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J. Stephen Schindler

Publications and source records attributed to J. Stephen Schindler.

14 recordsLinked to original sources
USGS2022

Preliminary geologic map of the Cherry Hill quadrangle, Dinwiddie, Sussex, and Greensville Counties, Virginia

The Cherry Hill 7.5-minute quadrangle straddles the Coastal Plain and Piedmont Provinces along the Tidewater Fall Line. Rocks of the eastern Piedmont Roanoke Rapids terrane crop out in the western part of the quadrangle and consist of greenschist- to amphibolite-facies Neoproterozoic felsic to intermediate metavolcanic rocks, some of which contain flattened quartz phenocrysts and are locally isoclinally folded; greenstone that locally preserves primary layering; and intrusive metadiorite and metagabbro, much of which has been altered to amphibolite. Most of these rocks are strongly foliated and jointed. Greenschist-facies metasiltstone that preserves primary bedding also occurs locally in the Roanoke Rapids terrane. Neoproterozoic mica schist, middle Paleozoic foliated metagranite, and late Paleozoic massive and porphyritic granite crop out in the eastern part of the quadrangle and are part of the Dinwiddie terrane and the late Paleozoic De Witt pluton. Upper greenschist- to lower amphibolite-facies mica schist consists of stringers and boudins of vein quartz and contains porphyroclasts of staurolite that preserve an earlier foliation as inclusion trails. Porphyroblasts of garnet, staurolite, and kyanite also occur locally. Foliation in granites of the De Witt pluton may be magmatic. Separating the Dinwiddie terrane from the Roanoke Rapids terrane are greenschist-facies, highly strained granitic mylonite and bodies of less deformed granite within the Nottoway River fault zone, which is a strand of the eastern Piedmont fault system. Paleozoic pegmatite dikes and quartz veins cross-cut rocks of the Dinwiddie terrane, and quartz veins and Jurassic diabase dikes cross-cut rocks of the Roanoke Rapids terrane. Sand and gravel deposits of the Atlantic Coastal Plain overlie Piedmont rocks. Two units assigned to the upper part of the Neogene Chesapeake Group occur at elevations up to 295 feet (90 meters) above sea level atop the Richmond plain in the central part of the quadrangle. Two units of the Quaternary Bacons Castle Formation occupy the Essex plain and Norge uplands at elevations up to 180 feet (55 meters) above sea level in the eastern part of the quadrangle. In the western part of the quadrangle, multiple levels of terrace deposits are the fluvial equivalent of estuarine to marine units of the Atlantic Coastal Plain to the east. Holocene alluvium occurs along creeks and the Nottoway River. Quaternary colluvial deposits occur locally. Numerous Carolina bays pock the landscape of the Richmond and Essex plains, and three abandoned channelways represent former locations of Sappony Creek, one of the major drainages of the quadrangle. Brittle faults juxtapose Piedmont basement rocks against Neogene sediments of the upper part of the Chesapeake Group. These Cenozoic faults were first uncovered in mine excavations in the late 1990s; new mapping indicates that many of these faults are reactivated silicified cataclasite zones that occur throughout the Piedmont basement rocks. Silicified cataclasites and associated quartz veins are typically mineralized with iron and iron sulfide minerals. The quadrangle was the focus of extensive mining for heavy minerals, including ilmenite and zircon, in upland Atlantic Coastal Plain deposits beginning in the mid-1990s. Other mineral resources, including precious metals, clay for structural brick, crushed stone, and building stone for millstones, have also been prospected or quarried in the quadrangle.

