14 September 2015

Awesome field trips at GSA Baltimore meeting

Posted by Callan Bentley

Hi everyone,

As the deadline for early registration for the annual meeting of the Geological Society of America nears, I’d like to call your attention to a suite of awesome field trips exploring mid-Atlantic region geology. If you’re traveling to the east coast for the first time for GSA, or if you’ve never ventured beyond the Smithsonian and NSF conference rooms, then you should consider one of these trips as an insight into a rich geologic heritage. While there are many terrific sounding trips on the docket, these three are being offered by my colleagues and me:


Trip Description
The Neoproterozoic era was a time of vast change as the Earth experienced dramatic climatic and paleoceanographic shifts involving global ice ages (a.k.a. Snowball Earth), the evolution and diversification of the earliest animals, and tectonic upheaval associated with the breakup of the Rodinian supercontinent. Neoproterozoic rocks in the central Appalachian Blue Ridge bear witness to the dynamism of that era. This field trip will examine Cyrogenian to Ediacaran sedimentary and volcanic rocks formed along the southeastern margin of Laurentia and currently exposed in central and northern Virginia. Planned stops include glacial diamictites, rift-basin sequences, post-glacial red beds and cap carbonates, as well as plume-related (?) tholeiitic flood basalts. Research during the past two decades has revealed much about the enigmatic Neoproterozoic rocks of the central Appalachians. This field trip will afford an opportunity to discuss advances, consider unanswered questions including the significance the Paleozoic structural and metamorphic overprint, and place these rocks in a better global framework. Field trip participants will visit locales in the Blue Ridge foothills as well as in scenic Shenandoah National Park.

Trip Description
This two-day field trip will focus on the Paleozoic tectonic and eustatic history and depositional environments of the Appalachian Foreland Basin as interpreted from selected exposures of Cambrian through Pennsylvanian strata in the Blue Ridge, Valley and Ridge and Allegheny Plateau Provinces of western Virginia and eastern West Virginia. We will see evidence of major events in the history of eastern Laurentian North America, from the rifting of Rodinia up-section through the Taconic and Acadian clastic wedges and the intervening periods of relative tectonic calm during which carbonate deposition was widespread in a variety of environments from deep shelf to sabkha. The final stop will be at the base of the Alleghanian clastic wedge. Emphasis will be on some of the more prominent stratigraphic transitions, and how these are interpreted in terms of corresponding tectonic and/or eustatic events including the Sauk, Tippecanoe I and II, and Kaskaskia sequences and their bounding discontinuities. A highlight of the trip will be stops at several of the extensive and superb new exposures along the recently constructed Corridor-H, U.S. Highway 48 in the Appalachian Development Highway System.

Trip Description
Washington, D.C. provides a world-class showcase for a diverse collection of American building stones, architectural styles, and landscape development and use—all situated in the internationally renowned area of the National Mall. This four-mile walking tour (intended for students and teachers) considers more than 22 National Mall buildings and monuments made of igneous, sedimentary, and metamorphic rock—formed during roughly 3.5 billion years of Earth history and erected during 220 years of American history. We will examine the lithology (macroscopic and thin section), provenance, structures, paleontology, facies interpretation, geologic history, architectural and political significance, and material degradation (weathering) of many classic American building stones (about 25), as well as the few exotic, foreign examples (e.g., Carrera marble). Local landscape evolution will be placed in geological context, and extend through the architectural design plans of L’Enfant (1791), Downing (1851), and McMillan (1902)—ending with recent flood-mitigation efforts in view of projected sea-level rise.