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Geological Sciences.

Paleoenvironmental Changes Recorded in Diatom Assemblages from a Small Coastal Dune Lake Near Holland, Michigan. Trevor Daly, Geological and Environmental Sciences Department, Hope College, Holland MI

Twenty nine diatom genera have been identified in 260 cm of core representing 5600 years of deposition in Gilligan Lake: a small inland lake at the edge of the Lake Michigan coastal dune complex southwest of Holland. Fragilaria and the predominantly epiphytic Cocconeis are abundant in the lowermost core suggesting the formation of a relatively shallow, nutrient rich lake towards the end of the Nipissing transgression. A change in lake chemistry is indicated by a decrease in Fragilaria and an increase in the acidophilic group Eunotia at 200cm. For the next 5,000, years several changes in water chemistry arc marked by shifts in the relative importance of the two dominant benthic genera Eunotia and Navicula. An increase in abundance of the predominantly planktonic centric genera (Cyclotella, Melosira and Coscinodiscus) above 200 cm probably reflects an increase in depth. Smaller shifts in the relative abundances of planktonic to benthic + epiphytic diatoms may represent smaller changes in water depth or clarity. The upper 10 cm is marked by a decrease in total centric diatoms, and an increase in the relative importance of Eunotia and Melosira, potentially indicating a recent increase in nutrient levels and turbidity and a decrease in pH.

Flood Mangnitude and Velocity from Boulder Transport Data: Wadi Isal, South Sinai, Egypt. Alan E. Kehew and Adam M. Milewski, Geosciences Department, Western Michigan University, Kalamazoo, MI; Farouk Soliman, Geology Department, Suez Canal University, Eqypt.

The Wadi Isla drainage basin, a narrow steep bedrock gorge and its tributaries, heads near the highest elevations of the Precambrian South Sinai massif. The canyon has a width of 30 m where it meets the alluvial plain and a minimum width of 17 m in the lower reach of the wadi. Stream-transported boulders within the lower reach of the rock-walled wadi and in a fan at the head of the alluvial-plain indicate extremely high competence. Imbricated boulders in bars at bends in the wadi reach 5 m in diameter. One reach contains a 60-m long boulder berm along the southern wall of the canyon. The berm ranges in height from 3 to 5 m and contains boulders 2-4 m in diameter. Application of empirical formulas for velocity and the Manning equation at this location yields peak velocity and discharge values of approximately 9 m/s and 2000 m3/s, respectively. This discharge was inversely used as an input parameter in the Soil & Water Assessment Tool (SWAT) model. Preliminary results suggest that a short-lived rainfall event of 10-15 cm over the drainage basin would be necessary to generate a flood of this magnitude.

History of the Geology Section of the Michigan Academy, 1920 to 1970. Diane K. Baclawski, Michigan State University, Dept. of Geological Sciences, East Lansing, MI

The Michigan Academy of Science Arts & Letters has been an important communications medium for geoscientists since it's founding in 1894. During its first 25 years, the Section for Geology and Geography was founded and developed into an important forum for the exchange of geologic research information. Substantial contributions to the understanding of the glacial geology of Michigan and the formation of the Great Lakes were made during this initial period. In its second period of development, roughly from 1920 to 1970, the talks given in the Geology & Mineralogy Section reflect the growth of the geosciences. Presentations on structure, petroleum geology and stratigraphy demonstrate a broader application of observation and theory while paleontologists were avidly describing new species and new occurrences. Changes in Section leadership also helped move the Section to explore new areas of the geosciences.

