Imaging the past and present Owen transform fault: preliminary results from the VARUNA seismic cruise

2020 ◽  
Author(s):  
Alexandre Janin ◽  
Mathieu Rodriguez ◽  
Nicolas Chamot-Rooke ◽  
Alain Rabaute ◽  
Matthias Delescluse ◽  
...  
Keyword(s):  
High Resolution ◽  
Early Stage ◽  
Plate Boundary ◽  
Plate Boundaries ◽  
Transform Fault ◽  
African Plate ◽  
Active Structure ◽  
Carlsberg Ridge ◽  
Regional Tectonic ◽  
Seismic Lines

<p>The Owen transform fault in the northwest Indian Ocean is a >300 km-long active structure that constitutes the active plate boundary between Somalia and India. The first-order fault geometry was reached in the Early Miocene when the Carlsberg Ridge propagated westward into the African plate to open the Gulf of Aden. Presently, it accommodates ~23 mm/yr of left-lateral strike-slip motion between the Sheba and Carlsberg spreading centers.  The fault was recently surveyed in the Spring of 2019 during the VARUNA and CARLMAG cruises on BHO Beautemps-Beaupré, an oceanographic ship operated by the French Navy. Along with geophysical measurements (multibeam bathymetry, gravity and magnetic fields) a set of high-resolution seismic lines (> 5000 km) was acquired across both the active and fossil traces of the fault between 9°N and 15°N. The area is largely buried under the distal Indus turbiditic sediments and therefore offers a fairly unique continuous high-resolution stratigraphic record of past regional tectonic events. Here we present the first multibeam map of the Owen Transform system. A remarkable transpressive ridge borders the active trace of the fault along most of its length. At the intersection with the Carlsberg Ridge, the Owen Transform marks an 11° bend characterized by ~1200 m of seafloor uplift.  Our preliminary interpretation of the seismic lines brings to light the key unconformities related to Global Plate Reorganization Events. Off the main fault, new data reveal the magmatic nature of the Varuna Bank and similar partially buried highs. These have likely grown in the very early stage of formation of the oceanic crust carrying them, although tectonic emplacement cannot be completely ruled out. Some of the highs show internal structure, which can be interpreted either as carbonate caps or layered volcanic formations. This dataset, combined with previous cruises, offers unprecedented coverage of a 1500 km-long transform corridor along the Arabia-India and India-Somalia plate boundaries.</p>

Active transpression along the Owen oceanic transform fault, India - Somalia plate boundary

2021 ◽  
Author(s):  
Alexandre Janin ◽  
Mathieu Rodriguez ◽  
Nicolas Chamot-Rooke ◽  
Alain Rabaute ◽  
Matthias Delescluse ◽  
...  
Keyword(s):  
High Resolution ◽  
Plate Boundary ◽  
Linear Structure ◽  
Historical Seismicity ◽  
Transform Fault ◽  
Seismic Profiles ◽  
Time Calibration ◽  
Carlsberg Ridge ◽  
Regional Tectonic ◽  
Seismic Lines

<p>The Owen oceanic transform fault is a 300-km long linear structure connecting the Carlsberg and Sheba spreading centers in the northwest Indian Ocean. It presently forms with the Carlsberg ridge the active plate boundary between India and Somalia. The Owen transform fault accommodates the left-lateral strike-slip motion between India and Somalia at a rate of about 23 mm/yr<strong>. </strong> Firstly identified by Tuzo Wilson in the 60s, this oceanic transform remains poorly described. The fault was recently surveyed in the Spring of 2019 during the VARUNA and CARLMAG cruises (https://doi.org/10.17600/18001108, https://doi.org/10.17600/18000872) along its entire length aboard BHO Beautemps-Beaupré, an oceanographic ship operated by the French Naval Hydrographic and Oceanographic Services (SHOM) and the French Navy.</p><p>During these missions a set of high-resolution seismic lines (>5000 km) were acquired together with high resolution multibeam bathymetry. The data cover both the active and fossil traces of the transform fault between 9°N and 15°N, at a place where continuous deposition of the distal Indus turbiditic sediments offers a unique high-resolution stratigraphic record of past regional tectonic events.</p><p>The new bathymetric mapping reveals two remarkable transpressive ridges on the active fault trace. A precise stratigraphic work using seismic profiles and drilling data of the ODP leg 117 allows the time calibration of the new seismic lines as far south as the Carlsberg ridge.</p><p>We show that a major compressive event occurred on the Owen Oceanic Transform Fault recently between 1.5 Ma and 2.4 Ma. Compression is still active today as evidenced by Sub-bottom profiler data (3.5 kHz) and two compressive focal mechanisms found in the historical seismicity records. At the intersection with the Carlsberg ridge, the southern transpressive ridge bends and stands ~1200 m above the seafloor at its apex, suggesting a maximum surrection rate near 800 m/Ma.  These new geophysical dataset combined with previous cruises offers an unprecedented window on the recent evolution of the India-Somalia plate boundary.</p>

