobaltinitrite and Amaranth which turned potassium feldspar grains yellow and plagioclase grains magenta respectively. The other major mineral phases, quartz (grey) and biotite/amphibole grains (black) remained unstained, thus producing four distinct color groups. Digitized images of those slabs were analyzed using ERDAS Imagine. The accuracy level of this technique for differentiating between plagioclase and potassium feldspar grains on a hand sample scale was independently checked by means of petrographic analyses. The classified images created were then opened on a GIS platform using ArcMap 9.2 software, and spatial patterns of the color-coded mineral phases were determined.
  Preliminary results show that the average size and number of potassium feldspar grains decrease with increasing deformation. Patches of fine grained plagioclase and quartz grains become progressively larger and more interconnected with distance towards the center of the shear zones.

• *Adams, Kristin M., *Aslesen, Andrew D., and Bhattacharyya, Prajukti (2007): Mineralogy and Chemistry of the Mountain Shear Zone of Northern Wisconsin. GSA Abstracts with Programs, Vol. 39, No. 3, p. 60
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  Ductile shear zones are formed when rocks change without breaking, and the causes behind shear zone formation are currently not completely understood. Our study focuses on the reasons behind the shear zone formation in Mountain, Wisconsin, located in Oconto County. The shear zone we studied was formed during the Proterozoic Penokean orogeny, and consists of granitic gneiss which has been locally intruded by basaltic dikes. The shear zone of Mountain, Wisconsin, is unique because while most of the other deformation sites in Wisconsin are covered with glacial deposition, this one is well exposed. Specimens from three different locations within the study area were collected. For samples containing small scale (several centimeters in width) shear zones, the mineralogy and chemistry of the deformed and relatively undeformed areas within the same hand sample were compared using a petrographic microscope and x-ray diffraction machine (XRD). The specimens with small dikes (centimeters in scale) that may have intruded within the shear zones were also mineralogically and chemically studied and compared with data from sheared samples to determine whether mineralogical or chemical heterogeneity due to the dike intrusion had any effect on deformation.

• Bhattacharyya, Prajukti, and Czeck, Dyanna (2006): Using GIS technology for fabric analyses in structural geology. GSA Abstracts with Programs, Vol. 38, No. 7, p. 19, paper 3-9, October 2006
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  Fabric analysis is an important part of structural studies and can be used to determine deformation history in regional-scale shear zones and tectonites. Fabric analysis is most powerful when a variety of fabric elements including foliations, lineations, small-scale shear zones, and shear bands are considered simultaneously. Here, we present an approach to fabric analyses using GIS techniques. For this study, we selected one orthogneiss outcrop within the Mountain Shear Zone in Oconto County, WI.
  The orthogneiss contains several generations of cross-cutting fabrics defined by alignment of biotite and hornblende. The fabrics exposed at this outcrop include a pervasive, subvertical foliation locally reoriented by centimeter scale anastomosing shear zones with varying orientations and discrete, millimeter scale shear zones. Other fabric elements include mafic enclaves and veins. Unfortunately, on much of the outcrop, these fabrics and structural elements are indistinguishable due to weathering or lichen cover.
  With the use of tape and compass, we constructed a local reference frame of 6 meters by 6 meters and recorded GPS coordinates for the corner points using a Trimble TSC1 datalogger and Asset Surveyor software with submetric accuracy. Where visible, we color coded and traced fabric elements onto transparent plastic sheets, which were oriented with respect to the local reference frame. We digitized the tracings into GIS by means of a digitizing tablet and digital photographs and created GIS layers for each group of fabric elements. Using the Spatial Analysis tools included in the ESRI ArcGIS 9 package, we characterized attributes including circular variance, sinuosity, and connectivity of the different fabrics. We also determined likely orientations of fabrics in the areas where they are not exposed.
  Our study shows promise for the use of GIS in future structural fabric studies. The spatial statistical tools in GIS allow us to further our understanding of fabric evolution and the linkages between fabric elements. It is possible to create detailed maps of various structural features, use standard data modeling to interpolate data in unexposed areas, and statistically determine spatial correlations between various structural features.

• Bhattacharyya, Prajukti, and Czeck, Dyanna (2005): Causes of shear localization and shear zone geometry in Precambrian granitic rocks. GSA Abstracts with Programs, Vol. 37, No. 7, paper 208-6, October 2005
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  The causes of deformation localization within ductile shear zones and the manner in which discrete ductile shear zones interact with each other to maintain strain compatibility are not yet clearly understood. The probable causes of shear localization are studied in deformed granitic rocks exposed around Mountain, Oconto county, northeastern WI. These rocks were subjected to multiple deformational events post-dating the major Penokean orogenic event in this region. In these rocks, zones of little or no apparent deformation contain clusters of mafic minerals such as amphibole and biotite. These less deformed zones are surrounded by anastomosing ductile shear zones. The shear zones are typically associated with higher concentrations of the mafic minerals and smaller grain size. Here we explore the role of pre existing mafic minerals in shear localization and in developing shear zone geometry within these rocks. Preliminary results show that within the less deformed regions, there are aggregates of bioitite and amphibole with random shape preferred orientation. The concentrated deformation bands are dark colored and have fine grain size. They are comprised mostly of distinctly smaller grains of quartz and feldspar, and the amphibole and biotite clusters do not necessarily form a preferred alignment as one would expect if they were either rigid or passive particles during deformation. One possible explanation for this may be due to recrystallization of these grains during or post deformation. Further work may demonstrate whether the chemistry of the shear zones is significantly distinct from the surrounding rocks. The shear zone localization may be geometrically and/or lithologically controlled.

