Abstract: Ctesias (fifth century BC) recounted contemporary Persian beliefs of white Indian animals which had a white horn, black in the centre and flaming red at the pointed tip, projecting from their forehead. Reinforced by classical and medieval writers, travellers, biblical warrant and trade in narwhal tusk, the unicorn became firmly established in European mythology. Increasing popularity as an alexipharmic, prophylactic and counter-poison through the fifteenth to seventeenth centuries led to rising demand and rapidly inflating prices. Debate raged as to which was the ‘true unicorn’ ( Unicornum Verum ), narwhal tusks or mammoth ivory ( Unicornu Fossile ); shavings and powders of both were incorporated into a bewildering array of medicinal mixtures while fraudulent alternatives flooding the markets required the employment of discriminatory tests. Further alternatives with supposedly similar properties included the (probably smectite) clays of Terra Sigillata Strigoniensis or Terra Silesiaca ( Unicornu Minerale ), and an alchemical preparation ( Unicornu Solare ). The supposed therapeutic application and wide range of delivery systems of all types of unicorn horn medicines are reviewed in detail for the first time. Particularly popular as an antidote in plague medicines, the use of alicorn (unicorn horn) simples declined to extinction with the increasingly empirical approach to pharmacy of the mid-eighteenth century.

Abstract The recent development of unconventional oil and natural gas resources in the United States builds upon many decades of research, which included resource assessment and the development of well completion and extraction technology. The Eastern Gas Shales Project, funded by the U.S. Department of Energy in the 1980s, investigated the gas potential of organic-rich, Devonian black shales in the Appalachian, Michigan, and Illinois basins. One of these eastern shales is the Middle Devonian Marcellus Shale, which has been extensively developed for natural gas and natural gas liquids since 2007. The Marcellus is one of the basal units in a thick Devonian shale sedimentary sequence in the Appalachian basin. The Marcellus rests on the Onondaga Limestone throughout most of the basin, or on the time-equivalent Needmore Shale in the southeastern parts of the basin. Another basal unit, the Huntersville Chert, underlies the Marcellus in the southern part of the basin. The Devonian section is compressed to the south, and the Marcellus Shale, along with several overlying units, grades into the age-equivalent Millboro Shale in Virginia. The Marcellus-Millboro interval is far from a uniform slab of black rock. This field trip will examine a number of natural and engineered exposures in the vicinity of the West Virginia–Virginia state line, where participants will have the opportunity to view a variety of sedimentary facies within the shale itself, sedimentary structures, tectonic structures, fossils, overlying and underlying formations, volcaniclastic ash beds, and to view a basaltic intrusion.

Abstract The Lagerstätte at Ashfall Fossil Beds—the result of supervolcanic eruption—preserves a mass-death assemblage of articulated skeletons of reptiles, birds, and mammals in a 3-m-thick pure volcanic ash near the base of the Cap Rock Member of the Ash Hollow Formation in Antelope County, Nebraska. The ash originated from the Bruneau-Jarbidge caldera in southwest Idaho, some 1600 km away, and it is geochemically matched with the Ibex Hollow tuff (11.93 Ma). Ashfall is a critical Clarendonian North American Land Mammal Age locality. More than 20 taxa—predominantly medium- and large-sized ungulates preserved in three dimensions—are buried in a late Miocene paleodepression (waterhole) filled with tephra reworked from the landscape by wind and water. Smaller taxa, such as birds, turtles, and moschids, died shortly after the pyroclastic airfall event and their remains are preserved in the basal ash. Remains from the medium-sized ungulates (equids and camelids) are separated from the underlying smaller skeletons by several centimeters of ash, indicating that these animals died at a slightly later time. In turn, more than 100 mostly intact skeletons of the barrel-bodied rhinoceros, Teleoceras major , overlie the remains of the medium-sized taxa. Pathologic bone on the limbs and skulls of the horses, camels, and rhinos suggests short-term survival and slow death several weeks or months after the pyroclastic airfall event. Exquisite preservation in an information-rich context allows aspects of the behavior, social structure, intraspecific variability, and pathology of extinct species to be reconstructed.

