Sedimentation rates and sediment content of Lake Lanier, implications for lakebed development and deposition
When: November 29, 2022
Abstract: Lake Sidney Lanier is an impoundment reservoir in North Georgia, U.S.A. that was completed in the late 1950’s for the purposes of municipal use and recreation. Lake Lanier was formed when Buford Dam to the southwest of the lake was completed. The geological setting of Lake Lanier is that of deeply folded ridges and interfluves trending SW-NE set within the high-grade metamorphic rock of the Southeastern Piedmont Physiographic Province. Throughout its short history Lake Lanier has significantly altered the ecosystem, geology, and hydrology of the area. These changes have included sediment budget imbalances, altered hydrochemistry through increased resident time, anthropogenic forcing through development and contamination, and lake bottom sedimentation. Prior to Lake Lanier, sediments did not collect on the bottom of that reach of the Chattahoochee River: it did not function as a depositional basin. The entirety of the Piedmont is that of an erosive geological setting due to the trend of differential stress place upon the country rock during the development of the Appalachian Mountains ~300 Mya. The entirety of this region drains streams southward. The artificial emplacement of Lake Lanier, as well as other reservoirs in North Georgia, provides a unique setting for upland sediment deposition from upland contributions These contributions include a wide variety of naturally weathered products from a variety of metamorphic rocks north of the lake – such as amphibolite, gneiss, and schist – as well as anthropogenic contributions. Furthermore, Buford Dam is an embankment dam within a tectonically quiescent region and as such has a possible lifespan of hundreds or more years. Lake Lanier has a maximum depth of 160 feet and as such may accumulate significant layers of sediment on its bottom annually. One can reasonably assume that these sedimentary layers, over time, are being altered through something akin to early-stage diagenesis.
Speaker bio: Steve Fitzpatrick has taught geology, environmental science, and integrated science at Perimeter College of Georgia State University for 12 years. He has a master’s degree (2011) in Geology from the University of Georgia, with specialties in subsurface runoff, soil structure, and shallow field geophysics. Throughout his career Steve has conducted geological, soil science, hydrology, and general environmental academic fieldwork as well as experimental design for geology and environmental science labs. Steve is currently writing an environmental science textbook based on a an empirical natural-science approach rather than the usual social-science driven one. He is also attempting to reinvigorate a program of doctoral study, a seemingly ongoing effort. Maybe this presentation will help with that effort! Who knows? Anyway, in his spare time Steve likes to watch movies, play music, spend time with family and friends, and errantly wander around the countryside
Hydrology of the Claiborne aquifer in Southwestern Georgia
When: October 25, 2022
Abstract: Competing demand for water supply in the Apalachicola-Chattahoochee-Flint River Basin in southwestern Georgia has led to interest in development of alternative sources of water, including aquifers beneath the Upper Floridan aquifer. In 2015-16, the U.S. Geological Survey, in cooperation with the Georgia Environmental Protection Division, conducted a study to define the hydrologic properties of the Claiborne aquifer and to evaluate its connection with the Upper Floridan aquifer. Borehole geophysical logs were collected from seven wells throughout the study area and two 72-hour aquifer tests were conducted in Mitchell and Early Counties, Georgia. The data collected from the wells and the aquifer tests, along with pre-existing data, were used to determine extent and properties of the Claiborne aquifer. Aquifer-test data from Mitchell County, Georgia indicate a small amount of leakage; however, no drawdown was measured in the overlying Upper Floridan aquifer as a result of pumping. This leakage was assumed to be coming into the Claiborne aquifer from the underlying Clayton aquifer, however the Clayton aquifer was not directly assessed as a part of this study. The two tests conducted during this study indicate that the Claiborne aquifer is a viable alternative to the Upper Floridan aquifer. Additional tests and monitoring are recommended to identify drawdown in adjacent aquifers in other areas.
Speaker bio: Debbie Gordon has a BS in geology from the University of West GA and an MS in hydrogeology from East Carolina University. She has been working at the USGS for 28 years doing groundwater studies, mainly in southwest Georgia. She has recently taken on the role of outreach coordinator for the South Atlantic Water Science Center of USGS which includes Georgia, North Carolina, and South Carolina.
How the Gulf Stream brings Warmth and Nutrients to the North Atlantic: Tales from the Past and Future Ocean
When: September 27, 2022
Abstract: The Atlantic Ocean circulation, including the Gulf Stream, delivers heat into the Northern Hemisphere. It also delivers the nutrients that feed the high biological productivity in the North Atlantic Ocean. This circulation will likely weaken as the globe warms. To better understand what the future may hold, we turn to the relatively recent past. I will show how the weakening of the Gulf Stream over the transition from full Ice Age conditions 20,000 years ago to the present impacted climate patterns and the nutrient availability and biological productivity in the North Atlantic Region.
Speaker bio: Jean Lynch-Stieglitz is professor in the School of Earth and Atmospheric Sciences and College of Science ADVANCE Professor at Georgia Tech where she has been on the faculty since 2003. Her research group investigates changes ocean circulation and climate since the height of the last ice age, combining geochemical methods for gathering data on the state of the past ocean with the analytical tools and approaches of modern oceanography. She also currently serves on the Board of Reviewing Editors at Science Magazine. Professor Lynch-Stieglitz graduated from Duke University with a B.S. in Geology and Physics in 1986, received her Ph.D. in 1995 from Columbia University, and was a post-doctoral fellow at the Woods Hole Oceanographic Institution. She was a faculty member at Columbia University’s Department of Earth and Environmental Sciences and Lamont-Doherty Earth Observatory from 1996-2003. She served as Editor of Earth and Planetary Science Letters from 2012-2015, and as Associate Chair in the school of Earth and Atmospheric Sciences at Georgia Tech from 2015-2022. She was elected Fellow of the American Association for the Advancement of Science in 2015 and Fellow of the American Geophysical Union in 2019 in recognition of her work on ocean circulation changes over the transition out of the last ice age. She was also named Cesare Emiliani Lecturer by the American Geophysical Union in 2018, recognizing outstanding contributions to the field of paleoceanography.
When Megafloods Attack! Recent observations from the eastern Himalaya
When: August 30, 2022
Abstract: During the last glacial period, expanding glaciers dammed many of rivers draining the eastern margin of the Tibetan Plateau, impounding vast, high elevation lakes. When these glacial dams inevitably failed, enormous floods cascaded through the narrow Himalayan valleys downstream, leaving behind a trail of sedimentary deposits along valley walls. In this talk, I will reconstruct the enormity of these floods from the curious sedimentary record they left behind.
Speaker Bio: Dr. Karl Lang is a broadly trained geologist with interests spanning areas of geomorphology, sedimentology and tectonics. He is an Assistant Professor at Georgia Tech. Prior to this he was a postdoctoral researcher in Germany and Sweden. He has a PhD from the University of Washington in Seattle and a BSc from the College of William and Mary in Virginia.
