Richmond Basin Research Articles

A new lizard-like reptile with unusual mandibular neurovasculature from the Upper Triassic of Virginia

ABSTRACT Here, we report a new small-bodied reptile taxon, Idiosaura virginiensis gen. et sp. nov., from the Upper Triassic (Carnian) Vinita Formation of the Richmond basin (Newark Supergroup) in east-central Virginia, U.S.A. The material consists of a fragmentary dentary bearing numerous tall cylindrical teeth implanted in a pleurodont fashion into spongy alveolar tissue. Micro-CT scan data reveal an unusual and complex network of interconnected neurovascular canals within the dentary with connections to the alveolar tissue and pulp cavities of the teeth. The external anatomy of the dentary is consistent with that of Triassic kuehneosaurid reptiles, suggesting affinities to that group; the results of a phylogenetic analysis were inconclusive but do not exclude kuehneosaurid relationships. Alongside the recently described Micromenodon pitti (Rhynchocephalia) and Vinitasaura lizae (Lepidosauromorpha), the new taxon adds to the relatively diverse assemblage of small-bodied reptiles known from the Tomahawk microvertebrate bonebed (USNM locality 39981). Relative tooth complexities of I. virginiensis and V. lizae were analyzed using the Orientation Patch Count Rotated method, and results suggest that the rise of lepidosauromorph ecomorphologies specializing for feeding on invertebrates occurred in Triassic communities alongside non-lepidosauromorph taxa with similar mandibulo-dental features, as in kuehneosaurs.

A new early-diverging sphenodontian (Lepidosauria, Rhynchocephalia) from the Upper Triassic of Virginia, U.S.A.

AbstractA new taxon of sphenodontian reptile,Micromenodon pittinew genus new species is described from the Upper Triassic (Carnian) Vinita Formation of the Richmond basin of the Newark Supergroup in Virginia. It is diagnosed by a dorsoventrally deep facial process of the maxilla that extends for almost the entire anteroposterior length of the bone and by obtusely conical, strongly ribbed additional teeth in the maxilla that comprise a greatly enlarged tooth followed by smaller teeth posteriorly. Phylogenetic analysis foundMicromenodon pittin. gen. n. sp. as an early-diverging sphenodontian with fully acrodont tooth implantation. The maxillary dentition appears functionally suited for processing hard arthropod exoskeletons and snail shells.UUID:http://zoobank.org/40ed7cb6-4867-464b-8bfb-db07febfe97c

Richard Cowling Taylor: Founder of Appalachian coal geology

Richard Cowling Taylor (1789–1851) was a British-born American geologist, generally specializing in the coal geology of the Pennsylvanian system and in the Triassic coals of Pennsylvania and Virginia. While he long clung to older, disproved age assignments and made some mistakes in structural geology, therefore missing coal-bearing synclines beyond the immediate study area, he did pioneer the use of cross sections of coal basins and made advancements in the uniform expression of geologic maps. His work in the western end of Pennsylvania's Southern Anthracite field, Broad Top coalfield, and the North-central coalfields and in Virginia's Richmond Basin provided valuable insights into the exploration and development of those areas in the 1830's and 1840's.

Anatomy and phylogenetic relationships of Boreogomphodon jeffersoni (Cynodontia: Gomphodontia) from the Upper Triassic of Virginia

ABSTRACT We present a detailed account on the skeletal structure of the traversodont cynodont Boreogomphodon jeffersoni on the basis of a considerable quantity of excellently preserved craniodental remains and several referred postcranial bones from the Tomahawk Creek Member of the Vinita Formation (Upper Triassic: Carnian) of the Richmond basin (Newark Supergroup) in eastern Virginia. The small size, proportionately short snout and mandible, low number of molariform postcanine teeth, and presence of up to three sectorial postcanines all indicate that most of the specimens recovered to date represent immature individuals. The superbly preserved dental material permits detailed inferences regarding tooth replacement and dental function during ontogeny. Boreogomphodon differs from other known traversodont cynodonts primarily in the possession of lower molariform postcanine teeth with three rather than two anterior cusps in all but the smallest specimens, zygomatic arches that are bowed laterally at about mid-length, and pronounced, irregular sculpturing on the dorsal surface of the snout. Plesiomorphic features of traversodont cynodonts retained by Boreogomphodon include the position of the paracanine fossa anterolingual to the upper canine as well as the presence of a distinct central cusp and a posterior cingulum on the upper molariform postcanines. Phylogenetic analysis suggests the existence of a clade comprising Boreogomphodon plus two other taxa (Arctotraversodon and Nanogomphodon) in the Northern Hemisphere that is the sister group to most other known Middle and Late Triassic traversodonts from Gondwana.