Virginia↗
USGS2016

Centimeter-scale surface deformation caused by the 2011 Mineral, Virginia, earthquake sequence at the Carter farm site—Subsidiary structures with a quaternary history

Centimeter-scale ground-surface deformation was produced by the August 23, 2011, magnitude (M) 5.8 earthquake that occurred in Mineral, Virginia. Ground-surface deformation also resulted from the earthquake aftershock sequence. This deformation occurred along a linear northeast-trend near Pendleton, Virginia. It is approximately 10 kilometers (km) northeast of the M5.8 epicenter and near the northeastern periphery of the epicentral area as defined by aftershocks. The ground-surface deformation extends over a distance of approximately 1.4 km and consists of parallel, small-scale (a few centimeters (cm) in amplitude) linear ridges and swales. Individual ridge and swale features are discontinuous and vary in length across a zone that ranges from about 20 meters (m) to less than 5 m in width. At one location, three fence posts and adjoining rails were vertically misaligned. Approximately 5 cm of uplift on one post provides a maximum estimate of vertical change from pre-earthquake conditions along the ridge and swale features. There was no change in the alignment of fence posts, indicating that deformation was entirely vertical. A broad monoclinal flexure with approximately 1 m of relief was identified by transit survey across surface deformation at the Carter farm site. There, surface deformation overlies the Carter farm fault, which is a zone of brittle faulting and fracturing along quartz veins, striking N40°E and dipping approximately 75°SE. Brecciation and shearing along this fault is interpreted as Quaternary in age because it disrupts the modern B-soil horizon. However, deformation is confined to saprolitized schist of the Ordovician Quantico Formation and the lowermost portion of overlying residuum, and is absent in the uppermost residuum and colluvial layer at the ground surface. Because there is a lack of surface shearing and very low relief, landslide processes were not a causative mechanism for the surface deformation. Two possible tectonic models and one non-tectonic model are considered: (1) tectonic, monoclinal flexuring along the Carter farm fault, probably aseismic, (2) tectonic, monoclinal flexuring related to a shallow (1–3 km) cluster of aftershocks (M2 to M3) that occurred approximately 1 to 1.5 km to the east of Carter farm, and (3) non-tectonic, differential response to seismic shaking between more-rigid quartz veins and soft residuum-saprolite under vertical motions that were created by Rayleigh surface waves radiating away from the August 23, 2011, hypocenter and propagating along strike of the Carter farm fault. These processes are not considered mutually exclusive, and all three support brittle deformation on the Carter farm fault during the Quaternary. In addition, abandoned stream valleys and active stream piracy are consistent with long-term uplift in vicinity of the Carter farm fault.

Virginia↗
USGS2015

Cenozoic stratigraphy and structure of the Chesapeake Bay region

The Salisbury embayment is a broad tectonic downwarp that is filled by generally seaward-thickening, wedge-shaped deposits of the central Atlantic Coastal Plain. Our two-day field trip will take us to the western side of this embayment from the Fall Zone in Washington, D.C., to some of the bluffs along Aquia Creek and the Potomac River in Virginia, and then to the Calvert Cliffs on the western shore of the Chesapeake Bay. We will see fluvial-deltaic Cretaceous deposits of the Potomac Formation. We will then focus on Cenozoic marine deposits. Transgressive and highstand deposits are stacked upon each other with unconformities separating them; rarely are regressive or lowstand deposits preserved. The Paleocene and Eocene shallow shelf deposits consist of glauconitic, silty sands that contain varying amounts of marine shells. The Miocene shallow shelf deposits consist of diatomaceous silts and silty and shelly sands. The lithology, thickness, dip, preservation, and distribution of the succession of coastal plain sediments that were deposited in our field-trip area are, to a great extent, structurally controlled. Surficial and subsurface mapping using numerous continuous cores, auger holes, water-well data, and seismic surveys has documented some folds and numerous high-angle reverse and normal faults that offset Cretaceous and Cenozoic deposits. Many of these structures are rooted in early Mesozoic and/or Paleozoic NE-trending regional tectonic fault systems that underlie the Atlantic Coastal Plain. On Day 1, we will focus on two fault systems (stops 1–2; Stafford fault system and the Skinkers Neck–Brandywine fault system and their constituent fault zones and faults). We will then see (stops 3–5) a few of the remaining exposures of largely unlithified marine Paleocene and Eocene strata along the Virginia side of the Potomac River including the Paleocene-Eocene Thermal Maximum boundary clay. These exposures are capped by fluvial-estuarine Pleistocene terrace deposits. On Day 2, we will see (stops 6–9) the classic Miocene section along the ~25 miles (~40 km) of Calvert Cliffs in Maryland, including a possible fault and structural warping. Cores from nearby test holes will also be shown to supplement outcrops.