Evolution of migrating transform faults in anisotropic oceanic crust: examples from Iceland

2019 ◽  
Vol 56 (12) ◽  
pp. 1297-1308 ◽  
Author(s):  
Jeffrey A. Karson ◽  
Bryndís Brandsdóttir ◽  
Páll Einarsson ◽  
Kristján Sæmundsson ◽  
James A. Farrell ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Fault Zones ◽  
Plate Boundaries ◽  
Transform Fault ◽  
Eurasian Plate ◽  
Transform Faults ◽  
The North ◽  
Rift Propagation ◽  
Oriented Parallel ◽  
Ocean Ridge

Major transform fault zones link extensional segments of the North American – Eurasian plate boundary as it transects the Iceland Hotspot. Changes in plate boundary geometry, involving ridge jumps, rift propagation, and related transform fault zone migration, have occurred as the boundary has moved relative to the hotspot. Reconfiguration of transform fault zones occurred at about 6 Ma in northern Iceland and began about 3 Ma in southern Iceland. These systems show a range of different types of transform fault zones, ranging from diffuse, oblique rift zones to narrower, well-defined, transform faults oriented parallel to current plate motions. Crustal deformation structures correlate with the inferred duration and magnitude of strike-slip displacements. Collectively, the different expressions of transform zones may represent different stages of development in an evolutionary sequence that may be relevant for understanding the tectonic history of plate boundaries in Iceland as well as the structure of transform fault zones on more typical parts of the mid-ocean ridge system.

The Reinga Basin, North Island, New Zealand

2010 ◽  
Vol 50 (1) ◽  
pp. 287 ◽  
Author(s):  
Chris Uruski ◽  
Eva Reid ◽  
Vaughan Stagpoole ◽  
Rick Herzer ◽  
Angela Griffin ◽  
...  
Keyword(s):  
New Zealand ◽  
Early Stage ◽  
Plate Boundary ◽  
Source Rocks ◽  
Seismic Survey ◽  
Quality Data ◽  
Data Set ◽  
Regional Tectonic ◽  
Sedimentary Succession ◽  
Sedimentary Fill

In early 2009, CGGVeritas, supported by the Crown Minerals Group of New Zealand’s Ministry of Economic Development, undertook a 5,900 km reconnaissance 2D seismic survey of the Reinga Basin, which is located to the northwest of the Northland Peninsula and Basin, New Zealand. Although very little data previously existed across this basin apart from low-fold reconnaissance seismic data, it was suspected of being an extension of the Northland Basin and to contain a thick sedimentary succession. It was thought to have formed as a rift basin near the Gondwana margin and to have been inverted during Neogene evolution of the present plate boundary. This paper is the result of the first interpretation of this new, high-quality data set. It confirms the presence of the basin and its sedimentary succession. Up to 9,000 m of sedimentary fill is imaged. The presence of coaly early rift packages and extensions of the Waipawa Formation black marine shale suggest that the basin contains voluminous source rocks. The basin appears to be more deformed in the northwest where large inversion structures are imaged. The northeastern margin is underlain by an extension of the Northland Allochthon which was obducted onto the New Zealand margin during initiation of the present plate boundary around 25 million years ago (Ma). The basin may also have been affected by strike-slip faulting associated with the Vening-Meinesz fracture zone, which developed during the Miocene. Several volcanic bodies are recognised, but in contrast to the adjacent Northland Basin where many large Miocene shield volcanos erupted, volcanic extrusions are rare in the Reinga region. Thermal modelling suggests that the basal source rocks are mature and expelling hydrocarbons and many direct hydrocarbon anomalies are present. Large trapping structures are apparent throughout the basin and even at this early stage of knowledge it appears that the region may have significant hydrocarbon potential. This paper will discuss the evolution of the basin in the regional tectonic context and summarise its petroleum prospectivity.

