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John E. Repetski

Publications and source records attributed to John E. Repetski.

At least 55 records · Page 3Linked to original sources
USGS2005

Thermal maturity patterns (CAI and %Ro) in the Ordovician and Devonian rocks of the Appalachian basin in West Virginia

The objective of this study is to enhance existing thermal maturity maps in West Virginia by establishing: 1) new subsurface CAI data points for the Ordovician and Devonian and 2) new %Ro and Rock Eval subsurface data points for Middle and Upper Devonian black shale units. Thermal maturity values for the Ordovician and Devonian strata are of major interest because they contain the source rocks for most of the oil and natural gas resources in the basin. Thermal maturity patterns of the Middle Ordovician Trenton Limestone are evaluated here because they closely approximate those of the overlying Ordovician Utica Shale that is believed to be the source rock for the regional oil and gas accumulation in Lower Silurian sandstones (Ryder and others, 1998) and for natural gas fields in fractured dolomite reservoirs of the Ordovician Black River-Trenton Limestones. Improved CAI-based thermal maturity maps of the Ordovician are important to identify areas of optimum gas generation from the Utica Shale and to provide constraints for interpreting the origin of oil and gas in the Lower Silurian regional accumulation and Ordovician Black River-Trenton fields. Thermal maturity maps of the Devonian will better constrain burial history-petroleum generation models of the Utica Shale, as well as place limitations on the origin of regional oil and gas accumulations in Upper Devonian sandstone and Middle to Upper Devonian black shale.

Open-File Report↗
USGS2003

Stratigraphic framework of Cambrian and Ordovician rocks in the central Appalachian Basin from Medina County, Ohio, through southwestern and south-central Pennsylvania to Hampshire County, West Virginia

A 275-mi-long restored stratigraphic cross section from Medina County, Ohio, through southwestern and south-central Pennsylvania to Hampshire County, W. Va., provides new details on Cambrian and Ordovician stratigraphy in the central Appalachian basin and the structure of underlying Precambrian basement rocks. From west to east, the major structural elements of the block-faulted basement in this section are (1) the relatively stable, slightly extended craton, which includes the Wooster arch, (2) the fault-controlled Ohio-West Virginia hinge zone, which separates the craton from the adjoining Rome trough, (3) the Rome trough, which consists of an east-facing asymmetric graben and an overlying sag basin, and (4) a positive fault block, named here the South-central Pennsylvania arch, which borders the eastern margin of the graben part of the Rome trough. Pre-Middle Ordovician structural relief on Precambrian basement rocks across the down-to-the-west normal fault that separates the Rome trough and the adjoining South-central Pennsylvania arch amounted to between 6,000 and 7,000 ft. The restored cross section shows eastward thickening of the Cambrian and Ordovician sequence from about 3,000 ft near the crest of the Wooster arch at the western end of the section to about 5,150 ft at the Ohio-West Virginia hinge zone adjoining the western margin of the Rome trough to about 19,800 ft near the depositional axis of the Rome trough. East of the Rome trough, at the adjoining western edge of the South-central Pennsylvania arch, the Cambrian and Ordovician sequence thins abruptly to about 13,500 ft and then thins gradually eastward across the arch to about 12,700 ft near the Allegheny structural front and to about 10,150 ft at the eastern end of the restored section. In general, the Cambrian and Ordovician sequence along this section consists of four major lithofacies that are predominantly shallow marine to peritidal in origin. In ascending stratigraphic order, the lithofacies are identified by the following descriptive names: (1) sandstone, shale, limestone, and dolomite unit, (2) dolomite and sandstone unit, (3) limestone and black shale unit, and (4) shale and sandstone unit. Each of these units and their associated subunits thicken from west to east across the restored section to a maximum near the depositional axis of the Rome trough and then thin eastward to the end of the section. The sandstone, shale, limestone, and dolomite unit is largely confined to the asymmetric graben that marks the initial phase of the Rome trough. This unit is Early and Middle Cambrian in age and consists, in ascending order, of a basal sandstone unit (undrilled but probably present), the Tomstown Dolomite (undrilled but probably present), the Waynesboro Formation, and the Pleasant Hill Limestone and its equivalent lower one-third of the Elbrook Formation at the eastern end of the section. The dolomite and sandstone unit forms the core of the Cambrian and Ordovician sequence. In the Rome trough and on the adjoining South-central Pennsylvania arch, this unit consists, in ascending order, of the Middle and Upper Cambrian Warrior Formation and the equivalent upper two-thirds of the Elbrook Formation at the eastern end of the section, the Upper Cambrian Gatesburg Formation, and the Lower Ordovician and Middle Ordovician (Whiterockian and Chazyan) Beekmantown Group. West of the Ohio-West Virginia hinge zone, the dolomite and sandstone unit consists, in ascending order, of the Conasauga Formation of Janssens (1973), the Krysik sandstone of driller's usage, the B zone of Calvert (1964), the Knox Dolomite and the associated Rose Run Sandstone Member, and the Wells Creek Formation. The widespread Knox unconformity is located at the base of the Wells Creek Formation and at or near the top of the adjoining Beekmantown Group, except near the depositional axis of the Rome trough, where the unconformity seems to be absent. The limestone and black shale unit i

