ABSTRACT Springfield, Greene County, Missouri, is the third largest city in Missouri and is located within the Springfield Plateau, a subregion of the Ozark Physiographic Region of the United States. This region is underlain by the Burlington-Keokuk Limestone, which is highly susceptible to solution and is host to more than 2500 sinkholes within Greene County. Springfield, as well as the surrounding communities, has been growing in recent years. Prime areas for development are scarce, thus, leaving more areas that are vulnerable to sinkholes targeted for development. Development next to, and sometimes within, a sinkhole has exacerbated flooding problems, caused structural damage to homes and businesses, and is prone to increasing pollution into the underlying shallow aquifer. Control of stormwater in and around sinkhole areas typically involved the use of several standard approaches: concrete-lined channels draining into sinkholes; installation of pipes into the sinkhole “eye” (swallow hole); filling of sinkholes; elaborate drain or pump systems to remove stormwater from one sinkhole and discharge into another basin or sinkhole; and enlargement of swallow holes by excavation to increase drainage capacity. In an effort to remedy these issues, the City of Springfield adopted a Sinkhole Ordinance around 1990, requiring a permit if a development will encroach upon a sinkhole, sinkhole drainage area, or impact a sinkhole area. This field trip will review examples of pre-ordinance and post-ordinance practices of development in and around sinkholes and sinkhole areas, view recent investigations within this karst area, and discuss approaches to matching geologic knowledge with urbanization in a karst area.

ABSTRACT The Early Mississippian Northview Formation is a siliciclastic deposit reaching 25 m in thickness along an east-west trend in southwest Missouri, USA. Along this trend, the formation coarsens upward from shale to coarse siltstone with shaley interbeds and channel fills. The siltstones have high concentrations of two trace fossils: Nereites missouriensis and Zoophycos . Thus, the ichnofauna is dominated by namesake genera of the two deepest marine ichnofacies. Nevertheless, the Northview was deposited on a shallow carbonate platform. The vertical succession of trace fossils is consistent with deltaic deposition. The lowest shale is dominated by common elements of the Phycosiphon prodelta ichnofacies, and the lowest overlying siltstone is dominated by elements of the Rosselia delta-front ichnofacies. N. missouriensis occurs abundantly and dominates the overlying siltstones, with Zoophycos covering bedding planes near the top, a pattern found within the lower plain of other Paleozoic deltas. Geochemical proxy measurements indicate paleosalinity decreasing upward through the formation and an approaching freshwater (fluvial) source, raising questions about Early Mississippian source areas and tectonics.

ABSTRACT The Viburnum Trend, a Mississippi Valley–type Pb-Zn-Cu-(Ag) ore district, USA, is primarily hosted within the Cambrian Bonneterre Formation. Primary ore mineralization consists of galena, sphalerite, and chalcopyrite. Primary gangue minerals include dolomite and calcite, with lesser amounts of quartz, pyrite, and marcasite also present. The paragenetic sequence is complex, involving multiple generations of sulfide ore minerals. Early minerals are disseminated throughout the host rock. The main ore-stage deposition mostly occurs as colloform ore, while late-stage deposition primarily includes vug-filling ore. The geochemistry of deposits within the trend requires a complex fluid history, consistent with the mixing of multiple chemically distinct fluids to initiate ore precipitation. Salinities of included fluids range from less than 5 to ~30 wt% equivalent NaCl. Fluid chemistries align with the presence of a northward-migrating fluid, likely propelled through the Arkoma Basin due to hydrologic head provided by the Ouachita orogen, and a southward- or westward-migrating fluid, likely escaping the Illinois Basin due to overpressuring during sediment compaction and associated subsidence. Ore deposition probably commenced through fluid mixing. Lead and sulfur isotope chemistries of included fluids and associated solid phases suggest that multiple sources contributed lead and sulfur present in ore-stage mineralization. Additionally, ore fluids seem to have interacted with igneous basement rocks, likely acquiring lead, copper, and sulfur during migration through faults and fractures. The Viburnum Trend is relatively well understood; however, significant questions persist regarding fluid flow–driving mechanisms and pathways, sulfur sources, sulfate reduction reactions, metal sources, interaction with basement rocks, and the role of organic material in the host rock.

