Abstracts - 2002

An Algonquin Shoreline in Southern Lake Michigan, Part II
Capps, D.K., Department of Geological Sciences, Indiana University, Bloomington, IN 47405.

Three former shorelines are present in northwest Indiana arcing along the southern boundary of modern-day Lake Michigan. These shorelines are the Glenwood (reference elevation of 195m [AMSL]), Calumet (189m), and the Toleston (183m) Beaches. They are differentiated by their geomorphic position, topography, stratigraphy, and radiocarbon ages. Algonquin shorelines, well-documented relict shorelines observed elsewhere throughout the Great Lakes, have not been recognized along southern Lake Michigan.

Recent data based on a series of 19 vibracores taken along transects at four locations in northwest Indiana indicate a previously unidentified shoreline position. This shoreline is located lakeward of the Calumet Beach. It is represented by basal foreshore deposits ranging in elevation from 183 to 187 m east of Deep River and by a pronounced erosional scarp cut directly into till at an elevation of 183 to 186 m west of Deep River. Samples collected from a peat found below foreshore deposits at Dune Acres, Indiana, yield 14C dates from the base, within, and top of 11,130 (±140), 10,570 (±50), and 10,740 (±130) years, respectively. These Algonquin dates, along with basal foreshore elevations and geomorphic position provide evidence for the existence of a high-level Algonquin shoreline along southern Lake Michigan.

The above data suggest that current isostatic rebound models, which place the Algonquin shoreline deposits below modern lake-level, are not adequately representing basin warping in southern Lake Michigan. The hinge model of Goldthwait (1908), which corresponds with modern lake-level gauge records, may better represent Lake Michigan basin rheology. This research establishes the Algonquin phase of ancestral Lake Michigan as a high-level water plane along southern Lake Michigan. The lake-level curve for southern Lake Michigan will need to be redrawn in order to accommodate the Algonquin shoreline features.

Planning Field Work in Southern Indiana with GIS
Adam M. Davis, Department of Geological Sciences, Indiana University, Bloomington, IN

Digital mapping techniques can be very helpful in planning field work associated with geological research. Geographic Information Systems (GIS) can combine many of these techniques, facilitating the use of background information and preliminary data to aid in finding research directions, hypothesis generation, planning field work, and sampling design. These GIS powers have been leveraged to plan a study of the geological controls on vegetation in Southern Indiana. By displaying background information and previous work together in a geographic context, GIS has helped elucidate patterns in the data that have helped with hypothesis generation, and subsequently field site selection and sampling design.

Initially, map patterns of bedrock, soils, landforms, and vegetation led to hypotheses regarding geological control on vegetation patterns. Then, to determine the best places in Southern Indiana to study geological influences on plant distributions, a targeting exercise was done with a GIS. The exercise revealed that some locations are more ideal than others for examining these influences. After the field sites are chosen, GIS facilitates experimentation with different sampling schemes and ways of specifying the sampling locations. For Southern Indiana sites, sampling locations are being selected with the help of grids and random numbers as well as several reference digital map layers. As the study progresses, GIS can help with stratified sampling of landforms, geological units, soil types, or hydrostratigraphic units.

Geographical Targeting techniques are helping to elucidate field sites and sample locations for an examination of geological influences on vegetation patterns in Southern Indiana. GIS have been used to help generate hypotheses, target field sites for study, plan field work, and choose sample locations.

A Methodology for Determining Palygorskite Presence in Sedminetary Rocks: A Study of Eight Samples from the Late Cretaceous Caribbean Region and Their Paleoclimate Significance
Ernest L. Johnson III
Indiana University Department of Geological Sciences, Bloomington, Indiana 47405

Palygorskite-sepiolite clays (palygorskite or attapulgite, sepiolite, pilolite, loughlinite, franclandite, etc) form in arid to semi-arid regions including perimarine facies (Callen, R. 1984). Singer (1980) suggested that palygorskites are neoformational with conditions of formation being alkaline pH, high Si and Mg, and low Al activity. Therefore, these clay minerals may be useful paleoclimatic indicators (Weaver and Beck, 1977; Millot, 1964; Singer, 1979, 1980, 1981). Results from eight samples from late Cretaceous sediments in the Caribbean region are presented here along with the method used to determine presence of palygorskites.

The methodology for determining the presence of palygorskites is the focus of this research project. X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) are the two tools used to determine the composition of the samples.