Shock-Metamorphic Effects in Lattice Structure of Sphalerite (ZnS) from Impact Breccia in the Kentland Crater, Indiana. Heather Brusnahan and John Weber, Department of Geology, Ross Reynolds, Dept. of Physics, Grand Valley State University, Allendale, MI

The majority of published research regarding shock-metamorphic effects primarily describes changes that occur in crystalline target rocks and in the minerals quart: and calcite. The Kentland crater is <13 km in diameter, <97 my. old, and consists of highly deformed and shocked Paleozoic sedimentary target rocks. A limestone quarry located within the central uplift (40[degrees]45'N, 87[degrees]24'W) provides a unique opportunity to view and sample these shocked rocks. Distinct breccia dikes cut steeply dipping beds in the central uplift. The breccias contain abundant carbonate clasts and some sphalerite clasts. We are studying the effects of shock-metamorphism on the crystal lattice structure of the shocked sphalerite (ZnS) grains. Eight samples of breccia containing sphalerite were collected from the central uplift. The sphalerite was analyzed using X-ray powder diffraction (XRD). Bragg's equation, together with full width at half maximum (FWHM) measurements, allowed us to calculate percent change in d-spacing for the shocked samples. We ate quantitatively interpreting these changes, to use the results to contribute to a better estimate of shock batometry.

How the Evolution of World Maps Led to Ideas of Continental Drift and Plate Tectonics. Charles Barker, Department of Geology, Wayne State University, Detroit, MI

Most discussions of the history of the theory of plate tectonics begin with ideas of continental drift put forth by Alfred Wegener in the early 1900s, and possibly mention earlier concepts of matching continental coastlines by Francis Bacon in 1620 (Bacon actually did not propose drift, and described matching continental forms rather than proposing separation and movement). Many would be surprised that ideas of continental drift have been traced back to the mapmaker Abraham Ortelius in 1596, as noted by the classicist James Romm. The evolution of world maps and concepts of the form and configuration of continental landmasses were the triggers for ideas of continental drift and ultimately the theory of plate tectonics. This talk will follow the evolution of world maps throughout history from around 600 B.C., and describe their influence on concepts of the Earth and early ideas of continental drift, while acknowledging the ideas of Howard Baker as presented to the Michigan Academy of Science at meetings in 1911 and 1912.

Analysis of Probable K-T Boundary Microtektites, Mississippi Embayment, Southeastern Missouri. Kathryn Barnard and John Weber, Department of Geology, Grand Valley State University, Allendale, MI; Carl E. Campbell, St. Louis Community College--Meramec, MO

Microtektites were found at a "kitty litter" strip-mine in the K-T boundary deposits of the Mississippi Embayment in Stoddard County, Missouri. These microtektites are located in a reworked limestone coquina at the base of the Paleocene Clayton Formation between the Cretaceous Owl Creek and Paleocene Porters Creek Formations. The Clayton Formation consists of graded beds and rip-up clasts containing microtektites as well as invertebrate fossils and palynomorphs from the Owl Creek Formation. Based on sedimentology and paleontology, the Clayton Formation is interpreted to be a mega tsunami deposit associated with the now well-documented K-T Chicxulub crater in the Yucatan Peninsula, Mexico. We are studying the composition and textures of the microtektites using standard microscopy, thin-section analysis, x-ray diffraction (XRD), and microprobe analyses. Our objective is to determine whether or not these microtektites originated in the Yucatan Peninsula by comparing the geochemistry of glasses in the Missouri microtektites to that of the target rocks and impact glasses in the Chicxulub crater.

The Relationship between Silt and Clay Mineralogy and Insect Occurrence in a Shallow Aquifer. Amanda M. Brisbin and Jonathan W. Petersen, Department of Geological & Environmental Sciences, Hope College, Holland, MI.

Folsomia Candida (Fc) is an arthropod that usually occurs in leaf litter, but not groundwater. Fc was discovered in a shallow (2.5 to 5.7 m below grade) lake-plain aquifer located along the southwestern coast of Michigan. Because Fc occurrence varies between locations, the research team has attempted to find correlations with aquifer physiochemical parameters. This presentation reports on the association of Fc in groundwater with the mineralogy of the very-fine silt and clay-sized sediment at the water table. Fc feeds on fungi attached to fine particles. Two sample types were collected. One was soil boring samples; the other was suspended particles present in water samples collected from wells. Both types were separated into three distinct size fractions: 35-5 [micro]m, 5-2 pm, and < 2 [micro]m. Fractions from each location were analyzed by X-Ray diffraction. Results indicate that fine particles are primarily: quartz, dolomite, calcite, kaolinite, chlorite, goethite and giniite. Analysis indicates that occurrence of Fc can be divided into 2 different mineralogical associations: (1) Absence of Fc is associated with chlorite, dolomite or calcite, goethite, and giniite; and, (2) Abundant Fc is associated with quartz-dominated sediments that lack a carbonate phase. Further work is in progress to delineate these relationships.

