Graptolites with Multiple Genicular Spines from the Upper Ordovician of Western North America

1974 ◽  
Vol 11 (10) ◽  
pp. 1455-1460
Author(s):  
John Riva
Keyword(s):  
North America ◽  
Distinct Species ◽  
Late Ordovician ◽  
Western North America ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
The Pacific

A careful restudy has been made of the types of Climacograptus innotatus var. pacificus Ruedemann from the topmost Ordovician of western North America and of topotype material of Climacograptus innotatus Nicholson from the Lower Silurian of Scotland. The study shows that these two forms are morphologically unrelated, the former being represented by short, stubby individuals with complex spinose growths, including double genicular spines, and the latter by slender, lanceolate individuals apparently provided with genicular flanges. Var. pacificus is here recognized as a distinct species, Climacograptus pacificus, and typifies and is restricted to Late Ordovician graptolite faunas of western North America and the Pacific Faunal Province.A deformed individual from Idaho characterized by three or four genicular spines is distinguished as Climacograptus pacificus pilosus, subspec. nov.

Late Ordovician - Early Silurian cryptospore occurrences on Anticosti Island (Île d'Anticosti), Quebec, Canada

2007 ◽  
Vol 44 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jeffery G Richardson ◽  
William I Ausich
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Land Plants ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Low Diversity ◽  
Anticosti Island ◽  
Early Land

Residues from Hirnantian (Upper Ordovician) and Aeronian (Lower Silurian) strata of Anticosti Island, Quebec, Canada, have yielded the oldest occurrence of terrestrial-based palynomorphs (cryptospores) from eastern North America. A low-abundance, low-diversity cryptospore assemblage containing specimens of Pseudodyadospora, Velatitetras, and alete monads has been recovered from the Velleda Member of the Ellis Bay Formation (Upper Ordovician, Hirnantian). The Gun River Formation (Lower Silurian, Aeronian) contains a low-abundance, low-diversity assemblage composed of specimens of Velatitetras, Laevolcancis, and alete monads. The occurrence of these assemblages provides evidence for early land plants in this part of North America during the Late Ordovician and Early Silurian, and documents the existence of a terrestrial-based flora during and after the Saharan (Late Ordovician) glaciation.

Supplemental material: Cenozoic to Recent plate configurations in the Pacific Basin: Ridge subduction and slab window magmatism in western North America

2006 ◽  
Author(s):  
J.K. Madsen ◽  
D.J. Thorkelson ◽  
R.M. Friedman ◽  
D.D. Marshall
Keyword(s):  
North America ◽  
Pacific Basin ◽  
Western North America ◽  
File Size ◽  
Tectonic Model ◽  
Ridge Subduction ◽  
The Pacific ◽  
Northwestern North America ◽  
Slab Window

Geosphere, February 2006, v. 2, p. 11-34, doi: 10.1130/GES00020.1. Movie 1 - Tectonic model for the Pacific Basin and northwestern North America from 53 Ma to 39 Ma. The file size is 1.3 MB.

scholarly journals Effect of Hydrothermal Activity on Organic Matter Enrichment of Shale: A Case Study of the Upper Ordovician and the Lower Silurian in the Lower Yangtze, South China

Minerals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 495 ◽  
Author(s):  
Yizhou Huang ◽  
Zhenxue Jiang ◽  
Kun Zhang ◽  
Yan Song ◽  
Shu Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Oxygen Isotope ◽  
Shale Gas ◽  
Organic Matter Content ◽  
Hydrothermal Activity ◽  
Late Ordovician ◽  
Sedimentary Organic Matter ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Activity Intensity

The effect of organic matter on hydrocarbon potential, storage space, and gas content of shale is well-known. Additionally, present-day content of sedimentary organic matter in shale is controlled by depositional and preservation processes. Therefore, a study of the enrichment mechanisms of sedimentary organic matter provides a scientific basis for the determination of favorable areas of shale gas. In this study the Upper Ordovician Xinkailing Fm. and the first member of the Lower Silurian Lishuwo Fm. were examined. Stratigraphic sequences were identified through conventional logs and elemental capture spectrum data. Oxygen isotope analysis was applied to recover paleotemperature of seawater in the study area. The excess silicon content was calculated and the origin of the silica was determined by the Fe-Al-Mn ternary plot. The enrichment mechanism of organic matter was analyzed by two aspects: redox conditions and paleoproductivity. As a result, the stratigraphic interval was divided into two 3rd-order sequences. Through oxygen isotope, the paleotemperature of seawater was 62.7–79.2 °C, providing evidence of the development of hydrothermal activity. Analysis of excess siliceous minerals identified two siliceous mineral origins: terrigenous and hydrothermal. It also revealed an upwards decreasing tendency in hydrothermal activity intensity. Strong hydrothermal activity during the Late Ordovician, recognized as TST1, formed a weak-oxidizing to poor-oxygen environment with high paleoproductivity, which promoted organic matter enrichment. During the Late Ordovician to the Early Silurian, identified as RST1, TST2, and RST2, weakening hydrothermal activity caused the decline of paleoproductivity and increased oxidation of bottom waters, leading to a relative decrease of organic matter content in the shale. Therefore, favorable areas of shale gas accumulation in the Upper Ordovician and Lower Silurian are determined stratigraphically as the TST1, with a high total organic carbonate content. Geographically, the hydrothermally-active area near the plate connection of the Yangtze and the Cathaysian is most favorable.