Raw samples were reduced to <2m (U.S.G.S. flow chart). Clay minerals are typically concentrated in the <2m size fraction. The <2m samples were then processed through three stages: 1. Air dried, 2. Treated with ethylene glycol, 3. Heated to 400°C. These treatments enabled the clay mineral structures to be confirmed since different clay minerals respond differently to these treatments. The samples containing possible palygorskite/sepiolite spacings have diagnostic tubular morphologies and were viewed under SEM.

Insight into Beach Ridge Formation Using Ground Penetrating Radar
JOHNSTON, John W., Dept. of Geol. Sci., Bloomington, IN 47405; THOMPSON, Todd A., Ind. Geol. Surv., Indiana Univ., 611 N. Walnut Grove, Bloomington, IN 47405; BAEDKE, Steve J., James Madison Univ., Dept. of Geol. and Env. Sci., Harrisonburg, VA 22807.

The internal architecture and formation of lacustrine beach ridges has long been a topic of debate, partly owing to the lack of continuous data through the ridges and their complex stratigraphy. Past interpretations were based on correlating isolated information from strategically placed vibracores across beach ridges. Today, ground penetrating radar (GPR) provides a method to view inside ridges and collect continuous data to define and correlate sedimentary units within beach ridges.

Baedke and Thompson (1995) proposed a theoretical model explaining beach ridge development as a product of changing rates of sediment supply and water level change. This model was based on information from numerous vibracores and current shoreline processes. Thompson and Baedke (1995) redrew the Curray (1964) diagram, focusing on the positive rate of sediment supply side of the diagram and placing importance on water level changes crossing the aggradation line for the development of individual beach ridges. Some of these theoretical ideas of beach ridge formation and shoreline development have been verified using GPR.

Several continuous GPR reflection surveys were collected across beach ridges in three embayments along the Lake Superior shoreline (Grand Traverse Bay, Tahquamenon Bay, and Au Train Bay). Digital GPR data was collected using a Noggin 250 SmartCart with a fixed 250 MHz antennae and a recording interval of 5 cm between traces. The depth of penetration was from 5 to 8 m. Information from vibracores were used to estimate the velocity of the radar signal and calibrate the GPR data before processing. Beach ridge topography was measured using a transit and used to correct GPR lines.

Although each beach ridge has a unique GPR signature, they all contain a series of lakeward-dipping reflectors and a strong concave reflector that extends lakeward from the base of swales. The strong reflector is interpreted as an erosional surface (ravinement) created during lake-level rises while the other reflectors are interpreted as the offlapping part of the progradational development of beach ridges.

Biogeochemical Pathways Leading to Selenium Enrichment in Upper Cretaceous Marine Strata
THOMAS R. KULP; Advisor: LISA M. PRATT
Indiana University Department of Geological Sciences, Bloomington, Indiana 47405

In geologic materials selenium occurs in various oxidation states (6, 4, 0, -2), mineralized forms, and organo-Se complexes. Each form is characterized by unique properties of solubility, toxicity, and bioavailability. Pathways in the global biogeochemical cycle of Se include volcanic eruption, weathering in terrestrial environments, and discharge of dissolved oxyanions to the marine environment. The sedimentary sequestration of this bioreactive element is primarily accomplished by biological transformations of dissolved oxyanions to insoluble, reduced forms either via assimilatory reduction by plants and algae or through anaerobic respiration by microbes. The Campanian Smoky Hill Member (Niobrara Formation) and the Sharon Springs Member (Pierre Shale) of the Great Plains were deposited in an extensive epicontinental seaway during an interval of enhanced, explosive volcanism on the western continental margin. These stratigraphic units are comprised of organic rich chalks and shales that are some of the most selenium-enriched stratigraphic intervals known, with Se concentrations exceeding values typical for sedimentary material by several orders of magnitude (commonly >30ppm). We used sequential extraction methodologies and HG-AAS to quantify the chemical speciation of selenium in these rocks among seven operationally defined fractions (water-soluble, ligand-exchangeable, adsorbed, elemental, carbonate, metallic, and organic). Our findings suggest that algal assimilation of dissolved species was the predominant process of sedimentary Se sequestration, and thus represents a likely pathway for the incorporation of excess selenium into the Western Interior Seaway ecosystem.

