Geology topics

Randall C. Orndorff

Publications and source records attributed to Randall C. Orndorff.

At least 19 recordsLinked to original sources

USGS2026

Capitalization of positional (Lower/Middle/Upper) and temporal (Early/Middle/Late) adjectives in the names of formal chronostratigraphic and geochronologic units of the Phanerozoic

Many authors are understandably confused about the capitalization of the words “lower,” “middle,” “upper,” “early,” and “late.” Where these words are used simply as descriptive adjectives, they should be in lowercase; where they form the first word of a formal chronostratigraphic or geochronologic unit name, they should be in uppercase.

Professional Paper↗

USGS2026

Cambrian and Ordovician stratigraphy, conodont biostratigraphy, and microfacies analysis to support 1:24,000-scale geologic mapping of the southern Lake Champlain valley, New York and Vermont

Introduction Geologic mapping in the southern Lake Champlain valley of New York and Vermont (fig. 1) has required evaluation of stratigraphic nomenclature used since the early 1900s. The paleogeography of the Cambrian and Ordovician adjacent to the Adirondack Highlands, the high-relief mountains of Proterozoic igneous and metamorphic rocks of northern New York, has impacted the lithostratigraphic succession, facies changes, and several hiatuses that occur within the package of clastic and carbonate rocks that demonstrates overall deepening consistent from the southern to northern Appalachians. The stratigraphic nomenclature used for the geologic mapping of the Cambrian and Ordovician strata of the study area is derived from evaluation of names put forth by previous workers from areas of northern New York and western Vermont. Descriptions of type localities or type sections and other criteria set forth by the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature [NACSN], 2021) were consulted. The North American Stratigraphic Code states that lithostratigraphic units, such as the fundamental unit, the formation, be defined by lithic character and be mappable (NACSN, 2021, Article 24). However, some early workers (Walcott, 1912; Kay, 1937; Fisher and Hanson, 1951; Oxley and Kay, 1959) have defined stratigraphic units based on fossil content, which may or may not be facies dependent, and hence may not be mappable as lithostratigraphic units. Although preservation of older names takes priority in stratigraphic nomenclature (NACSN, 2021, Article 7), some do not have adequately defined stratotypes or are located a distance away with different lithologies than that in the study area. Biostratigraphy can be a helpful tool for understanding correlations and facies changes. Herein, conodont biostratigraphy is utilized to date and correlate separate lithologic units. Further, microfacies analyses of units through inspection of petrographic thin sections provide paleogeographic information that helps in understanding the genesis of geologic units.

New York, Vermont↗

USGS2026

Preliminary bedrock geologic map of the Port Henry quadrangle, Essex County, New York, and Addison County, Vermont