Going Against the Grain: Linking Brittle Cross-Structures with Landslides, Hydrogeology, and Earthquakes in the North Carolina Blue Ridge and Piedmont
When: May 31, 2022
Abstract: Geologic studies from the 1990’s to present have identified brittle, post-orogenic bedrock structures that cut across the overall SW-NE structural and topographic pattern of the Blue Ridge and Piedmont of North Carolina. These families of brittle faults and associated fracture (joint) systems overprint older ductile structures, and correspond with ESE-WNW, WSW-ENE, and E-W topographic lineaments. Detailed geologic investigations indicate that some of these cross-structures can be linked to landslide occurrence, the hydrogeology of fractured rocks, and seismicity.
Landslide hazard mapping in the Blue Ridge of Watauga County in 2008 identified an ESE-WNW trending zone of rock slope instability associated with brittle faulting that overprints a segment Linville Falls fault, a ductile thrust fault bounding the Grandfather Mountain window. Subsequent investigations identified this zone of brittle deformation as the Boone fault, located in an area that experienced 2013-14 seismicity Topographic lineaments that parallel the Boone fault project into the Deep Gap reentrant on the Blue Ridge Escarpment (BRE) where the remnants of an August 1940 tropical cyclone triggered over 600 landslides. Recently completed landslide hazard mapping in Polk County identified an E-W trending fracture set that controls the North Pacolet River reentrant into the BRE, an area of concentrated landslide activity from a May 18, 2018 storm that triggered over 240 landslides.
Investigations in 2010 for the CTS superfund site in the Blue Ridge near Asheville identified the ESE-WNW trending Mills Gap fault and fracture zone that cross-cuts metasedimentary and meta-igneous rocks of the Ashe Metamorphic Suite. Detailed geologic and hydrogeologic studies identified the Mills Gap fault zone as primary structural feature that provides a pathway for groundwater flow to transmit contaminants. A strand of the Mills Gap fault juxtaposes weathered bedrock with deformed colluvial deposits indicating Cenozoic movement along the fault, which is in the epicentral area of the 1916 M5.2 Skyland earthquake. A series of ESE-WNW trending topographic lineaments extends through the Mills Gap fault zone into the Hickory Nut Gorge reentrant on the BRE, a location of concentrated landslide activity in Rutherford County. Anecdotal reports of rockfalls during an 1848-1874 earthquake swarm hint at the possibility of a link between seismicity and rock slope failures in Hickory Nut Gorge.
Studies in 1990’s for a proposed LLRW disposal site near Raleigh identified ESE-WNW and WSW-ENE striking extensional faults and associated fracture systems that cross-cut Triassic sedimentary rocks of the Deep River Basin in the NC Piedmont. Hydrologic tests were not completed on the cross-faults; however, an aquifer test along an intersecting SW-NE striking normal fault indicated that the fault and associated fractures influenced groundwater flow.
The August 9, 2021, Mw 5.1 earthquake near Sparta, NC caused over $15 million in damage. Ongoing collaborative investigations determined that the earthquake occurred along the newly discovered, ESE-WNW striking Little River fault that formed the first documented surface fault rupture directly linked to a modern earthquake in the southern Blue Ridge. Ground surface ruptures along the Little River fault parallel other linear topographic features that project to the ESE and WNW of the Sparta area.
Speaker bio: Richard Wooten has over 40 years of experience in applied geology in the Cascade Mountains of Washington State, and applied geologic research in the Piedmont, and Blue Ridge Mountains of North Carolina. He earned his B.S. and M.S. degrees in geology at the University of Georgia in 1973 and 1980. Rick recently retired from the North Carolina Geological Survey where he was the Senior Geologist for Geohazards and Engineering Geology from 1990 to 2021. His previous work includes mapping geologic resources and conditions for land-use planning, landslide investigations and applied geotechnical geology for the USDA-Forest Service on the Gifford Pinchot National Forest in Washington State from 1980 to 1990. His work with the North Carolina Geological Survey includes the scientific regulatory review and field investigations for a low-level radioactive waste disposal project, and bedrock geologic mapping in the Piedmont and Blue Ridge Mountains. Since 2003 his main focus has been on landslide hazard mapping and research, and responding to landslide events North Carolina Blue Ridge. He has a special interest in the relationships of ductile and brittle bedrock structures with geomorphology and landslides processes, and communicating landslide hazards information with stakeholders.
Geology for the Next Generation: Purposeful Training in Geoscience Education
When: March 29, 2022
Abstract: Education seems susceptible to a particular form of bias. An instructor learns a thing a certain way, and thus considers this is the way that instruction is done. Over time, the curriculum of a program builds, sometimes by the demands of the job market, and sometimes by the inertia of this bias from the faculty. In his talk to the Atlanta Geological Society, Dr Ricchezza will present a synopsis of the basics of Geoscience Education Research and how it fits with curriculum design for geoscientists. His talk will include selected case studies from his own research, and will discuss how we can move forward as a profession to a more diverse workforce that is trained with the skills suited the jobs they find upon graduation.
Speaker bio: Dr Victor J Ricchezza is an Assistant Professor of Geology working for Georgia State University’s Perimeter College at the Clarkston campus. Dr Ricchezza has worked at PC since Fall 2020. Before working at PC, he was an adjunct instructor for the School of Geosciences at the University of South Florida, where he previously earned a Doctorate in 2019 and a Master’s degree in 2016, both in Geology. While in graduate school, Dr Ricchezza focused research in the subfield of Geoscience Education Research (GER). Put simply, while most geologists study earth materials and processes, he studies how geologists are trained at the university level, and how that process can be continually improved. His specialty within GER is quantitative literacy for geoscience, measuring how geoscientists are taught the quantitative skills they need to succeed professionally. Prior to graduate school, Vic worked as a high school teacher in Fulton County after a decade in environmental consulting. Vic lives a bit outside Atlanta with his wife and 2 kids, far too many cats, and a pile of musical instruments.
Better Understanding Seismic Activity in the Southeast USA: Case studies of the Eastern Tennessee Seismic Zone and Vicinity of the Thurmond Reservoir
When: February 22, 2022
Abstract: The Eastern Tennessee Seismic Zone (ETSZ) is the second most active seismic zone in the eastern United States, after the New Madrid Seismic zone in the Mississippi Valley area. A few faults have been identified in the region, but many remain unknown or poorly constrained at depth. We apply a matched filter technique to detect earthquakes not previously catalogued in the ETSZ. We use 15 years of catalogued earthquakes in this region to detect missing events in the same time period (January 2005 to May 2020). We also calculate the magnitudes of new events and relocate the both the new detections and previously catalogued earthquakes to better constrain earthquake locations in the ETSZ. Relocated hypocenters are examined to resolve fault structures and orientations. Our ultimate goal is to use spatio-temporal changes of seismicity during the last 15 years reveal subsurface fault structures and the driving forces of seismicity along the ETSZ. We also present our findings on a notable earthquake in the vicinity of the Thurmond Reservoir, located at the border between Georgia and South Carolina. The Mw 4.1 earthquake on February 15, 2014 near Edgefield, South Carolina was one of the largest recorded by nearby modern seismometers, providing an opportunity to study its source properties and aftershock productivity. The low number of detected events in the weeks around the mainshock suggests that this sequence is deficient in aftershock production, as compared with expected aftershock productivities for other mainshocks of similar magnitudes.
