Mapping the continent-ocean transition in the Eastern Black Sea Basin

2020 ◽  
Author(s):  
Tim Minshull ◽  
Vanessa Monteleone ◽  
Hector Marin Moreno ◽  
Donna Shillington
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Black Sea ◽  
Seismic Data ◽  
Wide Angle ◽  
Seismic Velocities ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Rifted Margins ◽  
Geodynamic Processes

<p>The transition from continental to oceanic crust at rifted margins is characterised by changes in a variety of parameters including crustal thickness, basement morphology and magnetisation. Rifted margins also vary significantly in the degree of magmatism that is associated with breakup. The Eastern Black Sea Basin formed by backarc extension in late Cretaceous to early Cenozoic times, by the rotation of Shatsky Ridge relative to the Mid Black Sea High. Wide-angle seismic data show that anomalously thick oceanic crust is present in the southeast of the basin, while further to the northwest the crust is thinner in the centre of the basin. This thinner crust has seismic velocities that are anomalously low for oceanic crust, but is significantly magnetised and has a similar basement morphology to the thicker crust to the southeast. We synthesise constraints from wide-angle seismic data, magnetic anomaly data and new long-offset seismic reflection data into an integrated interpretation of the location and nature of the continent-ocean transition within the basin. Northwest to southeast along the axis of the basin, we infer a series of transitions from mildly stretched continental crust at the Mid Black Sea High to hyper-thinned continental crust, then to thin oceanic crust, and finally to anomalously thick oceanic crust. We explore the geodynamic processes that may have led to this configuration.</p>

Seismic evidence for the migration of fluids within the accretionary complex of western Canada

1991 ◽  
Vol 28 (4) ◽  
pp. 542-556 ◽  
Author(s):  
A. J. Calvert ◽  
R. M. Clowes
Keyword(s):  
Continental Slope ◽  
Seismic Data ◽  
Accretionary Prism ◽  
Western Canada ◽  
Accretionary Wedge ◽  
Seismic Velocities ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Subducting Plate ◽  
Important Evidence

Multichannel deep seismic reflection data from the subduction zone of western Canada delineate the wedge of accereted sediments and the principal terranes (Crescent, Pacific Rim, and Wrangellia) that form the convergent margin. The top of the igneous oceanic crust is defined by subhorizontal reflections extending at least 100 km landward of the deformation front. Upon incorporation into the accretionary wedge, the clearly defined stratigraphy of the incoming oceanic sedimentary section is destroyed over a distance of about 10 km. Initially, an unreflective zone, which correlates well with maximum fluid expulsion, is formed. Farther landward, a predominantly landward-dipping reflectivity exists. A number of reflections are thrust faults, which appear to merge at depth with the subhorizontal reflections, but most have another origin. These reflections may be related to the movement of fluids generated by the compaction of sediments or possibly by the dehydration of the subducting plate. They are strongest in a region of depressed seismic velocities beneath the continental slope, where an analysis of reflection amplitude with offset implies that a high Poisson's ratio exists; this is consistent with the presence of elevated pore pressures. Thus, pore pressure variations associated with the migration of fluids may be the cause of much of the reflectivity within the accreted wedge, although the precipitation of minerals from rising fluids could also be important. Evidence from the seismic data also indicates that fluids from the accretionary prism are being expelled into the sediments of the overlying Tofino basin. A number of anomalously strong reflections and disruption of the horizontally stratified sediments within the lower levels of the basin probably represent fluids that migrated upward from the accreted wedge and were trapped against impermeable barriers created through the deposition of sediments on the continental slope and in the basin.

Shifted-elliptical nonstretch moveout correction of wide-angle seismic data in the τ-p domain, using an example from the Faeroe-Shetland Basin

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. B227-B236 ◽  
Author(s):  
Hassan Masoomzadeh ◽  
Satish C. Singh ◽  
Penny J. Barton
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Wide Angle ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Angle Data ◽  
Vertical Heterogeneity ◽  
P Domain

We developed a method of moveout correction in the [Formula: see text] domain to tackle some of the problems associated with processing wide-angle seismic reflection data, including residual moveout and normal-moveout stretching. We evaluated the concept of the shifted ellipse in the [Formula: see text] domain as an alternative to the well-known concept of the shifted hyperbola in the [Formula: see text] domain. We used this shifted-ellipse concept to address the problem of residual moveout caused by vertical heterogeneity in the subsurface. We also addressed the stretching problem associated with dynamic corrections by combining selected strips from a set of constant-moveout stacks generated using a shifted-ellipse equation. Application of this method to a wide-angle data set from the Faeroe-Shetland Basin provided an enhanced image of the subbasalt structure.