Flexible crinoids from the Upper Ordovician Maquoketa Formation of the northern midcontinent and the evolution of early flexible crinoids

2001 ◽  
Vol 75 (2) ◽  
pp. 370-382 ◽  
Author(s):  
James C. Brower
Keyword(s):  
New Species ◽  
North America ◽  
Late Ordovician ◽  
Upper Ordovician ◽  
Middle Ordovician

Three flexible crinoids occur in the Upper Ordovician Maquoketa Formation of Illinois, Iowa, and Minnesota:Protaxocrinus girvanensisRamsbottom, 1961,Clidochirus anebosnew species, andProanisocrinus oswegoensis(Miller and Gurley, 1894).Protaxocrinus girvanensisis also found in the Upper Ordovician of Scotland which indicates that the ocean was narrow enough to allow at least one crinoid species to cross the barrier. The Upper Ordovician of North America and Scotland also share many common crinoid genera. Both phenetic and cladistic methods result in similar phylogenies of flexible crinoids.Protaxocrinuswas derived from a cupulocrinid ancestor during the Middle Ordovician.Clidochirusevolved fromProtaxocrinusor its ancestral stock prior to the Richmondian of the Late Ordovician. The RichmondianProanisocrinusand later anisocrinids are most closely related toClidochirusor its immediate predecessor. Thus, three major lineages of flexible crinoids,Protaxocrinus(taxocrinid group),Clidochirus(icthyocrinid), andProanisocrinus(anisocrinids and homalocrinids), appeared during the Ordovician. Despite their rarity during the Ordovician, all three flexible lineages survived the Latest Ordovician extinction, whereas their more abundant and successful cupulocrinid ancestors were eliminated.

Late Cambrian ptychaspidid trilobites from western Utah: implications for trilobite systematics and biostratigraphy

2005 ◽  
Vol 142 (4) ◽  
pp. 377-398 ◽  
Author(s):  
J. M. ADRAIN ◽  
S. R. WESTROP
Keyword(s):  
North America ◽  
Distinct Species ◽  
Western North America ◽  
Closely Related Species ◽  
Widespread Species ◽  
Late Cambrian ◽  
South Central ◽  
New Information ◽  
The Family ◽  
Notch Peak

The Notch Peak Formation (Late Cambrian, Sunwaptan) of western Utah yields diverse silicified trilobite faunas that provide new information on the anatomy of many taxa. The family Ptychaspididae Raymond, 1924, is represented by species of Keithiella Rasetti, 1944; Idiomesus Raymond, 1924; Euptychaspis Ulrich in Bridge, 1931; and Macronoda Lochman, 1964. At least four species are new, of which E. lawsonensis and M. notchpeakensis are named formally. Much previous work on Late Cambrian trilobites has emphasized biostratigraphic utility and the recognition of geographically widespread species. Data from new silicified collections indicate that this approach is difficult to justify because many putative ‘index species’ actually represent a plexus of closely related species whose biostratigraphic significance has yet to be determined. One such plexus is represented by E. kirki Kobayashi, 1935, whose previously reported occurrences in Texas, Oklahoma, Utah, Nevada and northern Canada record at least four distinct species. Similarly, Macronoda can now be shown to consist of at least five late Sunwaptan species in south-central and western North America.

A new genus of cassiduloid echinoid from the lower Eocene of the Pacific coast of western North America and a new report of Cassidulus ellipticus Kew, 1920, from the lower Eocene of Baja California Sur, Mexico

1995 ◽  
Vol 69 (3) ◽  
pp. 509-515 ◽  
Author(s):  
Richard L. Squires ◽  
Robert A. Demetrion
Keyword(s):  
North America ◽  
New Genus ◽  
Baja California ◽  
Pacific Coast ◽  
Middle Part ◽  
Baja California Sur ◽  
Western North America ◽  
Lower Eocene ◽  
Shallow Marine ◽  
The Pacific

The cassiduloid echinoid Calilampas californiensis n. gen. and sp. is described from middle lower Eocene (“Capay Stage”) shallow-marine sandstones in both the middle part of the Bateque Formation, Baja California Sur, Mexico, and the lower part of the Llajas Formation, southern California. The new genus is tentatively placed in family Pliolampadidae. The cassiduloid Cassidulus ellipticus Kew, 1920, previously known only from the “Capay Stage” in California, is also present in “Capay Stage” shallow-marine sandstones of the Bateque Formation.

