The consequences of Canadian Cordillera thermal regime in recent tectonics and elevation: a reviewThis article is one of a series of papers published in this Special Issue on the theme Lithoprobe — parameters, processes, and the evolution of a continent.Geological Survey of Canada Contribution 20090195.

2010 ◽  
Vol 47 (5) ◽  
pp. 621-632 ◽  
Author(s):  
R. D. Hyndman
Keyword(s):  
Thermal Regime ◽  
Upper Mantle ◽  
High Surface ◽  
Plate Boundary ◽  
High Elevation ◽  
Mantle Xenoliths ◽  
Tectonic Activity ◽  
Small Scale ◽  
Canadian Cordillera ◽  
Crust And Upper Mantle

The crust and upper mantle thermal regime of the Canadian Cordillera and its tectonic consequences were an important part of the Cordillera Lithoprobe program and related studies. This article provides a review, first of the thermal constraints, and then of consequences in high surface elevation and current tectonics. Cordillera and adjacent craton temperatures are well constrained by geothermal heat flow, mantle tomography velocities, upper mantle xenoliths, and the effective elastic thickness, Te. Cordillera temperatures are very high and laterally uniform, explained by small scale convection beneath a thin lithosphere, 800–900 °C at the Moho, contrasted to 400–500 °C for the craton. The high temperatures provide an explanation for why the Cordillera has high elevation in spite of a generally thin crust, ∼33 km, in contrast to low elevation and thicker crust, 40–45 km, for the craton. The Cordillera is supported ∼1600 m by lithosphere thermal expansion. In the Cordillera only the upper crust has significant strength; Te ∼ 15 km, in contrast to over 60 km for the craton. The Cordillera is tectonically active because the lithosphere is sufficiently weak to be deformed by plate boundary and gravitational forces; the craton is too strong. The Canadian Cordillera results have led to new understandings of processes in backarcs globally. High backarc temperatures and weak lithospheres explain the tectonic activity over long geological times of mobile belts that make up about 20% of continents. They also have led to a new understanding of collision orogenic heat in terms of incorporation of already hot backarcs.

Seismic anisotropy of mantle xenoliths and constraints on upper mantle structure beneath the southern Canadian Cordillera

2001 ◽  
Vol 339 (3-4) ◽  
pp. 403-426 ◽  
Author(s):  
Kazuko Saruwatari ◽  
Shaocheng Ji ◽  
Changxing Long ◽  
Matthew H Salisbury
Keyword(s):  
Upper Mantle ◽  
Seismic Anisotropy ◽  
Mantle Xenoliths ◽  
Canadian Cordillera ◽  
Mantle Structure ◽  
Upper Mantle Structure

scholarly journals Stratigraphic and tectonic framework of Late Cretaceous and Paleogene strata of southern Aotea Basin, northwest New Zealand

2021 ◽  
Author(s):  
◽  
Callum Skinner
Keyword(s):  
New Zealand ◽  
Late Cretaceous ◽  
System Analysis ◽  
Plate Boundary ◽  
Petroleum Exploration ◽  
Tectonic Activity ◽  
Small Scale ◽  
Southern Boundary ◽  
Seismic Reflection Data ◽  
Reflection Data

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>

NUMERICAL SIMULATIONS OF STRONG GROUND MOTION DURING DESTRUCTIVE EARTHQUAKES IN HOKKAIDO, JAPAN

2001 ◽  
Vol 09 (04) ◽  
pp. 1647-1657
Author(s):  
MITSUKO FURUMURA ◽  
TAKASHI FURUMURA
Keyword(s):  
Upper Mantle ◽  
Strong Ground Motion ◽  
Plate Boundary ◽  
Seismic Wave Propagation ◽  
Peak Ground Velocity ◽  
Lateral Heterogeneity ◽  
Crust And Upper Mantle ◽  
Inland Earthquake ◽  
Simulation Results ◽  
Strong Ground