Revisiting the deep structure of the Northern Carnarvon Basin: insights from new seismic reflection data

2015 ◽  
Vol 55 (2) ◽  
pp. 421
Author(s):  
Paul Bellingham ◽  
Leanne Cowie ◽  
Rod Graham ◽  
Brian Horn ◽  
Kenneth McDermott ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Seismic Reflection ◽  
Deep Structure ◽  
Hydrocarbon Exploration ◽  
Seismic Reflection Data ◽  
Exmouth Plateau ◽  
Reflection Data ◽  
Delta System ◽  
Carnarvon Basin

The Carnarvon Basin has long been a focus for hydrocarbon exploration and development. Many models have been proposed for the basin’s lithospheric structure, although the great thickness of the Mungaroo delta system has hampered the clear imaging of the underlying rift and break-up structure. New deep, long offset seismic reflection data acquired across the basin as a part of ION’s Westralia SPAN survey provide unique imaging of the deep basement structures and the complete overlying sedimentary section. The survey crossed the offshore terrains, from weakly stretched continental crust to oceanic crust. The margin has developed during two major events; one of Permo-Carboniferous age, prior to the Mungaroo delta system, and one of Middle to Upper Jurassic age. There is a possibility that the basement terrain under parts of the Exmouth Plateau is actually Permo-Carboniferous oceanic crust, rather than hyper-extended continental crust or exhumed continental lithospheric mantle. Deformation during the second major event in the Jurassic was focussed in the Barrow-Dampier Sub-basin and at the present day ocean-continent transition with little deformation across the Exmouth Plateau in-between. The only basement involved extension appears to be in the Barrow-Dampier system and appears to be non-volcanic. The outer margin along the northwest edge of the Exmouth Plateau includes significant volcanic input, likely underplating and emplacement of seaward-dipping reflectors.

Potentially Large Subsurface Gas Hydrate Bodies in the Mexican Ridges, Southwestern Gulf of Mexico

2021 ◽  
pp. 1-29
Author(s):  
Papia Nandi ◽  
Patrick Fulton ◽  
James Dale
Keyword(s):  
Gulf Of Mexico ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Poor Quality ◽  
Reflection Point ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
High Impedance ◽  
Acoustic Velocities ◽  
Seismic Images

As rising ocean temperatures can destabilize gas hydrate, identifying and characterizing large shallow hydrate bodies is increasingly important in order to understand their hazard potential. In the southwestern Gulf of Mexico, reanalysis of 3D seismic reflection data reveals evidence for the presence of six potentially large gas hydrate bodies located at shallow depths below the seafloor. We originally interpreted these bodies as salt, as they share common visual characteristics on seismic data with shallow allochthonous salt bodies, including high-impedance boundaries and homogenous interiors with very little acoustic reflectivity. However, when seismic images are constructed using acoustic velocities associated with salt, the resulting images were of poor quality containing excessive moveout in common reflection point (CRP) offset image gathers. Further investigation reveals that using lower-valued acoustic velocities results in higher quality images with little or no moveout. We believe that these lower acoustic values are representative of gas hydrate and not of salt. Directly underneath these bodies lies a zone of poor reflectivity, which is both typical and expected under hydrate. Observations of gas in a nearby well, other indicators of hydrate in the vicinity, and regional geologic context, all support the interpretation that these large bodies are composed of hydrate. The total equivalent volume of gas within these bodies is estimated to potentially be as large as 1.5 gigatons or 10.5 TCF, considering uncertainty for estimates of porosity and saturation, comparable to the entire proven natural gas reserves of Trinidad and Tobago in 2019.

scholarly journals Improved Interpretation of Deep Seismic Reflection Data in Areas of Complex Geology Through Integration With Passive Seismic Data Sets

2018 ◽  
Vol 123 (12) ◽  
pp. 10,810-10,830
Author(s):  
Michael Dentith ◽  
Huaiyu Yuan ◽  
Ruth Elaine Murdie ◽  
Perla Pina-Varas ◽  
Simon P. Johnson ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Data Sets ◽  
Seismic Reflection Data ◽  
Deep Seismic Reflection ◽  
Reflection Data ◽  
Passive Seismic ◽  
Complex Geology

scholarly journals Study on the limitations of travel-time inversion applied to sub-basalt imaging

