Conjugate volcanic rifted margins, seafloor spreading, and microcontinent: Insights from new high-resolution aeromagnetic surveys in the Norway Basin

The Iberian-Newfoundland conjugate margins are one of the most extensively studied non-volcanic rifted margins in the world. In recent years, researchers have focused their efforts at better understanding the earliest stages of continental rifting, often relying heavily on the identification of so-called &#8220;break-up features&#8221; imaged in seismic profiles or interpreted from potential field data. Along the Iberian-Newfoundland margins, widely used break-up markers include interpretations of old magnetic anomalies from the M-Series, as well as the J-anomaly, believed to mark the occurrence and spatial extent of first oceanic lithosphere. However, uncertainties in the location and interpretation of these features have led to discrepancies between modelled depictions of the palaeopositions of Iberia and Newfoundland during the early Cretaceous as well as the timing of first seafloor spreading between the two.&#160;Using new seismic data from the Southern Newfoundland Basin (SNB) we are able to illustrate the unsuitability of &#8220;break-up&#8221; features along the Iberian &#8211; Newfoundland Margin for plate kinematic reconstructions. Our data shows that basement associated with the younger M-Series magnetic anomalies is comprised of exhumed mantle and magmatic additions, and most likely represents transitional domains and not true oceanic lithosphere. Magmatic activity in the SNB as early as M4 times (128 Ma), and the presence of SDR packages onlapping onto basement faults suggest that, at this time, plate divergence was still being accommodated by tectonic faulting. Therefore, young M-series anomalies (including the J-anomaly) are not suitable basis on which to reconstruct plate positions during the early stages of continental separation.We instead follow an alternative modelling approach, not reliant on the identification of extended continental margin features, to robustly constrain North Atlantic tectonics pre-M0 (~121 Ma) times. We do this by using seafloor spreading data and a statistically robust inversion method as the basis for a number of purpose built two-plate models for Africa, Iberia, Eurasia, Greenland and North America, with quantified uncertainties. Together, these models will provide an invaluable framework within to study the evolution of the extended continental margins immediately prior to and during continental separation.&#160;&#160;&#160;&#160;&#160;

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Crustal accretion of thick mafic crust in Iceland: implications for volcanic rifted margins

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2016-0039 ◽

2016 ◽

Vol 53 (11) ◽

pp. 1205-1215 ◽

Cited By ~ 9

Author(s):

Jeffrey A. Karson

Keyword(s):

Plate Boundary ◽

Seafloor Spreading ◽

Seismic Velocities ◽

Mafic Intrusions ◽

Rifted Margins ◽

Composition And Structure ◽

Thickness Variations ◽

Transitional Crust ◽

Active Processes ◽

Plate Boundary Zone

Rifting near hotspots results in mantle melting to create thick mafic igneous crust at volcanic rifted margins (VRMs). This mafic crust is transitional between rifted continental crust with mafic intrusions landward and oceanic crust into which it grades seaward. Seismic velocities, crustal drilling, and exhumed margins show that the upper crust in these areas is composed of basaltic lava erupted in subaerial to submarine conditions intruded by downward increasing proportions of dikes and sparse gabbroic intrusions. The lower crust of these regions is not exposed but is inferred from seismic velocities (Vp > 6.5 km/sec) and petrological constraints to be gabbroic to ultramafic in composition. Limited access to crustal sections generated along VRMs have raised questions regarding the composition and structure of this transitional crust and how it evolves during the early stages of rifting and subsequent seafloor spreading. Active processes in Iceland provide a glimpse of subaerial spreading with the creation of a thick (40–25 km) mafic igneous crust that may be analogous to the transitional crust of VRMs. Segmented rift zones that propagate away from the Iceland hotspot, migrating transform fault zones, and rift-parallel strike-slip faults create a complex plate boundary zone in the upper, brittle crust. These structures may be decoupled from underlying lower crustal gabbroic rocks that are capable of along-axis flow that smooths-out crustal thickness variations. Similar processes may be characteristic of the early history of VRMs and volcanic hotspot ridges related to rifting and seafloor spreading proximal to hotspots.

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Initiation of a Proto-transform Fault Prior to Seafloor Spreading

10.26686/wgtn.13089095 ◽

2020 ◽

Author(s):

Finnigan Illsley-Kemp ◽

JM Bull ◽

D Keir ◽

T Gerya ◽

C Pagli ◽

...