A new procolophonid and a new tetrapod of uncertain, possibly procolophonian affinities from the Upper Triassic of Virginia

ABSTRACT Two jaw fragments of small tetrapods from the Turkey Branch Formation of the Richmond basin (Newark Supergroup; Upper Triassic: lower to middle Carnian) of Virginia have highly distinctive dentitions. The robust, transversely broadened, and bicuspid teeth of Gomphiosauridion baileyae, gen. et sp. nov. support its placement in the Procolophonidae. The two cusps are linked by a pronounced transverse ridge, which divides the occlusal surface of the crown into two deep fossettes. The cusps have strongly fluted enamel. The heterodont dentition of Xenodiphyodon petraios, gen. et sp. nov. comprises transversely broadened, tricuspid posterior teeth and transversely compressed anterior teeth with distinct apical ridges. The posterior teeth of Xenodiphyodon closely resemble those of the alleged trilophosaurid taxa Tricuspisaurus thomasi and Variodens inopinatus from Upper Triassic fissure-fillings in southwestern England and ?Trilophosaurus jacobsi from the Upper Triassic Chinle Formation of Arizona. The l...

A remarkable new armored archosaur from the Upper Triassic of Virginia

ABSTRACT An unusual new archosaurian reptile, Euscolosuchus olseni, gen. et sp. nov., is described from the Tomahawk Creek Member of the Turkey Branch Formation of the Richmond basin (Newark Supergroup; Upper Triassic: Carnian) in east-central Virginia. Its distinctive, narrow carapace comprises paired, sharply angulated paramedian osteoderms that bear much enlarged lateral spines and have crocodile-like external ornamentation. Euscolosuchus is referable to the Crurotarsi and closely resembles basal Crocodyliformes in the structure of its dorsal dermal armor.

Angiosperm-like pollen from the ammonite-dated Oxfordian (Upper Jurassic) of France

Two species of angiosperm-like pollen are described from an outcrop of lower Oxfordian Oxford Clay at Normandy, France. An Oxfordian age is established by ammonites (Quenstedtoceras mariae zone) and substantiated by associated age-diagnostic dinoflagellates. The angiosperm-like taxa are determined to be in place by their state of preservation and unique morphology. The more abundant taxon, Stellatopollis pocockii n. sp., closely resembles the pollen of extant Lilium bulbiferum in size and sculpture, but also closely resembles similar but smaller pollen found in the Lower Cretaceous. Stellatopollis Doyle 1975 is emended to include a wider range of Early Cretaceous reticulate monosulcate grains with crotonoid sculpture. A diporate species, Multimarginites sp. A, closely resembling the pollen of extant Bravaisia and Sanchezia (Acanthaceae) in size and sculpture is described and compared to a similar morphotype (Cornetipollis) from the late Triassic Richmond basin of Virginia The genus Multimarginites Germeraad, Hopping et Muller 1968 is emended as di- or triporate and polyplicate, since its multimarginate “colpi” are non-apertural harmomegathic furrows. The significance of these unusual pollen types in pre-Barremian strata is discussed and they are placed in perspective with angiosperm-like pollen and megafossils from the Late Triassic of North America. The new combination Carollina chateaunovii (Reyre) nov. com. was made.