ABSTRACT Correlations of Paleozoic strata from the southern Appalachian, Black Warrior, and Ouachita-Arkoma forelands show varying lithofacies and stratigraphic thicknesses for coeval deposits, as well as differences in the location of disconformities. This field trip will visit stops throughout the Ouachita Mountains and Arkoma basin to observe clastic strata variability in the Cambrian, Ordovician–Silurian, Mississippian, and Pennsylvanian periods. The spatial-temporal relationship between these units provides a first-order understanding of orogenic processes along the southeastern and southern Laurentian margin during the amalgamation of the supercontinent Pangea. We present a summary of detrital zircon geochronology from the three foreland systems and correlative stops in the Ouachita Mountains to discuss sediment provenance, paleo-reconstructions, and to identify needed geochronology information for future studies. Cambrian through Devonian units in the southern Appalachian foreland of Alabama and Ouachita thrust belt are dominated by Proterozoic Grenville (1250–900 Ma) and Granite-Rhyolite (1550–1300 Ma) province grains, with minor Archean grains. Mississippian and Pennsylvanian units in the southern Appalachian and Ouachita-Arkoma forelands exhibit similar age spectra and are primarily characterized by a dominant Grenville peak, alongside smaller Appalachian (490–270 Ma), Granite-Rhyolite, Yavapai-Mazatzal (1800–1600 Ma), and Wyoming (>2400 Ma) peaks. Proportional differences in the age spectra can be identified when comparing individual stratigraphic intervals in the forelands, and have been interpreted to represent influxes of different drainage systems associated with along strike versus perpendicular sediment routing. Mississippian strata in the Ouachita Mountains, Arkoma basin, and Black Warrior basin exhibit unique age spectra in comparison to other Ouachita and southern Appalachian signatures. A dominant Appalachian peak (<480 Ma), alongside smaller Grenville, Granite-Rhyolite, Yavapai-Mazatzal, and Wyoming peaks identified in the Batesville Sandstone of the Ouachita-Arkoma foreland, suggests a possible connection to barrier island depositional systems to the east. Pennsylvanian strata in the Black Warrior basin exhibit similar age spectra to those of samples from the southern Appalachian and Ouachita-Arkoma forelands.

The four guides in this volume are associated with the GSA 2024 Joint North-Central and South-Central Section Meeting in Springfield, Missouri, USA, near the heart of the Ozarks physiographic province. They explore urbanization in a karst terrane as well as the geology and genesis of the Viburnum Trend Mississippi Valley–type ore district. One chapter tackles the trace fossils and paleosalinity of the Northview Formation. The last chapter addresses the geology of the Ouachita Mountains and linkages to North American late Paleozoic orogenesis.

ABSTRACT The Saint Francois Mountains are the physiographic expression of the central part of the Ozark Dome of southeastern Missouri. The mountains are made up of a quaquaversal-dipping series of Paleozoic units cored by the Mesoproterozoic-aged rocks of the broader Saint Francois Mountains terrane. The Saint Francois Mountains terrane lies within the Eastern Granite-Rhyolite province along the eastern margin of Laurentia and contains at least four mapped caldera complexes (Eminence, Lake Killarney, Butler Hill, and Taum Sauk), associated volcanic and volcaniclastic rocks, and four distinct types of intrusive units. The Mesoproterozoic rocks represent two major pulses of magmatic activity: (1) an older 1.48–1.45 Ga episode of caldera-forming volcanism and associated subvolcanic to massif-type granitic intrusions; and (2) a younger 1.33–1.28 Ga episode of bimodal intrusions. Volcanism included primarily high-silica rhyolite and volcaniclastic sediments associated with caldera-forming volcanism with lesser amounts of basalt and basaltic andesite that formed as flows and subvolcanic intrusions. The older (ca. 1.4 Ga) intrusive rocks can be divided into three broad categories: (1) granite massifs including the Butler Hill/Breadtray massif-type granites, (2) caldera ring–type granites such as the Silvermine Granite, and (4) mafic- to intermediate-composition intrusive rocks such as the Silver Mines Mafic Series. The younger (ca. 1.3 Ga) bimodal intrusions are represented by the highly evolved felsic Graniteville-types granites and the gabbros of the Skrainka Mafic Group. This field guide provides an overview of the magmatic history of the Mesoproterozoic rocks exposed in the eastern Saint Francois Mountains. Field-trip stops are divided into two days, highlighting well-known stops and lesser-known localities that illustrate the magmatic activity of one the premier igneous locations in the midcontinent region. The field trip is focused on two main areas. Day 1 focuses on the rhyolite sequence and associated caldera-forming eruption of the Taum Sauk caldera. Day 2 focuses on the volcanic rocks and granitic intrusions related to the Butler Hill caldera and ends with a visit to one of the youngest granitoids in the terrane, the Graniteville Granite. The field guide presents a summary of the volcanic history and petrogenesis of the Saint Francois Mountains rhyolites and granites.