Speaker bio: Clara Daniels is a 5th year PhD student studying Seismology at Georgia Institute of Technology, getting ready to graduate this May! She has her Bachelor’s in Electrical Engineering, with a focus on Digital Signal Processing, also from Georgia Tech. She grew up in Pennsylvania and Georgia, which is why earthquakes on the East Coast are so interesting to her and the focus of her research.
Red and yellow ochres used by the Himba and Nama people of Namibia: Mineralogical composition and characterization by XRD and SEM-EDS
When: January 25, 2022
Abstract: Ocher is a natural iron oxide earth pigment that can vary from shades of light yellow to deep oranges to intense reds. The use of ochres as pigments is global and they have been recorded in many works of art in all periods and traditions. Ochre-derived pigments were and continue to be widely used as face and body decoration, sun protection, mosquito repellant, geophagic earths and coloring agents.
The Himba and Nama people of Namibia are among modern ethnic groups that still extensively use red and yellow ochre. Eight red ochre samples from Kunene Region, northern Namibia and two red and yellow ochre samples from Keetmanshoop area, southern Namibia used by the Himba and Nama people, respectively were studied by stereomicroscopy, XRD and SEM-EDS. All nine red ochre samples contain hematite, the primary mineral responsible for the red shades of the ochres. Quartz and biotite are also found in nearly all samples. Carbonates, magnetite, apatite, corundum, goethite, feldspar, and kaolinite are found as accessory phases. No hematite was detected in the only yellow ochre sample, which contains only goethite.
Speaker bio: Dr. Mengist Teklay, is an Assistant Professor of Geology in the Department of Life & Earth Sciences at Georgia State University Perimeter College. He holds a PhD from the University of Mainz, Germany with magna cum laude. Dr. Teklay holds fellowships with the Max Plank Institute, Germany; University of Muenster, Germany, University of Tasmania, Australia; and University of New Mexico, USA. He has taught at the University of Minnesota and Wisconsin Colleges, USA; University of Asmara, Eritrea; University of Namibia, Namibia; and Addis Ababa University, Ethiopia. Research topics include: Neoproterozoic Arabian-Nubian Shield; Damara Orogenic Belt, Namibia; Continental Flood Basalts (Afar Volcanic Province and Parana-Etendeka Province); Laterites.
Georgia State University Geology Department Presentations
November 30, 2021
Our November 30, 2021 Atlanta Geological Society program will feature several short presentations by a faculty member and three graduate students from the Department of Geosciences at Georgia State University, who will be speaking about their research.
Presentation 1: Overview of the Georgia State University Geosciences Department and its programs
Speaker Bio: Dr. Christy Visaggi, Senior Lecturer in Geosciences at Georgia State University, studies the ecology of ancient marine environments, especially through fossil snails, and she is passionate about sharing her love of science as an educator, paleontologist, and mentor to students. Her fieldwork has taken her to locations such as the Bahamas, Belize, Brazil, and Argentina, and many places across the U.S. Dr, Visaggi received her PhD at the University of North Carolina, Wilmington, and is currently Undergraduate Program Director in Geosciences at Georgia State University. She has been a leader with numerous science education organizations, is an advocate for diversity in the geosciences, and has received numerous awards for her teaching.
Presentation 2: Geologic map of the Tugaloo Terrane in the vicinity of the Brevard Fault Zone, north-half Chamblee Quadrangle, Atlanta
Abstract: Using a combination of existing and newly procured geologic data, we have constructed a geologic map of the northern-half portion of the 7.5minute Chamblee quadrangle in metropolitan Atlanta at a 1:24,000 scale. The mapped area is 31.3 square miles and lies in the complex Inner Piedmont region of southern Appalachia. Our aim was to remedy geologic uncertainties of regional delineations, fault zones, and structural locations based on geologic maps published in 1976 (1:500,000 scale) and 2003 (1:100,000 scale) across the tri-county area of Dekalb, Fulton, and Gwinnett counties. Unmanned aerial vehicle (UAV) drone surveying, digital terrain modeling, GIS file digitization, photogrammetry, and petrographic analyses were employed to support field mapping efforts.
Speaker Bio: Lisa Duong is a masters student at Georgia State University and expects to graduate in Spring 2022. She received her Bachelors degree from GSU in 2019 and her Associates degree from Perimeter College of GSU in 2017. Her Masters thesis research focuses on understanding how and why Costa Rican crust has evolved compositionally through time using 40Ar/39Ar dating and various petrographic and geochemical techniques. She also enjoys working on other passion projects, such as creating a USGS EDMAP geologic map for a portion of Atlanta, and more recently, establishing a campus organization (G.R.O.W.) working to attract, involve, and support those who identify as women in the geosciences with elevated learning experiences.
Presentation 3: Rare-Earth Element Occurrences in Heavy Mineral Sands, Southeast Georgia OLADENI, Ibrahim1, ELLIOTT, W. Crawford1, and RENNER, James F.2
1 – Department of Geosciences, Georgia State University, Atlanta GA. USA
2 – The Chemours Company FC, LLC, 2649 Zero Bay Patterson GA
Abstract: The rare-earth elements (REE) are currently of great interest due to their status as critical metals per the United States Department of Interior and their widespread use in high-tech applications. The heavy mineral sands in northeast Florida and southeast Georgia are Pleistocene and Holocene beach deposits that have been mined primarily for their reserves of titanium and zirconium minerals. They also contain notable concentrations of the REE-bearing phosphate minerals (monazite, and xenotime). A monazite-xenotime concentrate, prepared from Chemours’ Mission Mine in Charlton County, Georgia featured a high concentration of REE (ΣREE = 23,000 ppm). The monazite-xenotime concentrate is enriched in both the light rare-earth elements (Sc, La-Eu; LREE) and the heavy rare-earth elements (Y, Gd-Lu; HREE) relative to concentrations of REE in Upper Continental Crust (UCC). The HREE enrichment is attributed to their concentration in both xenotime and zircon. The LREE enrichment is attributed to their concentration in monazite. A slight positive Sc anomaly (2-3.5 times relative to UCC) was observed in ilmenite and rutile mineral separates. The heavy mineral sands in southeast Georgia are a significant resource for both LREE and HREE. Currently, REE-bearing minerals are being mined at only 2 sites in the United States: southeast Georgia/northeast Florida and Mountain Pass, California.
Speaker Bio: Ibrahim Oladeni is a master’s student and a teaching assistant in the Department of Geosciences, Georgia State University. His research focuses on geochemistry and mineralogy, with special attention to critical minerals and rare earth elements. He is a recipient of the Geological Society of America MPGV Student Travel Award, and National Association of Black Geoscientists Excellent Scholarship.
