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SESSION NO. 1 1-4 9:00 AM Johns, Elizabeth K. [218366] SITE SPECIFIC GEOCHEMICAL MODELING OF GROUNDWATER, ROCK AND CARBON DIOXIDE INTERACTIONS: IMPLICATIONS FOR GEOLOGIC CARBON SEQUESTRATION JOHNS, Elizabeth K., Geology, Geography, and Planning, MSU, 901 South National, Springfield, MO 65897, elizabeth4@live.missouristate.edu and GOUZIE, Douglas R., Department of Geography, Geology & Planning, Missouri State University, 901 S. National, Springfield, MO 65897 Geologic carbon sequestration is a process of mitigation that has the potential to reduce the impact of carbon dioxide emissions into the atmosphere through the injection of carbon dioxide into a saline aquifer. This research utilized geochemical modeling of groundwater, rock and carbon dioxide interactions for geologic carbon sequestration purposes. Long term storage of carbon dioxide is an important requirement of geologic carbon sequestration. Because geochemical processes are responsible for the long term storage of carbon dioxide, it is necessary to understand the extent to which carbon dioxide can be trapped by geochemical trapping mechanisms. This study investigated the extent to which carbon dioxide can be sequestered in the Lamotte Sandstone, a Cambrian aged saline aquifer, due to solubility and mineral trapping. A comparison of the geochemical suitability of three well sites in North-Central Missouri was also conducted. The program Geochemist’s Workbench was used for the geochemical modeling simulations performed for this study. Site specific data such as temperature, carbon dioxide fugacity, pH, mineral content and groundwater composition were the input parameters needed to simulate the sequestration of carbon dioxide in a saline aquifer due to geochemical trapping mechanisms. Preliminary simulations have been performed for the first site and for both hypothetical injection and post injection phases of carbon sequestration. For an example site, preliminary results show approximately 67 g/kg aqueous and 4 g/kg solid phase sequestered CO2, during the injection phase. Post injection phase results for this site indicate approximately 42 g/kg aqueous and 37 g/kg solid phase sequestered CO2. Aqueous species most involved in solubility trapping included CO2 (aq) , HCO3-, NaHCO3, CaHCO3+, MgHCO3+ and FeHCO3+. Mineral species involved in mineral trapping included dawsonite, dolomite and siderite. For this example site a possible preliminary effective sequestration capacity was calculated as .36 gigatons per 100 km². This material is based on work sponsored by the Department of Energy National Energy Technology Laboratory under Award Number DE-NT0006642 to City Utilities of Springfield MO. 1-5 9:20 AM Mayle, Emme [218072] RELATIONSHIP BETWEEN DEPTH AND HYDRAULIC CONDUCTIVITY WITHIN THE ST. FRANCOIS AQUIFER, MISSOURI MAYLE, Emme, Geography, Geology, Planning, Missouri State University, 901 S. National, Springfield, MO 65897, emme27@live.missouristate.edu and ROVEY, Charles W. II, Geography, Geology, and Planning, Missouri State University, 901 S. National, Springfield, MO 65897 The St. Francois aquifer is a prolific groundwater source near its outcrop area in southeastern Missouri, but is rarely tapped in the southwest part of the state due to the presence of the shallower Ozark aquifer. Nevertheless, the St. Francois aquifer may become an important supplementary source of groundwater in areas experiencing severe drawdowns within the Ozark aquifer. This aquifer is also a target for CO2 injection in northern Missouri where the pore water is saline. The main water-bearing unit within the St. Francois aquifer is the Lamotte Sandstone, the basal Cambrian sandstone above Precambrian basement. An overlying sandstone (Reagan), separated from the Lamotte by low-permeability siltstones and shales, is also present in portions of southwest Missouri. We measured the transmissivity and hydraulic conductivity of these sandstones at three sites with single-well pumping tests as part of the Missouri Carbon Sequestration Program. We also analyzed time-drawdown and specific-capacity