Introduction The bedrock geology of the 7.5-minute Port Henry quadrangle consists of deformed and metamorphosed Mesoproterozoic gneisses of the Adirondack Highlands unconformably overlain by weakly deformed lower Paleozoic sedimentary rocks of the Champlain Valley. The Mesoproterozoic rocks occur on the eastern edge of the Adirondack Highlands and represent an extension of the Grenville Province of Laurentia. Mesoproterozoic paragneiss, marble, and amphibolite hosted the emplacement of an anorthosite-mangerite-charnockite-granite (AMCG) suite, now exposed mostly as orthogneiss, at approximately 1.18–1.15 Ga (giga-annum). In the Port Henry quadrangle, the AMCG metaigneous rocks (Yhg, Ygb, Yanw) intruded older, mostly metasedimentary rocks of the Grenville Complex during the middle to late Shawinigan orogeny (~1,160–1,150 Ma [mega-annum]). All rocks were subsequently metamorphosed to upper amphibolite to granulite facies conditions during the 1,080–1,050 Ma Ottawan orogeny. New mapping reveals four periods of deformation: (1) D1 produced rarely preserved isoclinal folds in the paragneiss and marble and predates AMCG magmatism. (2) Subsequent D2 deformation produced the dominant gneissic fabric preserved in the rock, recumbent folding, and deformed all the Proterozoic units in the map area. Syn- to late-D2 felsic magmatism resulted in the regionally extensive Lyon Mountain Granite Gneiss, which hosts numerous magnetite ore bodies. (3) Mylonitic extensional shear zones and core complex formation marked the beginning of D3 deformation. Protracted D3 deformation resulted in F3 upright folding, dome and basin formation, pegmatite intrusion, reactivation of the S2 foliation, partial melting, metamorphism, metasomatism, iron-ore remobilization, and intrusion of magnetite-bearing pegmatite both as layer-parallel sills and crosscutting dikes. (4) D4 created northeast- and northwest-trending local high-grade ductile shear zones and boudinage, northwest-trending regional kilometer (km)-wide ductile shear zones, and crosscutting granitic pegmatite dikes. The development of the late-stage regional shear zones (D4) was likely due to the continuation of extensional doming and uplift from upper amphibolite facies conditions at the end of the Ottawan orogeny. The majority of iron-ore deposits in the Port Henry and adjacent Witherbee quadrangles are in the hanging wall of these extensional shear zones. In the Port Henry quadrangle, the km-wide Cheney Mountain shear zone is the result of D4 deformation. Kilometer-scale lineaments readily observed in lidar data are Ediacaran mafic dikes and Phanerozoic brittle faults. The Paleozoic rocks are part of the Early Cambrian to Late Ordovician carbonate bank on the ancient margin of Laurentia. The approximately 1-km-thick Cambrian to Ordovician stratigraphy records a transition from synrift clastics to passive-margin peritidal carbonate buildups to gradually deeper-water subtidal- to shelf-carbonates during foreland basin development associated with the Taconic orogeny. The Paleozoic rocks are weakly folded and block faulted. Large areas of the Champlain Valley are covered by undifferentiated glacial deposits, some of which contain mapped landslides. The map also shows waste rock piles and tailings from historical mining operations. This study was undertaken to improve our understanding of the bedrock geology in the Adirondack Highlands, establish a modern framework for 1:24,000-scale bedrock geologic mapping in the Adirondacks, provide a context for historical iron mines in the eastern Adirondacks, and update the stratigraphy of the Champlain Valley in New York and Vermont. This Open-File Report includes a bedrock geologic map; a description of map units; a correlation of map units; and a geographic information system database that includes bedrock geologic units, faults, outcrops, and structural geologic information.

New York, Vermont↗

USGS2026

Report 17—Revisions to the articles of organization and procedure of the Commission on Stratigraphic Nomenclature of the Americas

Several revisions to the Articles of Organization and Procedure for the North American Commission on Stratigraphic Nomenclature have been adopted following the 75th, 79th, and 80th annual meetings of the Commission in 2020, 2024 and 2025, respectively. Of these, the most substantial change was revision of Article III regarding membership composition of the Commission and the addition of new member organizations from Central and South America and the Caribbean region. As a result, the Commission also voted to change its name to be more inclusive of the expanding membership, with approval of the name: Commission on Stratigraphic Nomenclature of the Americas. A corresponding change to the Commission’s fundamental publication was also approved at the 2025 meeting as the Stratigraphic Code of the Americas (formerly the North American Stratigraphic Code). Additional revisions to the Articles include those aimed at ensuring gender neutrality of titles, permission to hold virtual meetings, and processes for designating new Commissioners. Article V was also modified to define quorum for meetings and the nature of a two-thirds majority vote, with the process for making amendments to the Articles modified to specify that a two-thirds majority vote is required. These revisions are reflected in the following bylaws, which otherwise are as adopted by the Commission under its former name (North American Commission on Stratigraphic Nomenclature) at its 62nd annual meeting in 2007 amended by mail ballot, and published by Owen et al. (2009). The amended bylaws printed below became effective at the close of the 80th annual meeting in 2025 and supersede all previous versions (Moore 1947; Hutchinson 1953; Owen et al. 1985; 2009)

Stratigraphy↗

USGS2025

Ordovician stratigraphy, structure, and karst of the Falling Spring Valley, Alleghany County, Virginia, USA

