Abstract The Battle of Gettysburg in south-central Pennsylvania was the largest ever fought on American soil and one of the most significant in its consequences. Moreover, more clearly than most, it demonstrates the roles which underlying geology and surface topography can play in military actions. Early Mesozoic happenings produced the rocks underlying and shaping the Gettysburg landscape, which influenced the flow of the battle and thereby impacted the course of American history. Integration of the battlefield’s geological and military aspects, however, has not yet been adequately presented in concise field-guide format, and so doing that is the intent of the present article. Inspired by Brown’s (1962) brief summary of the geology of the Gettysburg bat-tlefield, the present co-authors recently wrote a lengthy guidebook and reissued it for a 2006 Geological Society of America Annual Meeting field trip (Inners et al., 2006). A shorter field guide was also needed for that trip that could be used by many other geologists afterwards; therefore, Cuffey condensed the long guidebook into the article here, assisted particularly by Inners and Fleeger, but drawing on all of the authors’ contributions as well.

Abstract Tabular igneous intrusions (sills) are common features in sedimentary basins and have the potential to be useful seals for fluids (e.g. CO 2 or H 2 ) in geological storage scenarios, and may be important as the need for geological carbon sequestration and alternative fuel storage increases. This is advantageous in regions without ready access to large-volume reservoirs in depleted hydrocarbon plays and saline aquifers, such as the northeastern USA. Moreover, geological H 2 storage requires more demanding conditions than those typically associated with oil and gas. An enhanced seal will have the properties of a traditional seal – competent, low permeability and laterally extensive – with the addition of being able to self-seal pre-existing and induced fractures. Self-sealing will occur along fluid pathways like fractures where CO 2 , water and minerals like plagioclase, olivine and pyroxene react together. Dolerite sills from the Gettysburg Basin, Pennsylvania, have remarkably low permeability and homogeneous compositions that include minerals that will readily react with CO 2 dissolved in water. Here, we characterize the physical properties and chemical gradients within several mafic sills cored in five boreholes. In addition, preliminary CO 2 -reaction experiments on dolerite samples demonstrated rapid carbonate mineralization.

Abstract The 1863 Battle of Gettysburg in south-central Pennsylvania was one of the most important in American history, as well as the biggest ever fought within America’s boundaries. It shows clearly how underlying geology and surface topography can influence military actions. Thus, it continues to attract the attention of many specialists of varied interests, in addition to the general public (who came out for the 150th-anniversary reenactments two years ago). Previously, we prepared a concise field-trip guide (Cuffey et al., 2006a) for use on organized field trips across the battlefield, and for later self-guiding examination of critical sites thereon. Because that guide remains relevant and appropriate, it is available in its entirety, 1 for use with this year’s GSA Annual Meeting field trip. Please see the National Park Service battlefield map therein (Cuffey et al., 2006a, p. 2, Fig. 1). A few helpful updates can be added to that guide and are included in this introductory paper. They concern the most visibly battle-damaged building on the battlefield, the similar 1859 Battle of Solferino, and the new Gettysburg Battlefield Visitors’ Center. 1 GSA Data Repository Item 2015275, “Geology of the Gettysburg battlefi eld: How Mesozoic events and processes impacted American history” (Cuffey et al.,2006a), is available at www.geosociety.org/pubs/ft2015.htm, or on request from [email protected] or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.