scholarly journals A crucial geologic test of Late Jurassic exotic collision versus endemic re-accretion in the Klamath Mountains Province, western United States, with implications for the assembly of western North America

2021 ◽  
Author(s):  
Todd A. LaMaskin ◽  
Jonathan A. Rivas ◽  
David L. Barbeau ◽  
Joshua J. Schwartz ◽  
John A. Russell ◽  
...  
Keyword(s):  
North America ◽  
Sierra Nevada ◽  
Continental Margin ◽  
North American ◽  
Detrital Zircon ◽  
Late Jurassic ◽  
North American Plate ◽  
Klamath Mountains ◽  
Clastic Rocks ◽  
Plate Margin

Differing interpretations of geophysical and geologic data have led to debate regarding continent-scale plate configuration, subduction polarity, and timing of collisional events on the western North American plate margin in pre–mid-Cretaceous time. One set of models involves collision and accretion of far-traveled “exotic” terranes against the continental margin along a west-dipping subduction zone, whereas a second set of models involves long-lived, east-dipping subduction under the continental margin and a fringing or “endemic” origin for many Mesozoic terranes on the western North American plate margin. Here, we present new detrital zircon U-Pb ages from clastic rocks of the Rattlesnake Creek and Western Klamath terranes in the Klamath Mountains of northern California and southern Oregon that provide a test of these contrasting models. Our data show that portions of the Rattlesnake Creek terrane cover sequence (Salt Creek assemblage) are no older than ca. 170–161 Ma (Middle–early Late Jurassic) and contain 62–83% Precambrian detrital zircon grains. Turbidite sandstone samples of the Galice Formation are no older than ca. 158–153 Ma (middle Late Jurassic) and contain 15–55% Precambrian detrital zircon grains. Based on a comparison of our data to published magmatic and detrital ages representing provenance scenarios predicted by the exotic and endemic models (a crucial geologic test), we show that our samples were likely sourced from the previously accreted, older terranes of the Klamath Mountains and Sierra Nevada, as well as active-arc sources, with some degree of contribution from recycled sources in the continental interior. Our observations are inconsistent with paleogeographic reconstructions that are based on exotic, intra-oceanic arcs formed far offshore of North America. In contrast, the incorporation of recycled detritus from older terranes of the Klamath Mountains and Sierra Nevada, as well as North America, into the Rattlesnake Creek and Western Klamath terranes prior to Late Jurassic deformation adds substantial support to endemic models. Our results suggest that during long-lived, east-dipping subduction, the opening and subsequent closing of the marginal Galice/Josephine basin occurred as a result of in situ extension and subsequent contraction. Our results show that tectonic models invoking exotic, intra-oceanic archipelagos composed of Cordilleran arc terranes fail a crucial geologic test of the terranes’ proposed exotic origin and support the occurrence of east-dipping, pre–mid-Cretaceous subduction beneath the North American continental margin.

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

Overview of Naturally Occurring Asbestos in California and Southwestern Nevada

2020 ◽  
Vol 26 (1) ◽  
pp. 9-14
Author(s):  
R. Mark Bailey
Keyword(s):  
Sierra Nevada ◽  
North American ◽  
Volcanic Belt ◽  
Island Arc ◽  
North American Plate ◽  
Mountain Range ◽  
The North ◽  
Rock Types ◽  
Naturally Occurring ◽  
Naturally Occurring Asbestos

ABSTRACT Naturally occurring asbestos (NOA) is being discovered in a widening array of geologic environments. The complex geology of the state of California is an excellent example of the variety of geologic environments and rock types that contain NOA. Notably, the majority of California rocks were emplaced during a continental collision of eastward-subducting oceanic and island arc terranes (Pacific and Farallon plates) with the westward continental margin of the North American plate between 65 and 150 MY BP. This collision and accompanying accretion of oceanic and island arc material from the Pacific plate onto the North American plate, as well as the thermal events caused by emplacement of the large volcanic belt that became today's Sierra Nevada mountain range, are the principal processes that produced the rocks where the majority of NOA-bearing units have been identified.

Middle Miocene through Pliocene North American Vegetational History: 16.3-1.6 Ma

1999 ◽  
Author(s):  
Alan Graham
Keyword(s):  
North America ◽  
Sierra Nevada ◽  
North American ◽  
Middle Miocene ◽  
Middle Eocene ◽  
Alaska Range ◽  
Seasonally Dry ◽  
Middle Latitudes ◽  
The North ◽  
Dry Climates