Undergraduate conference presentations

• *Adams, Kristin M., and Bhattacharyya, Prajukti, (2009): Using ERDAS® Imagine Software to Determine the Spatial Distribution Characteristics of Minerals across Ductile Shear Zones. Student presentation at the 23rd. National Conference of Undergraduate Research (NCUR), April 16-18, 2009
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  Ductile shear zones are formed when rocks deform without breaking. The purpose of this study is to understand the relationship between weaker (e.g. mica or amphibole) and stronger (e.g. potassium feldspar) minerals regarding ductile deformation. This research examines the accuracy of an analysis technique using ERDAS® Imagine, software typically used for analyzing remotely sensed images, to determine spatial characteristics. We collected samples from the Mountain Shear Zone (Oconto County, Wisconsin), which was formed during the Penokean Orogeny (1.8 billion years ago), and consists of granitic rocks containing quartz, plagioclase, potassium feldspar, biotite, and amphiboles. The samples were stained using solutions of sodium cobaltinitrite and Amaranth, which turned the potassium feldspar grains yellow and plagioclase grains magenta. The other mineral phases, such as quartz and biotite/amphiboles remained their natural colors, enabling four distinct color groups. ERDAS® Imagine was then applied to analyze the digitized rock faces to quantify the results. The accuracy of this technique was determined by comparing the analyzed results to photomicrographs of the original, unstained rock face. Using petrographic identification, minerals of each of the four groups were chosen and compared to a coordinate system created from a digitized image of the original sample. Preliminary analysis shows that the new technique has a 94% confidence interval. When applied to determining the spatial characteristics across the Mountain Shear Zone, results show an inverse relationship between potassium feldspar grains and deformation, while plagioclase grains show a direct relationship.

• *Costello, Bethany J., and Bhattacharyya, Prajukti (2008): Spatial analysis of mineral grain size distribution at a Northern Wisconsin shear zone. Student presentation at 9th Annual UW System Symposium for Undergraduate Research and Creative Activity, April 25, 2008
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  Earth’s tectonic forces permanently deformed the rocks in the crust and mantle along narrow zones, called ductile shear zones, by bending them instead of actually breaking them; however, the exact mechanism that causes this weakening in the rocks is still unknown. The central goal of my research is to evaluate whether a critical concentration of smaller mineral grains in a particular area can make rocks weaker to ultimately create a shear zone,. It is important to study such shear zones to gain a better understanding of how and why they formed, which will teach us more about rock strength. I am studying a ductile shear zone that formed around 1.8 billion years ago, near the township of Mountain, in Oconto County. Shear zones of this age can potentially provide insight into the earliest mechanisms of plate tectonics on Earth. I have collected both deformed and non-deformed granite samples at various distances from the shear zone. Thin sections of the collected samples are being analyzed under a microscope so that I can take digitized micrograph images. The images are then being put into Geographic Information Systems (GIS) and a statistically significant number of individual mineral grains are being manually traced in order to create polygon shapefiles. Spatial statistical analyses on the shape files using this completely novel technique will allow me to determine the area of each mineral grain, the average grain size, pattern of grain size distribution, and whether there is a relationship between grain size and location relative to the shear zone.

• *Adams, Kristin M., *Aslesen, Andrew D., and Bhattacharyya, Prajukti (2008): Detailed quantitative analysis of variation of mineral composition in deformed and undeformed rocks from ancient orogenic boundary using ERDAS IMAGINE. Student presentation at the 22nd. National Conference of Undergraduate Research (NCUR), April 10-12, 2008
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  Ductile shear zones are formed when rocks deform without breaking. Our study focuses on the mechanisms of shear zone formation in Mountain, Wisconsin which formed during the Penokean Orogeny (1.8 billion years ago). The aim of the study is to better understand the impact of differing mineral composition on localization of shear deformation.
  Deformed and undeformed granitic rock samples were collected from different areas within the Mountain Shear Zone. Selected samples were cut and stained with sodium cobaltnitrite and Amaranth to differentiate potassium feldspars and plagioclase. Due to the staining, the potassium feldspar grains become yellow and the plagioclase grains become magenta. The other major mineral phases, quartz (grey) and darker mafic minerals (black) remained unstained, thus producing four distinct color groups which were classified and analyzed using ERDAS Imagine. We determined the different proportions of those minerals in selected deformed and undeformed samples.
  Preliminary results show a significant decrease in potassium feldspar concentration within deformed rock samples compared to the undeformed samples. This could indicate either a loss of potassium feldspar due to the shear deformation or the shear zone formed more intensely in areas where potassium feldspar, a stronger mineral phase, was initially lacking. Partially stained thin sections will be examined under a petrographic microscope to increase the confidence level of these results. Those analyses will be compared to the observations on the hand sample scale to see whether results obtained from these two independent analytical techniques are consistent with one another. The higher resolution of observation provided by microscopic analyses will also provide greater confidence in identifying minerals based on colors on a hand sample scale.