Presentation 4: New Perspectives on Prolific and Voluminous Rhyolite Volcanism of the Mahogany Mountain—Three Fingers Rhyolite Field, Eastern Oregon
Abstract: Voluminous silicic volcanism of the Mahogany Mountain—Three Fingers rhyolite field (MM—TFrf) is spatially and temporally associated with mid-Miocene flood basalts of the Columbia River Basalt province. Early studies of the area advocated for a two-caldera model consisting of the Mahogany Mountain and the slightly younger Three Fingers caldera with pre- and post-caldera effusive rhyolite eruptions. Although close in time, the calderas were thought to be spatially offset producing the tuff of Leslie Gulch and the tuff of Spring Creek. Finding that the tuff of Spring Creek, that is exposed in Leslie Gulch, is an altered product of the tuff of Leslie Gulch, Benson & Mahood (JVGR, 309: 96-117, 2016) suggested only one large caldera with pre- to post-caldera lavas. With the new data of our study, building on results by Marcy (2013; https://pdxscholar.library.pdx.edu/open_access_etds/1543/), we can address key outstanding questions regarding the stratigraphic and geochemical evolution of Mid-Miocene rhyolite volcanism at the MM-TFrf.
Speaker Bio: Drew Jackson is a geologist and aspiring volcanologist/ PhD student currently seeking to earn his doctorate. He recently acquired his Masters of Geology from Portland State University where he studied rhyolite volcanism associated with the Columbia River flood basalts and the Yellowstone mantle plume. He began his geology career at Georgia State University conducting research under Dr. Christy Visaggi.
Geological Wonders of Iceland
When: 645pm, October 26, 2021
Abstract: Iceland’s landscape has been shaped by dramatic forces over 30 million years. Its formation and ongoing evolution offers a masterclass in geophysical processes. Iceland is a dynamic place where the power and beauty of geology can be witnessed at every turn. It is a geologically young island – less than 33 million years old – and its majestic landscapes are shaped by active plate tectonics, volcanics, and glacial movement. It is one of the only places in the world where a divergent plate boundary is exposed at the Earth’s surface! Furthermore, with 33 active volcanoes, the vast majority of all volcanic features found on Earth can be seen on an island the size of Kentucky or Switzerland. The presentation will offer detailed descriptions linking the relationships between structure, process, and time to the island’s geological evolution.
Speaker Bio: Dr. Tamie Jovanelly is an Associate Professor of Geology at Berry College. She received her PhD from Kent State University, her MS from University of Nebraska, and her BS from University of Michigan. She is sole author of the award-winning monograph titled, Iceland: Tectonics, Volcanics, and Glacial Features (Wiley, 2020). In continuation with her investigations in climate change she received a Research Scientist position on a cruise to the International Territories of Svalbard in 2021. Additionally, she is classically trained as a hydrologist and has completed water quality assessments on 5 continents comparing developed, undeveloped, and developing countries while focusing on major river systems (Nile, Ganges, Amazon, Mississippi, etc.). In 2017-19 she was awarded a US Fulbright Research position with Nacional Universidad (Costa Rica) to study water resources in national parks. This came after she completed her first Fulbright Research assignment (2013-14) with Makerere University (Uganda) where she focused on forest hydrology; a project funded by the National Geographic Society. She has published journal articles in Sustainable Water Resources Management (2020), International Journal of One Health (2020), Journal of Public Health in Developing Countries (2016), Journal of Water and Health: World Health Organization Press (2014). Furthermore, she received a Rufford Foundation Conservation Trust Grant (2015) that supported a collaborative research project with the Kenyan Wildlife Service. Dr. Jovanelly just concluded an appoint as a US Fulbright Specialist whereby allowing her to consult on world-wide water conservation, allocation, and quality issues. In the Spring of 2021, Dr. Jovanelly was recognized for her sustained record of distinguished contributions to the geosciences and was awarded the Geological Society of America Fellow.
Impacts Great and Small—The Role of Hypervelocity Collisions in Sculpting Earth’s Geology
When: 6:45pm, September 28, 2021
Abstract: Only since the confirmation of shocked mineral phases at Barringer (Meteor) Crater by USGS geologists Gene Shoemaker and Ed Chao in the late 1950s has impact cratering by hypervelocity collisions with asteroids and comets been considered a significant agent of geologic change on the surface of Earth– despite having been recognized as the most ubiquitous source of upheaval on other solid planets decades before. Today the scars of approximately 200 impacts have been recognized in the Earth’s crust ranging in size from 10s of meters to more than 200 kilometers in diameter and in age from 14 years to 2.2 billion Ga. Dozens of deposits of ejecta have been identified throughout the stratigraphic record, a few well-correlated with impact structures and some apparently the only surviving remains of events both large and small, including a few likely produced by air bursts just above the ground.
Although spacecraft missions have only increased our understanding of the importance of impact cratering throughout the solar system, and the potential cataclysmic effects on life have been popularized by the K-Pg mass extinction; impact cratering still is unappreciated as a fundamental process responsible for sculpting the evolution of the Earth’s lithosphere at many scales. When many people imagine impacts, they likely think of Barringer Crater, which somewhat like our Sun to astronomers is easily accessible, instructive, and aesthetically pleasing but probably isn’t all that representative of the phenomenon. Thanks to the Carancas impact in Peru in 2007, we must look at every small pock mark across a barren plain with a more critical eye. And the other end of the spectrum, large impacts can produce enormous volumes of igneous rocks, large-scale tectonic deformation, and thick sedimentary deposits that can be and often have been interpreted as representing millions of years of geologic history– before geologists stumbled upon the evidence that everything had formed almost in the blink of an eye. We will examine the record of asteroid and comet impacts on Earth and what it means for understanding the geologic past of our planet.
Speaker Bio: R. Scott Harris is the planetary geologist and meteorite curator for Fernbank Science Center and the Jim Cherry Memorial Planetarium in Atlanta, Georgia. A Georgia native, he was educated at Arizona State University, the University of Georgia, and Brown University. A world traveler, field geologist, petrologist, and educator, he has spent most of his 30-year career studying the record of asteroid and comet impacts on Earth. The author or co-author of more than fifteen peer-reviewed papers and field guides and over a hundred conference abstracts, Scott also studies extraterrestrial volcanism and the ancient history of our solar system preserved in meteorites. He is the current Outstanding Earth Science Teacher for Georgia, awarded by the National Association of Geoscience Teachers, and serves as Communication Director for the Southeastern Section of NAGT. Scott also serves as the new Field Trip Coordinator for AGS.
Tuesday, June 29, 2021 AGS virtual meeting.
Abstract: The Fall Line is the landward edge of the Mesozoic and younger sediments of the Atlantic and Gulf Coastal Plains. Shoals and rapids upstream of the boundary, caused by exposure of older, harder rocks, localized many cities founded in pre-railroad times, by impeding river navigation and providing waterpower. The sinuous course of the Fall Line from Texas to New York City is traceable to tectonic events from the Cambrian Period down to the present, including the following (approximate ages in millions of years ago): separation of ancestral North America from the supercontinent Rodinia (570), collision of continents to make Pangaea (320), collapse of the mid-Pangaea mountains and subsequent rifting (280), opening of the Atlantic Ocean (170), Southern Appalachian present uplift (15). The history of uplift and erosion down to the present accounts for the fact that some parts of the Piedmont (Upper Flint River basin) are flatter than parts of the Coastal Plain (Fall Line Hills). Human land use may have widened floodplains downstream of the Fall Line.