Seismic wave propagation in Hokkaido, Japan, for large destructive earthquakes are simulated by the 3-D finite-difference method. The simulation results indicate that the peak ground velocity distribution for an inland earthquake is nearly circle, but for a plate-boundary earthquake it is irregular, due to influence of lateral heterogeneity in the crust and upper mantle beneath the Hokkaido region.

scholarly journals Stratigraphic and tectonic framework of Late Cretaceous and Paleogene strata of southern Aotea Basin, northwest New Zealand

2021 ◽  
Author(s):  
◽  
Callum Skinner
Keyword(s):  
New Zealand ◽  
Late Cretaceous ◽  
System Analysis ◽  
Plate Boundary ◽  
Petroleum Exploration ◽  
Tectonic Activity ◽  
Small Scale ◽  
Southern Boundary ◽  
Seismic Reflection Data ◽  
Reflection Data

<p>Seismic reflection data reveal thick sediment sequences of Late Cretaceous to Paleogene age in the region northwest of Taranaki Basin. A new stratigraphic framework for latest Cretaceous and Paleogene strata is created based on stacking patterns and stratal termination relationships of seismic reflectors. Sequence-bounding reflectors are tied to petroleum exploration wells, including recently-drilled Romney-1, to assign age and paleoenvironment interpretation. I identify the following sequences: (1) a late Haumurian to Teurian (68 – 56 Ma) aggradational shelf sequence, with at least two regressional events linked to eustatic sea-level falls; (2) a diachronous deepening of the basin that progressed from north to south during the late Waipawan to Heretaungan (53 – 46 Ma); (3) small-scale volcanism at the southern boundary with Taranaki Basin is contemporaneous with this deepening; (4) a prograding delta on Challenger Plateau during the Porangan to Runangan (46 – 35 Ma) that is evidence for tectonic uplift of the basin margins; and (5) an onlapping sequence from latest Runangan to present (35 – 0 Ma) that indicates Challenger Plateau subsided 1,300 m. A revised set of paleogeography maps and generalised stratigraphic chart summarise these observations. The Eocene phase (52-46 Ma) of tectonic subsidence and diffuse volcanism is one of the earliest signs of tectonic activity associated with development of the Cenozoic plate boundary through New Zealand. Petroleum system analysis reveals that southern Aotea Basin is prospective for petroleum exploration, with 3 plays identified in the Late Haumurian to Teurian (79 – 56 Ma) strata, in spite of Romney-1 proving unsuccessful.</p>

Thermal regime and state of hydration of the Antarctic upper mantle from regional-scale electrical properties

2021 ◽  
pp. M56-2020-4
Author(s):  
Philip E. Wannamaker ◽  
John A. Stodt ◽  
Graham J. Hill ◽  
Virginie Maris ◽  
Michal A. Kordy
Keyword(s):  
Great Basin ◽  
Thermal Regime ◽  
Upper Mantle ◽  
Large Scale ◽  
Regional Scale ◽  
Linear Inversion ◽  
Crust And Upper Mantle ◽  
The North ◽  
Moho Depths ◽  
The Antarctic

AbstractLarge-scale electrical resistivity investigations of the Antarctic crust and upper mantle utilizing the magnetotelluric method (MT) are limited in number compared to temperate regions, but provide physical insights hard to achieve with other techniques. Key to the method's success are the instrumentation advances that allow microvolt (µV)-level measurements of the MT electric field in the face of mega-ohm (MΩ) contact resistances. Primarily in this chapter, we reanalyse existing data from three campaigns over the Antarctic interior using modern 3D non-linear inversion analysis, and offer additional geophysical conclusions and context beyond the original studies. A profile of MT soundings over the transitional Ellsworth–Whitmore block in central West Antarctica implies near-cratonic lithospheric geothermal conditions with interpreted graphite–sulfide horizons deformed along margins of high-grade silicate lithological blocks. Reanalysis of South Pole soundings confirms large-scale low resistivity spanning Moho depths that is consistent with limited seismic tomography and elevated crustal thermal regime inferences. Upper mantle under a presumed adiabatic thermal gradient below the Ross Ice Shelf near the central Transantarctic Mountains appears to be of a moderately hydrated state but not sufficient to induce melting. The degree of hydration there is comparable to that below the north-central Great Basin province of the western USA.