• *Aslesen, Andrew D., *Adams, Kristin M., and Bhattacharyya, Prajukti (2008): Mapping mineral alignment in a shear zone using geographic information systems (GIS). Student presentation at the 22nd. National Conference of Undergraduate Research (NCUR), April 10-12, 2008
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  Plate tectonics causes rocks to move and change shape, sometimes they change shape without breaking, forming structures called ductile shear zone. The exact reason why certain rocks form shear zones as opposed to others is not clearly understood at this time. The purpose of our research is to gain a better understanding of what causes these deformations in rocks. Our research is focused on the Mountain Shear Zone exposed near the town of Mountain, Wisconsin. This shear zone was formed between 1.8 and 2 billion years ago through plate collision. Most similar shear zones in Wisconsin are now buried under glacial sediment, so the exposure of the Mountain Shear Zone provides a unique opportunity to study rock deformation that took place deep underground. The methods we are using to study mineral alignment in the rocks include an optical microscope and GIS. We are exploring the spatial distribution of deformed minerals within and around the shear zone. Our goal is to see how mineral grain size and alignment changes with respect to the shear zone. This could provide more information regarding possible causes of shear zone formation. We collected deformed and undeformed granitic rock samples from the field area, and determined sample locations using handheld GPS units. We plotted the locations on the geologic map using ArcMap9.2 to correlate the distance from the shear zone with mineral alignment and grain size. These results in combination with mineral alignment analyses on petrographic thin sections from the same samples using GIS and/or remote sensing software are presented here.

• *Aslesen, Andrew D., *Adams, Kristin M., and Bhattacharyya, Prajukti (2007): Ductile deformation in the Mountain Shear Zone of Northern Wisconsin. Student presentation at the 21st. National Conference of Undergraduate Research (NCUR), April 12-14, 2007
  Show/hide abstract
  Plate tectonics causes rocks to move and change shape. Sometimes they change shape without breaking, forming structures called ductile shear zone. The exact reason why certain rocks form shear zones as opposed to others is not clearly understood at this time. The purpose of my research is to gain a better understanding of what causes these deformations in rocks. I am using an optical microscope and an x-ray diffraction machine (XRD) to analyze the mineral composition of rocks within and around the shear zones exposed near the town of Mountain in Northeastern Wisconsin. These shear zones were formed between 1.8 and 2 billion years ago through plate collision. Most of these shear zones are now buried under glacial sediment, so the exposure of the Mountain Shear Zone provides a unique opportunity to study rock formations that are deformed deep underground. I am exploring whether there is a difference in mineral composition between the minerals within and outside the shear zones, and whether they cause the shear zones to form. The results will help us understand more about the effects of mineral composition on rock strength.

Selected professional conference presentations.* indicates student presenters/co-authors

• Bhattacharyya, Prajukti, (2009):Meeting SENCER ideals through authentic student research projects in a general education non-lab science course.SENCER Summer Institute 2009 Poster Abstract Volume

• Bhattacharyya, Prajukti, (2007): Incorporating GIS-based Authentic research activities in a lecture-based geology course for non-majors. GSA Abstracts with Programs Vol. 39, No. 6, paper 213-14, P579, October 2007

• Bhattacharyya, Prajukti, and Czeck, Dyanna (2005): Can the academic performance of athletes in science courses be related to their learning styles? GSA Abstracts with Programs, Vol. 37, No. 5, May 2005

• Bhattacharyya, Prajukti, and Branlund, Joy (2004): Learning outside the classroom: Assignments that encourage students to think critically about subject matter. GSA Annual Meeting Abstracts with Programs, Vol. 36, No. 5, page 277, November 2004

• *Henderson, Naomi M. and Bhattacharyya, Prajukti (2004): Nuclear waste management: educational models. GSA Abstracts with Programs, Vol. 36, No. 3, March 2004

• Bhattacharyya, Prajukti (2004): Learning style surveys as a tool to increase student participation in lecture based classrooms. GSA Abstracts with Programs, Vol. 36, No. 3, March 2004