ABSTRACT The geology, stratigraphy, and paleontology of the Santa Ana Mountains of Southern California span 150 m.y. of subduction and 30 m.y. of transform faulting, producing complex geologic, stratigraphic, and paleontological settings. The mountains are bounded by the Elsinore fault zone on their east side, uplifting the mountains and tilting them westward, where sediments eroded from them were deposited in a variety of marine to terrestrial environments; most of these formations yield fossils so that a rich history of life can be reconstructed. The most recent geologic history includes the continued transform faulting with displacements of many kilometers northwesterly, juxtaposing separate blocks and biotas. The modern sediments are dominated by the Santa Ana River, which flows westerly at the northern end of the Santa Ana Mountains onto the coastal plain of Orange County. It is the primary aquifer supplying significant amounts of water to the residents. Humans have occupied the region for the last 12,000 yr, developing large, sophisticated populations, which, in the most recent years, have impacted the geology significantly. This field-trip guide starts north of the mountains in Ontario, California, and describes the Elsinore fault zone, the east side of the Santa Ana Mountains, and the ascent of the steep eastern side of those mountains. Extensive vistas of the geology to the east of the mountains can be seen from stops along the way. In the mountains themselves, the guide describes the granitoids of the Peninsular Ranges batholith, sedimentary rocks of the Jurassic Bedford Canyon Formation, rocks of the Cretaceous Santiago Peak Volcanics, and overlying sedimentary rocks of Mesozoic and Cenozoic age. At Ronald W. Caspers Wilderness Park, stops show the early Tertiary Silverado and Santiago formations preserving terrestrial environments that rest unconformably on the marine Cretaceous Williams Formation. On the west side of the mountains, stops at Cretaceous to Miocene conglomerates through mudstones reveal abundant marine mollusks, foraminifera, and vertebrate faunas among others, and a wide variety of sedimentary structures. Younger sediments, faults, and river courses occur along the final leg of the trip from the northern Santa Ana Mountains back to Ontario. Humans have interacted with the geology and its resources for possibly the last 12,000 yr, in ancient times utilizing rock resources and in modern times dealing with geological hazards in developmental and infrastructural construction.

Abstract The Inner Piedmont extends from North Carolina to Alabama and comprises the Neoacadian (360–345 Ma) orogenic core of the southern Appalachian orogen. Bordered to west by the Blue Ridge and the exotic Carolina superterrane to the east, the Inner Piedmont is cored by an extensive region of migmatitic, sillimanite-grade rocks. It is a composite of the peri-Laurentian Tugaloo terrane and mixed Laurentian and peri-Gondwanan affinity Cat Square terrane, which are exposed in several gentle-dipping thrust sheets (nappes). The Cat Square terrane consists of Late Silurian to Early Devonian pelitic schist and metagraywacke intruded by several Devonian to Mississippian peraluminous granitoids, and juxtaposed against the Tugaloo terrane by the Brindle Creek fault. This field trip through the North Carolina Inner Piedmont will examine the lithostratigraphies of the Tugaloo and Cat Square terranes, deformation associated with Brindle Creek fault, Devonian-Mississippian granitoids and charnockite of the Cat Square terrane, pervasive amphibolite-grade Devonian-Mississippian (Neoacadian) deformation and metamorphism throughout the Inner Piedmont, and existence of large crystalline thrust sheets in the Inner Piedmont. Consistent with field observations, geochronology and other data, we have hypothesized that the Carolina superterrane collided obliquely with Laurentia near the Pennsylvania embayment during the Devonian, overrode the Cat Square terrane and Laurentian margin, and squeezed the Inner Piedmont out to the west and southwest as an orogenic channel buttressed against the footwall of the Brevard fault zone.

Abstract The Blue Ridge province in north-central Virginia forms a large basement massif at the hinterland edge of the central Appalachian fold-and-thrust belt. Rocks and structures exposed in the Blue Ridge record a long tectonic history that encompasses the Mesoproterozoic Grenvillian orogen, Neoproterozoic Iapetan crustal extension, multiple Paleozoic collisional events, and Mesozoic tectonism. The purpose of this field trip is to provide an overview of Blue Ridge tectonics, highlight the findings of recent studies, and discuss the outstanding questions that remain unanswered in Blue Ridge geology. The trip will traverse the Blue Ridge from southeast to northwest and includes stops along the Skyline Drive in Shenandoah National Park and the Shenandoah Valley.

Abstract The Delaware Water Gap National Recreation Area (DEWA) contains a rich geologic and cultural history within its 68,714 acre boundary. Following the border between New Jersey and Pennsylvania, the Delaware River has cut a magnificent gorge through Kittatinny Mountain, the Delaware Water Gap, to which all other gaps in the Appalachian Mountains have been compared. Proximity to many institutions of learning in this densely populated area of the northeastern United States (Fig. 1 ) makes DEWA an ideal locality to study the geology of this part of the Appalachian Mountains. This one-day field trip comprises an overview discussion of structure, stratigraphy, geomorphology, and glacial geology within the gap. It will be highlighted by hiking a choice of several trails with geologic guides, ranging from gentle to difficult. It is hoped that the “professional” discussions at the stops, loaded with typical geologic jargon, can be translated into simple language that can be understood and assimilated by earth science students along the trails. This trip is mainly targeted for earth science educators and for Pennsylvania geologists needing to meet state-mandated education requirements for licensing professional geologists. The National Park Service, the U.S. Geological Survey, the New Jersey Geological Survey, and local schoolteachers had prepared “The Many Faces of Delaware Water Gap: A Curriculum Guide for Grades 3–6” ( Ferrence et al., 2003 ). Copies of this guide will be given to trip participants and can be downloaded from the GSA Data Repository 1 . The trip will also be useful for instruction at the graduate level. Much of the information presented in this guidebook is modified from Epstein (2006) .