scholarly journals Unraveling rift margin evolution and escarpment development ages along the Dead Sea fault using cosmogenic burial ages

2014 ◽  
Vol 82 (1) ◽  
pp. 281-295 ◽  
Author(s):  
A. Matmon ◽  
D. Fink ◽  
M. Davis ◽  
S. Niedermann ◽  
D. Rood ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Dead Sea ◽  
Plate Motion ◽  
Plate Boundaries ◽  
Fluvial Sediments ◽  
Drainage Pattern ◽  
African Plate ◽  
Significant Extension ◽  
Quaternary History ◽  
The Dead

AbstractThe Dead Sea fault (DSF) is one of the most active plate boundaries in the world. Understanding the Quaternary history and sediments of the DSF requires investigation into the Neogene development of this plate boundary. DSF lateral motion preceded significant extension and rift morphology by ~10 Ma. Sediments of the Sedom Formation, dated here between 5.0 ± 0.5 Ma and 6.2−2.1+inf Ma, yielded extremely low 10Be concentrations and 26Al is absent. These reflect the antiquity of the sediments, deposited in the Sedom Lagoon, which evolved in a subdued landscape and was connected to the Mediterranean Sea. The base of the overlying Amora Formation, deposited in the terminal Amora Lake which developed under increasing relief that promoted escarpment incision, was dated at 3.3−0.8+0.9 Ma. Burial ages of fluvial sediments within caves (3.4 ± 0.2 Ma and 3.6 ± 0.4 Ma) represent the timing of initial incision. Initial DSF topography coincides with the earliest Red Sea MORB's and the East Anatolian fault initiation. These suggest a change in the relative Arabian–African plate motion. This change introduced the rifting component to the DSF followed by a significant subsidence, margin uplift, and a reorganization of relief and drainage pattern in the region resulting in the topographic framework observed today.

Automated high-resolution microscopy: the approaches so far

1987 ◽  
Vol 45 ◽  
pp. 58-61
Author(s):  
W. O. Saxton
Keyword(s):  
High Resolution ◽  
Early Stage ◽  
Automatic Recording ◽  
Microprocessor Control ◽  
Alternative Systems ◽  
Electron Image ◽  
Complete Automation ◽  
Analysis System ◽  
High Resolution Microscopy

Recent commercial microscopes with internal microprocessor control of all major functions have already demonstrated some of the benefits anticipated from such systems, such as continuous magnification, rotation-free diffraction and magnification, automatic recording of mutually registered focal series, and fewer control knobs. Complete automation of the focusing, stigmating and alignment of a high resolution microscope, allowing focal series to be recorded at preselected focus values as well, is still imminent rather than accomplished, however; some kind of image pick-up and analysis system, fed with the electron image via a TV camera, is clearly essential for this, but several alternative systems and algorithms are still being explored. This paper reviews the options critically in turn, and stresses the need to consider alignment and focusing at an early stage, and not merely as an optional extension to a basic proposal.

scholarly journals New seismological data from the Calabrian arc reveal arc-orthogonal extension across the subduction zone

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tiziana Sgroi ◽  
Alina Polonia ◽  
Graziella Barberi ◽  
Andrea Billi ◽  
Luca Gasperini
Keyword(s):  
Lateral Displacement ◽  
Tectonic Setting ◽  
Plate Boundary ◽  
Velocity Model ◽  
Tectonic Deformation ◽  
Accretionary Wedge ◽  
Tectonic Structures ◽  
Plate Convergence ◽  
Seismogenic Layer ◽  
Regional Tectonic

AbstractThe Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

Upper-plate structural controls on the segmentation of the Kefalonia Fault (Ionian Sea, Greece)