Geomorphic History of the Saugatuck Dunes: Clues from an Inland Dune Lake. Sarah Dean, Geological and Environmental Sciences Dept., Hope College, Holland MI

A combination of loss on ignition and wet sieving was used to obtain the weight percent organic detritus, sand and silt/clay in vibracores from Goshorn Lake at the eastern edge of the Saugatuck coastal dune complex. A stream flows into the eastern edge of the lake 600 meters from the dunes. The western edge abuts against a large parabolic dune. Sediments horn the western edge are rich in sand while sediments from the eastern edge are dominated by organic carbon and silt/clay. This suggests that most of the sand was derived from the dunes and chat peaks in sand concentrations can be used as proxies for aeolian activity. The amount of sand in the western core increases in the upper portion indicating that the last 2000 years has been a period of active dune growth and migration. In other dune complexes along the southeastern shore of Lake Michigan this was a period of dune stability: the critical difference was probably the sand delivered to the Saugatuck dunes by the Kalamazoo River. Variations in abundances of silt/clay in the eastern core may indicate changes in the amount of stream sediment that may reflect variations in erosion rates in the local watershed.

The Effects of Glacial and Post Glacial Transport on Lake Michigan Coastal Sands. Eric Johnson, Geological and Environmental Sciences Department, Hope College, Holland, MI

The mineralogy and trace element chemistry of Lake Michigan coastal sands and the sand size fractions of tills from the Lake Michigan and Saginaw lobes have been investigated optically and with the electron microprobe and PIXE (proton induced x-ray emission). Finer grained portions of Lake Michigan coastal sands (125 micron sieve fraction and smaller) are markedly enriched in oxides, garnets and ferromagnesian silicates compared to coarser grained size fractions. However the sand size fractions of tills from the Lake Michigan and Saginaw glacial lobes are dominated by quartz and feldspar at all size fractions and do not show an increase in denser minerals at finer grain sizes. A small enrichment in oxides in finer grained sand size fractions is evident in out wash collected near moraines. Thus, it appears as if less dense grains were winnowed out of the finer grained size fractions during post glacial transport. In some samples PIXE analyses show different trace element concentrations in quartz from larger and finer size fractions. This suggests that the quartz in the finer grained samples are not entirely fragments produced by impact and abrasion of larger grains during Transport but also include input from a distinctly different, finer grained, population.

New Geologic Map-Based Correlation of Glacial Landforms in Southeastern Livingston County, Michigan. Kevin A. Kincare, Michigan Geological Survey, Lansing, MI.

Existing glacial geology interpretations for southeastern Livingston County, Michigan rely on 1:125,000 scale mapping by Russell and Leverett (1908). Recent 1:24,000 scale mapping sponsored by the Central Great Lakes Geologic Mapping Coalition and STATEMAP show that the area denoted as the interlobate moraine of the Saginaw lobe is actually composed mainly of kames that lie within of a zone of collapsed outwash and lacustrine sediments. A surficial diamicton on many of the kames previously described as till is observed in gravel-pit exposures to exhibit characteristics of debris-flow deposits. These interpretations require that the ice margin be beyond these deposits. Therefore, deposits previously interpreted as the interlobate moraine cannot mark the ice margin of the Saginaw lobe because the deposits are not ice marginal in origin. The actual ice margin lies beyond these deposits.