Speaker Bio: Bill Witherspoon is co-author (with Pamela Gore) of Roadside Geology of Georgia, which has sold more than 8,000 copies. Since the book appeared in 2013, Bill has presented more than 100 walks, talks, and workshops throughout the state. From 1997 until his retirement in 2014, he was an instructor at Fernbank Science Center, part of DeKalb County Schools. In 2007, the National Association of Geoscience Teachers named him Georgia Outstanding Earth Science Teacher. He has worked as a research geologist for Shell Oil and taught at UT Chattanooga. His Ph.D. research at UT Knoxville concerned the structure of Blue Ridge front in Tennessee. Bill provides an events e-newsletter sign-up, event calendar, teacher resources, digital maps, and signed books at the web site georgiarocks.us.
U.S. Energy Sources: Where it has Changed in the Last Decade
presented by Ron Wallace, President of the Georgia Chapter of the American Association of Professional Geologists
Tuesday May 25, 2021 6:45 PM Eastern Standard Daylight Savings Time
Abstract: In 2009, Ron Wallace, was on an energy committee and the results were published and presented at conferences and at the Atlanta Geological Society. The presentation was a review of our sources of energy in the U.S. and where they are being used. His talk also looked at the world energy production and predicted energy use to 2035. There was a discussion on environmental issues resulting from all energy sources. Most of the information came from the U.S. Energy Information Administration.
This presentation will compare the change in energy sources from the original presentation to more recent data, prior to the downturn caused by the pandemic. There will also be discussion on where the original 2035 predictions were correct and where they missed. The current data will be used to predict changes in energy sources to 2050. There will be a short look at the world energy sources and predict how it will also change by 2050.
Speaker bio: Ron Wallace has a BS degree in Oceanographic Technology from Lamar University and a MS in Geology from University of Kansas. He was employed by Exxon in South Texas and East Texas Production, Offshore Alaska Exploration, and Marketing in Environmental Department. He worked in the Atlanta area for a number of environmental consulting firms, then worked for the Georgia Environmental Protection Division and retired as a Program Manager in the Underground Storage Tank Program. He is President of the Georgia Chapter of the American Association of Professional Geologists (AIPG).
Oil and Gas in the Gulf of Mexico Basin, with Tales from the Oil Patch
Tuesday April 27, 2021 6:45 PM
Abstract: The Gulf of Mexico Basin has been a prolific region for finding and producing oil and gas. A widespread, thick layer of salt was deposited during the early opening of the Gulf in mid-Jurassic time; then huge amounts of sediment eroded from the Rockies to the Appalachians were piled onto that unstable salt base, producing a cornucopia of structural opportunities to trap oil and gas, with much variation from region to region.
The first part of this presentation briefly reviews some of the basics of petroleum geology, oil well drilling, logs, and business environment, to set up a common understanding for the second part which discusses the geology of different subareas of the basin. Specific areas include the Texas onshore/shelf growth faults, the Louisiana onshore/shelf/deepwater salt dome region, an ultradeep fold belt near Mexico, and aeolian sands generally south of Alabama. The presentation will also include discussion of the root causes of some industry-related disasters, and other more benign tales of interest.
Speaker Bio: David Lynch was born and raised in the Atlanta area, and received his B.S. in Physics at the University of Georgia in 1976. He entered the graduate program at New Mexico State University in Las Cruces, where curious about the Rio Grande Rift that surrounded him, he discovered his love of geology and turned to a geophysics course of study. He received his Ph.D. in 1983 with a dissertation on computer models of continental rifting. He then joined Shell in Houston as an exploration geophysicist and held a series of international assignments involving acquisition, processing, and interpretation of seismic data, along with the drilling of numerous exploration wells. After a stint in Shell’s Research Center, he transferred in 1991 to the New Orleans office where he spent the first couple of years as a seismic interpreter seeking prospects on the Texas Shelf for Shell to bid on in federal lease sales. This was followed by a few years in borehole geophysics, solving special problems delineating flanks of salt domes. In 1997 he joined the deepwater producing assets division where he spent the rest of his career seeking locations to drill new wells in existing fields, and guiding these wells through drilling to final depth. This period also included being on occasional regional study teams to solve a special geo-related problems. He retired in 2014 and now spends most of his time on a country property in the woods northwest of Lake Pontchartrain, observing nature, and pursuing several geological interests.
Geophysical Log Database and Digital Surfaces for the Floridan Aquifer System in Florida and Parts of Georgia, Alabama, and South Carolina
Tuesday March 30, 2021 6:45 PM
Abstract: A database of borehole geophysical logs and other types of data files were compiled as part of studies of water availability and assessment of brackish- and saline-water resources (Williams and others, 2016). The database contains 4,883 logs from 1,248 wells in Florida, Georgia, Alabama, South Carolina, and from a limited number of offshore wells of the eastern Gulf of Mexico and the Atlantic Ocean. The logs can be accessed through a download directory organized by state and county for onshore wells and in a single directory for the offshore wells.
The objective of this study was to improve the overall understanding of the available fresh, brackish, and saline water resources for ongoing and potential future development. Specific tasks were to (1) develop a digital georeferenced database of borehole geophysical data to enable analysis and characterization of fresh, brackish, and saline aquifers (see locations in Fig. 1), (2) identify and map the regional extent of the fresh to saline aquifer systems and describe the thickness and character of hydrologic units that compose these systems, and (3) delineate salinity variations at key well sites and along section lines to provide a regional depiction of the freshwater-saltwater interfaces. Electrical resistivity and induction logs, coupled with a variety of different porosity logs (sonic, density, and neutron), were the primary types of borehole geophysical logs used to estimate the water quality in brackish and saline formations. The results from the geophysical log calculations were compared to available water-quality data obtained from water wells and from drill-stem water samples collected in test wells.
Gamma ray and resistivity markers were used to map the base of the aquifer system throughout much of the peninsular area with an example of these markers from a well in De Soto County Florida (Fig. 2). Mapped units include a low-resistivity zone near the base of the aquifer system often denoted by a basal gamma ray marker, a massive dolostone unit within the Oldsmar Formation, and the Glauconite marker unit. Although geophysical log response varies considerably throughout the area, individual high and low-permeability zones within the aquifer system could be mapped generally along distinct lithologic units such as shown for a well in Citrus County, Florida (Fig. 3). In this well the aquifer contains permeable zones near the top of the carbonate rock sequence, in the middle of the sequence (Avon Park Formation) and near the base of the system (Oldsmar Formation).