2021 ◽  
Author(s):  
Emmanuel Skourtsos ◽  
Haralambos Kranis ◽  
Spyridon Mavroulis ◽  
Efthimios Lekkas
Keyword(s):  
Eastern Mediterranean ◽  
Source Parameters ◽  
Plate Boundary ◽  
Temporal Distribution ◽  
Western Coast ◽  
African Plate ◽  
Plate Structure ◽  
The North ◽  
Macroseismic Effects ◽  
Spatio Temporal

<p>The NNE-SSW, right-lateral Kefalonia Transform Fault (KTF) marks the western termination of the subducting Hellenic slab, which is a part of the oceanic remnant of the African plate. The inception of the KTF, described as a STEP fault, is placed in the Pliocene. KTF is considered to be the most active earthquake source in the Eastern Mediterranean. During the last two decades, four significant earthquakes (M>6.0) have been associated with the KTF. These events are attributed to the reactivation of different segments of the KTF, which are (from North to South) the North Lefkada, South Lefkada, Fiskardo, Paliki and Zakynthos segments: the North Lefkada segment ruptured in the 2003 earthquake, the 2014 Kefalonia events are associated with the Paliki segment and the 2015 Lefkada earthquake with the South Lefkada (and possibly the Fiskardo) segments.</p><p>The upper plate structure in the islands of Lefkada and Kefalonia is characterized by the Ionian Unit, thrusted over the Paxi (or Pre-Apulian) Unit. The Ionian Thrust, which brings the Ionian over the Paxi Unit, is a main upper-plate NNW-SSE, NE-dipping structure. It runs through the island of Lefkada, to be mapped onshore again at the western coast of Ithaki and at SE Kefalonia. Two other major thrusts are mapped on this island: the Aenos thrust, which has a WNW-ESE strike at the southern part of the island and gradually curves towards NNW-SSE in the west and the Kalo Fault in the northern part. These Pliocene (and still active) structures developed during the late-most stages of thrusting in the Hellenides, strike obliquely to the KTF and appear to abut against it.</p><p>We suggest that these thrusts control not only the deformation within the upper plate, but also the earthquake segmentation of the KTF. This suggestion is corroborated by the spatio-temporal distribution and source parameters of the recent, well-documented earthquake events and by the macroseismic effects of these earthquakes. The abutment of the Ionian thrust against the KTF marks the southern termination of the Lefkada earthquake segment, which ruptured in the 2003 earthquake, while the Aenos, (or the Kalo) thrust mark the southern end of the Fiskardo segment. The spatial distribution of the Earthquake Environmental Effects related to the four significant events in the last 20 years displays a good correlation with our interpretation: most of the 2003 macroseismic effects are located in the northern part of Lefkada, which belongs to the upper block of the Ionian thrust; similarly, the effects of the 2014 earthquakes of Kefalonia are distributed mainly in the Paliki Peninsula and the southern part of the island that belong to the footwall of the Aenos thrust and the 2015 effects are found in SW Lefkada, which is part of the footwall of the Ionian thrust.</p><p>We suggest that correlation between upper-plate structure and plate boundary faulting can provide insights in the understanding of faulting pattern in convergent settings, therefore contributing to earthquake management plans.</p>

Accurate Thickness Inversion of Corrosion Using A1 Lamb Wave

2021 ◽  
Author(s):  
Min Lin ◽  
Yang Liu
Keyword(s):  
High Resolution ◽  
Oil And Gas ◽  
Residual Life ◽  
Early Stage ◽  
Corrosion Damage ◽  
Oil And Gas Industry ◽  
Forward Modeling ◽  
Guided Wave ◽  
Velocity Inversion ◽  
Wave Tomography

Abstract Corrosion is one of the most critical issues in the oil and gas industry, leading to severe environmental and economic problems. Due to the high cost and serious safety risk of corrosion, it is essential to improve current corrosion testing techniques to detect corrosion damages at an early stage. Guided wave tomography (GWT) demonstrates its great potential to inspect and quantify the corrosion damage. GWT is capable of determining the residual life of corrosion structures by quantifying the remaining wall thickness. In this paper, an accurate guided wave tomography technique incorporating full waveform inversion (FWI) and higher-order Lamb waves (A1 mode) is presented for plate-like structures, which is able to get high-resolution reconstruction results. The technique consists of three steps: forward modeling, velocity inversion and thickness reconstruction. The forward modeling is computed by solving the elastic full-wave equations in 2-D time domain by using the finite difference method. High-resolution phase velocity inversion can then be obtained by minimizing the waveform misfit function between simulated and recorded data using a second order optimization method, which updates the velocity model from low to high frequencies iteratively. Finally, the velocity variations can be transformed into depth profiles by using the dispersive characteristics of ultrasonic guided waves; therefore, the thickness reconstruction can be obtained. The numerical simulations are performed on an aluminum plate with a complicated corrosion defect. By comparing the thickness reconstruction maps using both A1 and A0 modes, the results demonstrate that FWI with A1 mode can achieve significantly better resolution of corrosion imaging than that with A0 mode.

