EAST TENNESSEE GEOLOGICAL SOCIETY

January 2025 Virtual Meeting

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Monday, January 13, 2025
6:00 pm - 7:00 pm

January Presentation

Stratigraphic correlation of sands and gravels in the uppermost Atlantic Coastal Plain, Virginia

 

By

Mark Carter¹, Kathleen Farrell², Marcie Occhi3, Diana Carriker¹, Tomonori Naya4, Masayuki Utsunomiya⁴, Will Odom¹, Michelle Nelson³,
Calley Anthony², McKenzie Hamilton², Roy Bassoo³, Stalin Rosero Pozo², David Hawkins³, Amy Edwards⁵, Bryan Landacre¹, Robert Poirier¹
 

Abstract

Researchers from the U.S. Geological Survey, the North Carolina Geological Survey, Virginia Energy, and the Geological Survey of Japan, are working to determine the age and stratigraphic position of Atlantic Coastal Plain (ACP) sand and gravel deposits in the Fall Zone of Virginia and North Carolina. This research is critical to U.S. economic stability and national security because these sand and gravel deposits host rare earth element (REE)-bearing heavy mineral resources in Virginia, North Carolina, and elsewhere in the southeastern U.S. The host sediments are not fossiliferous, and so there is little consensus as to their age, stratigraphic position, and even the nomenclature used to describe the units. We are combining regional geologic mapping with multiple biostratigraphic and isotopic dating techniques to achieve results. This research is funded by the USGS National Cooperative Geologic Mapping Program, FEDMAP and STATEMAP components, through the Southeastern Atlantic Coastal Plain Interstate Correlation Working Group.

Sand and gravel units in the Virginia Fall Zone underlie three distinct topographic surfaces and are separated by geomorphic scarps that represent paleoshorelines. These units have been conventionally assigned to fluvial, fluvial-deltaic, and marginal marine facies of marine Miocene to Pliocene Chesapeake Group formations to the east (e.g., Mixon and others, 1989). In the Richmond, Virginia, area, the sand and gravel unit west of the Chippenham scarp is situated up to about 275 ft above mean sea level (amsl), and is correlated with the Pliocene Yorktown Formation. By contrast, the sand and gravel unit west of the Thornburg scarp is situated above 300 ft amsl, and is correlated with Miocene Chesapeake Group units. In southeastern Virginia, sand and gravel are separated into three units; the topographically lowest unit is present west of the Broad Rock scarp up to an elevation of about 235 ft amsl, and is correlated with the Pleistocene Chowan River Formation of the Chesapeake Group (Weems and others, 2010). Mapping by Virginia Energy applied the term "Cold Harbor formation" to the topographically lower sand and gravel unit west of the Chippenham scarp in the Richmond area in the mid-2010s (Berquist and Gilmer, 2014). The topographically highest unit is assigned various regional names, including Appomattox (McGee, 1888), Bryn Mawr (Bascom, 1924), Midlothian (Goodwin and Johnson, 1970) or Altamaha (Huddleston, 1988); most of these terms are abandoned, informal, or questionably applied.

These units unconformably overlie crystalline rocks of the eastern Piedmont, or are nonconformable above fossiliferous Miocene sandy, silty, and clayey marine strata of the ACP Chesapeake Group. However, more precise maximum depositional age control points are few. In the Richmond area, the topographically highest sand and gravel unit west of the Thornburg scarp is younger than middle Miocene in age (dinoflagellate biostratigraphy; Edwards and others, 2018). The topographically lower sand and gravel unit west of the Chippenham scarp is younger than late Miocene in age (calcareous nannofossil biostratigraphy; this report). In southeastern Virginia, the topographically lowest two units are likely younger than early Pliocene in age (diatom biostratigraphy; this report). Pollen data from sand and gravel mapped as Cold Harbor formation by Virginia Energy near Petersburg, Virginia indicates at least a portion of the unit was deposited in a Pliocene swamp or freshwater marsh (Carriker and others, 2020). Additional stratigraphic control points are forthcoming. These include: 1) new biostratigraphy from core and outcrop near the proposed type section of the Cold Harbor formation northeast of Richmond, and 2) a first-of-its kind application of the cosmogenic nuclide burial dating technique to uppermost ACP stratigraphy on a core collected from sand and gravel unit(s) that host the Old Hickory heavy mineral deposit in southeastern Virginia (Carter and others, 2024).