A Study of North Ottawa Dunes, Ottawa County, Michigan. Michael Kingma and Deanna van Dijk, Department of Geology, Geography and Environmental Studies, Calvin College, Grand Rapids, MI

North Ottawa Dunes is a 500-acre property of wooded dunes in the northeast corner of Ottawa County. Ottawa County is turning this property into a park with an emphasis on preserving the property's natural features. As part of the park-planning process, this study undertook a physical inventory of North Ottawa Dunes including dune types and characteristics, trails, and human impacts. Dune heights, slopes and orientations were determined using Arc G1S software. Dune history was studied using relative-dating techniques, comparisons with nearby dunes of known ages in P.J. Hoffmaster State Patk, and examination of aerial photographs from 1974 to 2006 for recent changes. Results show that North Ottawa Dunes contains 58 dunes and 2 backdune ridges. All except five of the dunes are stabilized by vegetation; the five active dunes were also the most susceptible to erosion by human activity. Dune ages most likely range from 1750-8150 years before present, similar to dunes in PJ Hoffmaster State Park. The study identifies sites suitable for viewpoints and interpretation, as well as dune locations most vulnerable to human impacts.

Evolution of a Coastal Dune Blowout in Hoffmaster State Park, Michigan. Dave Koster and Deanna van Dijk, Department of Geology, Geography and Environmental Studies, Calvin College, Grand Rapids, MI.

Coastal dune blowouts ate active landforms that are shaped by wind, vegetation, and precipitation. This study focuses on a blowout in P.J. Hoffmaster State Park south of Muskegon, Michigan. The blowout is part of a coastal dune system that has been studied since 2000. Ground survey data collected several times each year were used to assess how the blowout has changed over the past six years. Additional measurements, using erosion pins, microclimate instrumentation and surface observations, provide information on blowout changes during the fall, winter, and spring months when winds are stronger. The ground surveys show that the crest of the blowout has migrated east because of high wind erosion in the blowout and sand transport to a depositional area on the dune slip face. Study results can be applied to the many similar dunes along the east coast of Lake Michigan.

Sedimentation Rates in Ravines on Grand Valley State University Campus, Allendale, Michigan. Rhiannon Mulligan and Patrick M. Colgan, Dept. of Geology, Grand Valley State University, Allendale, MI.

Ravines located on the Grand Valley State University campus are currently eroding due to an increase in runoff since the campus opened in 1960. The ravines are tributaries to the Grand River and are deeply eroded into basal till and lacustrine sand, silt, and clay. The purpose of this project is to determine the rate of sediment deposition in the lower parts of the ravines. Two ~ 3 meter sediment cores were obtained using the vibracoring method. Radiocarbon dates on wood within the cores as well as samples exposed in alluvial fill in stream banks are used to determine sediment age. Munsell color, grain size, magnetic susceptibility, and loss on ignition are used to describe the cores. Sediments are mostly silts, and clays, with interbedded layers of gravelly sand, humus, and wood. A conventional radiocarbon age of 180 + 40 14C yr B.P. suggests that wood could be modern or as old as 1650 A.D. Average sedimentation rates in the alluvial fill could be greater than ~6 cm/year over the last 46 years if wood in the bottom of the core is post 1.950 wood. More age data are needed to test this hypothesis.

Establishing a Terrestrial Cenozoic Fossil Record in South-Central Madagascar. Karel L. Rogers, Biology Department, Grand Valley State University, Allendale, MI.

Madagascar is a global biodiversity hotspot but it lacks a terrestrial Cenozoic fossil record that can be used to understand why evolution has been so prolific on this island. My purpose was to systematically sample tor fossils and to establish the age of the sediments that outcrop in south-central Madagascar, an area thought to supply basal species that form endemic species at the periphery of the island. The area near Fianaranrsoa has high relief with a mountain system that bus Madagascar's second highest mountain peak, so relatively young sediments are abundant near roadsides. During summer 2006, I systematically investigated sediments in road outcrops and lavukas (washouts) lor evidence of vertebrate fossils. Samples were washed over tine screen and then picked for inclusions. Samples for paleomagnetic analysis, sedimentary analysis, tephrochronology, and palynology were exported to the US for analysis. Although none of these analyses have been completed yet, a series of observations can he made that are of scientific interest. One is the complete lack of reaction to HCI, in. any sediment tested. An invitation is extended to people who would like to be involved in any aspect of the analysis of these samples.

The Glacial Section at Grand Valley State University: A Lake Michigan Lobe Advance into a Glacial Lake. Patrick M. Colgan, Geology Department, Grand Valley State University, Allendale, MI.