During the Middle Miocene through the Pliocene the Appalachian Mountains underwent continued erosion and approached modern elevations. The Rocky Mountains had undergone uplift to half or more of their present elevation during the Late Cretaceous to Middle Eocene Laramide Revolution; after a lull during the Middle Eocene through the Early Miocene, there was increased tectonic activity beginning ~12 Ma and especially between 7 and 4 Ma. Locally some highlands may have approached or attained modern elevations. The increasingly high mountains and plateaus of Asia and North America deflected the major air streams southward, bringing colder polar air into the middle latitudes of North America. An extensive Antarctic ice sheet further cooled ocean waters and contributed to the spread of seasonally dry climates. The elimination of most of the Asian exotics from the North American flora dates to the Late Miocene-Pliocene as a result of a decline in summer rainfall. The Sierra Nevada attained about two-thirds of their present elevation within the past 10 Ma. They were appreciably elevated at ~5 Ma, stood at ~2100 m at 3 Ma, and have risen ~950 m since 3 Ma (Huber, 1981). The California Coast Ranges and Cascade Mountains attained significant heights by 3 Ma, and there was a rapid rise of the Alaska Range at ~6 Ma. Temperatures increased between ~18 and 16 Ma. In the absence of major plate reorganization and intense volcanic activity and with increased erosion from continued replacement of the dense evergreen forest by deciduous forest and shrubland (increasing albedo), atmospheric CO2 concentration decreased and a sharp lowering of temperature occurred in the Middle Miocene between 15 and 10 Ma. Eolian dust deposits increased in the Late Cenozoic, suggesting greater aridity (Rea et al., 1985). This is supported by kaolinite records from North Atlantic deep sea sediments (Chamley, 1979). At ~4.8~4.9 Ma global cooling and a marine regression of ~40~50 m combined to isolate the Mediterranean Basin from the ocean and to concentrate large volumes of salt as water evaporated. The biota was destroyed, giving rise to the term Messinian salinity crisis.

Ancestral trans−North American Bell River system recorded in late Oligocene to early Miocene sediments in the Labrador Sea and Canadian Great Plains

2021 ◽  
Author(s):  
Julia I. Corradino ◽  
Alex Pullen ◽  
Andrew L. Leier ◽  
David L. Barbeau Jr. ◽  
Howie D. Scher ◽  
...  
Keyword(s):  
North America ◽  
Great Plains ◽  
North American ◽  
Detrital Zircon ◽  
Detrital Zircons ◽  
Labrador Sea ◽  
Western Canada ◽  
Zircon Age ◽  
North American Cordillera ◽  
The North

The Bell River hypothesis proposes that an ancestral, transcontinental river occupied much of northern North America during the Cenozoic Era, transporting water and sediment from the North American Cordillera to the Saglek Basin on the eastern margin of the Labrador Sea. To explore this hypothesis and reconstruct Cenozoic North American drainage patterns, we analyzed detrital zircon grains from the Oligocene−Miocene Mokami and Saglek formations of the Saglek Basin and Oligocene−Miocene fluvial conglomerates in the Great Plains of western Canada. U-Pb detrital zircon age populations in the Mokami and Saglek formations include clusters at <250 Ma, 950−1250 Ma, 1600−2000 Ma, and 2400−3200 Ma. Detrital zircons with ages of <250 Ma were derived from the North American Cordillera, supporting the transcontinental Bell River hypothesis. Oligocene−Miocene fluvial strata in western Canada contain detrital zircon age populations similar to those in the Saglek Basin and are interpreted to represent the western headwaters of the ancient Bell River drainage. Strontium-isotope ratios of marine shell fragments from the Mokami and Saglek formations yielded ages between 25.63 and 18.08 Ma. The same shells have εNd values of −10.2 to −12.0 (average = −11.2), which are consistent with values of Paleozoic strata in western North America but are more radiogenic than the modern Labrador Current, Labrador Sea Water, and North Atlantic Deep Water values (εNd ∼−12 to −25). As a freshwater source, the existence and termination of the Bell River may have been important for Labrador Sea circulation, stratification, and chemistry.

Detrital zircon evidence for Paleoproterozoic West African crust along the eastern North American continental margin, Georges Bank, offshore Massachusetts, USA

Geology ◽  
2017 ◽  
Vol 45 (9) ◽  
pp. 811-814 ◽  
Author(s):  
Yvette D. Kuiper ◽  
Margaret D. Thompson ◽  
Sandra M. Barr ◽  
Chris E. White ◽  
J. Christopher Hepburn ◽  
...  
Keyword(s):  
Continental Margin ◽  
North American ◽  
Detrital Zircon ◽  
West African ◽  
Georges Bank

scholarly journals Retroarc Jurassic burial and exhumation of Barrovian metamorphic rocks dated by monazite petrochronology, Funeral Mountains, California

2022 ◽  
Author(s):  
Suzanne Craddock Affinati ◽  
Thomas D. Hoisch ◽  
Michael L. Wells ◽  
Samuel Wright
Keyword(s):  
Sierra Nevada ◽  
Inductively Coupled Plasma ◽  
North American Plate ◽  
Pressure Increase ◽  
Metamorphic Rocks ◽  
Lower Grade ◽  
Inductively Coupled ◽  
Plate Margin ◽  
The Matrix ◽  
T Path