Solid Earth ◽  
2013 ◽  
Vol 4 (2) ◽  
pp. 543-554 ◽  
Author(s):  
I. Flecha ◽  
R. Carbonell ◽  
R. W. Hobbs
Keyword(s):  
Oil Industry ◽  
Velocity Model ◽  
Time Inversion ◽  
Wide Angle ◽  
Seismic Reflection Data ◽  
Additional Information ◽  
Velocity Models ◽  
Reflection Data ◽  
Travel Time Inversion ◽  
Tomographic Inversions

Abstract. The difficulties of seismic imaging beneath high velocity structures are widely recognised. In this setting, theoretical analysis of synthetic wide-angle seismic reflection data indicates that velocity models are not well constrained. A two-dimensional velocity model was built to simulate a simplified structural geometry given by a basaltic wedge placed within a sedimentary sequence. This model reproduces the geological setting in areas of special interest for the oil industry as the Faroe-Shetland Basin. A wide-angle synthetic dataset was calculated on this model using an elastic finite difference scheme. This dataset provided travel times for tomographic inversions. Results show that the original model can not be completely resolved without considering additional information. The resolution of nonlinear inversions lacks a functional mathematical relationship, therefore, statistical approaches are required. Stochastic tests based on Metropolis techniques support the need of additional information to properly resolve sub-basalt structures.

Late Cretaceous – Cenozoic history of the transition zone between the East European Craton and the Paleozoic Platform, Polish sector of the Baltic Sea, revealed by new offshore regional seismic reflection data (BALTEC project)

2021 ◽  
Author(s):  
Piotr Krzywiec ◽  
Łukasz Słonka ◽  
Quang Nguyen ◽  
Michał Malinowski ◽  
Mateusz Kufrasa ◽  
...  
Keyword(s):  
High Resolution ◽  
Late Cretaceous ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Upper Cretaceous ◽  
Seismic Reflection Data ◽  
East European ◽  
Reflection Data ◽  
Multichannel Seismic Reflection ◽  
Multichannel Seismic Reflection Data

<p>In 2016, approximately 850 km of high-resolution multichannel seismic reflection data of the BALTEC survey have been acquired offshore Poland within the transition zone between the East European Craton and the Paleozoic Platform. Data processing, focused on removal of multiples, strongly overprinting geological information at shallower intervals, included SRME, TAU-P domain deconvolution, high resolution parabolic Radon demultiple and SWDM (Shallow Water De-Multiple). Entire dataset was Kirchhoff pre-stack time migrated. Additionally, legacy shallow high-resolution multichannel seismic reflection data acquired in this zone in 1997 was also used. All this data provided new information on various aspects of the Phanerozoic evolution of this area, including Late Cretaceous to Cenozoic tectonics and sedimentation. This phase of geological evolution could be until now hardly resolved by analysis of industry seismic data as, due to limited shallow seismic imaging and very strong overprint of multiples, essentially no information could have been retrieved from this data for first 200-300 m. Western part of the BALTEC dataset is located above the offshore segment of the Mid-Polish Swell (MPS) – large anticlinorium formed due to inversion of the axial part of the Polish Basin. BALTEC seismic data proved that Late Cretaceous inversion of the Koszalin – Chojnice fault zone located along the NE border of the MPS was thick-skinned in nature and was associated with substantial syn-inversion sedimentation. Subtle thickness variations and progressive unconformities imaged by BALTEC seismic data within the Upper Cretaceous succession in vicinity of the Kamień-Adler and the Trzebiatów fault zones located within the MPS documented complex interplay of Late Cretaceous basin inversion, erosion and re-deposition. Precambrian basement of the Eastern, cratonic part of the study area is overlain by Cambro-Silurian sedimentary cover. It is dissected by a system of steep, mostly reverse faults rooted in most cases in the deep basement. This fault system has been regarded so far as having been formed mostly in Paleozoic times, due to the Caledonian orogeny. As a consequence, Upper Cretaceous succession, locally present in this area, has been vaguely defined as a post-tectonic cover, locally onlapping uplifted Paleozoic blocks. New seismic data, because of its reliable imaging of the shallowest substratum, confirmed that at least some of these deeply-rooted faults were active as a reverse faults in latest Cretaceous – earliest Paleogene. Consequently, it can be unequivocally proved that large offshore blocks of Silurian and older rocks presently located directly beneath the Cenozoic veneer must have been at least partly covered by the Upper Cretaceous succession; then, they were uplifted during the widespread inversion that affected most of Europe. Ensuing regional erosion might have at least partly provided sediments that formed Upper Cretaceous progradational wedges recently imaged within the onshore Baltic Basin by high-end PolandSPAN regional seismic data. New seismic data imaged also Paleogene and younger post-inversion cover. All these results prove that Late Cretaceous tectonics substantially affected large areas located much farther towards the East than previously assumed.</p><p>This study was funded by the Polish National Science Centre (NCN) grant no UMO-2017/27/B/ST10/02316.</p>

