Geology topics
Bruce R. Wardlaw
Publications and source records attributed to Bruce R. Wardlaw.
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.
Neoproterozoic(?) to Pennsylvanian inner-shelf, miogeoclinal strata in Sierra Agua Verde, Sonora, Mexico
No abstract available.
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.
Permian chronostratigraphic subdivisions
Names and boundary levels for series and stages of the Permian System, based on marine successions, have been approved by the Permian Subcommission, ICS. These are the Cisuralian, Guadalupian, and Lopingian Series and their constituent stages standardized respectively in the Urals, Southwest USA, and South China for the Lower; Middle, and Upper Permian.
Report on drilling activities in the Thar Desert, Sindh Province, Pakistan
Coal test drilling in the Thar Desert of southeast Pakistan was conducted as part of the Coal Exploration and Assessment Program (COALREAP) involving the United States Agency for International Development (USAID), the Geological Survey of Pakistan (GSP), and the U.S. Geological Survey. Drilling was performed in the Thar Desert, or Great Indian Desert, approximately 175 km northeast of Karachi. Twenty five exploration holes were drilled between January 1992 and May 1994. Drill core was described by geologists of the Pakistan Geological Survey and coal samples were analyzed in both the United States and Pakistan. U.S. Geological Survey geologists offered technical assistance, trained GSP personnel, and managed the drilling program according to an agreement with USAID under the Energy Planning and Development Project. Drilling was performed by the Geological Survey of Pakistan. During drilling, the first 50 m was rotary drilled and cuttings collected every 2 m for examination. Average depth for all coal beds is 214 m with a total average thickness of 10 m of coal per drill hole. Core was described, boxed, and stored at the Geological Survey of Pakistan core library at Sonda, near Hyderabad. Approximately 6,412 m of Paleocene to Eocene rock was drilled of which 3,990 m was cored and 1,113 m was rotary drilled. There was 1,309 m of core loss. Geophysical logging of each drill hole permitted detailed thicknesses of coal to be determined. Analysis of the coal indicated a rank of lignite B with an as-received heating value over 5,000 Btu. This report presents data collected at the drill sites and should be used in conjunction with the published interpretive report (Fassett and Durrani, 1994) and the USGS Open-File Report 94-167, which contains analysis of the coal samples. Tables provide quick reference to numeric data and results. Detailed index maps and specific data, for each drill hole are included. This report covers drill holes TP-5 to TP-31. Drill holes TP-16, 17, 21, 26, 27, and 29 were planned but not drilled due to time restraints and (or) a determination that those drill sites were not needed to effectively delineate the coal deposit. The basic data for drill holes TP-1 through TP-4 are included in SanFilipo and others, 1994 however, some data for these drill holes are included for consistency.
The record of Pliocene sea-level change at Enewetak Atoll
Detailed seismic stratigraphy, lithostratigraphy, and chemostratigraphy indicate that atoll-wide subaerial exposure surfaces (major disconformities) developed during major sea-level lowstands form prominent seismic reflectors and are coincident with biostratigraphic breaks in the Plio-Pleistocene on Enewetak Atoll. Sea-level models based on the stratigraphic position and age of major disconformities suggest a maximum sea-level highstand elevation of 36 m above present sea level and a maximum sea-level lowstand elevation of 63 m below present sea level for the Pliocene.
Pacific Enewetak Atoll Crater Exploration (PEACE) program, Enewetak Atoll, Republic of the Marshall Islands. Part 1: Drilling operations and descriptions of boreholes in vicinity of KOA and OAK craters
From mid-1984 through mid-1985, the United States Geological Survey (USGS) engaged in an investigation of two craters formed from high-yield, near-surface nuclear bursts in the Marshall Islands at Enewetak Atoll (figures 1 and 2). Supported by the Defense Nuclear Agency (DNA), this cooperative venture is referred to by the acronym PEACE, derived from its official name, Pacific Enewetak Atoll Crater Exploration Program. The craters studied, KOA and OAK, resulted from 1.4- and 8.9-megaton, near-surface bursts detonated near the northern perimeter of the Enewetak lagoon on May 12 and June 28, 1958, respectively. At that time, Enewetak was administered by the United States Government under the auspices of the Trust Territories of the Pacific Islands (TTPI) and formed a part of the Pacific Proving Grounds (PPG). OAK and KOA are among the only high-yield nuclear craters available for studies of cratering processes and crater-related effects.
Conodonts of the western Paleozoic and Triassic belt, Klamath Mountains, California and Oregon
Conodonts were extracted from 32 samples of limestone and 5 samples of chert obtained from the Western Paleozoic and Triassic belt of the Klamath Mountains province. Triassic conodonts were found in 17 samples, and late Paleozoic conodonts in 7 samples. Conodonts of the remaining 13 samples cannot be dated more closely than early or middle Paleozoic through Triassic. The late Paleozoic conodonts are restricted to the North Fork and Hayfork terranes. The Hayfork terrane also contains Early, Middle, and Late Triassic conodonts; mostly Neogondolella. Conodonts from samples of the Rattlesnake Creek terrane and the northern undivided part of the belt are all Late Triassic and are generally Epigondolella. The conodont data support the concept that many of the limestone bodies are olistoliths or tectonic blocks in melange. Color alteration of the conodonts indicates that the rocks of the Western Paleozoic and Triassic belt have been heated to temperatures between 300 degrees and 500 degrees C during regional tectonism.