This one-day trip highlights new findings on a preliminary bedrock geologic map that shows results from ongoing geologic mapping in the Falling Spring Valley of Alleghany County, Virginia, USA, which is the southern end of the larger Warm Springs Valley, an elongated anticlinal valley rimmed by Ordovician and Silurian siliciclastic rocks, and which is famous for its thermal springs. This mapping includes stratigraphic, structural, and karst field and lab research focused on the Ordovician strata exposed in the area, the oldest of which is the dolomitic upper part of the Beekmantown Formation (Lower Ordovician, Darriwilian), and the youngest of which is the Juniata Formation (Upper Ordovician, Katian), a sequence of siliciclastic redbeds. Warm Springs Valley is the location of the only known caves in the eastern United States—three at present—with thermal waters flowing in some of their passages. Stops on the trip will highlight key details from mapping efforts, primarily within the structurally deformed Ordovician carbonate sequence that is exposed in the core and limbs of the anticline, as well as the associated karst features that are developed in those carbonate rocks, including results of recent dye traces and water temperature monitoring that have improved our understanding of the karst hydrogeologic systems developed in these strata.

Virginia↗

USGS2025

The National Park Service stratotype inventory

Introduction An Inventory of Stratigraphic Origins within the National Park Service The geologic history of Earth is recorded in layers or bodies of rock that are classified in a hierarchical order with several different categories of geologic units, including: supergroup, group, formation, member, bed, supersuite, suite, or complex. Geologists analyze and classify rock types based on properties that include lithology, texture, thickness, sedimentary structures, fossils, geographic or geospatial distribution, and age. In instances where new geologic units are proposed, a stratotype is assigned to a designated section, locality, or area of well-exposed rock that displays diagnostic characteristics for identification and correlation. Stratotypes are also namesakes, in that formally recognized rock units are named for the places where they were first described, measured, and mapped. Thus, a vast majority of the stratigraphic nomenclature alludes to geographic or geologic features. Some particularly recognizable examples (and their stratotype assignments) include the Paleoproterozoic Vishnu Schist (Vishnu Canyon in Grand Canyon National Park, Arizona), the Early Cambrian Harpers Formation (Harpers Ferry National Historical Park, West Virginia), and the Late Cretaceous Whitney Granodiorite (Mount Whitney in Sequoia and Kings Canyon National Parks, California). Beginning in 2020, the National Park Service (NPS) began a systematic effort to document the occurrence of stratotypes exposed within, partially within, and near NPS administrative boundaries. The NPS stratotype inventory project represents an important component of a geologic resource inventory, as these designations are vital to our national geologic heritage (herein referred to as “geoheritage”) and possess significant scientific, historic, educational, cultural, and aesthetic values. The geoheritage significance of stratotypes is analogous to libraries and museums, in that they are geologic landmarks of Earth history and record the prodigious forces and evolving life forms that define our understanding of the planet. These designated exposures preserve knowledge, represent comparative geologic references where previous observations can be re-examined or reinterpreted, and can serve as valuable educational tools for future geoscientists (Brocx and others, 2019). The NPS stratotype inventory includes the following: Documentation of designated stratotype exposures to confirm their geospatial occurrence within, partially within, and near NPS administrative boundaries, compiled from published reports and maps; Compilation and visualization of the precise geographic locations of the stratotype exposures; and Recommendations that address potential land and resource management issues associated with NPS stratotypes. By achieving these goals, this project helps to raise awareness of stratotypes as a geologic resource by educating NPS staff and the public so that they may better understand, recognize, and protect these important park resources. The focused approach adopted for conducting the stratotype inventories throughout the NPS has centered on the 32 Inventory and Monitoring (I&M) networks established by the NPS during the late 1990s (for more information on each network, see https://www.nps.gov/im/networks.htm). The I&M networks represent groups or clusters of park units that are based on shared geography and natural resource characteristics. The Greater Yellowstone I&M Network, encompassing Bighorn Canyon National Recreation Area, Grand Teton National Park, John D. Rockefeller Jr. Memorial Parkway, and Yellowstone National Park, was used as the pilot network for initiating this stratotype inventory and was first published in November 2020 (Henderson and others, 2020). The 32d and final report on the Northeast Temperate I&M Network was published in October 2022 (Henderson and others, 2022). Currently, the NPS stratotype inventory project has identified more than 700 stratotypes within NPS administrative boundaries.