measurements from 13 additional tests on file at the Missouri Division of Geology and Land Survey. Transmissivity and hydraulic conductivity (K) vary inversely with depth. At depths less than ~ 370 m, K varies between 10-3 and 10-2 cm/sec; these wells generally yield > 600 gpm. Below this depth K decreases due to pervasive cementation. By 550 m, K decreases to ~10-4 cm/sec, and this depth seems to mark the lower practical limit of these sandstones as an aquifer. By 650 m, K decreases to around 10-5cm/sec and the sandstones become marginal for CO injection, 2 except in locations where the Lamotte fills in topographic lows on the Precambrian surface and is unusually thick. This material is based on work sponsored by the Department of Energy National Energy National Energy Technology Laboratory under Award Number DE-NT0006642 to City Utilities of Springfield, MO 1-6 10:00 AM Stratton, Stephanie L. [218223] SIMULATION OF CO INJECTION INTO ST. FRANCOIS AQUIFER, GREENE COUNTY, 2 MISSOURI STRATTON, Stephanie L., Department of Geography, Geology, & Planning, Missouri State University, 901 S. National Ave, Springfield, MO 65897, Stratton89@missouristate.edu and ROVEY, Charles W. II, Geography, Geology, and Planning, Missouri State University, 901 S. National, Springfield, MO 65897 Geologic carbon sequestration is being investigated as a means of reducing the CO emission 2 from anthropogenic sources in Missouri. The St. Francois aquifer is the deepest available reservoir in Missouri for carbon sequestration; however, the aquifer is not deep enough to allow injection of CO at supercritical phase within Greene County. The Missouri Carbon Sequestration 2 Project had hoped to establish an injection test into the aquifer at the City Utilities of Springfield Southwest Power Plant (SWPP) site, but the pore fluids were not saline. Since data was available from the site, it was used to learn more about simulating carbon sequestration. The program AQTESOLV Pro was used to evaluate pumping and pressure-injection data from SWPP to determine hydraulic conductivities. Those data were then implemented in the program PetraSim 5.2 to develop simulations to help determine how the CO might behave 2 hydrodynamically. Compositional simulations with pressure gradients of 0.98 Pa/m and 9.8 Pa/m were generated to reveal plume migration patterns under injection and retrograde conditions. Simulations were a thousand years in duration with an initial 30 year injection period followed by a shut-off period. Simulated injection was within two high hydraulic conductivity zones in the Reagan Sandstone and Lamotte Sandstone of the St. Francois aquifer. A polygonal grid mesh was also used with high resolution around the injection well. The highest achievable injection rates were within the Reagan Sandstone. This was in correlation to the upper Reagan Sandstone having a permeability of 1.35E-13 m2 ; whereas the Lamotte Sandstone’s highest permeability was only 8.92E-15 m2 . The maximum migration of gas as a separate phase was approximately 4.0 km after a thousand years for simulations with well completion through the Reagan Sandstone. The maximum migration of gas as a separate phase with injection into the Lamotte Sandstone was approximately 700 meters. This material is based on work sponsored by the Department of Energy National Energy Technology Laboratory under Award Number DEFG2610FE0001790 to Missouri State University. 2 2013 GSA Abstracts with Programs 1-7 10:20 AM Smolenski, Rebecca Lynn [218774] GREENHOUSE GAS EMISSIONS FROM A TEMPERATE AGRICULTURAL RESERVOIR SMOLENSKI, Rebecca Lynn, Geological Sciences, University of Cincinnati, 3352 Jefferson Ave, Apt 2, Cincinnati, OH 45220, smolenrl@gmail.com, BEAULIEU, Jake, Environmental Protection Agency, Cincinnati, OH 45268, and TOWNSEND-SMALL, Amy, Department of Geology and Department of Geography, University of Cincinnati, 605 Geology-Physics Building, Cincinnati, OH 45221 Reservoirs are being built at an increasing rate each year to provide humans with resources such as hydroelectric power and drinking water. These man made systems have provided society with important