Grand Valley State University is located on a broad north-south trending ridge of the Lake Border moraine. The ridge is buried to the west by glaciolacustrinc sediments of Glacial Lake Chicago and to the east it is eroded by the Grand River and covered by alluvial sediments. Ravine exposures and bore holes show that the ridge is capped by diamicion. Overconsobdared matrix and striated and flat-iron shaped, polymictic clasts indicate that this is basal till, most likely correlating with the Sagatuck Till. Underlying diamicton is a coarsening upward sequence. Laminations and interbedded sand suggest that the lower part of this sequence is offshore lacustrine or distal delta sediments. Climbing ripples and cross-bedding suggest that the upper part is near shore lacustrine or proximal deltaic sediments deposited in a precursor to Glacial Lake Chicago. The contact between the basal till and lacustrine sediment is generally abrupt and erosional. Load casts, faults, and folding indicate deformation in the lacustrine sediments. Blocks of basal till are included in the upper sand. This mode of deposition suggests that the Lake Border moraine may be more accurately thought of as a morainal bank deposited in a glacial lake rather than a purely terrestrial end moraine.

Patterned Ground as Evidence of Extensive Permafrost in the Saginaw Lowlands, Michigan, During the Late Pleistocene, Randal! Schaetzl and David P. Lusch, Department of Geography; Remke van Dam, Department of Geological Sciences, Michigan State University, East Lansing, MI

Aerial photography and on-site reconnaissance were used to identify large areas of patterned ground in the Saginaw Lowlands. The purpose of this presentation is to document and describe these features, and therefore to begin to explain their formation and paleoclimatic significance. Aerial photographs clearly show vast tracts (>800 sq km) of patterned ground, mainly in Tuscola, Saginaw and Bay Counties. Most lies topographically above the shoreline of Glacial Lake Elkton (Lundy), but below the highest shoreline of Glacial Lake Warren, on wet, flat landscapes dominated by silty clay loam soils formed in glacial till. Patterned ground polygons are typically 50-90 m across; many are capped with a thin layer of sandy sediment. Inter-polygon sutures, probably originating as sites of former ice wedges, typically are slightly lower (50-100 cm) in elevation, having been infilled with highly clay- and silt-rich material. Based on our preliminary research, we conclude that the patterned ground has resulted from a period of extensive, Late Pleistocene permafrost, probably contemporaneous with the existence of Glacial Lake Elkton. Areas higher and farther from the lake that lack patterned ground were probably too steeply sloping, or contained soils that were much sandier and/or drier, to form and retain these patterns.

Mineralogy and Chemistry of Sediments from a Small Coastal Dune Lake. Carrie Thomason, Geological and Environmental Sciences Dept., Hope College, Holland MI.

X-ray powder diffraction and Proton Induced X-ray Emission were used to characterize the mineralogy and chemistry of sediments in a 2.6 meter long core representing ~5500 years of deposition from Gilligan Lake: a small lake in the coastal dune complex southwest of Holland Michigan. During periods of dune mobility the sediments were characterized by detrital quartz, feldspar, illite and clinoclore and have relatively high K concentrations and K/Ca ratios. During periods of dune stability the mineralogy was dominated by amorphous silica from diatom shells and sponge spicules and the biogenic calcium oxalate whewellite, (CaC204). Chemically these sediments have low K/Ca and Fe/Ca ratios. Thus, chemistry and mineralogy of the lake appear to be responsive to changes in the surrounding dunes. High iron concentrations, Fe/Mn and Fe/Ca ratios occur in an interval of the core deposited from ~3500 to ~5000 cal YBP. Hematite was found in these samples. However, calcium sulphate was found in some samples suggesting that relatively reduced sulphide bearing samples may have formed sulphates and hematite upon treatment with hydrogen peroxide (used to remove organic carbon). The origin of the elevated iron in the lake sediments remains unresolved.

A Ground Penetrating Radar Study of an Interdune Depression near Holland Michigan. Emily Timmons, Geological and Environmental Sciences Department, Hope College, Holland, MI.