Professional Paper↗

USGS2023

Hydrogeology, karst, and groundwater availability of Monroe County, West Virginia

Monroe County is in southeastern West Virginia, encompassing an area of 474 square miles. The area consists of karst and siliciclastic aquifers of Ordovician, Silurian, Devonian, and Mississippian age and is in parts of two physiographic provinces: the Valley and Ridge Province to the east of Peters Mountain, and the Appalachian Plateau Province to the west of Peters Mountain. This study was developed in response to inquiries from the Monroe County Commission requesting assessment of the water resources of the county to better understand the quantity of the county’s groundwater resources, for both current [2023] and future demand, and to provide information to support protection and management of the county’s valuable groundwater resources. Various products were developed for this study that provide knowledge with respect to water availability and contamination susceptibility of the karst aquifers within the county. U.S. Geological Survey (USGS) geologists conducted extensive geologic mapping in support of the project, producing (1) a countywide bedrock geologic map, (2) a countywide hydrogeologic map, and (3) a light detection and ranging (lidar)-derived countywide digital elevation model and associated sinkhole map. A significant part of this work was to map in detail the Greenbrier Group at the formation level, which prior to this study had only partially been completed. The report also includes (4) a description of the lithologic units identified as part of the geologic mapping process. U.S. Geological Survey hydrologists completed several additional products for the hydrology part of the effort, including development of (1) a countywide potentiometric surface (water-table) map, (2) a countywide base-flow stream assessment, (3) countywide water-budget estimates, (4) well log surveys for 15 wells to better understand subsurface controls on groundwater flow within the study area, (5) two groundwater tracer tests to better refine the groundwater divide from the northern and southern parts of the karst aquifer in Monroe County; and finally, based on all available data collected for the study including the potentiometric surface map, geologic map, current [2023] and legacy fluorometric groundwater tracer tests, and base-flow stream assessments, (6) groundwater-basin delineations were reassessed for principal groundwater basins within the Greenbrier aquifer. In Monroe County, four principal hydrogeologic settings produce large yields of water for residential, agricultural, and other uses. The most relied upon water-bearing zone with respect to current [2023] public water supply is from springs along Peters Mountain. These springs are derived from intervals of fractured sandstone and resultant alluvial deposits. Groundwater flows downslope through these permeable alluvial deposits and discharges at the contact with less permeable strata, such as the Reedsville Shale. The second most relied upon water-bearing zone in Monroe County is within the karstic Greenbrier Group aquifer, in which the basal Hillsdale Limestone overlies the less permeable Maccrady Shale. This geologic contact between the Hillsdale Limestone and Maccrady Shale is not only targeted as a source of water for agricultural supply but also is targeted as a source of water for residential supply. The third most relied upon water-bearing zone is composed of shallow perched aquifers within the Greenbrier Group. The discontinuous nature of these perched aquifers makes mapping their extent impossible, but they are related to permeable geologic strata, such as karstified limestones with solutionally enhanced permeability that overlies less permeable shale or chert bedrock. During geologic mapping of the county, several of these perched aquifers were documented in the Pickaway, Union, and Alderson Limestones. A fourth zone consists of springs from Ordovician carbonates at the base of Peters Mountain, which are influenced by sinking streams as well as upwelling along faults. In terms of water quantity, the most sustainable springs are those having deeper-sourced flows. Public supplies are a principal source of water used for residential and commercial supply in the region, accounting for 0.49 million gallons per day (Mgal/d) of fresh-water withdrawals (0.14 Mgal/d of groundwater and 0.35 Mgal/d of surface water) for residential and commercial use and serving 6,645 individuals (49.2 percent of the population). An estimated 6,861 people, (50.8 percent of the population) primarily rely on private wells or other unregulated sources, such as springs, and withdraw 0.55 Mgal/d of groundwater for their residential use. Public water supply in the region is primarily (71.4 percent) derived from springs and augmented by stream withdrawals (backup sources mainly during low-flow periods), with the remaining portion (28.6 percent) derived from groundwater withdrawals from wells. For rural residents, however, 100 percent of their withdrawals are derived from groundwater (wells or springs).