Coalbed Methane Exploration and Results: Richmond Basin, Virginia

Coalbed Methane Exploration and Results: Richmond Basin, Virginia

Triassic Vertebrates of Gondwanan Aspect from the Richmond Basin of Virginia

A new locality of early Late Triassic age in the Richmond basin of east-central Virginia has yielded abundant remains of a diversified assemblage of small to medium-sized tetrapods that closely resembles Southern Hemisphere (Gondwanan) assemblages in the predominance of certain synapsids. Associated palynomorphs indicate an early middle Carnian age for the fossiliferous strata. The discovery suggests that previously recognized differences between tetrapod assemblages of early Late Triassic age from Gondwana and Laurasia at least in part reflect differences in stratigraphic age, rather than geographic separation.

Diagenetic History and Porosity Development of Triassic Arkosic Sandstones: Implications for Hydrocarbon Exploration: ABSTRACT

The Richmond basin of Virginia is one of several frontier Triassic basins of the Newark rift system of eastern North America currently being explored for hydrocarbons. There are numerous penetrations but limited core samples available for examination. In one well, however, 33 rotary sidewall cores have been collected and used for this study. Examination of these cores using thin section, X-ray diffraction (XRD) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques has revealed a complex diagenetic history for arkosic sandstones near potential hydrocarbon source beds. An atypical mineral assemblage has developed as a result of dissolution of feldspar, quartz, mafic silicate, and other minerals and subsequent precipitation of laumontite (a zeolite), quartz, and trace amounts of clay. In thin section and with the SEM, these rocks have impressive intragranular and grainmoldic porosity and virtually no porosity-inhibiting clay. Consequently, a mechanism for creating significant secondary porosity in arkosic sandstones has been documented. This mechanism is probably related to the migration of hydrocarbons and associated fluids from source lithologies.

Depositional Environments and Sedimentology of Vinita Beds, Richmond Basin, Virginia: ABSTRACT

The Carnian (middle to late Middle Triassic Age) Richmond basin of northeast Virginia is the oldest of the exposed Newark rift basins of the eastern seaboard. These basins formed during the Mesozoic divergence of the continents. As presently defined, the Richmond basin is a large synclinal feature measuring 32 mi (53 km) long by 8 mi (13 km) wide, and is located west of Richmond, Virginia, and east of Amelia, Virginia. Sediments of the Richmond basin have been assigned to the Richmond Group and have been stratigraphically subdivided into the following informal units, oldest to youngest: coarse boulder breccias, coal measures, Vinita Beds, and Otterdale Sandstone. The Vinita Beds are composed of arkosic sandstones, shales, siltstones, and minor amounts of coal, and are mineralogically immature. They are composed of angular to subrounded rock fragments, quartz, and feldspars, and are highly micaceous and kaolinitic. In places, feldspars make up as much as 50% of the rock. Sandstones and conglomerates are cross-bedded and channeled, and shales and siltstones are thinly laminated. The Vinita Beds are rich in fossil fish, branchiopods, and plant fragments. These rocks were deposited in braided streams as well as in paludal and possible lacustrine environments in a humid and heavily vegetated setting. End_of_Article - Last_Page 275------------

Depositional Environments and Sedimentology of Vinita Beds, Richmond Basin, Virginia: ABSTRACT

Depositional Environments and Sedimentology of Vinita Beds, Richmond Basin, Virginia: ABSTRACT

Depositional and Structural Histories of Richmond and Taylorsville Triassic Rift Basins: ABSTRACT

The Richmond and Taylorsville basins of Virginia display similar structural and sedimentological histories, which differ somewhat from those of other eastern North American rift basins. Both basins formed during the middle Carnian in response to the initial opening of the North Atlantic Ocean. Both are westward tilted half grabens whose border faults share a reactivated Paleozoic basement thrust (the Hylas zone). A dipmeter log from the Bailey 1 well (Richmond basin) shows that bedding dips toward the border fault and increases with depth. These relationships are interpreted to reflect syndepositional rotation and tilting of the basin above a listric normal fault. Unlike the red beds typical of other eastern North American rift basins, sediments of the Richmond and Taylorsville basins are mostly unoxidized gray sandstones and siltstones. The sediments of both basins can be divided into three facies associations. The lowest is a poorly sorted, coarse-grained, lithic arkose rapidly deposited in alluvial fans and braided streams. This was succeeded by sand, silt, and mud of a lower End_Page 1449------------------------------ gradient, fluvial-paludal setting. Organic-rich black shales accumulated in lakes (oxbows?) and overbank deposits. An influx of cross-bedded fluvial sands, possibly triggered by renewed border faulting on the west, characterizes the final stage of basin fill. These sediments represent fan-delta systems that prograded northeastward across the lacustrine-paludal lowlands. End_of_Article - Last_Page 1450------------