Keyword(s):

Plate Tectonics ◽

Seafloor Spreading ◽

Continental Rift ◽

Formation Mechanisms ◽

Transform Fault ◽

Transform Faults ◽

Local Seismicity ◽

Ocean Ridges ◽

Rifted Margins ◽

Direct Observations

©2018. The Authors. Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of mid-ocean ridges in ocean basins worldwide. The current consensus is that oceanic transform faults initiate after the onset of seafloor spreading. However, this inference has been difficult to test given the lack of direct observations of transform fault formation. Here we integrate evidence from surface faults, geodetic measurements, local seismicity, and numerical modeling of the subaerial Afar continental rift and show that a proto-transform fault is initiating during the final stages of continental breakup. This is the first direct observation of proto-transform fault initiation in a continental rift and sheds unprecedented light on their formation mechanisms. We demonstrate that they can initiate during late-stage continental rifting, earlier in the rifting cycle than previously thought. Future studies of volcanic rifted margins cannot assume that oceanic transform faults initiated after the onset of seafloor spreading.

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Magmatic evolution in a sedimented margin and implications for lithospheric breakup: insights from high-resolution seismic data from the South China Sea

10.5194/egusphere-egu2020-6710 ◽

2020 ◽

Author(s):

Cuimei Zhang ◽

Xiong Pang ◽

Ming Su ◽

Jinyun Zheng ◽

Hongbo Li ◽

...

Keyword(s):

High Resolution ◽

South China Sea ◽

Oceanic Crust ◽

South China ◽

Northern South China Sea ◽

Magmatic Activity ◽

Magmatic Evolution ◽

Seismic Profiles ◽

China Sea ◽

Rifted Margins

The interaction between magmatic and extensional processes related to the formation of rifted margins has been and still is highly debated. The interpretation of magmatic additions, timing of onset and budget of magma during rifting and lithospheric breakup remain controversial and poorly understood. In contrast, the emplacement of magmatic additions in rift systems with high sedimentation rates provides an exceptional perspective towards resolving some of these problems.In this paper, we present two new high-resolution seismic profiles imaging the complete transition from the hyperextended crust to oceanic crust in the northern South China Sea (SCS). Based on the observation of magma-related structures and the interrelationship with the sedimentary sequence, we define forms and timing of magmatic additions. We show that magmatic activity initiated during necking and then propagated together with the seaward formation of &#8220;new&#8221; basement , as indicated by the occurrence of sills and laccoliths during hyperextension, and ENE striking cone-shaped volcanos during the final breakup stage before the establishment of an embryonic and then steady-state oceanic crust.First order estimations of the magmatic budget in order to decipher the magmatic evolution show that it strikingly increased during final hyperextension and the breakup stage and lasted until 23.8 Ma. Thus, magmatic activity continued even after cessation of rifting. This study enables for the first time to provide a semi-quantitative estimate of when, where and how much magma formed during final rifting and breakup at a magma-intermediate margin.

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Oceanic basement roughness alongside magma-poor rifted margins: insight into initial seafloor spreading

Geophysical Journal International ◽

10.1093/gji/ggx439 ◽

2017 ◽

Vol 212 (2) ◽

pp. 900-915 ◽

Cited By ~ 6

Author(s):

Daniel Sauter ◽

Julie Tugend ◽

Morgane Gillard ◽

Michael Nirrengarten ◽

Julia Autin ◽

...

Keyword(s):

Seafloor Spreading ◽

Rifted Margins ◽

Oceanic Basement ◽

Insight Into

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Aspects of the structure on the coast of the West Greenland volcanic province revealed in seismic data

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-2007-55-05 ◽

2007 ◽

Vol 55 ◽

pp. 65-80

Author(s):

N. Skaarup ◽

T.C.R. Pulvertaft

Keyword(s):

Seismic Data ◽

Volcanic Rocks ◽

Structural Features ◽

Seafloor Spreading ◽

Second Phase ◽

Early Eocene ◽

West Greenland ◽

Rifted Margins ◽

Extensional Faulting ◽

Ocean Boundary

The coastal structure in central West Greenland is expressed by Palaeogene basalts which show pronounced seaward dip. Traced along strike the tilted basalts occur in two segments, separated by an area in which dips are low. Within these segments the lavas have been displaced by extensional faults with strike parallel to the strike of the lavas and dip and downthrow to the landward side. This structural pattern bears many similarities to regional structural features in volcanic rifted margins in other parts of the world, although in West Greenland the continent-ocean boundary is situated more than 100 km west of the coast. The structure has previously been studied onshore and has now been studied in high-resolution seismic data acquired both west of the coast and in the sounds between the Nuussuaq and Svartenhuk peninsulas. From the offshore data it can be seen that within the sections correlated with mid-Paleocene volcanic rocks onshore, the tilting of the lavas took place almost entirely after eruption, as there is little or no indication of any increase of dip towards the faults or of fan-shaped geometry in cross-section. However, southwest of Ubekendt Ejland and stratigraphically within Early Eocene lavas, dips can be seen to increase with depth in several fault blocks, indicating that tilting was active during eruption of these lavas. It is therefore concluded that tilting of the volcanic rocks in the coastal zone took place largely in the Eocene. This conclusion is corroborated by the following onshore evidence: Firstly, the angle of discordance between seaward-dipping Eocene lavas and the underlying tilted Paleocene lavas is small, where observed at all, so the mid-Paleocene lavas must owe their seaward dip largely to tilting during the Eocene. Secondly, Early Eocene ages have been obtained from sequentially tilted dykes onshore. This tilting and concomitant extensional faulting was contemporaneous with the second phase of seafloor spreading in the Labrador Sea which took place during the Eocene. The first phase of seafloor spreading in this sea took place between magnetochrons 27r and 24r and was not accompanied by significant rifting of lavas in central West Greenland. It can also be seen from the seismic data that the tilted lavas level out less than 25 km from the coast. West of this, the volcanics generally show very low dips and thin gradually towards the continent-ocean boundary.