Integrated geophysical-petrological modelling of the Eifel region

2020 ◽  
Author(s):  
Agnes Wansing ◽  
Jörg Ebbing ◽  
Eva Bredow
Keyword(s):  
Mantle Plume ◽  
Upper Mantle ◽  
West Germany ◽  
Small Scale ◽  
Low Velocity ◽  
Crust And Upper Mantle ◽  
Quaternary Volcanism ◽  
Velocity Anomaly ◽  
Type Composition ◽  
Eifel Region

&lt;p&gt;We present an integrated geophysical-petrological model of the Eifel region. The Eifel is a volcanic active region in West Germany that exhibits Tertiary as well as Quaternary volcanism. One suggestion for the source of this volcanism is a small-scale upper mantle plume.&lt;/p&gt;&lt;p&gt;The 3D model includes the crust and upper mantle and was generated by combined modelling of topography and the gravity field with constraints from seismology and geochemistry. In the best-fit model, the subcontinental lithospheric mantle is associated with a Phanerozoic-type composition, resulting in a depth of 80 km for the lithosphere-asthenosphere boundary (LAB) beneath the Eifel and in comparison 110 - 130 km beneath the Paris basin. A Proterozoic-type composition in contrast results in a LAB depth of 120 km in the Eifel. While the model fits the geophysical observables and features a thin lithosphere, it does not lead to a plume-like structure and does not feature a seismic low-velocity anomaly.&lt;/p&gt;&lt;p&gt;The measured low-velocity anomaly can be reproduced by introducing (1) an even thinner lithosphere or (2) a plume-like body above the thermal LAB with a composition based on data from Eifel xenoliths, which have a mainly basanitic composition. This additional structure results in a thermal anomaly and has an effect on the isostatic elevation of c. 360 m, but it does not result in a significant signal in the gravity anomalies. Further modelling showed how crustal intrusions could additionally mask the gravitational effect from such a small-scale upper mantle plume.&lt;/p&gt;&lt;p&gt;The model does not conclusively explain the source of the Eifel volcanism, but the models and the calculation of synthetic dispersion curves help to assess the possibility to resolve a small-scale upper mantle plume with joint inversion in future analysis.&lt;/p&gt;

Towards 3D multiscale adjoint waveform tomography of the crust and upper mantle beneath Southeast Asia

2020 ◽  
Author(s):  
Deborah Wehner ◽  
Nienke Blom ◽  
Nick Rawlinson
Keyword(s):  
Southeast Asia ◽  
Upper Mantle ◽  
Signal To Noise Ratio ◽  
Data Availability ◽  
Tectonic Activity ◽  
Initial Model ◽  
Crust And Upper Mantle ◽  
Banda Arc ◽  
Waveform Tomography ◽  
Krakatoa Eruption