Abstract Geological field trips are a fundamental part of the development of geoscientists both in academia and in industry. The principles learned in the field are often directly translated into everyday work and therefore maintenance of field time is critical. Across the world, the focus on health, safety and the environment for geological field trips is increasing and it is no longer acceptable to pile onto a bus and go out for an afternoon with no prior planning. This paper will address why field trip safety is of increasing importance, considerations that should be taken in order to keep geoscientists safe in the field and practical guidance on how to enable planning for safe field trips in the future.

Abstract Recent field and associated studies in eight 7.5-minute quadrangles near Mount Rogers in Virginia, North Carolina, and Tennessee provide important stratigraphic and structural relationships for the Neoproterozoic Mount Rogers and Konnarock formations, the northeast end of the Mountain City window, the Blue Ridge–Piedmont thrust sheet, and regional faults. Rocks in the northeast end of the Mountain City window constitute an antiformal syncline. Overturned Konnarock and Unicoi formations in the window require a ramp-flat geometry in the hanging wall of the Blue Ridge thrust sheet or stratigraphic pinch-out of the Konnarock Formation. Undulose and ribbon quartz, fractured feldspars, and mylonitic foliations from the Stone Mountain and Catface faults indicate top-to-NW motion, and ductile deformation above ∼300 °C along the base of the Blue Ridge thrust sheet on the southeast side of the window. The Stone Mountain fault was not recognized northeast of Troutdale, Virginia. The Shady Valley thrust sheet is continuous with the Blue Ridge thrust sheet. The ∼750 Ma Mount Rogers Formation occurs in three volcanic centers in the Blue Ridge thrust sheet. Basal clastic rocks of the lower Mount Rogers Formation nonconformably overlie Mesoproterozoic basement in the northeasternmost Razor Ridge volcanic center, but the basal contact in parts of the Mount Rogers and Pond Mountain volcanic centers is strongly tectonized and consistent with a NW-directed, greenschist-facies high-strain zone. The contact between the Mount Rogers Formation and Konnarock Formation is nonconformable, locally faulted. Metarhyolite interbedded with lacustrine and fluvial rocks suggests that volcanism and glaciation were locally coeval, establishing an age of ∼750 Ma for the Konnarock Formation, a pre-Sturtian glaciation. Multiple greenschist-facies, high-strain zones crosscut the Blue Ridge thrust sheet including the Fries high-strain zone (2–11 km wide). Foliations across the Fries and Gossan Lead faults have similar orientations and top-to-NW contractional deformation.

Abstract This field trip examines the geology and geohydrology of a dissected part of the Salem Plateau in the Ozark Plateaus province of south-central Missouri. Rocks exposed in this area include karstified, flat-lying, lower Paleozoic carbonate platform rocks deposited on Mesoproterozoic basement. The latter is exposed as an uplift located about 40 mi southwest of the St. Francois Mountains and form the core of the Ozark dome. On day 1, participants will examine and explore major karst features developed in Paleozoic carbonate strata on the Current River; this will include Devil’s Well and Round Spring Cavern as well as Montauk, Round, Alley, and Big Springs. The average discharge of the latter is 276 × 10 6 gpd and is rated in the top 20 springs in the world. Another, Alley Spring, is equally spectacular with an average discharge of 81 × 10 6 gpd. Both are major contributors to the Current and Eleven Point River drainage system which includes about 50 Mesoproterozoic volcanic knobs and two granite outcrops. These knobs are mainly caldera-erupted ignimbrites with a total thickness of 7–8 km. They are overlain by post-collapse lavas and intruded by domes dated at 1470 Ma. Volcaniclastic sediment and air-fall lapilli tuff are widely distributed along this synvolcanic unconformity. On day 2, the group will examine the most important volcanic features and the southernmost granite exposure in Missouri. The trip concludes with a discussion of the Missouri Gravity Low, the Eminence caldera, and the volcanic history of southern Missouri as well as a discussion of geologic controls on regional groundwater flow through this part of the Ozark aquifer.

Abstract Fourteen previously unpublished manuscripts by Archibald Geikie are reproduced here for the first time in approximate date order. The earliest identified manuscripts date from 1847: ‘Fable One’ and ‘Frogs Desiring a King’. Geikie was only 12 years old when he wrote these compositions. Others are dated 1852, 1853 and 1857 and were all written early in Geikie’s life and are very important for understanding his intellectual development at that time.