Using point data compiled from geophysical logs and water samples from wells, digital surfaces and thicknesses of selected hydrogeologic units of the Floridan aquifer system were developed to define an updated hydrogeologic framework (Williams and Dixon, 2015). The dataset contains structural surfaces depicting the top and base of the aquifer system, its major and minor hydrogeologic units and zones, geophysical marker horizons, and the altitude of the 10,000-milligram-per-liter total dissolved solids boundary that defines the approximate fresh and saline parts of the aquifer system. The thicknesses of selected major and minor units or zones were determined by interpolating points of known thickness or from raster surface subtraction of the structural surfaces. Additional data contained include clipping polygons; regional polygon features that represent geologic or hydrogeologic aspects of the aquifers and the minor units or zones; data points used in the interpolation; and polygon and line features that represent faults, boundaries, and other features in the aquifer system.
Speaker Bio: Lester Williams received B.S. 1986 and MS 1990 degrees University of Louisiana at Lafayette.
Independent consulting hydrologist with a passion for developing sustainable groundwater resources for agricultural, industrial, and commercial supplies. Worked as a practicing hydrogeologist in the engineering/consulting field from 1990 to 2000 working on industrial and military sites investigating extents of contamination and developing corrective actions in North Carolina, South Carolina and Georgia. Starting from about May 2000 and extending to 2015, worked tirelessly at U.S. Geological Survey conducting various groundwater studies in the Piedmont and Coastal Plain of Georgia including a major revision of the Floridan Aquifer System which is the main source of water in Florida and in parts of Georgia, South Carolina, and Alabama. Insights gained through these studies have greatly increased the understanding of regional stresses on groundwater availability and interaction with underlying and overlying water-bearing units.
Tuesday February 23, 2021 6:45 PM Eastern Standard Time
“Structural and Stratigraphic Controls on Saltwater Intrusion, St. Catherines Island, Georgia” presented by Robert Kelly Vance (Georgia Southern University)
Authors: Robert Kelly Vance, Jim Reichard and Jacque Kelly (Georgia Southern University) and Brian Meyer (Georgia State University)
With support from Georgia Sea Grant and the St. Catherines Island Foundation.
Abstract: St. Catherines Island (SCI), Georgia consists of a Pleistocene Silver Bluff shoreline sedimentary core flanked by Holocene ridge and swale, and salt marsh deposits. Holocene dunes cover the higher (4.3 – 7.9 m elevation) northern and eastern core, thinning to the west. A NE-SW trending lowland (2.5 – 5.0 m elevation) occupies the central and western portions of SCI and contains Holocene freshwater wetland deposits. Coring and radiocarbon dating in the lowlands revealed substantial variation in thickness (<1 m to > 3 m) of Holocene sediments, and variation in elevation (0.6 m to 4.3 m) of the Holocene/Pleistocene contact. Plant clasts from cores provided conventional ages of > 37,410 BP for Pleistocene strata. A wood clast in a core from the southern lowlands gave the oldest Holocene conventional radiocarbon age of 8,410 +/- 30 BP. Some relief on the Pleistocene erosional surface may be due to fault displacement as suggested by offsets in specific clay beds and distinct NE-SW and NW-SE linear geomorphic features. The former artesian springs and the active saltwater intrusion (by upconing) in the Upper Floridan of SCI require faults. The shallow aquifer systems are also experiencing localized pulses of saltwater intrusion. Coring and monitoring well installation reveal a water table aquifer (< 11 m depth) in Holocene and Pleistocene sands, and a semi-confined aquifer (>12.2 m depth) in Pleistocene sands, separated by an aquitard of Pleistocene clay and clayey sand. Head, specific conductivity and chemical data from 24 monitoring wells indicate very high tides and storm surges drive saltwater along permeable pathways to specific wells in the SCI interior. Certain wells in the semi-confined aquifer also react to tidal events, but have a lower background salinity than the unconfined wells. Geophysical profiles (GPR, ER) indicate permeable pathways are associated with faults and sag structures. Periodic influx of saltwater into the shallow aquifers of SCI should increase in frequency and extent with rising sea level and increased storm surge activity. The most recent well logger downloads reveal major storm surge and king tide salinity spikes in 2020, supporting this conclusion.
Biography of Robert Kelly Vance:
Ph.D. – 1989 New Mexico Institute of Mining and Technology
M.S. – 1984 University of Kentucky
B.S. – 1978 University of Kentucky
Kelly Vance grew up on a family farm in Kentucky and decided to major in geology after taking an introductory geology course at Elizabethtown Community College. He transferred to the main U.K. campus in Lexington where he completed his B.S. and M.S. degrees. He worked in DOE-funded Devonian oil shale field and geochemical research with the UK Geology Dept., the Kentucky Geological Survey, and the Institute for Mining and Minerals Research as a graduate student. Kelly did his Ph.D. work at New Mexico Tech and took a two year temporary position at Appalachian State University as he finished writing his dissertation. He has been teaching at Georgia Southern since the fall of 1989. The regular courses He teaches at GSU include Mineralogy, Petrology and Petrography, and Economic Geology as well as the field-based Sea Turtle Natural History and Barrier Island Environmental Geology courses on St. Catherines Island (SCI), Georgia. Research interests and activities include tectonic and geologic environment of Volcanogenic Massive Sulfide deposits, igneous petrology, applications of Ground Penetrating Radar, and barrier island hydrogeology. He also supports sea turtle conservation by monitoring SCI beaches for the GA DNR in the summer and teaching students while serving as co-director of the GSU Sea Turtle Program at St. Catherines Island.
Tuesday January 26, 2021 6:45 PM
“Ice Station T-3: Its Exciting History and its Importance for Science and U.S. Defense” presented by John Berry, FGS, PG(TX), CPG
Abstract: Ice Island T-3, a large (63 sq.miles) tabular iceberg, was manned by the U.S.Air Force and Navy for four different periods of time between 1952 and 1978. It was visited by USS Skate in 1958, and by the icebreaker Northwind in 1962. This latter visit led to some tragedy. The Iceberg circled the Canada Basin of the Arctic Ocean twice, even though it ran aground for several years on the northern shelf of Alaska. It drifted through the Fram Strait in 1983, and melted in the North Atlantic.
Over the years a tremendous variety of Geological and Geophysical research projects were carried out from the Island, besides routine charting of the ocean floor and mapping of the gravity and magnetic fields. These projects included studies of the aurora, measurement of the earth’s heat flow, detection of Russian nuclear blasts, studies of ocean-, sound-, and seismic-wave propagation beneath the ice, and sampling and dating of the ocean bottom sediments.
Biography: John Berry, FGS, PG(TX), CPG is a semi-retired geologist who worked on T-3 in the summer between college and graduate school. He began his professional career in Zambia exploring for copper, cobalt, limestone, and water. After moving back to the U.S., he taught at a Technical College in western North Carolina until joining Earth Satellite Corporation in Maryland to work on mineral and oil exploration projects worldwide. He joined Shell in 1982 to explore for gold, and then spent 15 years in exploration research and frontier oil exploration: he pioneered the use of natural oil slicks as an oil exploration tool in off-shore basins.
Tuesday Nov 24, 2020 6:45 PM
“Black Granite from Hell” presented by Steven Stokowski.