Permian and Triassic rocks near Quinn River Crossing, Humboldt County, Nevada
Permian and Triassic rocks near Quinn River Crossing, Humboldt County, Nevada, consist of four structural blocks: (1) a Lower Permian volcanic block; (2) a Permian(?) chert-arenite block; (3) a Lower Permian limestone block; and (4) a Permian and Triassic block. The contacts between the Permian volcanic block and the others are interpreted as thrust faults or glide surfaces. None of these rocks are metamorphosed, in contrast to those of the surrounding mountain ranges. Each of the blocks is lithically similar in some respects to rocks of the Osgood Mountains area 80 km to the southeast. The fusulinid and brachiopod faunas of two of the blocks display affinities to those of the McCloud Limestone of northern California and the Coyote Butte Limestone of central Oregon, and the fauna of another block has elements in common with autochthonous rocks of eastern Nevada and Utah. All four blocks probably are allochthonous with respect to the rocks exposed in the surrounding mountain ranges, but their points of origin remain obscure. The rocks at Quinn River Crossing provide a link among the Permian rocks of north-central Nevada, northern California, and central Oregon and a possible key to their original relations, but more comparative data are needed.
Studies of the Permian Phosphoria Formation and related rocks, Great Basin-Rocky Mountain region
PART A: The transgression of the Permian Retort Phosphatic Shale Member of the Phosphoria Formation is dated by the occurrence of diagnostic brachiopods. The complex pattern of this transgression reflects the paleogeography and indicates two initial basins of deposition: one in southwestern Montana and one in southeastern Idaho. PART B: A new formation is proposed for middle Permian rocks of a transitional facies positioned laterally between the Rex Chert Member of the Phosphoria Formation in northeastern Utah and southeastern Idaho and the Plympton Formation in northeastern Nevada and northwestern Utah. PART C: The relationships of the Permian Park City Group to the Phosphoria and Park City Formations are clarified by the stratigraphy of four sections in northwestern Utah, northeastern Nevada, and southern Idaho. PART D: Five biostratigraphic zones based on the distribution of brachiopods and conodonts are proposed for the Park City Group. They are: the Peniculauris ivesi-Neostreptognathodus prayi Zone, the Peniculauris bassi-Neostreptognathodus sulcoplicatus Zone, the Peniculauris bassi-Neostreptognathodus sp. C Zone, the Thamnosia depressa Zone, and the Yakovlevia. multistriata-Neogondolella bitteri Zone. They range in age from Leonardian to Wordian.
Update and revision of brachiopod collections of the Phosphoria, Park City, and Shedhorn Formations (Permian) of the U.S. Geological Survey
The numerous collections amassed by the U.S. Geological Survey's study of the Western Phosphate Field have been examined. Many collections already have been discarded; and only those still housed at the Smithsonian are dealt with in this paper. Future studies of the biostratigraphy and paleogeography of the Phosphoria Formation and related rocks will be based on this data. Sections and samples are those presented by Yochelson (1968). In this paper, the brachiopods of each sample are listed. New and undescribed forms (in quotations) are presented as the closest allied and described taxon. Lingula and Orbiculoidea are not listed.
The biostratigraphy and paleoecology of the Gerster limestone (Upper Permian) in Nevada and Utah
The Gerster Limestone contains three minor lithofacies: the packstone, wackestone, and mixed facies, differentiated largely on the basis of the carbonate matrix and mud content of the rocks. Five biostratigraphic zones ranging in age from Roadian-Wordian to Wordian are, in ascending order, the Thamnosia, Kuvelousia, transition, Yakovlevia, and upper zones. The Gerster was probably deposted in a protected coastal basin separated from the Phosphoria Basin by a shallow marine positive area. The brachiopod fauna is divided into fifteen bioassociations. The fauna is part of a continental margin suite of faunas distributed from west Texas to the Canadian Arctic and belongs to the Tethyan-nonreef biogeographica[ province.
Biostratigraphic zonation of the Park City Group
Five biostratigraphic zones based on the distribution of brachiopods and conodonts are proposed for the Park City Group. They are: the Peniculauris ivesi-Neostreptognathodus prayi Zone, the Peniculauris bassi-Neostreptognathodus sulcoplicatus Zone, the Peniculauris bassi-Neostreptognathodus sp. C Zone, the Thamnosia depressa Zone, and the Yakovlevia multistriata-Neogondolella bitteri Zone. They range in age from Leonardian to Wordian.