services but these have come at the cost of enhanced greenhouse gas (GHG) emissions. Recent estimates suggest reservoirs are a globally significant source of GHG emissions but these estimates are largely based on studies of oligotrophic boreal and tropical reservoirs. Reservoirs draining agricultural basins are common throughout much of the developed and are subject to high nutrient loading rates from the watershed. Excess nutrient loading stimulates algae blooms and degrades water quality in these reservoirs but surprisingly little is known about how nutrients and algal blooms affect GHG dynamics. To assess GHG dynamics in an agricultural reservoir we measured GHG emission rates, dissolved concentrations and nutrient chemistry in William H. Harsha Lake, an agricultural reservoir located in southwestern Ohio on a monthly basis since October 2011. Average daily emissions of methane (CH ) were 50 mg CH -C m 4 4 -2 d-1 . The highest emissions rates of CH were observed during the summer months and during fall turnover, and the lowest 4 emissions were observed during the winter. Depth profiles of dissolved CH throughout the 4 summer show an accumulation of CH in the hypolimnium while the lake is thermally stratified. 4 Average daily nitrous oxide (N O) emissions were 0.80 mg N O-N m 2 2 -2 d-1 . The highest emissions were during fall turnover. During late summer, parts of the lake became a sink for N O, 2 and depth profiles of N O show a similar trend with the water column becoming undersaturated 2 with N O during this time. Without N O accumulation in the water column during thermal 2 2 stratification, it is likely that the source of N O during fall turnover is nitrification of remineralized 2 ammonium. SESSION NO. 2, 8:00 AM Thursday, 2 May 2013 Geophysics, Geodynamics, etc. Fetzer Center, Room 2040 2-1 8:00 AM Larson, Mark [218656] GRAVITY AND MAGNETIC ANALYSIS OF PLUTONS, RING PLUTONS AND MAFIC BODIES IN THE ST FRANCOIS MOUNTAINS, SE MISSOURI LARSON, Mark and MICKUS, Kevin, Geology, Missouri State University, Springfield, MO 65897, Mark3@live.missouristate.edu The St. Francois Mountains of southeast Missouri are a Proterozoic volcanic complex composed of felsic plutons, ring intrusions, and massifs, and is the largest exposure of Proterozoic lithologies in the south-central US. The development of the St. Francois Mountains is not well understood and there are three main theories that are currently under consideration: 1) hotspot/melting, 2) subduction volcanism, and 3) rift related volcanism. Since the proterozoic volcanic activity, the region has been faulted by forces related to the Reelfoot Rift in the Cambrian and reactivation in the Cretaceous, and more recently by the New Madrid Fault zone. Geologic mapping and regional magnetic anomaly interpretation has proposed that the region consists of a few large felsic calderas. Our research focuses on analyzing gravity and magnetic data to determine the upper crustal structure of the region in order to relate these data to the location of proposed caldera rims, as well as mafic bodies, and better understand their origin. Using existing gravity and magnetic data as a guideline for the location of new data, we first conducted a gravity survey to add data to regions without data. The merged data, in the form of Bouguer gravity anomaly maps, identified anomalies that agreed with existing structural data of the region. Then additional detailed (1 mile spacing) gravity data were collected along two profiles that cut across the large amplitude anomalies associated with the calderas. These data were be modeled by 2D forward modeling to determine the subsurface geometry of the calderas constrained by surface density measurements and surface features. Additionally, a series of residual, regional and derivative gravity and magnetic anomaly maps have been constructed to aid in the interpretation of the 2D models. Collection of rock samples at the surface has given density data to constrain our models. Core samples will be analyzed for densities and magnetic susceptibilities in order to further constrain the gravity models. Using the final anomaly maps and models we will interpret them in order to determine the nature and origin of the calderas in the St. Francois Mountains region. 