The Eastern North American Margin Community Seismic Experiment: An Amphibious Active‐ and Passive‐Source Dataset

2019 ◽  
Vol 91 (1) ◽  
pp. 533-540 ◽  
Author(s):  
Colton Lynner ◽  
Harm J. A. Van Avendonk ◽  
Anne Bécel ◽  
Gail L. Christeson ◽  
Brandon Dugan ◽  
...  
Keyword(s):  
North American ◽  
Passive Margin ◽  
North American Plate ◽  
Ocean Bottom ◽  
Wide Angle ◽  
Seismic Profiles ◽  
The North ◽  
Seismic Experiment ◽  
Short Period ◽  
Eastern North American Margin

Abstract The eastern North American margin community seismic experiment (ENAM‐CSE) was conceived to target the ENAM Geodynamic Processes at Rifting and Subducting Margins (GeoPRISMS) primary site with a suite of both active‐ and passive‐source seismic data that would shed light on the processes associated with rift initiation and evolution. To fully understand the ENAM, it was necessary to acquire a seismic dataset that was both amphibious, spanning the passive margin from the continental interior onto the oceanic portion of the North American plate, and multiresolution, enabling imaging of the sediments, crust, and mantle lithosphere. The ENAM‐CSE datasets were collected on‐ and offshore of North Carolina and Virginia over a series of cruises and land‐based deployments between April 2014 and June 2015. The passive‐source component of the ENAM‐CSE included 30 broadband ocean‐bottom seismometers (OBSs) and 3 onshore broadband instruments. The broadband stations were deployed contemporaneously with those of the easternmost EarthScope Transportable Array creating a trans‐margin amphibious seismic dataset. The active‐source portion of the ENAM‐CSE included several components: (1) two onshore wide‐angle seismic profiles where explosive shots were recorded on closely spaced geophones; (2) four major offshore wide‐angle seismic profiles acquired with an airgun source and short‐period OBSs (SPOBSs), two of which were extended onland by deployments of short‐period seismometers; (3) marine multichannel seismic (MCS) data acquired along the four lines of SPOBSs and a series of other profiles along and across the margin. During the cruises, magnetic, gravity, and bathymetric data were also collected along all MCS profiles. All of the ENAM‐CSE products were made publicly available shortly after acquisition, ensuring unfettered community access to this unique dataset.

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.

Bryozoa of the Mission Argillite (Permian), northeastern Washington

2000 ◽  
Vol 74 (4) ◽  
pp. 545-570 ◽  
Author(s):  
Ernest H. Gilmour ◽  
Edward M. Snyder
Keyword(s):  
New Species ◽  
Pacific Ocean ◽  
North American ◽  
Type Species ◽  
New Genus ◽  
Western Pacific ◽  
North American Plate ◽  
Western Pacific Ocean ◽  
Late Permian ◽  
The North

Fifteen species of Late Permian bryozoans occur in a biohermal bank in the Mission Argillite of northeastern Washington. These include two species conspecific with species described from Japan and 13 new species, one of which is the type species of a new genus. The presence of two species, Dyscritella iwaizakiensis Sakagami, 1961, and Hayasakapora cf. erectoradiata Sakagami, 1960, previously reported from Japan, and the similarity of new species with those previously described from Japan, China and Russia supports the idea that these rocks were originally deposited in the southeastern or central western Pacific Ocean and subsequently accreted to the North American Plate.Bryozoans and previously reported fusulinids indicate that the biohermal bank is latest Wordian (Kazanian).Newly described bryozoans include the new genus and type species Sakagamiina easternensis belonging to the Timanodictyidae. Other new species are Fistuliramus pacificus, Meekoporella inflecta, Neoeridotrypella missionensis, Coeloclemis urhausenii, Tabulipora colvillensis, Rhombotrypella kettlensis, Pamirella oculus, Pinegopora petita, Wjatkella nanea, Alternifenestella vagrantia, Polypora arbusca, and Mackinneyella stylettia.

The southern Mexico block: main boundaries and new estimation for its Quaternary motion

2008 ◽  
Vol 179 (2) ◽  
pp. 209-223 ◽  
Author(s):  
Louis Andreani ◽  
Xavier Le Pichon ◽  
Claude Rangin ◽  
Juventino Martínez-Reyes
Keyword(s):  
North American ◽  
Triple Junction ◽  
Strike Slip ◽  
North American Plate ◽  
Southern Mexico ◽  
Active Deformation ◽  
Lateral Strike Slip ◽  
Counterclockwise Rotation ◽  
The North ◽  
Slip Partitioning

Abstract Numerous studies, mainly based on structural and paleomagnetic data, consider southern Mexico as a crustal block (southern Mexico block, SMB) uncoupled from the North American plate with a southeast motion with respect to North America, accommodated by extension through the central Trans-Mexican volcanic belt (TMVB). On the other hand, the accommodation of this motion on the southeastward boundary, especially at the Cocos–Caribbean–North American triple junction, is still debated. The boundary between the SMB and the North American plate is constituted by three connected zones of deformation: (1) left-lateral transtension across the central TMVB, (2) left-lateral strike-slip faulting along the eastern TMVB and Veracruz area and (3) reverse and left-lateral strike-slip faulting in the Chiapas area. We show that these three active deformation zones accommodate a counterclockwise rotation of the SMB with respect to the North American plate. We specially discuss the Quaternary motion of the SMB with respect to the surrounding plates near the Cocos–Caribbean–North American triple junction. The model we propose predicts a Quaternary counterclockwise rotation of 0.45°/Ma with a pole located at 24.2°N and 91.8°W. Finally we discuss the geodynamic implications of this counterclockwise rotation. The southern Mexico block motion is generally assumed to be the result of slip partitioning at the trench. However the obliquity of the subduction is too small to explain slip partitioning. The motion could be facilitated by the high thermal gradient and gravitational collapse that affects central Mexico and/or by partial coupling with the eastward motion of the Caribbean plate.

scholarly journals Deep structure of the Porcupine Basin from wide-angle seismic data

2016 ◽  
Vol 8 (1) ◽  
pp. 199-209 ◽  
Author(s):  
Louise Watremez ◽  
Manel Prada ◽  
Tim Minshull ◽  
Brian O'Reilly ◽  
Chen Chen ◽  
...  
Keyword(s):  
North Atlantic Ocean ◽  
Deep Structure ◽  
Petroleum Exploration ◽  
Wide Angle ◽  
The South ◽  
Seismic Profiles ◽  
The North ◽  
Volcanic Feature ◽  
Porcupine Basin ◽  
Mud Diapir

AbstractThe Porcupine Basin, part of the frontier petroleum exploration province west of Ireland, has an extended history that commenced prior to the opening of the North Atlantic Ocean. Lithospheric stretching factors have previously been estimated to increase from <2 in the north to >6 in the south of the basin. Thus, it is an ideal location to study the processes leading to hyper-extension on continental margins. The Porcupine Median Ridge (PMR) is located in the south of the basin and has been alternatively interpreted as a volcanic feature, a serpentinite mud diapir or a tilted block of continental crust. Each of these interpretations has different implications for the thermal history of the basin. We present results from travel-time tomographic modelling of two approximately 300 km-long wide-angle seismic profiles across the northern and southern parts of the basin. Our results show: (1) the geometry of the crust, with maximum crustal stretching factors of up to 6 and 10 along the northern and southern profiles, respectively; (2) asymmetry of the basin structures, suggesting some simple shear during extension; (3) low velocities beneath the Moho that could represent either partially serpentinized mantle or mafic under-plating; and (4) a possible igneous composition of the PMR.

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