Abstract Grand Caverns is the oldest show cave in continuous operation in the contiguous United States. Discovered in 1804, Grand Caverns has been offering at least one tour per year continuously from 1806 until now. For more than two centuries Grand Caverns – which is host to diverse and uncommon solution cave speleothems, such as cave shields – has served as the centre for multidisciplinary research related to limestones in Virginia and has accrued historical accounts relevant to the Shenandoah Valley (nestled between the Blue Ridge Mountains to the east and the Allegheny Mountains to the west) in the Commonwealth of Virginia. In this article, we explore the geological, historical, mapping and geotourism legacies of Grand Caverns, using its geoheritage as a narrative framework. In addition, we discuss the intersection of historical and diverse concurrent heritages at Grand Caverns and their relevance for understanding national show caves and cave development processes, and we share ongoing efforts towards the construction of a proposal to elevate Grand Caverns to the United Nations Educational, Scientific and Cultural Organization World Heritage list.

Abstract The Great Valley of Virginia (GVV) is a section of a much larger geological structure that spans from the northeastern USA through the mid-Atlantic and to the SE. While the structural formation of the region represents nearly 1.2 billion years of geological history, the rocks that remain record vast cycles of tectonic change. The legacy of that geology is a rich and aesthetically attractive region that has drawn many peoples over time to its agricultural fertility and geological resources. This contribution traces the geological development of the GVV, the relationship of the GVV to the peoples, both indigenous and European colonizers, who have inhabited the GVV over thousands of years and the geological resources that the inhabitants found. Although relatively under-expressed from a geoheritage perspective, the GVV possesses a rich legacy of how its resources supported each society's needs and interests and the role its geological environment has played at critical moments in the historical development of the USA over the last 400 years.

ABSTRACT This field guide presents a one-day trip across the northern Virginia Blue Ridge geologic province and highlights published geologic mapping of Mesoproterozoic rocks that constitute the core of the Blue Ridge anticlinorium and Neoproterozoic cover-sequence rocks on the fold limbs. The guide presents zircon SHRIMP (sensitive high-resolution ion microprobe) U-Pb crystallization ages of granitoid rocks and discusses the tectonic and petrologic evolution of basement rocks during the Mesoproterozoic. U-Pb data show more of a continuum for Blue Ridge Mesoproterozoic magmatic events, from ca. 1.18–1.05 Ga, than previous U-Pb TIMS (thermal ionization mass spectrometry)-based models that had three distinct episodes of plutonic intrusion. All of the younger dated rocks are found west of the N-S–elongate batholith of the Neoproterozoic Robertson River Igneous Suite, suggesting that the batholith occupies a fundamental Mesoproterozoic crustal boundary that was likely a fault. Narrow belts of paragneiss may represent remnants of pre-intrusive country rock, but some were deposited close to 1 Ga according to detrital zircon U-Pb ages. For late Neoproterozoic geology, the guide focuses on lithologies and structures associated with early rifting of the Rodinia supercontinent, including small rift basins preserved on the eastern limb of the anticlinorium. These basins have locally thickened packages of clastic metasedimentary rocks that strike into and truncate abruptly against Mesoproterozoic basement along apparent steep normal faults. Both basement and cover were intruded by NE-SE–striking and steeply dipping, few-m-wide diabase dikes that were feeders to late Neoproterozoic Catoctin Formation metabasalt that overlies the rift sediments. The relatively weak dikes facilitated the deformation that led to the formation of the Blue Ridge anticlinorium during the middle to late Paleozoic as the vertical dikes were transposed and rotated during formation of the penetrative cleavage. This field trip generally follows the GSA guide published in GSA Field Guide 57 (available at https://pubs.geoscienceworld.org/gsa ): Burton, W.C., and Schindler, J.S., 2020, Proterozoic and Paleozoic evolution of the Blue Ridge geologic province in northern Virginia, USA, in Swezey, C.S., and Carter, M.W., eds., Geology Field Trips in and around the U.S. Capital: Geological Society of America Field Guide 57, p. 1–19, https://doi.org/10.1130/2020.0057(01) .