Current models assign heavy mineral paleoplacers in southeastern Virginia to two zones (Shafer, 2000) within at least two sand and gravel units (Carter and others, 2022). Heavy minerals may have been sourced from the Blue Ridge, transported across the Piedmont in now abandoned paleodrainage systems, and deposited with host sands and gravels along paleoshorelines (Newton and Romeo, 2006). Syn-depositional faulting likely further concentrated heavy mineral occurences (Berquist and others, 2015). Significantly, after extensive mining for zircon and titanium oxide minerals from 1997 to 2015 (Van Gosen and Ellefsen, 2018), recent USGS Earth Mapping Resources Initiative airborne radiometric survey data exhibit elevated thorium anomalies over heavy mineral deposits in southeastern Virginia and northeastern North Carolina (Shah and Connell, 2022). These anomalies are attributed to detectable levels of REE-bearing monazite (Shah and others, 2022). Precise ages and stratigraphic positions will improve our understanding of these locally heavy mineral-bearing sand and gravel units, lead to higher quality maps that show their surface and subsurface distribution and allow for targeted exploration throughout the Fall Zone from Virginia to Georgia.

References Cited:

• Bascom, Florence, 1924, The resuscitation of the term Bryn Mawr gravel, IN Shorter contributions to general geology, 1923-24: U.S. Geological Survey Professional Paper, 132-H, p. H117-H119.

• Berquist, C.R. Jr., and Gilmer, A.K., 2014, Progress of Coastal Plain geological mapping from Richmond to the Virginia Eastern Shore: Geological Society of America, Abstracts with Programs, v. 46, no. 3, p.13.

• Berquist, C.R., Jr., Shah, A.K., and Karst, A., 2015, Placer Deposits of the Atlantic Coastal Plain: Stratigraphy, Sedimentology, Mineral Resources, Mining, and Reclamation: Society of Economic Geologists, Guidebook Series v. 50, 52 p.

• Carriker, D., Occhi, M., Carter, M.W., Bernhardt, C., and Berquist, C., 2020, Determining the age and depositional environment of Coastal Plain sediments at the Jack Quarry, VA using palynology: Geological Society of America Abstracts with Programs, v. 52, n. 2, doi: 10.1130/abs/2020SE-343992.

• Carter, M., Seidenstein, J., Farrell, K., Nelson, M.S., Rodysill, J., Odom, W., Holm-Denoma, C., Occhi, M.E., and Hawkins, D.W., 2024, Using the U.S. Geological Survey Geotek multi-sensor core logger system to analyze and preserve core from the Old Hickory heavy mineral deposit, southeastern Virginia: Geological Society of America Abstracts with Programs, v. 56, n. 2, doi: 10.1130/abs/2024SE-398116.

• Carter, M.W., Karst, A.T., Berquist, C.R., Jr., Schindler, J.S., Weems, R.E., Weinmann, B.R, and Crider, E.A., 2022a, Preliminary geologic map of the Cherry Hill quadrangle, Dinwiddie, Sussex and Greensville Counties, Virginia: U.S. Geological Survey Open-File Report 2021-1106, 1 sheet, scale 1:24,000, https://doi.org/10.3133/ofr20211106.

• Edwards, L.E., Weems, R.E., Carter, M.W., Powars, D.S., and Spears, D.B., 2018, The significance of dinoflagellates beneath the Midlothian gravels in the southeastern Virginia Piedmont: Stratigraphy, v. 15, n. 3, p. 179-195; doi: 10.29041/strat.15.179-195.

• Goodwin, B.K., and Johnson, G.H., 1970, Geology of upland gravels near Midlothian, Virginia: Eleventh Annual Field Conference of the Atlantic Coastal Plain Geological Association Guidebook, Part 2, 30 p.

• Huddlestun, P.F., 1988, A revision of the lithostratigraphic units of the coastal plain of Georgia; the Miocene through the Holocene: Georgia Geologic Survey Bulletin, no. 104, 162 p.

• McGee, W.J., 1888, Three formations of the middle Atlantic slope [Potomac, Appomattox, Columbia]: American Journal of Science, 3rd series, v. 35, p. 120-143, 328-330, 367-388, 448-466.

• Mixon, R.B., Berquist, C.R. Jr., Newell, W.L., and Johnson, G.H., 1989, Geologic map and generalized cross sections of the Coastal Plain and adjacent parts of the Piedmont, Virginia: U.S. Geological Survey Miscellaneous Investigations Series Map 1-2033, 2 sheets, scale 1:250,000.