West Virginia↗

USGS2023

“Stratigraphic Notes”—An outlet for stratigraphic studies

Introduction Welcome to the resurrected series of U.S. Geological Survey (USGS) reports on stratigraphy, entitled “Stratigraphic Notes”; this initial volume is called “Stratigraphic Notes— Volume 1, 2022.” For several decades, until the mid-1990s, the USGS published volumes of short papers that highlighted stratigraphic studies, changes in stratigraphic nomenclature, and explanations of stratigraphic names and concepts used on published geologic maps. The purpose was to encourage formal documentation on these topics. Today (2023) the need for such documentation has become especially important because of the increasing number of published field-trip guidebooks and open-file reports that use new or updated stratigraphic nomenclature; however, field-trip guidebooks and open-file reports cannot be referenced as authoritative documentation of stratigraphic studies because the North American Stratigraphic Code (NASC) considers such guidebooks and reports to be informal and does not recognize them as proper publications to formalize stratigraphic studies (see Article 4 of the NASC, in North American Commission on Stratigraphic Nomenclature [NACSN], 2021). Hence, a report series such as “Stratigraphic Notes” is needed to bridge this gap.

Professional Paper↗

USGS2023

Divisions of geologic time—Major chronostratigraphic and geochronologic units

Introduction Effective communication in the geosciences requires consistent use of stratigraphic nomenclature, especially divisions of geologic time. A geologic time scale is composed of standard stratigraphic divisions that are based on rock sequences and is calibrated in years (Harland and others, 1982). Over the years, the development of new dating methods and the refinement of previous ones have stimulated revisions to geologic time scales. Since the mid-1990s, geologists from the U.S. Geological Survey (USGS), State geological surveys, academia, and other organizations have sought a consistent time scale that can be used in communicating ages of geologic units in the United States. Many international debates have occurred over the names and boundaries of units, and various time scales have been used by the geoscience community in years past (for example, U.S. Geological Survey Geologic Names Committee [USGS GNC], 2007, 2010, 2018). However, the numerical ages assigned to geochronologic units frequently change as the science of stratigraphy moves forward. Once ratified, changes in numerical ages are recorded by the International Commission on Stratigraphy (ICS) on their website ( https://stratigraphy.org/chart ). In addition, such advances in stratigraphy and changes in geochronology require that any time scale be periodically updated. Therefore, the time scale presented in this report (hereafter referred to as “Divisions of Geologic Time”) is dynamic, and it is modified as needed to include accepted changes of unit names and boundary age estimates (USGS GNC, 2007, 2010, 2018).

Professional Paper↗

USGS2023

Guidance on geologic names usage for authors and peer reviewers of geologic maps and reports—A primer on stratigraphic nomenclature

Introduction Consistent and effective communication is essential for scientific publications. Scientific communication requires clear explanations and precise discussion of data and interpretations. “Authors must strive for clarity, consistency, and correct usage of both formal and informal terminology because of the complex interactions between time and space interpreted from the presently existing stratigraphic record” (Owen, 2009). The importance of consistent stratigraphic nomenclature as a means of effective geologic communication has been recognized since the U.S. Geological Survey (USGS) established the Geologic Names Committee (GNC) in 1899 to evaluate and address issues of stratigraphic nomenclature. The GNC currently consists of geologists from the USGS and the Association of American State Geologists. In an effort towards codifying stratigraphic nomenclature, the North American Commission on Stratigraphic Nomenclature developed the North American Stratigraphic Code (referred to hereafter as “the Code”; North American Commission on Stratigraphic Nomenclature [NACSN], 2021) in 1983 by revising and updating preexisting codes that were then in use, such as the International Stratigraphic Guide [ISG] (International Subcommission on Stratigraphic Classification [ISSC], 1976; see also, ISSC, 1994). Consistency in geologic names usage increases accuracy and quality of scientific publications. All formal USGS publications require a geologic names review (GNR) if any stratigraphic, lithodemic, geochronologic, or chronostratigraphic terminology is used. This review of, and guidance for, geologic names usage and stratigraphic principles should be referred to by authors and peer reviewers, not just those who conduct GNRs, and its guidance should be incorporated into their publications to improve geoscience communication. The notes and guidance in the sections that follow should be considered by USGS geologists and editors while writing or reviewing manuscripts that include geologic names and stratigraphic concepts. This primer may also be used by geologists and editors outside of the USGS for consistency with their publications.