Chesapeake Bay↗
USGS2015

Stafford fault system: 120 million year fault movement history of northern Virginia

The Stafford fault system, located in the mid-Atlantic coastal plain of the eastern United States, provides the most complete record of fault movement during the past ~120 m.y. across the Virginia, Washington, District of Columbia (D.C.), and Maryland region, including displacement of Pleistocene terrace gravels. The Stafford fault system is close to and aligned with the Piedmont Spotsylvania and Long Branch fault zones. The dominant southwest-northeast trend of strong shaking from the 23 August 2011, moment magnitude M w 5.8 Mineral, Virginia, earthquake is consistent with the connectivity of these faults, as seismic energy appears to have traveled along the documented and proposed extensions of the Stafford fault system into the Washington, D.C., area. Some other faults documented in the nearby coastal plain are clearly rooted in crystalline basement faults, especially along terrane boundaries. These coastal plain faults are commonly assumed to have undergone relatively uniform movement through time, with average slip rates from 0.3 to 1.5 m/m.y. However, there were higher rates during the Paleocene–early Eocene and the Pliocene (4.4–27.4 m/m.y), suggesting that slip occurred primarily during large earthquakes. Further investigation of the Stafford fault system is needed to understand potential earthquake hazards for the Virginia, Maryland, and Washington, D.C., area. The combined Stafford fault system and aligned Piedmont faults are ~180 km long, so if the combined fault system ruptured in a single event, it would result in a significantly larger magnitude earthquake than the Mineral earthquake. Many structures most strongly affected during the Mineral earthquake are along or near the Stafford fault system and its proposed northeastward extension.

Virginia↗
USGS2015

Bedrock geologic map of the Spring Valley, West Plains, and parts of the Piedmont and Poplar Bluff 30'x60' quadrangles, Missouri, including the upper Current River and Eleven Point River drainage basins

This map covers the drainage basins of the upper Current River and the Eleven Point River in the Ozark Plateaus physiographic province of southeastern Missouri. The two surface drainage basins are contiguous in their headwaters regions, but are separated in their lower reaches by the lower Black River basin in the southeast corner of the map area. Numerous dye-trace studies demonstrate that in the contiguous headwaters areas, groundwater flows from the Eleven Point River basin into the Current River basin. Much of the groundwater discharge of the Eleven Point River basin emanates from Big Spring, located on the Current River. This geologic map and cross sections were produced to help fulfill a need to understand the geologic framework of the region in which this subsurface flow occurs. The map includes all of the Ozark National Scenic Riverways, a national park created by an Act of Congress in 1964 to protect 134 miles of the Current and Jacks Fork Rivers in south-central Missouri. Located within the park are numerous large springs, including Big Spring, the largest spring in Missouri and one of the ten largest springs in the world. Also within the map area is Greer Spring, which is the main source of the Eleven Point River. Greer Spring is the largest spring on National Forest land in the United States. During flood, flow from Greer Spring is almost as large, volumetrically, as that from Big Spring. The Wild and Scenic Rivers Act in 1968 established a 44-mile section of the Eleven Point River as the Eleven Point National Scenic River, which is entirely within the boundaries of this map. Potentially economic mineral resources are present in the subsurface in the map area. Exploration drill-hole data indicate that anomalously high concentrations of base-metal sulfides locally occur within the Cambrian Bonneterre Formation. The geologic setting of these anomalous concentrations is similar to that found in the Viburnum Trend, part of the largest lead-mining district in the world. The southernmost part of the Viburnum Trend extends into the northern part of the map area and is exploited by the Sweetwater Mine. Undeveloped and potentially economic occurrences of base metals are known also beneath Blair Creek, a tributary to the Current River in the north-central part of the map area.