Four ground penetrating radar (GPR) transects were carried out in a large depression within the dune complex southwest of Holland Michigan. A prominent reflector towards the bottom (~9 meters deep) of each profile lies roughly at the elevation of wave-base during peak Nipissing lake levels. If this surface represents the Nipissing transgression the current dune complex is built almost entirely on post-Nipissing sediments. To the east, this reflector is overlain by a sequence of short (2-5 m) doubly dipping reflectors stacked onto each other. Sediment collected from auger holes is medium to fine grained homogenous sand skewed to finer grain sizes. To the west the reflector is overlain by short (1 to 2 m) predominantly eastward dipping reflectors on lapping onto longer (10- 2.0 m) dipping reflectors. This sequence is overlain by lenses of predominantly eastward dipping short (I to 2 m) reflectors. Sediment from auger holes is medium grained sand. The upper part of each transect contains a well developed spodic soil profile. A similar soil in the adjacent dunes is developed on a surface that has been dated by OSL as between 4,000--3,000 years old.

Urbanization Induced Changes to a Ravine System and Evaluation of Land Use and Infrastructure Sustainability at Grand Valley State University, Allendale, MI. Patrick Womble, Peter Wampler, Ted LaCross, Department of Geology, Grand Valley State University, Allendale, MI

Land use practices at Grand Valley State University have dramatically altered runoff, erosion, and slope stability in an adjacent ravine system. The impacts of urbanization at the GVSU Allendale campus were evaluated using a combination of Geographic Information System analysis, current and historic data, continuous water level data, and discrete water volume measurements. A 189% increase of impermeable surfaces has occurred between 1973 and 2004, and an increase from virtually zero acres of impermeable surfaces in 1963 to 168 acres in 2004. Lag times during 2006 flooding events ranged from 10 to 25 minutes. In one of the largest ravines, the primary storm drain contributes 50% of the total discharge. Only 25% of the flow measured in this ravine can he attributed to natural runoff and accretion processes. Modeled peak discharges increased by as much as 32 cubic feet per second due to redirected storm water during a 1 inch/hr rain event. Storm water volume reduction should be integrated into infrastructure changes on campus. More runoff should be directed toward the west part of campus, perhaps into vegetated wetlands. The general practice of concentrating runoff into a few locations is resulting in numerous failures of engineered structures.

Origin of Esker and Tunnel Valley Assemblages in the Saginaw Lobe, Barry County, Michigan. Caleb J. Woolever, Alan E. Kehew, William A. Sauck, Department of Geosciences, Western Michigan University; Andrew L. Kozlowski, New York State Geologic Survey/New York State Museum, Albany, NY

Surficial mapping funded by the USGS EDMAP Program, ground penetrating radar, and borehole analysis were used to reconstruct conditions leading to the formation of eskers and tunnel valleys in the Saginaw Lobe of the Laurentide Ice Sheet, Barry-County, MI In this area, prominent northeast-southwest trending eskers lie within tunnel channels of the same orientation. A rotasonic borehole drilled at the crest of an esker reveals a fining upward sequence beginning with coarse sand and gravel in the tunnel channel, and fining to interbedded fine sand and silt near the top of the esker. The stratigraphy suggests that the subglacial tunnel persisted for a long period of time and flow gradually declined, with occasional periods of standing or slowly moving meltwater. Ground penetrating radar surveys show dipping bed structures conforming to the topographic profile of the esker. The eskers and other landforms in the area, including kames, suggest a model of ice stagnation and gradual downwasting of the Saginaw Lobe. Newly completed surficial mapping reveals sandy diamictons interpreted as meltout tills occurring discontinuously on the landscape. One previously proposed explanation for stagnation and/or early retreat of the Saginaw Lobe involves "beheading" of the Saginaw Lobe by the strengthening Huron-Erie Lobe.