ABSTRACT Here we present an overview of the geology of the Manhattan Prong and a specific guide for field stops in northern Central Park. This guide is intended to provide a brief introduction to these complex rocks for researchers, undergraduate students, and teachers. Given the easy access to Central Park and numerous schools and institutions nearby, these outcrops provide ideal teaching outcrops for students of all levels. We also present new geochemical and isotopic results for the Manhattan and Hartland Schists. Previous work has focused primarily on field mapping, structural relationships, or infrastructure-related mapping, whereas our new geochemistry data allow for more detailed discussions of provenance and overall tectonic history of these rocks. Our results suggest that all of the rocks in northern Central Park (regardless of mapped unit) are derived from Laurentia.

ABSTRACT Georgia’s coastline is composed of a series of short, wide, mixed-energy (tide-dominated) barrier islands, each backed by extensive marsh, topped with mobile dunes, and flanked by deep inlets. Many of the islands, particularly those along the southern Georgia coast, consist of Pleistocene cores surrounded by mobile deposits that attached during the Holocene sea-level transgression. Positioned within the head of the funnel-shaped South Atlantic Bight, tidal ranges here commonly reach ~2–3 m. As a result, inlets are numerous and the back-barrier environment hosts nearly 400,000 acres of salt marsh. Today, many of the barriers are transgressive, and hard structures such as revetments and groins are becoming increasingly more common to stabilize shorelines along the four developed islands. This field guide presents evidence of island formation, modern ecologic function, and likely future changes for three island groups: (1) Blackbeard, Cabretta, and Sapelo Islands; (2) Sea Island and St. Simons Island; and (3) Jekyll Island. The field trip provides evidence of the Pleistocene-age island cores, the natural southward migration of the mobile Holocene-age sandy shorelines, and the impacts of storm erosion and hard structures built to combat that erosion. This field guide serves as the static, print companion to an online virtual field trip ( https://storymaps.arcgis.com/stories/0aa3fd921cc4458da0a19a928e5fa87c ).

ABSTRACT This guide presents an eight-hour, in-person tour of intersecting geologic and human history in western Nevada, USA. A 25 megaton phreatomagmatic blast created a mile-wide (1.6-km-wide) maar, now filled by Soda Lake. The magnitude 7 Dixie Valley earthquake ripped along more than 45 km of the Stillwater Range front in 1954. The 12 kiloton Shoal nuclear test in 1963 created a 50-m-wide cavity in solid granite.

ABSTRACT Rocks of the Upper Cretaceous Tuscaloosa Formation (Cenomanian) and Eutaw Formation (Santonian) in southwestern Georgia and southeastern Alabama record an interval of fluvial and nearshore marine deposition. In the vicinity of Columbus, Georgia, basal units of the Tuscaloosa Formation consist of a residual paleosol built on crystalline rocks of the Appalachian Piedmont covered by conglomeratic sandstones deposited in braided stream systems flowing across the mid-Cenomanian Coastal Plain unconformity. The unconformity, which separates Cretaceous detrital rocks from underlying metamorphic rocks and residual paleosols built on those metamorphic rocks, lies primarily within the Tuscaloosa Formation in this region and is marked at the modern surface by the geomorphic Fall Line. Mapping of the unconformity across the region reveals areas of significant paleorelief associated with a number of distinct paleovalleys incised into the mid-Cenomanian surface. The most distinct of these lie immediately east of the Alabama-Georgia state line, within 15 km of the modern Lower Chattahoochee River Valley. Spatially, these distinct paleovalleys lie immediately north of a Santonian estuarine environment recorded in the Eutaw Formation, disconformably above the Tuscaloosa Formation. Collectively, paleo-valleys in the mid-Cenomanian surface, the fluvial nature of the Tuscaloosa Formation in southwestern Georgia and southeastern Alabama, and the estuarine environment in the younger Eutaw Formation suggest a persistent (~10 m.y.) paleodrainage system that may be a forerunner to the modern Chattahoochee River.