&lt;p&gt;Southeast Asia is one of the most complex tectonic regions on Earth. This is mainly a result of its location within the triple junction of the Australian, Eurasian and Philippine Sea plates which has created a complicated configuration of active plate tectonic boundaries. High plate velocities have generated thousands of kilometers of subducted material and ongoing subduction along the Sunda Arc represents a significant natural hazard (such as the 2004 Sumatra-Andaman earthquake, 2012 Indian Ocean earthquakes and 2018 Anak Krakatoa eruption). However, recent tectonic activity around Borneo may be related to postsubduction processes which could be the key to understanding how the tectonic subduction cycle terminates. Further east, the region is dominated by several minor tectonic plates and the spectacular 180-degree curvature of the Banda Arc. Our work aims to further improve the understanding of this area by providing detailed images of the upper mantle.&lt;/p&gt;&lt;p&gt;Adjoint waveform tomography is especially suitable for imaging such complex regions. By simulating the 3D wavefield, it is possible to directly compare observed and simulated seismograms, thereby taking into account both body and surface waves. The method can account for the effects of anisotropy, anelasticity, wavefront healing, interference and (de)focusing that can hamper other seismological methods, and is thus especially suitable for strongly heterogenous areas such as Southeast Asia.&lt;/p&gt;&lt;p&gt;To date, sparse instrument coverage in the region has contributed to a heterogeneous path coverage. In this project, we make use of publicly available data as well as our recently deployed networks of broadband seismometers on Borneo and Sulawesi. This, in addition to access to national permanent networks promises a significant improvement in data coverage around the Banda Arc, Borneo and Sulawesi, thereby providing new opportunities to untangle the region&amp;#8217;s complexity.&lt;/p&gt;&lt;p&gt;We compiled a catalogue of well-constrained earthquakes, optimising for coverage, signal-to-noise ratio and data availability across a wide frequency band, and compared our observed data to synthetics generated from an initial model. In the first part of the inversion, we use long periods of 100 - 150 s to update our initial model using a gradient-based optimisation scheme. We use adjoint methods to obtain sensitivity kernels as the corresponding gradients and initial results will be documented in this presentation. In subsequent iterations, we permit increasingly shorter periods in order to progressively recover finer scales structure and avoid cycle skipping issues.&lt;/p&gt;

Transcontinental crustal sections of the U.S.S.R. and adjacent areas

1968 ◽  
Vol 5 (4) ◽  
pp. 1067-1078 ◽  
Author(s):  
N. A. Beliayevsky ◽  
A. A. Borisov ◽  
I. S. Volvovsky ◽  
Yu. K. Schukin
Keyword(s):  
Pacific Ocean ◽  
Upper Mantle ◽  
Far East ◽  
Crustal Thickness ◽  
Tien Shan ◽  
Tectonic Activity ◽  
Crust And Upper Mantle ◽  
The Pacific ◽  
Crustal Structures ◽  
The Pacific Ocean

Transcontinental sections of the earth's crust and Upper Mantle from the Kuril Islands to the Carpathians, and along other principal directions, in all about 15 000 km long, show the following features:(1) The depth of an asthenosphere horizon agrees well with the position of a high-conductivity layer in the Upper Mantle.(2) Hypocenters of earthquakes are located in fault zones. In the zone of the Kuril Island arc, they plunge into the Upper Mantle to depths of hundreds of kilometers, dipping towards the continent.(3) Boundary velocities along the Mohorovičić discontinuity are not dependent on its depth, for they are always in the range 8.0–8.2 km/s; velocities within the crust are correlated with the depths of layers; in the roots of high mountains a layer of 7.5–7.8 km/s has been distinguished near the base of the crust.(3) The crustal thickness in folded areas is in a certain accordance with the altitude of the surface of the earth's solid cover, with Bouguer anomalies and amplitudes of neotectonic movements. It varies from 8 km in margin areas of the Pacific Ocean basin to 60 km in the Tien Shan. Average crustal thicknesses within the platforms are in the region of 40 km, increasing to 50 km in the southern outlying areas of the East-European platform and to 46 km in areas of recent tectonic activity within the Turanian and Siberian Platforms.(4) In deep depressions, internal and outlying seas, the crustal thickness is reduced, and 'granite' layer (6.0–6.5 km/s) is absent. Mesozoic formations of the Far East and adjacent zones of transition from the Pacific Ocean to the continent are distinguished by reduced thicknesses. In Alpine formations the 'basalt' layer dominates over the 'granite' layer.(5) Subhorizontal crustal stratification complicated by deep faults has been found everywhere. Plicate geosynclinal folding is not reflected in deep crustal structures.(6) Temperature of the platform folded basement is mainly related to thickness and composition of the sediments.The transcontinental sections provide a clearer idea of the relationship between anomalous geophysical fields and deep and shallow crustal structures than is given in corresponding maps.

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