Structural Styles and Tectonic Implications of Richmond-Taylorsville Rift System, Eastern Virginia: ABSTRACT

Recent drilling and seismic surveys in the Richmond basin have revealed unexpected results. Alternating episodes of extension and compression have created overprints of structural styles, and generated syndepositional unconformities as sediments were uplifted and rotated. Eroded Triassic sediments from structural highs were redeposited in adjacent synclinal or fault-controlled lows. In addition, lithologic correlation has revealed the existence of large deltaic complexes prograding across the basins, followed by Mississippi-size meander-belt channel deposits in the subsurface. The early lacustrine-deltaic deposits (Vinita beds, etc) appear to have been deposited in a basin much larger than the apparent outcrop limits of the Richmond or Taylorsville basins. As much as 3,000 ft of these deposits accumulated prior to a compressional event that folded them into enormous anticlines and synclines, as Paleozoic thrust sheets were reactivated and sub-Triassic buried hills grew in height, raising the overlying Triassic sediments by as much as 2,000 ft over a distance of less than 2 mi. End_Page 1434------------------------------ The synclines contain a nearly continuous sedimentary sequence, whereas the anticlines have the uppermost Otterdale Sandstone facies as a blanket deposit over their truncated tips and steeply dipping Vinita beds below the unconformity on their flanks. Extensional events followed the main phase of folding and pulled the limbs of the anticlines apart, causing normal listric faults to form and blocks of Vinita beds to separate into North Sea-type fault-block structure. Based on maturation and porosity trends with depth, at least 7,000 ft of overburden have apparently been removed from the basins. Either the structural style changed dramatically from listric faults to horst and graben mechanics, thereby dropping the Richmond-Taylorsville sequences below the present erosional level, or an enormous gravity slide from the east covered the basins, and erosion has created windows through this detached Paleozoic thrust sheet into a much larger Triassic rift system below it. End_of_Article - Last_Page 1435------------

Paleopalynological Insights on Dating of Newark Supergroup Rocks and Their Correlation with European Sections: ABSTRACT

Once thought to be prevailingly barren of palynomorphs, sediments from all of the known Newark basins have now yielded correlatable palynofloras. However, for various reasons, only poorly preserved florules (Danville-Dan River basin) or scarce productive zones (Fundy basin) have been found in some of the basins. Sedimentation in the Newark rift zone apparently began in late Ladinian to late Carnian time along most of the front. New analytical data from a buried basin in southern Georgia now extend this observation about 400 km (two stages) farther south. From south Georgia to the Richmond basin in Virginia, the youngest sediments are Carnian or Carnian/Norian. In the Culpeper basin, Virginia, new information indicates sedimentation beginning during the Carnian, in keeping with the other southern basins. However, in the Culpeper basin and all of the northern basins, sedimentation persisted much longer. Latest Triassic to late Liassic floras are found in all of them. Palynoflorules as young as Toarcian have been studied in the Hartford-Deerfield basin of Connecticut-Massachusetts. Ultimately, these dates depend on correlation with palynofloras from classic marine fossil zones in south-central Europe, work which is in flux and progressing rapidly in European laboratories, boding probable changes in the Newark basin palynostratigraphic framework. End_of_Article - Last_Page 1450------------