Abstract: In the center of the Rhode Island Veterans Cemetery is a large Ceremonial and Commemorative area. This dramatic, horseshoe-shaped memorial has sweeping cast-in-place concrete walls with fifty-eight, inlaid, 6-foot high, black granite panels having engraved veterans’ names. During the initial 1998-99 construction phase, the project was relatively trouble-free except that the availability of the large stone panels delayed the project for 7 months. The original granite specified was from Zimbabwe, but the architect actually wanted stone from South Africa, which was not available because of sanctions. Of the “black granites” available, the architect then approved a very dark and coarse-grained “granite” from Canada. Soon after installation, most of the stone panels progressively developed popouts and cracks. The only realistic solution to the pervasive failure was to replace all the panels, although the manufacturer would not admit to any materials problem and supply replacement panels free-of-charge. Ultimately, there was no inexpensive and amicable solution for any of the participants in this project. The state declared non-performance and suspended the project engineer, the design architect, and the contractor from bidding on state projects for two years. This resulted in many lawsuits that were resolved to nobody’s satisfaction, but with the vindication of some of the parties. The state ultimately slightly redesigned the memorial, demolished the 1999 construction, and caused a new memorial to be constructed with stone from another source.
The stone panels deteriorated because the dimension stone product was inherently defective at the microscopic level. Saponite, a water-sensitive, swelling clay, is present in the stone. It did not swell in the 1999 Rhode Island drought that followed the installation, but, as soon as it began to rain, the iron-rich saponite absorbed water, causing popouts and stressing the stone until it cracked. Black granite is a stone industry term for black, hard, crystalline rocks such as norite, gabbro, and anorthosite, as compared to fine-grained crystalline rocks such as basalt, or the black varieties of softer calcitic rocks such as limestone or marble. In addition to saponite alteration, the Peribonka® anorthosite contains deleterious ore minerals such as chalcopyrite, younger veins of secondary calcite, and later antigorite veins. The calcite and antigorite veins are weak planes in the stone that cracked when the panels became stressed by the swollen saponite. These natural weak points are not defects, but the natural locus of cracks when the stone was stressed to failure.
Steven Stokowski, a registered Professional Geologist, is the owner and materials geologist of Stone Products Consultants. Steve has extensive geological and petrographic experience across the US. He has a MS in Geology from the South Dakota School of Mines and Technology and a BS in Geology from George Washington University. Steve is the 2014 recipient of the Herbert C. Hoover Award from the Washington DC Section of the Society for Mining, Metallurgy and Exploration (SME), the 2017 Robert W. Piekarz Award from SME, and the Chair of the Industrial Minerals and Aggregates Division of SME. He is Registered or Certified as a Geologist in Georgia, Maine, Virginia and other states.
Tuesday October 27, 2020 at 6:30 pm Eastern Time
“HIDING IN PLAIN SIGHT”: EVIDENCE FOR A MESOZOIC GENESIS OF THE PHREATIC KARST NETWORK IN THE APPALACHIAN GREAT VALLEY” presented by Robert Denton, CPG, of Terracon Consulting.
Ever since the seminal research of William Davis in the early 20th century, the paradigm for the development of Appalachian cavern systems has regarded regional downcutting and lowering of the base level since the Late Miocene epoch as the primary mechanism of speleogenesis. The majority of cave systems were considered no older than the Irvingtonian North American Land Mammal Age (Early through Middle Pleistocene), based on dating of vertebrate index fossil remains found in cavern fill sediments. Nevertheless, since the mid-19th century, there have been reports that suggest the parent phreatic network of the Appalachian Great Valley region may be far older.
Paleogene dates were first suggested for lignite deposits found in karst depressions at Brandon, Vermont, and Pond Bank, Pennsylvania, as early as 1864. Studies of the iron deposits along the west pediment of the Blue Ridge revealed a continuous lineament of karst-related features, often associated with kaolin and lignite. In the 1940s, kaolin and karst bauxite deposits stretching from Virginia to Alabama were discovered. Subsequent palynological analysis of the cave fill and lignite revealed these features ranged from the Turonian stage (93.8 – 89.8 Ma) of the Late Cretaceous through the Early Miocene (20.4 – 16.0 Ma), with most dating from the Early Paleogene.
We propose that the majority of karst-associated laterites (kaolin, bauxite) were probably formed by intense weathering during the Paleocene/Eocene Thermal Maximum (PETM), although a brief period of warming during the Late Miocene may have contributed to the development of laterites present at the Brandon lignite locality. Fossil pollen in karst fills as old as the Turonian stage of the Late Cretaceous suggests an Early Mesozoic age for the probable hypogene speleogenesis of the parent network. Thus, the existing epikarst cavern systems of the Great Valley may be the exposed remnants of an ancient phreatic network that has been repeatedly filled and emptied of sediment since its origin. The recent discovery of karst bauxite in a cave in Virginia suggests that ancient sediments may be more widespread in existing cavern systems than previously thought, but may have been overlooked.
Biography – Robert K. (“Bob”) Denton Jr. was born in 1953 in Montclair, New Jersey. He received his Bachelor’s Degree in Natural Science from Thomas Edison State College in Trenton, NJ in 1988. Bob worked as a research scientist in the chemical and medical device industries for over 20 years, specializing in physical methods of analysis. He relocated to Winchester, Virginia in 1995, and is currently a senior geologist and karst geology “Subject Matter Expert” (SME) with Terracon’s DC Metro office, located in Ashburn, VA. His specialties include environmental science, engineering geology, hydrogeology, and karst characterization, remediation and management. He is considered a national expert on stormwater management in karst terrains.
Bob has been an avid caver since his teen years, and this led to his interest in geology from a very early age. He received formal training in geology and vertebrate paleontology field methods during the summer of 1972 while serving on an expedition to the Bighorn Basin of Wyoming and Montana sponsored by the Museum of Comparative Zoology at Harvard University. Bob is the discoverer of the Ellisdale Fossil Site in NJ, and the Zuni Basin dinosaur site in New Mexico, and has formally described two new taxa. He has been a research associate with the New Jersey State Museum since 1979, and continues in that role today.
Bob is a Certified Professional Geologist (CPG), a State of Virginia Certified Professional Soil Scientist (CPSS) and a State of West Virginia Licensed Environmental Remediation Specialist (LRS). He is a member of the National Speleological Society (NSS), Society of Vertebrate Paleontology (SVP), Association of Environmental and Engineering Geologists (AEG), and the American Chemical Society (ACS). Bob has published numerous articles on subjects including karst, vertebrate paleontology, and materials science. He has been awarded five (5) United States Patents for materials science “discovery of matter” and chemical (process) engineering.
Tuesday, August 25, 2020 at 6:30 pm Eastern Time
Dr. Paul Santi of the Colorado School of Mines.
Geology and the Birth of Landscape Photography: Following Vittorio Sella, Bradford Washburn, and Ansel Adams.