• Newton, M.C., III, and Romeo, A.J., 2006, Geology of the Old Hickory heavy mineral sand deposit, Dinwiddie and Sussex counties, Virginia, in Reid, J. C., editor, Proceedings of the 42nd Forum on the Geology of Industrial Minerals: Information Circular 34, North Carolina Geological Survey, p. 464-481.

• Shafer, P.L., 2000, Mineralogical and geochemical variations in the Old Hickory heavy mineral sand deposit, Sussex and Dinwiddie Counties, VA [MS Thesis]: Blacksburg, Virginia Polytechnic Institute and State University, 77 p.

• Shah, A.K., and Connell, D., 2022, Airborne magnetic and radiometric survey, Virginia and North Carolina Fall Zone, 2021: U.S. Geological Survey data release, doi: 10.5066/P9RQCG2I.

• Shah, A.K., Carter, M., Blake, D., Spears, D., Merschat, A., Deasy, R., McAleer, R., Lassetter, W., and Farrell, K., 2022, New high resolution airborne geophysics in southeastern Virginia and northeastern North Carolina: Breaking fresh ground along the fall zone, in Thorleifson, L. H., ed., Geologic Mapping Forum 21/22 Abstracts, Minnesota Geological Survey Open File Report OFR-22-2, 62 p.

• Van Gosen, B.S, and Ellefsen, K.J., 2018, Titanium mineral resources in heavy-mineral sands in the Atlantic Coastal Plain of the southeastern United States: U.S. Geological Survey Scientific Investigations Report 2018-5045, 32 p., https://doi.org/10.3133/sir20185045.

• Weems, R.E., Schindler, J.S., and Lewis, W.C., 2010, Detailed section from auger holes in the Emporia 1:100,000-scale Quadrangle, North Carolina and Virginia: U.S. Geological Survey Open-File Report 2010-1121, 293 p.
  
   

Biography
 

Mark W. Carter has been a professional geologist since 1996. Mark's expertise is geologic mapping throughout the southern Appalachian crystalline core and Coastal Plain. He has produced geologic maps and reports in three states (Tennessee, North Carolina, and Virginia) and from four geologic provinces (Valley and Ridge, Blue Ridge, Piedmont, Coastal Plain). As a USGS Research Geologist, he is currently project chief of the National Cooperative Geologic Mapping Program Eastern Piedmont and Upper Coastal Plain, Virginia to Georgia Project. Mark is mapping in southeastern Virginia for critical mineral framework studies, and in central Georgia for resource management.

 

 

Greetings, and welcome to the January 13, 2025 ETGS virtual meeting.
 

If you attend via Zoom as a courtesy please mute your cell phone or the microphone in your laptop/tablet to minimize background noise and feedback echoes. We will also make an effort to mute all participants - at least until the presentation is finished. Please use the chat feature to type any comments or questions you may have. We recommend that you send questions for the speaker to "everyone" so all participants can see the question. In the interest of time, we may hold the Q&A at the end of the presentation.

We will create a virtual attendance list. It is not always possible to tell who is participating on-line, especially for those joining by phone, so please email etgs@live.com to be listed on the attendance sheet. Let us know exactly how your name should appear on the list. We will add a note explaining the lack of signatures due to remote participation and have an ETGS officer sign as usual.

As always, we welcome and appreciate your feedback and suggestions for improvement.

 

 

Greetings, and welcome to the January 13, 2025 ETGS virtual meeting.
 

If you attend via Zoom as a courtesy please mute your cell phone or the microphone in your laptop/tablet to minimize background noise and feedback echoes. We will also make an effort to mute all participants - at least until the presentation is finished. Please use the chat feature to type any comments or questions you may have. We recommend that you send questions for the speaker to "everyone" so all participants can see the question. In the interest of time, we may hold the Q&A at the end of the presentation.

We will create an in-person and virtual attendance list. It is not always possible to tell who is participating on-line, especially for those joining by phone, so please email etgs@live.com to be listed on the attendance sheet. Let us know exactly how your name should appear on the list. We will add a note explaining the lack of signatures due to remote participation and have an ETGS officer sign as usual.

Thank you for your patience and understanding as we try this online format. As always, we welcome and appreciate your feedback and suggestions for improvement.

 

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David Carlone

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Open

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Page updated January 04, 2025