ABSTRACT The four largest spring systems in the mid-continent receive recharge through large interconnected voids in fractured and solution-weathered dolostones of the Ordovician and Cambrian systems. Cumulative thickness of the carbonate bedrock aquifer ranges up to 700 m in the Ozark region. Recharge from the surface occurs through weathered overburden, sinkholes, and losing streams and has been traced up to 60 km (straight-line horizontal distance) using fluorescent dyes. Mean discharge of the combined flow of these four spring systems is ~1400 cubic feet/second (ft 3 /s) or 40 m 3 /second (m 3 /s). All four spring systems will be visited while discussing the karst terrane that recharges them. Environmental and engineering challenges in the region will be discussed, such as wastewater treatment systems, solid waste disposal, and failed reservoirs. Hodgson Mill Spring represents a branch of the Rainbow/North Fork/Hodgson Mill System. While it receives base flow from the main system, it also receives local recharge that Rainbow and North Fork springs do not. A portion of the Mammoth Spring recharge system will be viewed at Grand Gulf State Park in Missouri, where a cave collapse has created cliffs and a natural bridge and exposed a small losing tributary that flows into a cave that has been traced to the spring. Mammoth Spring State Park in Arkansas offers a historical perspective of the development and use of large springs. Greer Spring in Missouri was used as a power source for grist, flour, and lumber mills, but has now largely returned to its predevelopment state and is managed by the U.S. Forest Service. Big Spring, featured in a former state park in Missouri, is now part of the Ozark National Scenic Riverways.

ABSTRACT This field trip traverses the Sahwave and Nightingale Ranges in central Nevada, USA, and northward to Gerlach, Nevada, to the Granite, northern Fox, and Selenite Ranges. Plutonic bodies in this area include the ca. 93–89 Ma Sahwave nested intrusive suite of the Sahwave and Nightingale Ranges, the ca. 106 Ma Power Line intrusive complex of the Nightingale Range, the ca. 96 Ma plutons in the Selenite Range, and the ca. 105–102 Ma plutons of the Granite and Fox Ranges. Collectively these plutons occupy nearly 1000 km 2 of bedrock exposure. Plutons of the Sahwave, Nightingale, and Selenite Ranges intrude autochthonous rocks east of the western Nevada shear zone, while plutons of the Granite and Fox Ranges intrude displaced terranes west of the western Nevada shear zone. Integrated structural, geochemical, and geochronological studies are used to better understand magmatic and deformation processes during the Early Cretaceous, correlations with Cretaceous plutons in adjacent areas of Idaho and California, and regional implications. Field-trip stops in the Sahwave and Nightingale Ranges will focus on: (1) microstructure and orientation of magmatic and solid-state fabrics of the incrementally emplaced granodiorites-granites of the Sahwave intrusive suite; and (2) newly identified dextral shear zones hosted within intrusions of both the Sahwave and Nightingale Ranges. The Sahwave intrusive suite exhibits moderate to weak magnetic fabrics determined using anisotropy of magnetic susceptibility, with magnetic foliations that strike NW-NE and magnetic lineations that plunge moderately to steeply. Microstructural analysis indicates that these fabrics formed during magmatic flow. The older Power Line intrusive complex in the Nightingale Range is cross-cut by the Sahwave suite and contains a N-S–trending solid-state foliation that reflects ductile dextral shearing. Field-trip stops in the plutons of the Gerlach region will focus on composition, texture, and emplacement ages, and key differences with the younger Sahwave suite, including lack of evidence for zoning and solid-state fabrics. The field trip will utilize StraboSpot, a digital data system for field-based geology that allows participants to investigate the relevant data projects in the study areas.