Bulletin↗
USGS2002

Paulanoblella , nomen novum (Radiolaria) replaces Noblella Kozur, Mostler & Repetski, 1996, a homonym of Noblella Barbour, 1930 (Amphibia)

Kozur et al . ( 1996 ) reported and described some well-preserved Lower Ordovician (Tremadocian) Radiolaria from central Nevada and established several new taxa, among them a new genus Noblella , assigned to the Family Protoentactiniidae Kozur , Mostler & Repetski , 1996 . Dr J . K. Page kindly informed us that the genus Noblella already was established for an amphibian genus, Family Brachycephalidae, type species N. peruviana (Noble), byBarbour ( 1930 ; p . 81). Therefore, the genus name Noblella Kozur , Mostler & Repetski , 1996 non! Noblella Barbour , 1930 , is invalid because of homonymy. We here replace this junior homonym with Paulanoblella Kozur & Repetski , nomen novum .

Journal of Micropalaeontology↗
USGS2002

Lithostratigraphic, conodont, and other faunal links between lower Paleozoic strata in northern and central Alaska and northeastern Russia

Lower Paleozoic platform carbonate strata in northern Alaska (parts of the Arctic Alaska, York, and Seward terranes; herein called the North Alaska carbonate platform) and central Alaska (Farewell terrane) share distinctive lithologic and faunal features, and may have formed on a single continental fragment situated between Siberia and Laurentia. Sedimentary successions in northern and central Alaska overlie Late Proterozoic metamorphosed basement; contain Late Proterozoic ooid-rich dolostones, Middle Cambrian outer shelf deposits, and Ordovician, Silurian, and Devonian shallow-water platform facies, and include fossils of both Siberian and Laurentian biotic provinces. The presence in the Alaskan terranes of Siberian forms not seen in wellstudied cratonal margin sequences of western Laurentia implies that the Alaskan rocks were not attached to Laurentia during the early Paleozoic. The Siberian cratonal succession includes Archean basement, Ordovician shallow-water siliciclastic rocks, and Upper Silurian–Devonian evaporites, none of which have counterparts in the Alaskan successions, and contains only a few of the Laurentian conodonts that occur in Alaska. Thus we conclude that the lower Paleozoic platform successions of northern and central Alaska were not part of the Siberian craton during their deposition, but may have formed on a crustal fragment rifted away from Siberia during the Late Proterozoic. The Alaskan strata have more similarities to coeval rocks in some peri-Siberian terranes of northeastern Russia (Kotelny, Chukotka, and Omulevka). Lithologic ties between northern Alaska, the Farewell terrane, and the peri-Siberian terranes diminish after the Middle Devonian, but Siberian afµnities in northern and central Alaskan biotas persist into the late Paleozoic.

Alaska↗
USGS2002

Geologic Map of the Scott City 7.5-Minute Quadrangle, Scott and Cape Girardeau Counties, Missouri

The Scott City quadrangle is located at the northern end of the Mississippi embayment (fig. 1). The quadrangle contains parts of three physiographic features: the abandoned channel of the ancestral Mississippi River, the Benton Hills, and the flood plain of the ancestral Ohio River and modern Mississippi River. These features are largely the manifestation of the Quaternary evolution of the Mississippi and Ohio Rivers, the chronology and analysis of which has been discussed by Fisk (1944), Saucier (1968, 1974, 1994), Guccione and others (1990), Madole and others (1991), Autin and others (1991), Porter and Guccione (1994), and Blum and others (1995a,b).

IMAP↗
USGS2002

Thermal maturity patterns (CAI and %Ro) in the Ordovician and Devonian rocks of the Appalachian basin in Pennsylvania

This report presents a series of new thermal maturation maps for Pennsylvania, based on conodont color alteration index (CAI) and vitrinite reflectance (%R o ). Also, RockEval and total organic carbon (TOC) data are included in the report. Two Paleozoic intervals were studied: Middle Ordovician carbonate rocks and Lower and Middle Devonian carbonate rocks and black shale. These intervals were chosen for several reasons: A) they represent target reservoir zones for most of the oil and gas exploration and drilling in Pennsylvania; B) they are stratigraphically near probable source rocks for the oil and gas; C) they include contiguous geologic formations that extend across most of Pennsylvania; D) they contain carbonate grainstone/packstone which give a reasonable to good probability of recovery of conodont elements from small samples of drill cuttings; and E) the Middle Devonian black shale contains large amounts of organic matter for geochemical analysis.

