Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015

Prepared in conjunction with the 2015 GSA Annual Meeting in Baltimore, Maryland, this volume contains guides to field trips in this historic region. Emanating from the Fall Line city of Baltimore, these trips reflect the diversity of geological features in the mid-Atlantic region including the Piedmont, Appalachian Mountains, and Coastal Plain, and the importance of geology on the development and construction of the Baltimore-Washington, D.C., metropolitan area. Trips to the core of the Appalachian orogen concern themselves with the tectonic and metamorphic history, early Paleozoic carbonate platform development, Devonian paleoclimate, and coal-mine fire hazards. Excursions to the Coastal Plain examine various aspects of Cenozoic stratigraphy, structure, barrier island formation, and wetland and ecosystem development. A variety of trips also explore urban geology, including building and monument stones of Baltimore and Washington, D.C., urban hydrogeology, and Civil War battlefield geology.
Cenozoic stratigraphy and structure of the Chesapeake Bay region Available to Purchase
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Published:January 01, 2015
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CiteCitation
David S. Powars, Lucy E. Edwards, Susan M. Kidwell, J. Stephen Schindler, 2015. "Cenozoic stratigraphy and structure of the Chesapeake Bay region", Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015, David K. Brezinski, Jeffrey P. Halka, Richard A. Ortt, Jr.
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Abstract
The Salisbury embayment is a broad tectonic downwarp that is filled by generally seaward-thickening, wedge-shaped deposits of the central Atlantic Coastal Plain. Our two-day field trip will take us to the western side of this embayment from the Fall Zone in Washington, D.C., to some of the bluffs along Aquia Creek and the Potomac River in Virginia, and then to the Calvert Cliffs on the western shore of the Chesapeake Bay. We will see fluvial-deltaic Cretaceous deposits of the Potomac Formation. We will then focus on Cenozoic marine deposits. Transgressive and highstand deposits are stacked upon each other with unconformities separating them; rarely are regressive or lowstand deposits preserved. The Paleocene and Eocene shallow shelf deposits consist of glauconitic, silty sands that contain varying amounts of marine shells. The Miocene shallow shelf deposits consist of diatomaceous silts and silty and shelly sands. The lithology, thickness, dip, preservation, and distribution of the succession of coastal plain sediments that were deposited in our field-trip area are, to a great extent, structurally controlled. Surficial and subsurface mapping using numerous continuous cores, auger holes, water-well data, and seismic surveys has documented some folds and numerous high-angle reverse and normal faults that offset Cretaceous and Cenozoic deposits. Many of these structures are rooted in early Mesozoic and/or Paleozoic NE-trending regional tectonic fault systems that underlie the Atlantic Coastal Plain. On Day 1, we will focus on two fault systems (stops 1-2; Stafford fault system and the Skinkers Neck-Brandywine fault system and their constituent fault zones and faults). We will then see (stops 3-5) a few of the remaining exposures of largely unlithified marine Paleocene and Eocene strata along the Virginia side of the Potomac River including the Paleocene-Eocene Thermal Maximum boundary clay. These exposures are capped by fluvial-estuarine Pleistocene terrace deposits. On Day 2, we will see (stops 6-9) the classic Miocene section along the ~25 miles (~40 km) of Calvert Cliffs in Maryland, including a possible fault and structural warping. Cores from nearby test holes will also be shown to supplement outcrops.
- algae
- Aquia Formation
- Atlantic Coastal Plain
- biostratigraphy
- Cenozoic
- Chesapeake Bay
- Delaware
- Eocene
- faults
- field trips
- Invertebrata
- lower Eocene
- Maryland
- microfossils
- Mollusca
- nannofossils
- outcrops
- Paleocene-Eocene Thermal Maximum
- paleoclimatology
- Paleogene
- Plantae
- Pleistocene
- Potomac Group
- Potomac River
- Quaternary
- road log
- Salisbury Embayment
- tectonics
- Tertiary
- United States
- Virginia
- Calvert Cliffs
- Fairhaven Member
- Stafford Fault
- Paspotansa Member
- Piscataway Member
- Skinkers Neck-Brandywine Fault System