2-2 8:20 AM Evans, Kevin R. [217445] PRE-OUACHITA TECTONISM, DEVELOPMENT OF A BACK-STEPPING SHELF MARGIN, AND SYN-TECTONIC SEDIMENTATION (MIDDLE DEVONIAN THROUGH MISSISSIPPIAN) ON SOUTHERN LAURENTIA: A REGIONAL SYNTHESIS OF THE OZARKS EVANS, Kevin R., Geography, Geology, & Planning Dept, Missouri State University, Springfield, MO 65897, kevinevans@missouristate.edu, BASSETT, Damon J., Geological Sciences, University of Missouri, 101 Geological Sciences Bldg, Columbia, MO 65211, ETHINGTON, Raymond L., Geological Sciences Dept, University of Missouri-Columbia, Columbia, MO 65211, MANGER, Walter L., Department of Geosciences, Univ of Arkansas, Fayetteville, AR 72701, MICKUS, Kevin L., Geosciences, Missouri State Univ, 901 S National Ave, Springfield, MO 65804-0087, and MILLER, James F., Geography, Geology, & Planning Dept, Missouri State University, Springfield, MO 655897 Southern Laurentia in the Ozarks region has been characterized as a Late Proterozoic rift shoulder that developed into a passive margin; docking with the Ouachita allochthon during the Early Pennsylvanian led to development of the Arkoma Basin and Ozark Uplift. Yet, why were pre-Mississippian strata progressively truncated to the north and west? Why was the Chattanooga Shale preserved in southwestern Missouri and northwestern Arkansas but eroded below the Mississippian in the Boston Mountains? Why did deep-water Mississippian carbonates accumulate in southern Missouri on peritidal lower Paleozoic strata? We consider that much of the epeirogenic uplift and denudation of the Ozarks preceded the Ouachita orogeny, occurring in the Early to Middle Devonian, and structural evolution persisted through Mississippian and Early Pennsylvanian time. The onset of convergence led to development of the Arkansas Novaculite foredeep, and in the Ozarks, loading and flexure resulted in progressive truncation of much of the post-lower Ordovician to pre-Mississippian succession. Up to 500 m of strata were cut out, yet impact
structures, isolated sink-fills, and faults record the presence of stratigraphic units that are missing regionally. Upper Ordovician to middle Silurian clasts are incorporated into the Decaturville breccia (pre-Devonian impact) in lower Ordovician country rock. Middle Devonian marine sandstone filled a sink in lower Ordovician dolomite near Rolla. Upper Devonian Chattanooga Shale blanketed the eroded western Ozark platform. Most of this unit was removed below the sub-Mississippian unconformity in the central Ozarks but was preserved in an embayment that we informally refer to as the Northwest Arkansas Basin. Clasts of Chattanooga Shale have been recovered from the Weaubleau breccia (mid-Mississippian impact), a thin interval is preserved along the Highlandville Fault, along the lower Buffalo River, and in sink-fills in northern Arkansas. During the Early Mississippian, continued flexure resulted in back-stepping of the shelf margin, so deep-water facies accumulated on erosional remnants or peritidal lower Paleozoic strata. Major faults in southern Missouri are associated with some anomalous units of sandstone, limestone, or olistoliths, providing a record of syn-tectonic sedimentation. 2-3 8:40 AM Pennington, Wayne D. [218074] THE MENOMINEE CRACK AND CLINTONVILLE BOOMS: SEISMIC EVENTS IN MICHIGAN’S UPPER PENINSULA AND NORTHEASTERN WISCONSIN PENNINGTON, Wayne D., Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Dr, Houghton, MI 49931, wayne@mtu.edu and WAITE, Gregory P., Geological and Mining Engineering and Sciences, Michigan Technological Univ, 1400 Townsend Dr, Houghton, MI 49931 In spite of its reputation as an aseismic area, there were intriguing occurrences of seismic events in Upper Michigan and northern Wisconsin in 2010 and 2012. Although these two occurrences were only about 100 km apart, there is no evidence indicating that they are related or even due to a similar mechanism. The Menominee Crack: On October 4, 2010, a loud noise and shaking were observed in