Pennsylvania↗
USGS2000

The East Range, northwestern Nevada: A neglected key to the tectonic history of the region

The East Range occupies a strategic position at the western edge of the exposed western facies terrane near the Paleozoic continental margin. There a Cambrian and Ordovician deep-water sequence including the Preble and Valmy Formations is overlain by middle to upper Paleozoic strata that are assigned to three separate stratigraphic sequences on published geologic maps of the range. The three sequences, which include the Havallah sequence, the Inskip Formation, and the Harmony Formation, originally were perceived to be of different ages and lithic composition. The strata assigned to the Havallah are now known to contain conodonts of Late Devonian to Permian ages, and fusulinids of Permian age; those assigned to the Inskip contain conodonts of Early Mississippian and Permian ages and corals of Mississippian age. Strata assigned to the Harmony are undated paleontologically. All three are composed mainly of siliceous deep-water sedimentary deposits. Lower beds of the Havallah and Inskip totalling hundreds of meters in thickness are composed of arkosic sandstone and conglomerate identical to that composing most of the Harmony. The Havallah and Inskip lie disconformably on the quartzitic, middle part of the Valmy Formation. The Harmony lies concordantly on distinctive chert beds at the top of the Valmy Formation. Assuming the latter contact is disconformable rather than a bedding-parallel fault, the East Range displays the stratigraphic bases of all three arkosic map units. The disconformable relation of the Havallah and Inskip to the Valmy Formation indicates elevation of deep-water deposits, subaerial erosion down to Middle Ordovician, and in Late Devonian a return to deep immersion. There is no evidence here of Late Devonian to Early Mississippian folding. Major folds in the East Range must be of Jurassic or younger age because Upper Triassic strata are involved. Evidence of large-scale thrust-faulting is notably scarce. The existence of the Willow Creek thrust shown on published maps of the East Range was based on the mistaken belief that strata below the Valmy Formation are of Triassic age whereas they are actually of Cambrian and earliest Ordovician age.

Nevada↗
USGS1998

An outline of tectonic, igneous, and metamorphic events in the Goshute-Toano Range between Silver Zone Pass and White Horse Pass, Elko County, Nevada; a history of superposed contractional and extensional deformation

Seven kinds of fault-bounded tracts are described. One of the tracts provides a good example of Mesozoic contractional folding and faulting; six exemplify various aspects of Miocene extensional faulting. Massive landslide deposits resulting from Tertiary faulting are described. Mesozoic intrusive rocks and extensive exposures of Miocene volcanic rocks are described and dated. The age ranges of stratigraphic units were based on numerous conodont collections, and ages of igneous rocks were determined by argon/argon and fission-track methods. The geologic complexity of the Goshute-Toano Range provides opportunities for many additional productive structural studies.

Professional Paper↗
USGS1995

Correlation of Ordovician rocks of northern Alaska

The Ordovician sequences presented in this report were chosen to cover a range of depositional and structural settings found in northern Alaska. Consequently, the quality of lithostratigraphic, paleontologic, and sedimentologic data is variable. Until 1982, Ordovician rocks in northern Alaska were known only from a few, widely separated localities. Since then, several hundred Ordovician conodont collections were obtained during geologic mapping of chiefly metacarbonate rocks; some are from measured sections that contain a succession of pelagic and (or) warm, shallow-water index species, but others are isolated, single collections that merely contain species that are long-ranging, within the Ordovician. Graptolite collections are fewer than conodont collections, but they provide invaluable ties between carbonate and siliciclastic sequences. New macrofossil localities are rare. All these collections have increased the known areal extent of Ordovician rocks in northern Alaska (Fig. 1) at least thirtyfold. Faunal assemblages from carbonate rocks in northern Alaska indicate that this area was situated in low latitudes during the Ordovician.

Alaska↗
USGS1994

Conodont color alteration index (CAI) map and conodont-based age determinations for the Winchester 30' x 60' Quadrangle and adjacent area, Virginia, West Virginia, and Maryland

Most of the conodont data presented in this report (table 1) were acquired to support 1:100,000-scale geologic mapping of the Winchester 30' X 60' quadrangle by the U.S. Geological Survey (USGS). Conodonts were chosen to provide a biostratigraphic framework for the Upper Cambrian to Mississippian marine carbonate rocks that make up about 25 percent of the Paleozoic strata exposed in the quadrangle (~2,130 m of the approximately 9,450 m) of Paleozoic strata exposed in the quadrangle). Thickness of stratigraphic units are from McDowell (1991), our own measurements, and from many of the stratigraphic reports and geologic maps listed in the references cited. Conodont biostratigraphic and color alteration index (CAI) analyses help identify stratigraphic units and structural discontinuities, particularly in the Upper Cambrian to Middle Ordovician chiefly carbonate rocks of the Shenandoah Valley and North Mountain fault zone. Conodont biofacies analyses provide additional information about the provincial affinities of the conodonts and the depositional environment of the rocks that contain them. Lithostratigraphic, biostratigraphic, paleoenvironmental, and CAI data for all conodont samples are given in table 1.

Maryl;Virginia;West Virginia↗