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Initiation of a Proto-transform Fault Prior to Seafloor Spreading

10.26686/wgtn.13089095.v1 ◽

2020 ◽

Author(s):

Finnigan Illsley-Kemp ◽

JM Bull ◽

D Keir ◽

T Gerya ◽

C Pagli ◽

...

Keyword(s):

Plate Tectonics ◽

Seafloor Spreading ◽

Continental Rift ◽

Formation Mechanisms ◽

Transform Fault ◽

Transform Faults ◽

Local Seismicity ◽

Ocean Ridges ◽

Rifted Margins ◽

Direct Observations

©2018. The Authors. Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of mid-ocean ridges in ocean basins worldwide. The current consensus is that oceanic transform faults initiate after the onset of seafloor spreading. However, this inference has been difficult to test given the lack of direct observations of transform fault formation. Here we integrate evidence from surface faults, geodetic measurements, local seismicity, and numerical modeling of the subaerial Afar continental rift and show that a proto-transform fault is initiating during the final stages of continental breakup. This is the first direct observation of proto-transform fault initiation in a continental rift and sheds unprecedented light on their formation mechanisms. We demonstrate that they can initiate during late-stage continental rifting, earlier in the rifting cycle than previously thought. Future studies of volcanic rifted margins cannot assume that oceanic transform faults initiated after the onset of seafloor spreading.

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Observations of the spatial structure of interstellar hydrogen

Symposium - International Astronomical Union ◽

10.1017/s007418090010066x ◽

1967 ◽

Vol 31 ◽

pp. 45-46

Author(s):

Carl Heiles

Keyword(s):

High Resolution ◽

Spatial Structure ◽

Velocity Dispersion ◽

Temperature Variations

High-resolution 21-cm line observations in a region aroundlII= 120°,b11= +15°, have revealed four types of structure in the interstellar hydrogen: a smooth background, large sheets of density 2 atoms cm-3, clouds occurring mostly in groups, and ‘Cloudlets’ of a few solar masses and a few parsecs in size; the velocity dispersion in the Cloudlets is only 1 km/sec. Strong temperature variations in the gas are in evidence.

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Combining integrated systems-biology approaches with intervention-based experimental design provides a higher-resolution path forward for microbiome research

Behavioral and Brain Sciences ◽

10.1017/s0140525x18002911 ◽

2019 ◽

Vol 42 ◽

Author(s):

J. Alfredo Blakeley-Ruiz ◽

Carlee S. McClintock ◽

Ralph Lydic ◽

Helen A. Baghdoyan ◽

James J. Choo ◽

...

Keyword(s):

Systems Biology ◽

High Resolution ◽

Experimental Design ◽

Integrated Systems ◽

Microbiome Research ◽

Constructive Criticism

Abstract The Hooks et al. review of microbiota-gut-brain (MGB) literature provides a constructive criticism of the general approaches encompassing MGB research. This commentary extends their review by: (a) highlighting capabilities of advanced systems-biology “-omics” techniques for microbiome research and (b) recommending that combining these high-resolution techniques with intervention-based experimental design may be the path forward for future MGB research.

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Very High Resolution Analysis of the Dynamics of a Coronal Plasmoid

International Astronomical Union Colloquium ◽

10.1017/s0252921100026117 ◽

1994 ◽

Vol 144 ◽

pp. 593-596

Author(s):

O. Bouchard ◽

S. Koutchmy ◽

L. November ◽

J.-C. Vial ◽

J. B. Zirker

Keyword(s):

High Resolution ◽

Solar Eclipse ◽

Total Solar Eclipse ◽

Field Of View ◽

Small Field ◽

High Resolution Analysis ◽

Ccd Observations ◽

Resolution Analysis ◽

Very High ◽

Small Field Of View

AbstractWe present the results of the analysis of a movie taken over a small field of view in the intermediate corona at a spatial resolution of 0.5“, a temporal resolution of 1 s and a spectral passband of 7 nm. These CCD observations were made at the prime focus of the 3.6 m aperture CFHT telescope during the 1991 total solar eclipse.

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