A heat-flow reconnaissance of southeastern Alaska

1985 ◽  
Vol 22 (3) ◽  
pp. 416-421 ◽  
Author(s):  
J. H. Sass ◽  
L. A. Lawver ◽  
R. J. Munroe
Keyword(s):  
Heat Flow ◽  
Plate Boundary ◽  
Thermal Spring ◽  
High Heat ◽  
Transform Fault ◽  
High Heat Flow ◽  
Queen Charlotte Islands ◽  
Late Tertiary ◽  
The Mean ◽  
Strain Heating

Heat flow was measured at nine sites in crystalline and sedimentary rocks of southeastern Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte – Fairweather transform fault, have an average heat flow of 59 ± 6 mW m−2. This value is significantly higher than the mean of 42 mW m−2 in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, to the south, and is lower than the mean of 72 ± 2 mW m−2 for 81 values within 100 km of the San Andreas transform fault, even farther south. This intermediate value suggests the absence of significant heat sinks associated with Cenozoic subduction and of heat sources related to either late Cenozoic tectono-magmatic events or significant shear-strain heating. At Warm Springs Bay, 75 km from the plate boundary, an anomalously high heat flow of 150 mW m−2 can most plausibly be ascribed to the thermal spring activity from which its name is derived. At Quartz Hill, 240 km landward of the plate boundary, a value of 115 mW m−2 might indicate a transition to a province of high heat flow resulting from late Tertiary and Quaternary extension and volcanism.

scholarly journals High-Resolution Petrographic Evidence Confirming Detrital and Biogenic Magnetites as Remanence Carriers for Zongpu Carbonates in the Gamba Area, South Tibet

2021 ◽  
Vol 9 ◽  
Author(s):  
Qian Zhao ◽  
Baochun Huang ◽  
Zhiyu Yi ◽  
Pengfei Xue
Keyword(s):  
High Resolution ◽  
Electron Backscatter Diffraction ◽  
Early Stage ◽  
Electron Microscopic Observation ◽  
Optical Microscope ◽  
Magnetic Minerals ◽  
Electron Microscopic ◽  
Magnetic Carriers ◽  
Magnetic Extraction ◽  
South Tibet

Paleocene carbonates from the Gamba area of South Tibet provide the largest paleomagnetic dataset for constraining the paleogeography of the India-Asia collision in the early stage. Previous studies argued that the characteristic remanences (ChRMs) obtained from this unit were remagnetized via orogenic fluids. This study carries out a high-resolution petrographic study on the Paleocene carbonates from Gamba aiming to test the nature of the ChRMs. Electron microscopic observation on magnetic extracts identified a large amount of detrital magnetite that are multi- to single domain in sizes and nanoscale biogenic magnetite. Minor framboidal iron oxides were also identified, which were previously interpreted as authigenic magnetite that substitutes pyrite. However, our scanning and transmission electron microscopic (SEM/TEM) observations, along with optical microscope and Raman spectrum investigations further suggest that these magnetic minerals are pigmentary hematite and goethite that are incapable of carrying a stable primary magnetization. We therefore argue that the ChRMs of the limestones from the Zongpu Formation in the Gamba area are carried by detrital and biogenic magnetites rather than authigenic magnetite. The paleomagnetic data from the Gamba area are interpreted as primary origin and can thus be used for tectonic reconstructions. We emphasize that magnetic extraction, integrated with advanced mineralogic studies (e.g., electron backscatter diffraction and electron diffraction) are effective approaches for investigating the origin of magnetic carriers in carbonate rocks.

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