ABSTRACT In this study, we determined the timing of burial and subsequent exhumation of Barrovian metamorphic rocks from the Chloride Cliff area of the Funeral Mountains in southeastern California by constraining the ages of different portions of a pressure-temperature (P-T) path. Using a split-stream laser-ablation inductively coupled plasma–mass spectrometry (ICP-MS) system, we analyzed 192 domains from 35 grains of monazite within five samples with a spot size of 8 µm to determine U-Pb ages and trace-element abundances from the same samples (same polished sections) that were analyzed to produce the P-T paths. Changes that took place within individual monazite grains reflect localized equilibrium and captured the changes in heavy rare earth element (HREE) abundances in the matrix reservoir that occurred as garnet grew, resorbed, and then regrew, thus constraining ages on different portions of the P-T path. The results show that garnet began growing ca. 168 Ma, began resorbing ca. 160 Ma, began retrograde regrowth ca. 157 Ma, and continued to regrow at least through ca. 143 Ma. The early garnet growth corresponds to a period of pressure increase along the P-T path. The subsequent partial resorption corresponds to the prograde crossing of a garnet-consuming reaction during decompression, and the retrograde garnet regrowth occurred when this same reaction was recrossed in the retrograde sense during further decompression. These results are consistent with previously determined ages, which include a Lu-Hf garnet age of 167.3 ± 0.72 Ma for the early pressure-increase portion of the P-T path, and 40Ar/39Ar muscovite cooling ages of 153 and 146 Ma in the lower-grade Indian Pass area 10 km southeast of Chloride Cliff. The 40Ar/39Ar muscovite ages document cooling at the same time as retrograde garnet regrowth was taking place at Chloride Cliff. The oldest monazite age obtained in this study, 176 ± 5 Ma, suggests that southeast-directed thrusting within the Jurassic retroarc was ongoing by this time along the California portion of the western North American plate margin, as a consequence of east-dipping subduction and/or arc collision. The Funeral Mountains were likely located on the east side of the northern Sierra Nevada range in the Jurassic, taking into account dextral strike-slip displacement along the Cretaceous Mojave–Snow Lake fault. The Late Jurassic timing of burial in the Funeral Mountains and its Jurassic location suggest burial was associated with the East Sierran thrust system. The timing of prograde garnet resorption during exhumation (160–157 Ma) corresponds to a change from regional dextral transpression to sinistral transtension along the Jurassic plate margin inferred to have occurred ca. 157 Ma. The recorded exhumation was concurrent with intrusion of the 148 Ma Independence dike swarm in the eastern Sierra Nevada and Mojave regions, which developed within a regime of northeast-southwest extension.

REVISION OF NORTH AMERICAN AGABUS LEACH (COLEOPTERA: DYTISCIDAE): LUTOSUS-, OBSOLETUS-, AND FUSCIPENNIS-GROUPS

1994 ◽  
Vol 126 (1) ◽  
pp. 135-181 ◽  
Author(s):  
D.J. Larson
Keyword(s):  
North America ◽  
Pacific Northwest ◽  
Sierra Nevada ◽  
Great Basin ◽  
Great Plains ◽  
North American ◽  
Pacific Coast ◽  
The Pacific ◽  
Sierra Nevada Mountains ◽  
Wide Range

AbstractSpecies of Agabus of the lutosus-, obsoletus-, and fuscipennis-groups, as defined by Larson (1989), are revised. Members of the lutosus- and obsoletus-groups are restricted to the Cordilleran and Great Plains regions of temperate western North America. Within this region, the species of each group are largely parapatric. Three species are assigned to the lutosus-group: A. lutosus LeConte along the Pacific Coast; A. griseipennis LeConte in the Great Basin, Rocky Mountain, and Great Plains regions; and A. rumppi Leech in the southern deserts. Agabus lutosus and A. griseipennis hybridize in the Pacific Northwest; A. lutosus mimus Leech is synonymized with A. lutosus. The obsoletus-group contains five species: A. obsoletus LeConte, A. morosus LeConte, and A. ancillus Fall along the Pacific Coast and the Sierra Nevada Mountains; A. hoppingi Leech in the Sierra Nevada Mountains; and A. obliteratus LeConte, containing two subspecies, A. o. obliteratus and A. o. nectris Leech, new status, with a wide range including the Great Plains and Cordillera but not reaching the Pacific Coast. The four species of the fuscipennis-group, A. ajax Fall, A. coxalis Sharp, A. fuscipennis (Paykull), and A. infuscatus Aubé, are boreal and all except A. ajax are Holarctic. Agabus coxalis is restricted to northwestern North America, the other three species are transcontinental.For each species the following information is provided: synonymy, description, and illustrations of taxonomically important characters; notes on relationships, variation, distribution, and ecology; and a map of North American collection localities. Group diagnoses and keys to the species of each group are presented. A correction to the key to species groups of North American Agabus (Larson 1989) is made with the addition of a couplet to include the obsoletus-group. Lectotypes are designated for A. discolor LeConte and A. obliteratus LeConte.

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