Abstract: The Foothills Art Center in Golden, Colorado hosted an extensive landscape photography exhibit in 2015, including works from Ansel Adams’ Legacy collection, from Vittorio Sella, the early photographer who inspired him, and from Bradford Washburn, the pioneering aerial photographer. Recognizing the importance of geology in these images, the Center contacted the Colorado School of Mines and requested help preparing geology labels to accompany labels written by the curator. Over a five month period, seven students selected by application prepared labels to accompany 37 of the photos, directed by two faculty: a geologist and a science historian. Students independently researched the geology of the photographs, which often required a fair amount of detective work for some of the century-old images. They then wrote, edited, and trimmed the label text, struggling to stay under the 120 word limit, yet keeping the content interesting, unique, and understandable by a lay audience. Every student edited every label at least four times. Alpine scenes dominated, but subjects also included glaciated landscapes, arid terrain, sand dunes, rivers, and contrasts in weathering. The exhibit ran from June 13 – August 30, with several thousand visitors exposed to the linkage between the stunning landscapes and the geology that created them. In this presentation, we will view many of these images, learning the geologic setting, how the geology contributed to the artistic elements of the photo, and how to look at geology from an artist’s eye.
Paul M. Santi
Director – Center for Mining Sustainability
Dept. of Geology and Geological Engineering
Colorado School of Mines
Golden, CO 80401
Tuesday, July 28, 2020 at 6:45 pm
“ITRC’s Characterization & Remediation of Fractured Rock Webinar”
Presented by Kris McCandless, Virginia DEQ
From 2015 to 2018, when it was published online, the Interstate Technology and Regulatory Council (ITRC’s) Characterization and Remediation of Fractured Rock web-based document and subsequent internet-based training have enlightened thousands of new and experienced geologists and environmental scientists with the practical and applicable aspects of structural geology, hydrogeology, and geography that we all had as core classes in our training. I helped to draft portions of the document starting in 2015 when I joined the Virginia Department of Environmental Quality, but more importantly, I was asked in late 2018 to provide the introduction for the internet-based training of this important document. And I have done that at least seven times in the past 2 years, learning something new every time I listen to my fellow speakers present their parts. Knowing not everyone in this audience works in the environmental field, I will focus the training on some of the structurally geologic points as they dictate groundwater flow through the fractured media, and will use examples of “floaters and sinkers” (types of contaminants) in that discussion and why their characteristics are important for investigation and remediation. In my consulting days (25 of my 30 year career), I took it as a compliment that one boss called me a “rabid geologist”, as I kept my Brunton compass and my two types of rock hammer in my field vehicle, always clambering on an outcrop for strike and dip measurements, or standing back from it to find the fracture pattern that would give me a clue to how groundwater might be flowing beneath an impacted site.
From 1998 until about 2012, I was active in AEG (Assoc of Engineering and Environmental Geologists), serving in all offices except treasurer of the local Virginia-Maryland-DC Chapter, where Steve Stokowski and I crossed paths. I graduated from George Mason University in Fairfax, VA in 1988 with a BS in Geology, took Indiana University’s Field Camp in Cardwell, Montana in 1987 and passed the ASBOG exam in Virginia to obtain my CPG license in 2002, which I have maintained. After presiding for many AEG dinner meeting presentations and now here at the Atlanta Geological Society, this will NOT be a boring presentation. There might be one graph, but I’ll cover it quickly!
Notes from the June Meeting:
June 30th, 2020 at 6:45 pm
“Carolina Bays are relict thermokarst lakes from the time of the last glaciation“
Presented by: Dr. Chris Swezey, U.S. Geological Survey, Reston, VA
New studies combining LiDAR imagery and field work have revealed the presence of widespread eolian sands that are now stabilized by vegetation throughout the U.S. Atlantic Coastal Plain. Optically stimulated luminescence (OSL) dates from these sands have yielded ages ranging from ~92–5 thousand years ago (ka), but most of the dates are approximately coincident with the last glacial maximum (LGM). These eolian sands are present in river valleys, in the Carolina Sandhills region, and on upland areas of the northern coastal plain. Eolian sands are also present as low-relief ridges on the south and east margins of Carolina Bays, which are oriented oval to circular depressions on the Atlantic Coastal Plain. Cores in Carolina Bays and their associated ridges reveal that they are primarily surficial features consisting of a few meters of sand and/or muddy sand above an unconformity on various older fine-grained substrates that do not show signs of disturbance. Furthermore, some Carolina Bays show distinct stratigraphic relations with respect to eolian dune fields in river valleys, for example:
(1) Dukes Pond is a Carolina Bay that is inset into (i.e., younger than) eolian dunes in the valley of the Ohoopee River (Tattnall County, Georgia);
(2) Bear Swamp is a Carolina Bay that is inset into (i.e., younger than) eolian dunes in the valley of the Great Pee Dee River (Marion County, South Carolina);
(3) Big Bay is a Carolina Bay that is overlain by (i.e., older than) eolian dunes in the valley of the Wateree River (Sumter County, South Carolina).
Most published OSL ages from Carolina Bay sand ridges range from ~40–11 ka. Some Carolina Bays have multiple sand ridges, and ridges closer to individual bays yield younger OSL ages. The stratigraphic relations and the range of OSL ages suggest that Carolina Bays are relict features that did not form during one event of limited duration. Instead, they formed episodically during the same time interval as other eolian sands of the coastal plain (e.g., mostly during the last glaciation when conditions were colder, drier, and windier). This interpretation suggests that Carolina Bays are relict thermokarst lakes. Such lakes are present today in high-latitude regions, and they develop as a result of thaw and collapse of frozen ground with subsequent modification by lacustrine and eolian processes. Thus, the distribution of Carolina Bays may provide information about the former distribution of frozen ground. Although the southern limit of continuous permafrost during the last glacial maximum (LGM) is usually thought to have been located in northern Virginia ~300 km south of the LGM ice sheet margin, the interpretation of Carolina Bays as relict thermokarst lakes suggests that permafrost may have extended as far south as Georgia ~1000 km south of the LGM ice sheet margin. This distance of ~1000 km from the LGM ice margin compares favorably with studies in Europe (where permafrost is thought to have extended 800-1200 km south of the LGM ice margin) and in Asia (where permafrost is thought to have extended 2000-4500 km south of the LGM ice margin).
Research Geologist (2018-Present), U.S. Geological Survey (USGS) Florence Bascom Geoscience Center, Reston, Virginia. I conduct basic geologic mapping and research on stratigraphy, sedimentology, and geomorphology. This work is focused primarily on Paleozoic basins of the eastern United States, and potential applications for water, energy, and mineral resources.
Research Geologist (2009-2018), USGS Eastern Geology & Paleoclimate Science Center, Reston, Virginia. I conducted basic geologic mapping and research on stratigraphy, sedimentology, and geomorphology. This work was focused on the U.S. Atlantic Coastal Plain, for the purpose of understanding the geologic framework and for characterizing Cretaceous and Cenozoic strata that are major aquifers.
Research Geologist (2000-2009), USGS Eastern Energy Resources Team, Reston, Virginia. I conducted assessments of undiscovered oil and gas resources, and research on stratigraphy and petroleum systems. This work was focused primarily on Paleozoic strata of the Appalachian, Michigan, and Illinois basins (USA), for the purpose of understanding National energy supplies, providing input for economic analysis of petroleum resources, and improving knowledge of the stratigraphy and petroleum systems of the basins.