Deep structure of the Atlantic margins and neighboring oceanic crust from wide-angle seismic data and plate kinematic reconstructions.

2021 ◽  
Author(s):  
Frauke Klingelhoefer ◽  
Youssef Biari ◽  
Dieter Franke ◽  
Thomas Funck ◽  
Lies Loncke ◽  
...  
Keyword(s):  
Oceanic Crust ◽  
Seismic Data ◽  
Deep Structure ◽  
Volcanic Eruptions ◽  
Wide Angle ◽  
Seismic Profiles ◽  
Initial Rupture ◽  
Mechanisms Of Formation ◽  
Break Up ◽  
Transform Margin

<p>In order to study opening mechanisms and their variation in the Atlantic ocean basins, we compiled existing wide-angle and deep seismic data along conjugate margins and performed plate tectonic reconstructions of the original opening geometries to define conjugate margin pairs. A total of 23 published wide-angle seismic profiles from the different margins of the Atlantic basin were digitized, and reconstructions at break-up and during early stages of opening were performed. Main objectives were to understand how magma-rich and magma-poor margins develop and to define more precisely the role of geologic inheritance (i.e., preexisting structures) in the break-up phase. At magma-poor margins, a phase of tectonic opening without accretion of a typical oceanic crust often follows initial rupture, leading to exhumation of serpentinized upper mantle material. Along volcanic margins the first oceanic crust can be overthickened, and both over- and underlain by volcanic products. The first proto-oceanic crust is often accreted at slow to very slow rates, and is thus of varied thickness, mantle content and volcanic overprint. Accretion of oceanic crust at slow to very slow spreading rates can also be highly asymmetric, so the proto oceanic crust at each side of conjugate margin pairs can differ. Another major aim of this study was to understand the mechanisms of formation and origins of transform marginal plateaus. These are bathymetric highs located at the border of two ocean basins of different ages and are mostly characterized by one or several volcanic phase during their formation. They often form conjugate pairs along a transform margin as it evolves and might have been the last land bridges during breakup, thereby influencing mammal migration and proto-oceanic currents in very young basins. At these plateaus, volcanic eruptions can lead to deposits of (at least in part subaerial) lava flows several km thick, better known by their geophysical signature as seaward dipping reflectors. Continental crust, if present, is heavily modified by volcanic intrusions. These marginal plateaus might form when rifting stops at barriers introduced by the transform margin, leading to the accumulation of heat in the mantle and increased volcanism directly before or after the cessation of rifting.</p>

Fault whispers: Transmission distortions on prestack seismic reflection data

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 377-389 ◽  
Author(s):  
Paul J. Hatchell
Keyword(s):  
Seismic Data ◽  
Seismic Waves ◽  
Shallow Gas ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Amplitude Versus Offset ◽  
Velocity Changes ◽  
Transmission Distortions ◽  
Amplitude Versus ◽  
Buried Faults

Transmission distortions are observed on prestack seismic data at two locations in the Gulf of Mexico. These distortions produce anomalous amplitude versus offset (AVO) signatures. The locations of the distortion zones are determined using acquisition geometry and ray tracing. No obvious reflection events, such as shallow gas zones, are observed at the predicted locations of the distortion zones. Instead, the distortion zones correlate with buried faults and unconformities. It is postulated that the distortions are produced by velocity changes across buried faults and unconformities. The distortions result from an interference pattern resulting from seismic waves arriving from different sides of the faults. A simple model is developed to explain many of the characteristics of the distortion pattern.

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