Professional Paper↗

USGS2023

Guidelines for conducting reviews of geologic names and aquifer names in U.S. Geological Survey hydrogeologic maps and reports

Introduction The U.S. Geological Survey (USGS) is officially charged with assessment of various aspects of geology and hydrogeology throughout the Nation. Hence, USGS publications adhere to broadly uniform procedures in the classification and nomenclature of geologic and hydrogeologic units. Responsibility for this uniformity is under the technical guidance of the Geologic Names Committee (GNC), which formulates general policy and advises on specific nomenclatural issues. Central to the GNC proceedings is the North American Stratigraphic Code (hereafter referred to as “the Code”) (North American Commission on Stratigraphic Nomenclature [NACSN], 2021). Geologic reports typically contain geologic maps and cross sections, geologic unit names, lithologic descriptions, and stratigraphic correlation charts, as well as results of drilling activities and structure-contour, depth-to-top, depth-to-base, or sediment-thickness maps. Groundwater-resource maps and other hydrogeologic maps and reports can also contain many of these same elements. Groundwater-resource reports rarely contain original geologic mapping, revisions of stratigraphic nomenclature, or redefinitions or changes in the ranks or ages of geologic units; however, these reports usually contain descriptions and classifications of hydrogeologic units, and they also may introduce new or modify existing aquifer nomenclature. The following general guidance is published for those designated as geologic and aquifer names reviewers.

Professional Paper↗

USGS2022

Bedrock geologic map of the Crown Point quadrangle, Essex County, New York, and Addison County, Vermont

The bedrock geology of the 7.5-minute Crown Point quadrangle consists of deformed and metamorphosed Mesoproterozoic gneisses of the Adirondack Highlands unconformably overlain by weakly deformed lower Paleozoic sedimentary rocks of the Champlain Valley. The Mesoproterozoic rocks occur on the eastern edge of the Adirondack Highlands and represent an extension of the Grenville Province of Laurentia. Granulite facies Mesoproterozoic paragneiss, marble, and amphibolite hosted the emplacement of granitic orthogneiss at approximately 1.18–1.15 giga-annum (Ga, billion years before present). The earliest of four phases of deformation (D1) is characterized by gneissosity, rarely preserved F1 isoclinal folds, and migmatite in the host rocks. Subsequent D2 deformation produced a composite penetrative gneissosity, migmatite, and isoclinal F2 folds. Towards the end of D2, felsic magmatism (including the regionally extensive Lyon Mountain Granite Gneiss, abbreviated “LMG”) spread by penetrative migration as semiconcordant alkali feldspar granite sheets subparallel to S2 into previously deformed lithologies. The LMG crystallized at approximately 1.15 Ga and displays synkinematic F2 folds thus constraining the time of D2 deformation. Exhumation during D3 produced F3 folds exhibited in regional domes and basins, such as the Keeney Mountain synform, local reactivation of the S2 foliation, partial melting, metamorphism, metasomatism, iron ore remobilization, and intrusion of magnetite-bearing pegmatite both as layer-parallel sills and crosscutting dikes. D4 created NE- and NW-trending boudinage, local high-grade ductile shear zones, and crosscutting granitic pegmatite dikes. Kilometer (km)-scale lineaments readily observed in lidar data are Ediacaran mafic dikes and Phanerozoic brittle faults. The Paleozoic rocks are part of the Early Cambrian to Late Ordovician great American carbonate bank on the ancient margin of Laurentia. Cambrian-Ordovician stratigraphy records an approximately 1-km-thick section and a transition from synrift clastics to passive margin peritidal carbonate buildups to gradually deeper water subtidal to shelf carbonates during foreland basin development associated with the Taconic orogeny. The Paleozoic rocks are weakly folded and block faulted. Large areas of the Champlain Valley are covered by undifferentiated glacial deposits, some of which contain mapped landslides. The map also shows waste rock piles and tailings from historical mining operations and large areas of artificial fill. This study was undertaken to improve our understanding of the bedrock geology in the Adirondack Highlands, establish a modern framework for 1:24,000-scale bedrock geologic mapping in the Adirondacks, provide a context for historical iron mines in the eastern Adirondacks, and update the stratigraphy of the Champlain Valley in New York and Vermont. This Scientific Investigations Map of the Crown Point 7.5-minute quadrangle consists of a map sheet, an explanatory pamphlet, and a geographic information system database that includes bedrock geologic units, faults, outcrops, and structural geologic information. The map sheet includes a bedrock geologic map, a correlation of map units, a description of map units, an explanation of map symbols, three cross sections, and a simplified surficial geologic map that includes lidar percent slope. The explanatory pamphlet includes a discussion of the geology. The bedrock geologic map on the map sheet is multi-layered and has been designed to enable the user to turn off the surficial map layer to view the concealed bedrock map units.