Newark Rift System: A Potentially Prolific Hydrocarbon Province: ABSTRACT

Many oil tests in the Newark rift system have been encouraging. The data from these tests combined with data collected previously indicate that the geologic and geochemical criteria required to produce significant quantities of hydrocarbons have been met in several of the basins. Most of the wells drilled heretofore were not positioned using specific geologic or geophysical data. In fact, the industry only recently recognized the play as viable and has applied geophysical techniques to the search for potential hydrocarbon-bearing structural or stratigraphic traps. This activity has partially revealed the geologic processes involved in the development of the basins. The Sanford basin of North Carolina, for example, is a simple half graben, whereas the Richmond basin of Virginia seems to be more complex structurally and may have been affected more by wrench tectonics, producing structures similar to those found in the lake basins of the East Africa rift system. Each basin's hydrocarbon migration history, however, cannot be fully documented at this embryonic stage of exploration. It is, therefore, necessary to continue to build the geophysical, geological, and geochemical data bases until a well-substantiated model of the migration history can be established. The migration history together with the tectonic evolution of the basin enhances the chances of finding where hydrocarbons are presently trapped. Currently, prospects are being evaluated in several basins. There is a reasonable chance that reserves will be found. At the very least, the wells will aid the exploration effort and refine the exploration theories. End_of_Article - Last_Page 1452------------

Hydrocarbon Potential of Newark Rift System, Eastern North America: ABSTRACT

Rift basins contain only 5% of the earth's sedimentary volume yet yield 10% of the world's hydrocarbon production. They consist of graben, half-graben, tilted fault blocks, and synclinal downwarps and are commonly preserved along continental margins. The Newark rift system represents the sediments preserved End_Page 574------------------------------ along the eastern seaboard which were deposited during the Triassic-Jurassic rifting of Pangea. Continental rifting creates a linear series of tectonic depressions which form rift valleys. Commonly, these valleys are ponded, yielding long, narrow, deep lakes. The best modern example of this geologic setting is the East Africa rift system. Lake Tanganyika is 300 mi (483 km) long, 40 mi (64 km) wide and as deep as 4,000 ft (1,220 m). A fluviolacustrine depositional system is developed here where deltaic, littoral, shallow lake, and deep lake facies are well defined. Drastically fluctuating lake levels cause cyclic onlap and offlap resulting in a finely bedded stratigraphic section. The interfingering of these facies conveniently create a favorable source (deep lake) and reservoir (littoral, deltaic) relationship. The lakes in rift valleys support prolific biologic ecosystems. The equatorial lakes are thermally stratified inducing anoxic conditions which preserve the organic material raining down from the surface. East African lake-bottom sediments often exceed 10% TOC. Some organic rift lake shales from the Cabinda basin contain more than 20% TOC. The Green River formation lake shales contain as much as 40% TOC. The Newark shales contain between 2 and 35% TOC and are up to 4,000 ft (1,220 m) thick. The shales from these basins often qualify as shales. The quantities cited are well above the general requirements for legitimate hydrocarbon source rocks. There are other rift systems, analogous to the Newark rift system, that produce significant quantities of hydrocarbons. The Cabinda, Angola, and the Reconcavo (Brazil) basins of the southern hemisphere combined produce nearly 200,000 BOPD and have total recoverable reserves in excess of 2 billion bbl. There is notable production from rift basins in Australia, the southern North Sea, the Rhine graben, and China. Reservoir rocks are fluviolacustrine, deltaic, and alluvial siliciclastics, fractured shales, freshwater carbonates, intrusives, and turbidites. Attractive reservoir sandstones with up to 25% porosity are documented in the Newark basins. The Newark rift system remains essentially unexplored. The archaic theory that oil does not occur in continental settings has stifled exploration. There have been encouraging signs. Oil has been recovered from the Richmond basin, a major discovery was made in the Triassic rift sediments of western Morocco in 1981, and significant and gas shows were found in the buried Georgia rift basin. Obviously the Newark rift system needs to be reevaluated. The current state of knowledge indicates that all of the necessary criteria of and gas generation and accumulation have been met. These basins warrant a thorough investigation. End_of_Article - Last_Page 575------------

Deformation and metamorphism in the Hylas zone and adjacent parts of the eastern Piedmont in Virginia