Climate Changes in Southern Lower Michigan over the Last 2000 Years: Differentiating Between "Lake Effect" and Regional Climate Patterns. Catherine H. Yansa, Department of Geography, Michigan State University, East Lansing, MI; Jennifer Nelson, Department of Geology, Indiana University-Purdue University; J. Elmo Rawling III, Department of Geology and Geography, University of Wisconsin--Platteville, WI

Sediment cores were collected and analyzed from two lakes in southern Lower Michigan for a comparative multi-proxy (pollen, plant macrofossils, particle size, % organic matter, and % calcium carbonate) study with the objectives of reconstructing climate changes and testing for a "lake effect" signal. Miner Lake (42.7[degrees]N, 85.8[degrees]W) in Allegan County is located 30 km east of Lake Michigan and today has a lake-mediated climate. Duck Lake (42.4[degrees]N, 84.8[degrees]W), 117 km east of Lake Michigan in Calhoun County, has a modern climate reflecting regional patterns. Both sites had similar pre-settlement vegetation, that of beech-maple forest. The data from Duck Lake show that this lake was more responsive to large-scale climate perturbations than Miner Lake, which produced an invariant climate signal for the last 2000 years, at least. The inland location of Duck Lake provided a regional temperature/moisture record, which included the Medieval Warm Period signal from ca. 1200 to 800 cal yr BP and Little Ice Age cooling from about 500 to 150 cal yr BP. Spectral analysis of gray scale data for Duck Lake exhibited dominant periodicities of 207 and 96 years for cool/wet events, which may indicate a global climate signal, possibly induced by solar forcing.

On the Adams Rd. Mastodon, Two Creeks Phase Sedimentation and Paleoclimate, Oakland County, MI. J. M. Zawiskie, Cranbrook Institute of Science, Bloomfield Hills, MI and Department of Geology, Wayne State University, Detroit, MI

An American mastodon (Mammut americanum) was discovered during roadwork near M-59 and Adams Rd. during the summer of 2006. Staff from Cranbrook Institute of Science undertook a one-day rescue excavation and conserved the bones and associated plant and mollusk macrofossils. Roughly 30% of a large young adult male was recovered. The bone-bearing layer occurs in gray lacustrine clay to sandy clay in direct association with abundant spruce cones (Picea?glauca), branches, logs, reed stems and mollusks and is overlain by black muck and pear beds. The associated spruce macrofossils allow a provisional age inference, pending radiocarbon dating. Based on comparisons with published data from other nearby well-dated mastodon localities in Oakland County (Pontiac and Shelton sites), the mastodon-bearing sediments at Adams Rd. were likely deposited during the Two Creeks Phase (~12,000 to 11,500 C-14 yr BP) in an ice block depression on the Port Bruce Phase Inner Defiance Moraine--proximal outwash complex. Landforms, ice wedge polygons, and published reports on diatoms, insects, palynomorphs, plant and vertebrate fossils record the transition from glacial to periglacial climate to the Bolling-Allerod warming in Northern Oakland County.

An Anomalous Silt Cap on the Outer Port Huron Outwash Plain near Buckley, Michigan--Could it be Loess? (Poster) James C. Hook and Randall Schaetzl, Department of Geography, Michigan State University, East Lansing, MI

This poster provides the first information about a silty layer of surficial sediment--a silt "cap"--that exists above glacial outwash in northwestern Lower Michigan. The study area is locally known as the Buckley Flats; it is the high, perched, outwash plain of the Outer Port Huron moraine. This outwash surface slopes toward the Manistee River, which presumably carried the meltwater front this stagnant ice stillstand. The Buckley Flats are a rich agricultural area, largely because of the silt cap that exists there. The cap. usually silt loam or very fine sandy loam in texture, is typically 50-50 cm thick, but can he as thick as 75 cm in the center of the region, where postglacial erosion has been minimal. It overlies sand or gravelly sand outwash. The genetic origin of this cap remains somewhat unclear. Origins such as a weathering mantle, a glaciolacustrine deposit and a till will be discussed and effectively discounted. Instead, our data support an eolian origin for this cap, which would establish it as the first documented loess deposit in Lower Michigan.

These abstracts were edited by the Geological Section Chair, John Zawiskie
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Author:Zawiskie, John
Publication:Michigan Academician
Geographic Code:1USA
Date:Jan 1, 2008
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