New York, Vermont↗

USGS2022

Geologic maps of the Stephenson and Winchester quadrangles, Frederick and Clarke Counties, Virginia, and Inwood and White Hall quadrangles, Berkeley and Jefferson Counties, West Virginia

The study area consists of four contiguous 7.5-minute quadrangles and is located in Frederick and Clarke Counties, Virginia, and Berkeley and Jefferson Counties, West Virginia. The individual quadrangles are Stephenson, Winchester, Inwood, and White Hall. The study area lies within the Great Valley subprovince of the Valley and Ridge physiographic province where about 23,000 feet (ft) (7,000 meters [m]) of Middle Cambrian to Upper Devonian sedimentary rocks are exposed and are overlain by Holocene and older surficial deposits. The area of the four maps is divided into three geologic regions based on the following primary lithologies: (1) Cambrian and Ordovician carbonate rocks of the Great Valley southeast of the North Mountain fault zone and east and west of the core of the Massanutten synclinorium; (2) shale, graywacke, and calcareous shale of the Ordovician Martinsburg Formation of the Great Valley and Massanutten synclinorium; and (3) Ordovician through Devonian clastic rocks and minor limestone and dolostone northwest of and within the North Mountain fault zone. Rocks of all three regions were folded and faulted during the late Paleozoic Alleghanian orogeny (roughly 320 to 250 million years before present). The terrain of this portion of the Great Valley generally is gently to moderately rolling with low local relief with elevations in the study area ranging from about 425 ft (130 m) where Opequon Creek flows out of the eastern edge of the Inwood quadrangle to about 950 ft (290 m) adjacent to Round Hill in the western part of the Winchester quadrangle. Sinkholes and other karst features are common in the carbonate rocks of the Great Valley. The area west of the North Mountain fault zone is underlain by middle Paleozoic strata and consists of a series of ridges and valleys with higher local relief, with elevations ranging from about 785 ft (240 m) in the vicinity of Green Spring in the central part of the White Hall quadrangle to about 1,435 ft (437 m) at the summit of North Mountain in the northeastern part of the White Hall quadrangle.

Virginia, West Virginia↗

USGS2020

Memorial to Jack B. Epstein 1935-2020

Jack Burton Epstein, a career geologist with the U.S. Geological Survey (USGS) passed away in May 2020 at his home in Great Falls, Virginia. His career and contributions to the USGS spanned more than 60 years from his time as a summer field assistant while attending college, through 40 years as a research geologist, and more than 15 years as an emeritus scientist. Jack was born December 27, 1935 in Brooklyn, New York and attended CUNY- Brooklyn College where he received his Bachelor of Science degree in geology in 1956. He earned his Master of Science degree in 1958 from the University of Wyoming, and his doctorate degree in geology in 1970 from The Ohio State University. His master’s thesis was geologic mapping of the Fanny Peak quadrangle, Black Hills of Wyoming and South Dakota, and his Ph. D. dissertation focused on the geology of the Stroudsburg quadrangle and adjacent areas, Pennsylvania and New Jersey.