The Inland Penetration of Atmospheric Rivers over Western North America: A Lagrangian Analysis

2015 ◽  
Vol 143 (5) ◽  
pp. 1924-1944 ◽  
Author(s):  
Jonathan J. Rutz ◽  
W. James Steenburgh ◽  
F. Martin Ralph
Keyword(s):  
Water Vapor ◽  
North America ◽  
Pacific Coast ◽  
Water Vapor Transport ◽  
Western North America ◽  
Lagrangian Analysis ◽  
Initial Water ◽  
Atmospheric Rivers ◽  
The Pacific ◽  
Synoptic Conditions

Abstract Although atmospheric rivers (ARs) typically weaken following landfall, those that penetrate inland can contribute to heavy precipitation and high-impact weather within the interior of western North America. In this paper, the authors examine the evolution of ARs over western North America using trajectories released at 950 and 700 hPa within cool-season ARs along the Pacific coast. These trajectories are classified as coastal decaying, inland penetrating, or interior penetrating based on whether they remain within an AR upon reaching selected transects over western North America. Interior-penetrating AR trajectories most frequently make landfall along the Oregon coast, but the greatest fraction of landfalling AR trajectories that eventually penetrate into the interior within an AR is found along the Baja Peninsula. In contrast, interior-penetrating AR trajectories rarely traverse the southern “high” Sierra. At landfall, interior-penetrating AR trajectories are associated with a more amplified flow pattern, more southwesterly (vs westerly) flow along the Pacific coast, and larger water vapor transport (qυ). The larger initial qυ of interior-penetrating AR trajectories is due primarily to larger initial water vapor q and wind speed υ for those initiated at 950 and 700 hPa, respectively. Inland- and interior-penetrating AR trajectories maintain large qυ over the interior partially due to increases in υ that offset decreases in q, particularly in the vicinity of topographical barriers. Therefore, synoptic conditions and trajectory pathways favoring larger initial qυ at the coast, limited water vapor depletion by orographic precipitation, and increases in υ over the interior are keys to differentiating interior-penetrating from coastal-decaying ARs.

scholarly journals Partial Characterization of a Closterovirus Associated with Apple Mealybug-Transmitted Little Cherry Disease in North America

2001 ◽  
Vol 91 (3) ◽  
pp. 268-273 ◽  
Author(s):  
K. C. Eastwell ◽  
M. G. Bernardy
Keyword(s):  
North America ◽  
Rna Polymerase ◽  
Sweet Cherry ◽  
Distinct Species ◽  
Economic Problem ◽  
Western North America ◽  
Rna Dependent Rna Polymerase ◽  
Virus Particles ◽  
Similar Disease

Little cherry disease (LChD) is a serious economic problem of sweet cherry production in western North America where apple mealybug is the principle vector. LChD is associated with a distinct species of double-stranded (ds) RNA. In this study, filamentous virus particles were purified from LChD-infected trees and shown to contain single-stranded RNA corresponding to the previously reported dsRNA isolated from infected trees. The virus particles were characterized and were similar to monopartite members of the genus Closterovirus. A portion of the genome was sequenced and found to be most closely related to the RNA-dependent RNA polymerase of Grapevine leafroll-associated virus-3, a mealybug-transmitted closterovirus. The characteristics of the mealybug-transmitted Little cherry virus in North America are very different from those of a closterovirus associated with a similar disease in Europe.

scholarly journals Glacier retreat creating new Pacific salmon habitat in western North America

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kara J. Pitman ◽  
Jonathan W. Moore ◽  
Matthias Huss ◽  
Matthew R. Sloat ◽  
Diane C. Whited ◽  
...  
Keyword(s):  
North America ◽  
Climate Models ◽  
Pacific Salmon ◽  
Global Climate ◽  
Global Climate Models ◽  
Glacier Retreat ◽  
Western North America ◽  
Mountain Ranges ◽  
Proactive Management ◽  
The Pacific

AbstractGlacier retreat poses risks and benefits for species of cultural and economic importance. One example is Pacific salmon (Oncorhynchus spp.), supporting subsistence harvests, and commercial and recreational fisheries worth billions of dollars annually. Although decreases in summer streamflow and warming freshwater is reducing salmon habitat quality in parts of their range, glacier retreat is creating new streams and lakes that salmon can colonize. However, potential gains in future salmon habitat associated with glacier loss have yet to be quantified across the range of Pacific salmon. Here we project future gains in Pacific salmon freshwater habitat by linking a model of glacier mass change for 315 glaciers, forced by five different Global Climate Models, with a simple model of salmon stream habitat potential throughout the Pacific Mountain ranges of western North America. We project that by the year 2100 glacier retreat will create 6,146 (±1,619) km of new streams accessible for colonization by Pacific salmon, of which 1,930 (±569) km have the potential to be used for spawning and juvenile rearing, representing 0 to 27% gains within the 18 sub-regions we studied. These findings can inform proactive management and conservation of Pacific salmon in this era of rapid climate change.

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