an area north of Menominee. This was associated with the appearance of 110m long crack at the crest of a ridge, 1.5m in height and up to 9m wide. The crack is apparently a surficial feature, resulting from stretching of the uppermost soil and clay layers to accommodate the creation of a ridge at some shallow depth. A reasonable model (first proposed by Dr. Norm Sleep) is that the limestone underneath the clay experienced a “pop-up” due to high lateral stresses. Usually, pop-ups occur as a result of recent unloading, as at the base of a quarry or immediately following glacial retreat; neither of these describes this site, so the cause remains speculative. Clintonville Booms: Residents of Clintonville began hearing infrequent deep, rumbling sounds on March 18, 2012; the booms were sometimes accompanied by felt shaking. Following a relatively large event on March 20 that was clearly a M1.5 earthquake, four seismometers and eight sound sensors were deployed within and around Clintonville to improve the locations of subsequent events. Two events were located beneath the southeastern part of Clintonville at less than 1 km below the surface within the granitic basement. These events were close enough to the surface so that seismic energy of sufficiently high frequency coupled to the atmosphere and propagated as sound. The Clintonville booms were indeed due to earthquakes, most of which were too small to record. 2-4 9:00 AM Tupper, M. Tobias [218762] IDENTIFICATION OF LOW-LEVEL SEISMICITY IN OHIO TUPPER, M. Tobias, Geological Sciences, Ohio University, 316 Clippinger Laboratories, Athens, OH 45701, mt833511@ohio.edu and GREEN, Douglas H., Dept. of Geological Sciences, Ohio University, 316 Clippinger, Athens, OH 45701 OhioSeis records are examined to identify previously undocumented low-level earthquakes in Ohio and surrounding regions. Records are scanned at multiple stations (at least four) to identify peak amplitude arrivals within a time window specified by the lowest likely arrival phase velocity and the maximum inter-station distance. A potential arrival peak must have an amplitude of at least 1.5 times the RMS amplitude over an entire hour containing that peak. The location (epicenter) of the potential earthquake is obtained using a velocity-independent-arrival-orderlocation (AOL) technique. The event is classified as a probable earthquake if it is similarly identified and located using a different set of four stations. Five probable earthquakes in 2011 were each identified using at least five combinations of stations of four seismic stations. This includes the documented 2011 New Year’s Eve M4.0 event in Youngstown OH, which was located by this technique within 14 km and 10 seconds of the epicenter and origin time reported by the USGS. An additional three events were identified using at least three sets of four stations, and thirteen possible 2011 earthquakes were identified using two sets of four stations. Most of these locations extend from Lake Erie up the Cuyahoga Valley, through east-central Ohio towards Marietta OH. 2-5 9:20 AM Malcuit, Robert J. [217936] A JUPITER ORBIT -- LUNAR ORBIT RESONANCE MODEL: POSSIBLE CAUSE FOR THE BEGINNING OF THE MODERN STYLE OF PLATE TECTONICS MALCUIT, Robert J., Geosciences Department, Denison University, Granville, OH 43023, malcuit@denison.edu Since the Plate Tectonics Revolution in the earth sciences, there has been this lingering debate about when plate tectonics began. There are two end-member schools of thought: (1) that plate tectonics has been operating throughout geologic time (Shervais, 2006, GSA SP-405, p. 173) and (2) that plate tectonics, as we understand it today, can only occur when the Earth has cooled sufficiently to permit plates to attain negative buoyancy (Davies, 1992, Geology, 20, p. 963; Stern, 2005, Geology, 33, p. 556). Stern (2005) proposes that the modern style of plate tectonics began ~1.0 Ga ago. The Late Proterozoic also appears to be a critical time in the history of the lunar orbit. Peale and Cassen (1978, Icarus, 36, p. 245) identified an orbital resonance state between Jupiter’s orbit and the lunar orbit when