Structural and petrographic studies of the Hylas zone northwest of Richmond, Virginia, reveal that late Paleozoic ductile shearing produced mylonites and ultramylonites from pre-existing biotite gneiss, granite gneiss, and amphibolite in the Goochland complex and from Petersburg(?) granite. Rocks in the Goochland complex west of the Hylas zone underwent at least two deformations (D 1 , D 2 ) prior to ductile shearing in the Hylas zone (D 3 ). D 3 caused a pervasive mylonitic foliation (S c ) and a later widely spaced shear cleavage (S s ) to be formed in rocks in the Hylas zone. Brittle deformation in the form of high-angle faulting and locally intense fracturing (D 4 ) was superimposed on the Hylas zone about 220 m.y. ago and is probably equivalent to the Palisades disturbance of New England. D 4 was associated throughout the Piedmont with synchronous downwarp and dominantly continental sedimentation to form a series of parallel Triassic basins represented in the study area by the Richmond Basin. Northwest-oriented high-angle faults that apparently displace Triassic sedimentary rocks are interpreted to predate the Late Cretaceous. Regional prograde metamorphism of the Goochland complex to amphibolite facies (M 1 ) was inclusive of D 1 and D 2 , because structural elements that compose these deformational events consist primarily of oriented metamorphic minerals. Well-equilibrated microstructures in the gneisses suggest that the M 1 peak persisted past D 2 . M 1 is inferred to have occurred about 340 m.y. ago. D 3 was accompanied by retrograde metamorphism (m 2 ) to greenschist facies in the Hylas zone during late Paleozoic time. The presence of laumontite, quartz, and calcite in brecciated zones suggests that brittle deformation during D 4 occurred under zeolite facies conditions. Cenozoic reverse faulting 90 km along strike of the study area in the Brandywine area of the Coastal Plain in Maryland may indicate a continuation of the Hylas zone to the north. Superposed deformation and intermittent reactivation of zones of instability similar to that of the Hylas zone are reported in the Eastern Piedmont fault system, which extends from Alabama to Virginia. Current stress release beneath the Coastal Plain may be influenced by the instability of the Hylas zone and analogous fault systems throughout the Piedmont.

Late Triassic palynofloras of North America and their European correlatives

Upper Triassic continental strata in the United States contain rare horizons which yield pollen assemblages. The Dockum Group and Chinle Formation of the American Southwest, as well as certain rock units within the Deep River, Richmond, and Taylorsville Basins of the Newark Group, contain palynomorphs which exhibit stratigraphically restricted ranges in Europe. The presence of Vallasporites ignacii, Camerosporites secatus and Ovalipollis ovalis in the Dockum Group, Chinle Formation, Cumnock Formation of the Deep River Basin, Vinita Formation of the Richmond Basin, and unnamed units in the Taylorsville Basin suggest that all these units are approximately contemporaneous. The occurrence of these and other stratigraphically diagnostic pollen taxa, particularly Patinasporites densus, further indicates a Middle to Late Karnian age for these units. The palynostratigraphy also implies that the Pekin Formation of the Deep River Basin is slightly older than the above mentioned units.

Former extent of the Newark system

Research Article| January 01, 1902 Former extent of the Newark system WILLIAM HERBERT HOBBS WILLIAM HERBERT HOBBS Search for other works by this author on: GSW Google Scholar GSA Bulletin (1902) 13 (1): 139–148. https://doi.org/10.1130/GSAB-13-139 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation WILLIAM HERBERT HOBBS; Former extent of the Newark system. GSA Bulletin 1902;; 13 (1): 139–148. doi: https://doi.org/10.1130/GSAB-13-139 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Views held by American GeologistsAmerican geologists have quite generally held to the view that the former extent of the Newark system along the Atlantic border was not much greater than at present, the assumption being made that the deposits were laid down in local basins practically coextensive with the present Newark areas. Russell alone of those who have made special study of the system has advocated a “broad terrane” as against a “local basin” hypothesis for the origin of these deposits.* Davis has expressed the view that the Newark trough of the Connecticut valley was at least 8 or 10 miles wider than the present valley,† but he has thrown the weight of his authority in favor of a strictly “local basin” of deposition. Shaler and Woodworth in their joint monograph treating of the Richmond basin discuss the evidence from that area without reaching a very definite conclusion, . . . This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.