Monthly AGS Meeting
Join us Tuesday October 27, 2020 at 6:30 pm Eastern Time for our monthly AGS virtual meeting via Zoom. This month’s presentation is “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.
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Join us Tuesday, August 25, 2020 at 6:30 pm Eastern Time, for our monthly AGS meeting via Zoom. This month’s presentation is coming from 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
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Join us Tuesday, July 28, 2020 at 6:45 pm for a Virtual AGS Meeting on Zoom. https://us02web.zoom.us/j/89579296351
Presentation at 7 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 for a Virtual AGS Meeting on Zoom.
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“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).
Christopher S Swezey
Florence Bascom Geoscience Center
U.S. Geological Survey
12201 Sunrise Valley Drive, MS 926A
Reston, VA 20192
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.
PG Candidate Workshop
The classes are open to all, membership in the AGS is not required. Please consider joining, the AGS is the most active geologic organization in the Southeast. An application is available here.
Two hours of professional development credit are available for attendees.
Atlanta Geological Society
Professional Registration/Career Development Committee Ken Simonton, P.G.