ABSTRACT Discoveries in the 1980s greatly expanded speleologists’ understanding of the role that hypogenic groundwater flow can play in developing caves at depth. Ascending groundwater charged with carbon dioxide and, especially, hydrogen sulfide can readily dissolve carbonate bedrock just below and above the water table. Sulfuric acid speleogenesis, in which anoxic, rising, sulfidic groundwater mixes with oxygenated cave atmosphere to form aggressive sulfuric acid (H 2 SO 4 ) formed spectacular caves in Carlsbad Caverns National Park, USA. Cueva de Villa Luz in Mexico provides an aggressively active example of sulfuric acid speleogenesis processes, and the Frasassi Caves in Italy preserve the results of sulfuric acid speleogenesis in its upper levels while sulfidic groundwater currently enlarges cave passages in the lower levels. Many caves in east-central Nevada and western Utah (USA) are products of hypogenic speleogenesis and formed before the current topography fully developed. Wet climate during the late Neogene and Pleistocene brought extensive meteoric infiltration into the caves, and calcite speleothems (e.g., stalactites, stalagmites, shields) coat the walls and floors of the caves, concealing evidence of the earlier hypogenic stage. However, by studying the speleogenetic features in well-established sulfuric acid speleogenesis caves, evidence of hypogenic, probably sulfidic, speleogenesis in many Great Basin caves can be teased out. Compelling evidence of hypogenic speleogenesis in these caves include folia, mammillaries, bubble trails, cupolas, and metatyuyamunite. Sulfuric acid speleogenesis signs include hollow coralloid stalagmites, trays, gypsum crust, pseudoscallops, rills, and acid pool notches. Lehman Caves in Great Basin National Park is particularly informative because a low-permeability capstone protected about half of the cave from significant meteoric infiltration, preserving early speleogenetic features.

ABSTRACT A succession of Ordovician and Mississippian carbonates, separated unconformably, is exposed across the southern flank of the Ozark Dome in southwest Missouri. Deposits of both periods exemplify typical facies of the Midwestern United States: carbonate tidal-flat assemblages for the Early Ordovician and carbonate shelf environments for the Early–Middle Mississippian. The basic stratigraphic sequence of these deposits has been known for over a century, but interesting features remain to be addressed. Thin discontinuous sandstones are present within the Early Ordovician Cotter Dolomite, but the informal Swan Creek sandstone member seems anomalous. This sandstone can exceed 5 m in thickness and is fairly continuous across southwest Missouri. Most Ordovician sandstones in Missouri mark major transgressions above regional unconformities, but not the Swan Creek, and there is no obvious source of the sand. Therefore, we hypothesize that the Swan Creek represents reworked eolian dunes blown across the broad peritidal environment. Clastic sandstone dikes, apparently sourced from the Swan Creek, cut across beds of Cotter Dolomite near faults. We propose that these dikes are evidence of local faulting and seismicity during the Early Ordovician. Early and Middle Mississippian limestones comprise a sequence of shelf deposits, although mud mounds and other facies changes near the Missouri-Arkansas line mark the edge of the Mississippian shelf and the transition to a ramp setting. Early Mississippian carbonate deposition was interrupted by a short and localized influx of siliciclastic sediment comprising the Northview Formation. The Northview has additional characteristics consistent with a river-dominated deltaic deposit, which we suggest as its origin. If correct, this hypothesis implies that the history of tectonic features in the Midwest is more complicated than yet known. Finally, facies changes within and between the local Mississippian formations may record an early crustal response to the impending Ouachita orogeny farther to the south.

ABSTRACT The Appalachian Mountains expose one of the most-studied orogenic belts in the world. However, metamorphic pressure-temperature-time ( P-T-t ) paths for reconstructing the tectonic history are largely lacking for the southernmost end of the orogen. In this contribution, we describe select field locations in a rough transect across the orogen from Ducktown, Tennessee, to Goldville, Alabama. Metamorphic rocks from nine locations are described and analyzed in order to construct quantitative P-T-t paths, utilizing isochemical phase diagram sections and garnet Sm-Nd ages. P-T-t paths and garnet Sm-Nd ages for migmatitic garnet sillimanite schist document high-grade 460–411 Ma metamorphism extending south from Winding Stair Gap to Standing Indian in the Blue Ridge of North Carolina. In the Alabama Blue Ridge, Wedowee Group rocks were metamorphosed at biotite to staurolite zone, with only local areas of higher-temperature metamorphism. The Wedowee Group is flanked by higher-grade rocks of the Ashland Supergroup and Emuckfaw Group to the northwest and southeast, respectively. Garnet ages between ca. 357 and 319 Ma indicate that garnet growth was Neoacadian to early Alleghanian in the Blue Ridge of Alabama. The P-T-t paths for these rocks are compatible with crustal thickening during garnet growth.