the lunar orbital radius is at 53.4 ER (earth radii). Orbital traceback calculations suggest that the earth-moon distance would be ~53.4 ER in Late Proterozoic time. The key element in such an orbital resonance is the perigean cycle of the lunar orbit (the prograde progression of the perigee position of the lunar orbit). At present the perigean cycle is 8.85 years (60.3 ER). At 53.4 ER the perigean cycle would be ~12 years, the approximate period of Jupiter’s orbit. Under these conditions the major axis of the lunar orbit would be increased to the resonant value by a forced ECC (eccentricity) but the orbital angular momentum would remain near that of a 50 ER orbit and then slowly increase in time to that of a 53.4 ER orbit. As the lunar orbital ECC reaches a maximum of up to ~0.3, the rock and ocean tidal amplitudes would be ~2.5 times higher than that of a circular orbit of 53.4 ER. Such rock tidal activity could lead to the development of tidal vorticity induction cells in the upper mantle (Bostrom, 2000, Oxford Univ. Press) that would aid in the initiation of subduction. This model can be tested via the tidal rhythmite record of the Late Proterozoic. The two predictable constants are that the semi-major axis of the lunar orbit should be near 53.4 ER and the number of sidereal months per year should be about 16 throughout this era. Assuming that the earth rotation rate at 1.1 Ga (before the forced ECC episode) is ~16.9 hr/d, the number SESSION NO. 3 of days per year would change from ~519 d/yr at ~1.1 Ga to 466 d/yr at the end of this orbital resonance era. SESSION NO. 3, 8:00 AM Thursday, 2 May 2013 T4. Quaternary Research in the Great Lakes Region I: The Pleistocene Fetzer Center, Kirsch Auditorium 3-1 8:00 AM Lepper, Kenneth [218517] AGE CONSTRAINTS FOR AN UPDATED LAKE AGASSIZ PALEOHYDROGRAPH LEPPER, Kenneth, Department of Geosciences, North Dakota State University, P.O. Box 6050, Dept. #2745, Fargo, ND 58108-6050, ken.lepper@ndsu.edu, FISHER, Timothy G., Environmental Sciences, University of Toledo, MS #604, Toledo, OH 43606, and LOWELL, Thomas V., Department of Geology, University of Cincinnati, 500 Geology/Physics Building, University of Cincinnati, Cincinnati, OH 45221 Meltwater releases from Lake Agassiz to the Mississippi, Mackenzie and Great Lakes waterways have been implicated as triggers of abrupt climate change events during the last deglacial cycle. To evaluate these assertions a paleohydrograph for Lake Agassiz is needed with robust chronologic controls. Shorelines represent static water planes and transitions between shoreline positions represent significant water-level fluctuations. However, geologic ages constraining the timing of shoreline development, and thereby water-level fluctuations for Lake Agassiz, have been difficult to obtain, and therefore, sparse. In recent years we have had success in applying OSL dating techniques to shoreline deposits of Lake Agassiz that are more easily mapped using LiDAR data. This report will summarize a growing chronologic data set that includes 35 independent OSL ages from five different study areas around the southern basin, but thus far mostly focused around the southern outlet. The cumulative OSL data set for Lake Agassiz’s southern basin provides robust age constraints for the Herman, Norcross and Campbell strandlines with averages and standard deviations of 14.1 ± 0.3 ka, 13.6 ± 0.2 ka, and 10.5 ± 0.3 ka, respectively. In addition, the new age constraints are used to develop an updated paleohydrograph for Lake Agassiz spanning the time period of approximately 14.5 to 10 ka which includes rapid climate changes at the end of the last ice age. 3-2 8:20 AM Fisher, Timothy G. [218507] RECENT STRATIGRAPHIC AND CHRONOLOGIC RESULTS FROM THE HURON-ERIE LAKE PLAIN OF ANCESTRAL LAKE ERIE, OHIO FISHER, Timothy G. 1 , BLOCKLAND, Joseph2 , HIGLEY, Melinda3 , ANDERSON, Brad1 , GOBLE, Ronald J. 4 , and LEPPER, Kenneth5 , (1) Environmental Sciences, University of Toledo, MS #604, Toledo, OH 43606, timothy.fisher@utoledo.edu, (2) Department of Environmental Sciences, University of Toledo, 2801 West Bancroft Street MS604, Toledo, OH 