Influence of Maturity and Organic Matter Types on Hydrogen Exchangeability and Carbon and Hydrogen Isotopic Signatures: Example from the New Albany Shale
Lis, Grzegorz¹, Werner-Zwanziger, Ulrike², Schimmelmann, Arndt^1$, and Mastalerz, Maria^3$
(1) Department of Geological Sciences, Indiana Univ, 1001 E. 10th St. Bloomington, IN 47405-1405, (2) Department of Chemistry, Indiana Univ, 800 E. Kirkwood Avenue Bloomington, IN 47405, (3) Indiana Geological Survey, Indiana Univ, 611 North Walnut Grove, Bloomington, IN 47405
$=advisors

A suite of New Albany Shale (Devonian and Mississippian) samples from the Illinois Basin containing different types of organic matter, with vitrinite reflectance (Ro) from 0.29 to 1.4%, has been analyzed using 13C CP-MAS NMR, FTIR, carbon and hydrogen isotopic ratios, as well as organic hydrogen isotopic exchangeability (Hex). Thermal maturity was first specified via Ro, then evaluated using NMR and FTIR. There is a good correlation (R2~0.8) among all three independent parameters for thermal maturity. Carbon isotopic values of the kerogens range from -27.4 to -30.8‰ and do not correlate either with thermal maturity or with maceral composition. Values of dD of isotopically nonexchangeable organic hydrogen range from -125‰ (Ro=0.29) to -67‰ (Ro=1.27) and exhibit a linear trend towards enrichment in deuterium with increasing maturity. This trend may indicate thermally mediated interchange between D-depleted organic hydrogen and relatively D-enriched formation water hydrogen. The abundance of exchangeable organic hydrogen decreases from 7.3% to 2.4% with Ro increasing up to 0.6%, followed by a reverse trend of increasing Hex up to 6.6% at higher Ro. No clear relationship has been noted between hydrogen exchangeability and hydrogen isotopic values and petrographic composition, (for example, proportions of alginite and amorphinite) of kerogen.

Tracking Biodegradation of Crude Oils in the Illinois Basin through Geochemical Analysis: A Field Experiment
Sarah Pietraszek-Mattner, Department of Geological Sciences, Indiana University, Bloomington, IN 47403. -- Advisor: Lisa Pratt

Tar sands, marine petroleum seeps and seep mineralization are well documented, but these types of seeps represent site-specific phenomena. In contrast, small amounts of petroleum are constantly and unobtrusively seeping at the earth's surface in continental settings. Organic matter is being recycled continually during the normal degradation of these surface seeps, but trace-level residuals are usually masked by vegetation and soil making them difficult to detect. In the Illinois basin, there is an unusual opportunity to study the fate of these seeps. This mid-continental petroleum-rich basin is home to world-class open-pit limestone quarries in which migrating petroleum is exposed, thus providing a window to investigate the fate of continental petroleum seeps.

This project tracks the biodegradation of Illinois basin crude oils (obtained from well heads) at the surface of the earth in a relatively homogeneous soil plot, simulating first surface exposure of seep oils. The field experimental samples have been allowed to degrade for four months and have been retrieved for analysis at intervals of weeks to months. Geochemical signatures of these samples have been determined using gas chromatography (GC), GC-mass spectroscopy and stable carbon isotope analysis. The incremental results of these degradation experiments are compared with the geochemistry of the seep oils (which record various stages of degradation under natural conditions).

Provenance Comparison of Two Illinois Basin Crude Oils
McKendry, Michael
Advisors: Pratt, L.M., and Pietraszek-Mattner, S.R., Dept. of Geological Sciences, Indiana University, Bloomington, IN, 47405-2208
March 1, 2002

Two oils from a producing well in southeastern Indiana were received for analysis. While the oils are known to be from the Illinois Basin, both their age and source are unknown. Either the two oils are from the same source and exhibit different stages of degradation, or they are from different source rocks. The oils have exhibited viscosity differences, which may be due to variations in degradation or different source rock origins.

Using Gas Chromatography and Mass Spectroscopy, the geochemistry between these oils will be compared to determine if they share the same source rock origin. Through column chromatography the hydrocarbon fractions were separated using hexane, toluene, and methanol for the saturated, aromatic and N-S-O fractions respectively. Soluble "salts" present in the oils were dissolved in water to allow the hydrocarbon fractions to be extracted using dichloromethane (DCM). The n-alkane chromatographic pattern of each oil sample will be compared to the three know patterns of Illinois Basin oils derived from three source rocks: (1) New Albany Group, (2) Champlainian Rocks and (3) Maquoketa Group. Biomarkers from both the saturated and aromatic fractions will be analyzed to establish a correlation or non-correlation between the two samples.