Missouri↗
USGS2014

Geology and neotectonism in the epicentral area of the 2011 M5.8 Mineral, Virginia, earthquake

This fi eld guide covers a two-day west-to-east transect across the epicentral region of the 2011 M5.8 Mineral, Virginia, earthquake, the largest ever recorded in the Central Virginia seismic zone. The fi eld trip highlights results of recent bedrock and surficial geologic mapping in two adjoining 7.5-min quadrangles, the Ferncliff and the Pendleton, which together encompass the epicenter and most of the 2011–2012 aftershocks. Tectonic history of the region includes early Paleozoic accretion of an island arc (Ordovician Chopawamsic Formation) to Laurentia, intrusion of a granodiorite pluton (Ordovician Ellisville pluton), and formation of a post-Chopawamsic successor basin (Ordovician Quantico Formation), all accompanied by early Paleozoic regional deformation and metamorphism. Local transpressional faulting and retrograde metamorphism occurred in the late Paleozoic, followed by diabase dike intrusion and possible local normal faulting in the early Mesozoic. The overall goal of the bedrock mapping is to determine what existing geologic structures might have been reactivated during the 2011 seismic event, and surfi cial deposits along the South Anna River are being mapped in order to determine possible neotectonic uplift. In addition to bedrock and surfi cial studies, we have excavated trenches in an area that contains two late Paleozoic faults and represents the updip projection of the causative fault for the 2011 quake. The trenches reveal faulting that has offset surfi cial deposits dated as Quaternary in age, as well as numerous other brittle structures that suggest a geologically recent history of neotectonic activity.

Virginia↗
USGS2012

Linking river management to species conservation using dynamic landscape scale models

Efforts to conserve stream and river biota could benefit from tools that allow managers to evaluate landscape-scale changes in species distributions in response to water management decisions. We present a framework and methods for integrating hydrology, geographic context and metapopulation processes to simulate effects of changes in streamflow on fish occupancy dynamics across a landscape of interconnected stream segments. We illustrate this approach using a 482 km 2 catchment in the southeastern US supporting 50 or more stream fish species. A spatially distributed, deterministic and physically based hydrologic model is used to simulate daily streamflow for sub-basins composing the catchment. We use geographic data to characterize stream segments with respect to channel size, confinement, position and connectedness within the stream network. Simulated streamflow dynamics are then applied to model fish metapopulation dynamics in stream segments, using hypothesized effects of streamflow magnitude and variability on population processes, conditioned by channel characteristics. The resulting time series simulate spatially explicit, annual changes in species occurrences or assemblage metrics (e.g. species richness) across the catchment as outcomes of management scenarios. Sensitivity analyses using alternative, plausible links between streamflow components and metapopulation processes, or allowing for alternative modes of fish dispersal, demonstrate large effects of ecological uncertainty on model outcomes and highlight needed research and monitoring. Nonetheless, with uncertainties explicitly acknowledged, dynamic, landscape-scale simulations may prove useful for quantitatively comparing river management alternatives with respect to species conservation.