43606, (3) Illinois State Geological Survey, Champaign, IL 61820, (4) Department of Earth and Atmospheric Sciences, University of Nebraska - Lincoln, 214 Bessey Hall, Lincoln, NE 68588, (5) Department of Geosciences, North Dakota State University, P.O. Box 6050, Dept. #2745, Fargo, ND 58108-6050 An understanding of deglacial events in the Huron-Erie Lake Plain is known in general, but poorly understood in detail. During east–northeast recession of the Erie and Huron lobes of the Laurentide Ice Sheet, Ancestral Lake Erie evolved through fluctuating lake levels and changing outlets. Strandlines are well known, having been mapped ~100 years ago, but detailed stratigraphic and sedimentologic analyses and age control is left wanting. To increase our knowledge of this lake, and in the process develop a more four-dimensional understanding of the surficial geology, we have been dating strandlines and sand dunes using mostly OSL techniques. To evaluate the Ypsilanti low event, rhythmic lake sediments were analyzed at elevations that would have experienced subaerial emergence during this low event. Most of the sand dunes are 4000–9000 years younger than the oldest strandlines. Because sand was sourced from older ice marginal and strandline deposits, dunes either initially formed or were remobilized under a deteriorating climate during stadials, and post-date disappearance of Ancestral Lake Erie. Only 507 rhythmites were observed between till and the overlying dune sand and shallow water sediment, which is fewer than expected. A stratigraphic break within the lacustrine sedimentary sequence necessary to support the low-water Ypsilanti Phase was not observed. In summary, our data thus far suggests that stable water levels were short lived and that the lake evolved over a shorter period of time than is commonly assumed. 3-3 8:40 AM Lowell, Thomas V. [218702] DO THE ICE MARGIN CHANGES OF THE LAURENTIDE GREAT LAKE LOBES MATCH THE GREENLAND ISOTOPE RECORD? LOWELL, Thomas V., Department of Geology, University of Cincinnati, Cincinnati, OH 45221, thomas.lowell@uc.edu The Greenland Ice Cores have long been held as a reference for climate change during the late Pleistocene. The isotopes from multiple cores now provide a detailed record that many paleoclimate records have been compared to. Glaciers are taken as being most responsive to temperatures during the summer ablation season. Oerlemans (2005) has show that a global network of small glaciers can provide a temperature record over the last two hundred years that matches the global temperature derived from instrumented records. It would be informative to ask if the margins of ice sheets match the reference for climate change. The lobes of the Laurentide ice sheet that occupied the Great Lakes are examined here in that context. For the last glacial maximum records show that the ice sheet was south of the Great Lakes by 27.2 ka cal and continued to reach its maximum at 24.0 ka cal and started to retreat as early as 21.7 ka cal with major retreat underway by 17.0 ka cal. Superposed on this general pattern were advances at 24.0, 24.0, 22.2 and 21.2 ka cal. With the exception of a warm interstadial at 27.5 and 23.5 ka cal, the ice core is nearly linear during this time. In other words examination of the ice core alone would not suggest the growth, decay pattern, nor major advances of the ice sheet margin. Possible explanations for this disconnect are 1) the ice core record does not represent the climate of the Great Lakes region; 2) the concept of seasonality, whereby the ice core records mean annual, not summer temperatures; 3) the dynamics of ice sheets are not driven by climate changes. Given that the above record was derived from and is consistent with both the Lake 2013 GSA North-Central Section Meeting 3
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25-5 9:20 AM Gebrehiwet, Tsigabu [2
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Crane, Renee 21-5* Crisp, Alexis A.
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Abstracts with Programs - Geological Society of America

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