Age of the Rockland tephra, western USA

2004 ◽  
Vol 62 (1) ◽  
pp. 94-104 ◽  
Author(s):  
M.A. Lanphere ◽  
D.E. Champion ◽  
M.A. Clynne ◽  
J.B. Lowenstern ◽  
A.M Sarna-Wojcicki ◽  
...  
Keyword(s):  
North America ◽  
National Park ◽  
Fall Deposit ◽  
Ion Microprobe ◽  
Western North America ◽  
Weighted Mean ◽  
Central California ◽  
Ash Fall ◽  
Lassen Peak ◽  
Eruption Age

The age of the Rockland tephra, which includes an ash-flow tuff south and west of Lassen Peak in northern California and a widespread ash-fall deposit that produced a distinct stratigraphic marker in western North America, is constrained to 565,000 to 610,000 yr by 40Ar/39Ar and U–Pb dating. 40Ar/39Ar ages on plagioclase from pumice in the Rockland have a weighted mean age of 609,000 ± 7000 yr. Isotopic ages of spots on individual zircon crystals, analyzed by the SHRIMP-RG ion microprobe, range from ∼500,000 to ∼800,000 yr; a subpopulation representing crystal rims yielded a weighted-mean age of 573,000 ± 19,000 yr. Overall stratigraphic constraints on the age are provided by two volcanic units, including the underlying tephra of the Lava Creek Tuff erupted within Yellowstone National Park that has an age of 639,000 ± 2000 yr. The basaltic andesite of Hootman Ranch stratigraphically overlies the Rockland in the Lassen Peak area and has 40Ar/39Ar ages of 565,000 ± 29,000 and 565,000 ± 12,000 yr for plagioclase and groundmass, respectively. Identification of Rockland tephra in ODP core 1018 offshore of central California is an important stratigraphic age that also constrains the eruption age to between 580,000 and 600,000 yr.

Two Fired-Clay Figurines from Central California

1963 ◽  
Vol 29 (1) ◽  
pp. 118-120 ◽  
Author(s):  
A. B. Elsasser
Keyword(s):  
North America ◽  
Clear Picture ◽  
Archaeological Sites ◽  
Western North America ◽  
Central California

AbstractFragmentary human figurines from archaeological sites in Sacramento and Marin counties are described. It is suggested that noting slight variations in decorative and other characteristics within the type may aid in providing a clear picture of the geographical and chronological distributions of these specimens in western North America.

The late-surviving ‘duck-billed’ dinosaur Augustynolophus from the upper Maastrichtian of western North America and crest evolution in Saurolophini

2014 ◽  
Vol 152 (2) ◽  
pp. 225-241 ◽  
Author(s):  
ALBERT PRIETO-MÁRQUEZ ◽  
JONATHAN R. WAGNER ◽  
PHIL R. BELL ◽  
LUIS M. CHIAPPE
Keyword(s):  
North America ◽  
Distal Region ◽  
New Combination ◽  
Cranial Morphology ◽  
Western North America ◽  
Central California ◽  
Skull Roof ◽  
New Tribe ◽  
Anatomical Information ◽  
Upper Maastrichtian

AbstractWe amend the taxonomy and provide new anatomical information on the hadrosaurid dinosaur Saurolophus morrisi (upper Maastrichtian Moreno Formation, central California, USA) derived from full preparation of the referred skull roof. The cranial morphology of this species is distinct enough to justify the new combination Augustynolophus morrisi gen. nov. The morphology of the nasals and surrounding cranial bones indicates that A. morrisi sported a solid nasal crest ending in an elongate triangular plate that extended above the skull roof. Autapomorphies include a crescentic base of the frontal caudodorsal process and extension of the process caudal to the frontal ‘dome’; distal end of nasal crest with knob-like process inflected rostrally; circumnarial depression lightly incised and weakly emarginated, adjacent to caudolateral margin of nasal and occupying two-thirds the width of lateral surface of distal region of crest; and caudal surface of distal nasal crest subrectangular. We formally establish the new tribe Saurolophini consisting of Prosaurolophus, Augustynolophus and Saurolophus. Saurolophin synapomorphies include a premaxilla with broad arcuate contour of rostrolateral region of thin everted oral margin and flat and steeply inclined occlusal surface of dentary dental battery, among other characters. Saurolophin crests evolved towards increasing caudodorsal length, along with caudal extension of the circumnarial fossa and involvement into the crest of adjacent facial elements. Augustynolophus is the second described genus of North American late Maastrichtian hadrosaurids. Its recognition implies a greater diversity among late Maastrichtian dinosaur faunas than previously recognized and is congruent with hypotheses of endemism and/or provinciality during Late Cretaceous time.