Georgia↗
USGS2010

Detailed Sections from Auger Holes in the Emporia 1:100,000-Scale Quadrangle, North Carolina and Virginia

The Emporia 1:100,000-scale quadrangle straddles the Tidewater Fall Line in southern Virginia and includes a small part of northernmost North Carolina. Sediments of the coastal plain underlie the eastern three-fifths of this area. These sediments onlap crystalline basement rocks toward the west and dip gently to the east, reaching a maximum known thickness of 821 feet in the extreme southeastern part of the map area. The gentle eastward dip is disrupted in several areas due to faulting delineated during the course of mapping. In order to produce a new geologic map of the Emporia 1:100,000-scale quadrangle, the U.S. Geological Survey drilled one corehole to a depth of 223 feet and augered 192 shallow research test holes (maximum depth 135 feet) to supplement sparse outcrop data available from the coastal plain part of the map area. The recovered sediments were studied and data from them recorded to determine the lithologic characteristics, spatial distribution, and temporal framework of the represented coastal plain stratigraphic units. These test holes were critical for accurately determining the distribution of major geologic units and the position of unit boundaries that will be shown on the forthcoming Emporia geologic map, but much of the detailed subsurface data cannot be shown readily through this map product. Therefore, the locations and detailed descriptions of the auger test holes and one corehole are provided in this open-file report for geologists, hydrologists, engineers, and community planners in need of a detailed shallow-subsurface stratigraphic framework for much of the Emporia map region.

Open-File Report↗
USGS2008

Bedrock Geologic Map of the Greater Lefkosia Area, Cyprus

The island of Cyprus has a long historical record of earthquakes that have damaged pre-Roman to modern human settlements. Because the recurrent damaging earthquakes can have a significant economic and social impact on Cyprus, this project was initiated to develop a seismic-hazard assessment for a roughly 400 square kilometer area centered on Cyprus' capital and largest city, whose European name is Nicosia and whose local name is Lefkosia. In addition, geologic and seismotectonic evaluations for the project extended beyond the perimeter of the geologic map. Additional structural, stratigraphic, and paleontological data were collected island-wide as well as data from literature research throughout the eastern Mediterranean region, in order to accurately place the geology and seismic hazards of the Lefkosia area in a regional tectonic framework.

Scientific Investigations Map↗
USGS2006

Geologic Map of Loudoun County, Virginia

Introduction The geology of Loudoun County, Va., was mapped from 1988 through 1991 under a cooperative agreement between the U.S. Geological Survey (USGS) and the Loudoun County Office of Mapping and Geographic Information. This geologic map was compiled in 1993 from a series of detailed published and unpublished field investigations at scales of 1:12,000 and 1:24,000. Some of these same data were compiled as a digital geologic map at 1:100,000 scale (Burton and others, 1992a) and were the basis for a cost-benefit analysis of the societal value of geologic maps (Bernknopf and others, 1993).

IMAP↗
USGS2005

Geologic map of the Stafford quadrangle, Stafford County, Virginia

Introduction The Stafford 7.5-minute quadrangle, comprising approximately 55 square miles (142.5 square kilometers) of northeastern Virginia, is about 40 miles (mi) south of Washington, D.C. The region's main north-south transportation corridor, which connects Washington, D.C., and Richmond, Va., consists of Interstate 95, U.S. Highway 1, and the heavily used CSX and Amtrak railroads. Although the northern and eastern parts of the Stafford quadrangle have undergone extensive suburban development, the remainder of the area is still dominantly rural in character. The town of Stafford is the county seat. The Stafford 7.5-minute quadrangle is located in the Fredericksburg 30'x60' quadrangle, where information on the regional stratigraphy and structure is available from Mixon and others' (2000) geologic map and multichapter explanatory text. In addition to straddling the 'Fall Zone' boundary between the Appalachian Piedmont and the Atlantic Coastal Plain provinces, this quadrangle contains the best preserved and best studied segment of the Stafford fault system, an important example of late Cenozoic faulting in eastern North America (Mixon and Newell, 1977). This 1:24,000-scale geologic map provides a detailed framework for interpreting and integrating topical studies of that fault system. Our geologic map integrates more than two decades of intermittent geologic mapping and related investigations by the authors in this part of the Virginia Coastal Plain. Earlier mapping in the Piedmont by Pavlides (1995) has been revised by additional detailed mapping in selected areas, particularly near Abel Lake and Smith Lake, and by field evaluation of selected contact relations.

Virginia↗