Research Proposal: Determination of PGE Source Origin at Birch Lake, Minnesota Using Oxygen and Sulfur Isotopes
Paual Shafer, Department of Geological Sciences, Indiana University, Bloomington, IN, 47405; Ed Ripley, Advisor

The Birch Lake deposit, within the Duluth Complex of northeastern Minnesota, has shown high levels of PGE (platinum group elements) in recent exploratory drill cores. Platinum and palladium assays range from nearly zero up to 8 ppm, eight times the economic limit in such deposits. Initial thin section study has indicated that the Bushveld Complex in South Africa can be used as an analog for the Birch Lake deposit, though the source of the Birch Lake PGE is in some doubt. The layered mafic intrusives containing the PGE intruded through the Biwabik Iron Formation during emplacement, approximately 1.1 Ga. This poses the question of whether or not the PGE within the layered mafics are strictly mantle derived, or if the PGE are a mixing product between mantle mafics and continental rocks of the Biwabik Iron Formation. Determination of the PGE source will be made using d 18O values of mineral separates (plagioclase and oxides) taken from core samples, and sulfur isotopes taken from any minor, visible sulfide phases therein. This will allow partial determination of the extent of mixing within the intrusion, and point to the PGE source. Oxygen isotope work will also help focus the scope of further research into the extent of mixing by determining which areas, or drill cores, could be used for detailed Re-Os analyses to fully determine the possible extent of source mixing. This can then be used for other avenues of research in the deposit, such as the relationship between the PGE and chromite within ore zones and the possible relationship to visible chlorine droplets within the drill core.

Paleoecological Data Analysis of the Lower Bangor Limestone, Fox Trap, Alabama
Laura L. Slade, Indiana University, Department of Geological Sciences, 1001 East 10th St., Bloomington, IN 47405

In 1978 Dr. Johnny A. Waters analyzed an erosional outlier of the lower Bangor Limestone (Chesterian) in Fox Trap, Alabama for faunal composition and community evolution. Trophically, a single community was interpreted as a typical middle-upper Paleozoic suspension feeding association. In this study, Waters' interpretation of a single community indicating a change from nearshore to offshore environments is tested with a variety of multivariate techniques including cluster analysis, polar ordination, and correspondence analysis. The resulting clusters, ordinations, and plots of the fossil abundances from the sampled beds are hypothesized to represent actual faunal associations and environmental gradients. The specific purpose for using cluster analysis with this data set is to delineate distinct associations of taxa and identify stratigraphic beds correlating with the clusters of taxa. Groups from a cluster analysis of the same data were plotted on the polar ordination in order to define distinct associations of beds or taxa. The evaluation of this comparison revealed three groups of taxa and three groups of beds that are understood to represent nearshore, transitional, and offshore settings. The primary axis from the correspondence analysis is interpreted to represent an environmental gradient from nearshore to offshore conditions. In general, the lithologies of the beds increase in grain size, the abundance of gastropods and bivalves decreases, the abundance of echinoderms and bryozoans increases through the section, and brachiopods are present throughout the section. The results of this study agree with Waters' interpretation of a single but maturing community that represents a shift from a low-energy nearshore environment to a higher energy offshore environment.

Olivine Dissolution in Basaltic Magmas
Jenny Waters and Neil Whitmer

Crustal assimilation is an important process in igneous systems. Several variables factor into crustal assimilation, one factor being the dissolution rates of those silicate minerals present in the material being assimilated (i.e. country rock). Since little is known about mineral dissolution rates in high temperature basaltic magmas it is impossible to infer how country rock will react with the intruding magma. It is necessary to determine mineral dissolution rates in basaltic melts to better understand crustal assimilation. Spheres of a single olivine composition (San Carlos, Fo 90) were dissolved at one atmosphere in a high temperature furnace. Two different basalts of known compositions were used at several different temperatures (Olivine Tholeiite Basalt at 1225, 1250, 1275°C; Alkali Olivine Basalt at 1275, 1300°C). The diameter of a spherical olivine crystal was measured, placed in 0.25 grams of powdered basalt and pressed into a pellet. The pellet was then suspended from a platinum loop and placed into the furnace at a specific temperature and for a specific amount of time. The experimental charge was then removed from the furnace, quenched to a glass and thin-sectioned. The size of the sphere was measured again and the difference in size was used to calculate a dissolution rate. For a given basalt at a given temperature the following rates were calculated.

Olivine Tholeiite Basalt		Alkali Olivine Basalt
Temperature (°C)	Dissolution Rate (cm/sec)	Temperature (°C)	Dissolution Rate (cm/sec)
1225	3.1x10-7	1275	1.3x10-6
1250	3.6x10-7	1300	2.14x10-6
1275	1.19x10-6

These data show that, for a given basalt composition, the dissolution rate increases with increasing temperature. At 1275°C the two basalts yield different dissolution rates implying that basaltic composition is an important factor in dissolution rates.