Geological Society of America Memorials↗

USGS2018

Geologic map of the Timberville quadrangle, Virginia

This map of the Timberville 7.5-minute quadrangle in Rockingham and Shenandoah counties, Virginia shows the distribution of Paleozoic-age sedimentary rocks in map and cross-section. Surficial deposits including alluvium and colluvium are also shown. The characteristics of each map unit are described and a brief report discusses the stratigraphy, structure and mineral resources of the area.

Virginia↗

USGS2017

North American Commission on Stratigraphic Nomenclature Report 12 – Revision of article 37, lithodemic units, of the North American Stratigraphic Code

At the 71st Annual Meeting of the North American Commission on Stratigraphic Nomenclature, 26 September, 2016, in Denver, Colorado, the Commission voted unanimously to accept the revision of Article 37 of the North American Stratigraphic Code (North American Commission on Stratigraphic Nomenclature, 2005), printed below. It replaces all older versions of this Article. An application for this revision (Easton et al. 2015) was published in Stratigraphy more than one year prior to the meeting; thus, the vote on this application for revision follows Article 21 of the Code.

Stratigraphy↗

USGS2016

Digital geologic map data for the Ozark National Scenic Riverways and adjacent areas along the Current River and Jacks Fork, Missouri

The geology of the Ozark National Scenic Riverways (ONSR) in southern Missouri has been mapped at 1:24,000 scale. This endeavor was achieved through the combined efforts of U.S. Geological Survey and Missouri Geological Survey individual quadrangle mapping and additional fieldwork by the authors of this report. Geologic data covering the area of the ONSR and a 1-mile (1.6-kilometer) buffer zone surrounding the park, as well as geologic data from a few key adjoining areas, have been compiled into a single, seamless geographic information system database. The intent is to provide base geologic information for natural science research and land management in the park and surrounding areas. The data are served online at ScienceBase ( https://www.sciencebase.gov/catalog/ ), where they are provided in Environmental Systems Research Institute (ESRI) file geodatabase format, and are accompanied by metadata files. These data can be accessed at: http://dx.doi.org/10.5066/F7CJ8BKB . Additional detailed geologic information about the ONSR and surrounding areas is available in the separate 1:24,000-scale quadrangle maps and in a 1:100,000-scale map and report on the regional geology.

Missouri↗

USGS2016

Geologic context of large karst springs and caves in the Ozark National Scenic Riverways, Missouri

The ONSR is a karst park, containing many springs and caves. The “jewels” of the park are large springs, several of first magnitude, that contribute significantly to the flow and water quality of the Current River and its tributaries. Completion of 1:24,000-scale geologic mapping of the park and surrounding river basin, along with synthesis of published hydrologic data, allows us to examine the spatial relationships between the springs and the geologic framework to develop a conceptual model for genesis of these springs. Based on their similarity to mapped spring conduits, many of the caves in the ONSR are fossil conduit segments. Therefore, geologic control on the evolution of the springs also applies to speleogenesis in this part of the southern Missouri Ozarks. Large springs occur in the ONSR area because: (1) the Ozark aquifer, from which they rise, is chiefly dolomite affected by solution via various processes over a long time period, (2) Paleozoic hypogenic fluid migration through these rocks exploited and enhanced flow-paths, (3) a consistent and low regional dip of the rocks off of the Salem Plateau (less than 2° to the southeast) allows integration of flow into large groundwater basins with a few discreet outlets, (4) the springs are located where the rivers have cut down into structural highs, allowing access to water from stratigraphic units deeper in the aquifer thus allowing development of springsheds that have volumetrically larger storage than smaller springs higher in the section, and (5) quartz sandstone and bedded chert in the carbonate stratigraphic succession that are locally to regionally continuous, serve as aquitards that locally confine groundwater up dip of the springs creating artesian conditions. This subhorizontal partitioning of the Ozark aquifer allows contributing areas for different springs to overlap, as evidenced by dye traces that cross adjacent groundwater basin boundaries, and possibly contributes to alternate flow routes under different groundwater flow regimes. A better understanding of the 3-dimensional hydrogeologic framework for the large spring systems in the ONSR allows more precise mapping of the contributing areas for those springs, will guide future studies of groundwater flow paths, and inform development of groundwater resource management strategies for the park.

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