Notes on the Lodgepole Needle Miner, Recurvaria milleri Busck (Lepidoptera: Gelechiidae), and Its Parasites in Western North America

1951 ◽  
Vol 83 (11) ◽  
pp. 295-301 ◽  
Author(s):  
J. H. McLeod
Keyword(s):  
Life History ◽  
New Species ◽  
North America ◽  
National Parks ◽  
National Park ◽  
Western North America ◽  
Banff National Park ◽  
History Of ◽  
Heavy Infestation ◽  
A New Species

The lodgepole needle miner, Recurvaria milleri Busck, was discovered in 1903 in the Yosemite National Park, California, and was described as a new species by Busck (1914). The infestation has persisted in that area, with irregular periods of abundance and scarcity. The latest heavy infestation was reported (G. R. Struble, in litt.) to have started in 1947, and has continued to intensify. The history of the outbreak to 1919 was reported by Patterson (1921).In 1942 a second important infestation was reported in the Banff National Park, Alberta. Details concerning the area of infestation and life-history notes were given by Hopping (1946). This infestation has continued to spread and has reached Yoho, Kootenay, and Revelstoke National parks.

scholarly journals Colorado Plateau Coring Project, Phase I (CPCP-I): a continuously cored, globally exportable chronology of Triassic continental environmental change from western North America

2018 ◽  
Vol 24 ◽  
pp. 15-40 ◽  
Author(s):  
Paul E. Olsen ◽  
John W. Geissman ◽  
Dennis V. Kent ◽  
George E. Gehrels ◽  
Roland Mundil ◽  
...  
Keyword(s):  
North America ◽  
Environmental Change ◽  
National Park ◽  
Colorado Plateau ◽  
Global Environmental Change ◽  
Magnetic Polarity ◽  
Late Triassic ◽  
Western North America ◽  
Petrified Forest National Park ◽  
Petrified Forest

Abstract. Phase 1 of the Colorado Plateau Coring Project (CPCP-I) recovered a total of over 850 m of stratigraphically overlapping core from three coreholes at two sites in the Early to Middle and Late Triassic age largely fluvial Moenkopi and Chinle formations in Petrified Forest National Park (PFNP), northeastern Arizona, USA. Coring took place during November and December of 2013 and the project is now in its post-drilling science phase. The CPCP cores have abundant detrital zircon-producing layers (with survey LA-ICP-MS dates selectively resampled for CA-ID-TIMS U-Pb ages ranging in age from at least 210 to 241 Ma), which together with their magnetic polarity stratigraphy demonstrate that a globally exportable timescale can be produced from these continental sequences and in the process show that a prominent gap in the calibrated Phanerozoic record can be filled. The portion of core CPCP-PFNP13-1A for which the polarity stratigraphy has been completed thus far spans ∼215 to 209 Ma of the Late Triassic age, and strongly validates the longer Newark-Hartford Astrochronostratigraphic-calibrated magnetic Polarity Time-Scale (APTS) based on cores recovered in the 1990s during the Newark Basin Coring Project (NBCP). Core recovery was ∼100 % in all holes (Table 1). The coreholes were inclined ∼60–75∘ approximately to the south to ensure azimuthal orientation in the nearly flat-lying bedding, critical to the interpretation of paleomagentic polarity stratigraphy. The two longest of the cores (CPCP-PFNP13-1A and 2B) were CT-scanned in their entirety at the University of Texas High Resolution X-ray CT Facility in Austin, TX, and subsequently along with 2A, all cores were split and processed at the CSDCO/LacCore Facility, in Minneapolis, MN, where they were scanned for physical property logs and imaging. While remaining the property of the Federal Government, the archive half of each core is curated at the NSF-sponsored LacCore Core Repository and the working half is stored at the Rutgers University Core Repository in Piscataway, NJ, where the initial sampling party was held in 2015 with several additional sampling events following. Additional planned study will recover the rest of the polarity stratigraphy of the cores as additional zircon ages, sedimentary structure and paleosol facies analysis, stable isotope geochemistry, and calibrated XRF core scanning are accomplished. Together with strategic outcrop studies in Petrified Forest National Park and environs, these cores will allow the vast amount of surface paleontological and paleoenvironmental information recorded in the continental Triassic of western North America to be confidently placed in a secure context along with important events such as the giant Manicouagan impact at ∼215.5 Ma (Ramezani et al., 2005) and long wavelength astronomical cycles pacing global environmental change and trends in atmospheric gas composition during the dawn of the dinosaurs.

Isoetes × truncata: a newly considered pentaploid hybrid from western North America

1993 ◽  
Vol 71 (8) ◽  
pp. 1016-1025 ◽  
Author(s):  
Donald M. Britton ◽  
Daniel F. Brunton
Keyword(s):  
British Columbia ◽  
North America ◽  
National Park ◽  
Morphological Characteristics ◽  
Lake Area ◽  
Western North America ◽  
Pyramid Lake ◽  
Cytological Data ◽  
Pentaploid Hybrid ◽  
Scanning Electron

Three Isoetes found in Pyramid Lake, Jasper National Park, Alberta, constitute populations of tetraploid (2n = 44)I. maritima, hexaploid (2n = 66)I. occidentalis, and an abortive-spored, pentaploid hybrid (2n = 55) with intermediate morphological characteristics. Although the hybrid has been present in the lake since at least 1918, I. maritima and I. occidentalis were previously unknown in Alberta. The presence of these aquatics hundreds of kilometres from their next known populations in central British Columbia is suspected to reflect the floristic and faunal affinity of the Pyramid Lake area to biotic regions in the interior of British Columbia. Morphological, scanning electron microscopy, and cytological data are provided to support our conclusion that the Alaskan type material of I. × truncata is synonymous with the Pyramid Lake pentaploid. Investigations of similar taxa in western North America detected several I. occidentalis populations in Alaska where it was previously unknown. This represents the first report of a pentaploid Isoetes hybrid in North America and the first western North American hybrid to be described in detail. Key words: Isoetes, Isoetes maritima, Isoetes occidentalis, Isoetes × truncata, hybrid, Alberta, Alaska.

Sign in / Sign up

Export Citation Format

Share Document