Deep structure of the North Tyrrhenian Sea from multi-channel seismic profiles and on land wide angle reflection/refraction seismic recording (LISA cruise): Geodynamical implications

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

10.5194/egusphere-egu21-4078 ◽

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>

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The GROSMarin experiment: three dimensional crustal structure of the North Ligurian margin from refraction tomography and preliminary analysis of microseismic measurements

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.182.4.305 ◽

2011 ◽

Vol 182 (4) ◽

pp. 305-321 ◽

Cited By ~ 13

Author(s):

Jean-Xavier Dessa ◽

Soazig Simon ◽

Marjorie Lelievre ◽

Marie-Odile Beslier ◽

Anne Deschamps ◽

...

Keyword(s):

Preliminary Analysis ◽

Deep Structure ◽

Three Dimensional ◽

Ocean Bottom ◽

Deep Basin ◽

The North ◽

Refraction Tomography ◽

Refraction Seismic ◽

Ocean Bottom Seismometers ◽

Using Data

Abstract The deep structure of the North Ligurian margin and its contiguous Ligurian basin as well as the seismicity recorded in these zones are neither well understood nor precisely constrained. In order to better address these questions, there is a need for offshore instrumenting, which was realised for a duration of nearly 6 months during the GROSMarin (Grand Réseau d’Observation Sous-Marin) experiment. An array of 21 ocean bottom seismometers was deployed over the most active area of the margin and was complemented on land by mobile seismological stations that densified existing permanent networks. We also realised the acquisition of deep refraction seismic shots at sea in order to get a 3D distribution of velocities along the margin through travel time tomography. We present here a preliminary analysis of the seismicity recorded during this experiment and a tomographic model of the margin structures obtained using data from the offshore network only. Our results support the existence of a high velocity zone at the base of a domain interpreted as transitional between continental and oceanic ones, on the northern part of the deep basin. A very similar pattern is observed across the neighbouring margin of the Gulf of Lions and is most likely related to serpentinisation of the underlying mantle during late rifting and continental break-up. North of this transition zone, we observe the basinward crustal thinning of the continental crust beneath the margin that seemingly narrows eastward. To the south, our results hint at transition to the oceanic domain. In contrast, our velocity distribution does not reveal a transition along strike between transitional and oceanic domains, as previous works suggest. Some microseismic activity was recorded throughout the duration of the experiment, on land and at sea. The number of detected events and precision of location were both improved by our considering French and Italian permanent networks. The detection capabilities of our dense network still need to be fully exploited.

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Deep Structure of the North Natal Valley (Mozambique) Using Combined Wide‐Angle and Reflection Seismic Data

Journal of Geophysical Research Solid Earth ◽

10.1029/2020jb021171 ◽

2021 ◽

Vol 126 (4) ◽

Cited By ~ 2

Author(s):

A. Leprêtre ◽

P. Schnürle ◽

M. Evain ◽

F. Verrier ◽

D. Moorcroft ◽

...

Keyword(s):

Seismic Data ◽

Deep Structure ◽

Wide Angle ◽

Reflection Seismic ◽

The North

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

Seismological Research Letters ◽

10.1785/0220190142 ◽

2019 ◽

Vol 91 (1) ◽

pp. 533-540 ◽

Cited By ~ 3

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.

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Structural settings of the carbonatic "basament" and its relationship with magma uprising in the gulf of Naples (Southern Italy)

Annals of Geophysics ◽

10.4401/ag-3985 ◽

1996 ◽

Vol 39 (3) ◽

Author(s):

N. Fusi

Keyword(s):

Normal Faults ◽

Tyrrhenian Sea ◽

Seismic Profiles ◽

North West ◽

Gulf Of Naples ◽

The North ◽

Phlegraean Fields ◽

Western Side ◽

Seismic Reflection Profiles ◽

Tyrrhenian Basin

The carbonatic "basement" of the Gulf of Naples, a peri-tyrrhenian basin located on the western side of the Southern Apenninic chain, was studied in detail by means of seismic reflection profiles both on the mainland and in the sea. The carbonatic "basement" dips toward the north-west with an angle of 100 and is affected by brittle extensional tectonics. This structural setting is related to the extension of the Tyrrhenian Sea, which caused the development of horst and graben-like structure along the western margin of the Apennines. Some normal faults with a regional relevance were recognised: 1 ) a N 110° trending fault responsible for the sinking of the carbonic "basement" below Mount Somma-Vesuvius; 2) a N 1O° trending fault, along which five sub- marine volcanoes are aligned; 3) a N70° fault, which separates the Gulf of Naples from the Gulf of Salerno. The first two faults, arranged radially with respect to the shallow magmatic chamber of Phlegraean Fields, are interpreted as the main uprising route for magma in this area. The carbonatic "basement"cannot be recognized in seismic profiles in the Phlegraean area; a tectonic feature responsible for this is hypothesised.

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Seismic wide-angle constrains on the structure of the northern Sicily margin and Vavilov Basin: implications for the opening of the Tyrrhenian back-arc basin

10.5194/egusphere-egu2020-5130 ◽

2020 ◽

Author(s):

Ingo Grevemeyer ◽

Cesar Ranero ◽

Nevio Zitellini ◽

Valenit Sallares ◽

Manel Prada

Keyword(s):

Continental Crust ◽

Seismic Refraction ◽

Seismic Profile ◽

Passive Margin ◽

P Wave ◽

Tyrrhenian Sea ◽

Wide Angle ◽

Central Mediterranean ◽

The North ◽

Back Arc

<p>The Tyrrhenian Sea in the central Mediterranean Sea was form by Neogene slab roll-back of the retreating Ionian slab about 6 to 2 Myr ago. Yet, little is known about the structure of its southern margin off Sicily as well as back-arc extension and spreading in the southern Tyrrhenian Sea to the north of Sicily. The Sicilian margin is generally classified as a passive margin bounding a young back-arc basin. However, focal mechanisms from regional earthquakes suggest that the margins suffers presently from compressional tectonics. New seismic refraction and wide-angle data were collected along seismic profile WAS4 during the CHIANTI survey of the Spanish research vessel Sarmiento de Gamboa in 2015. The profile runs from the centre of the Tyrrhenian Sea &#8211; the Vavilov Basin &#8211; across the margin of Sicily, approaching the Gulf of Castellammare to the northwest of Sicily. Reanalyzed multi-channel seismic data supports compressional tectonics across a small basin paralleling the coastline of Sicily, revealing recent inversion of the Tyrrhenian Basin. Offshore of Sicily WAS4 indicates a roughly 120-140 km wide domain showing seismic P-wave velocities characteristic for continental crust (Vp ~4-6.7 km/s) and a base of crust defined by a wide-angle Moho reflection. Continental crust reaches a maximum thickness of 22 km to the north of the Gulf of Castellammare and is thinning to ~9 km to the north of the Ustica Ridge. The compressional belt occurs in continental crust to the south of Ustica Ridge. In the Vavilov Basin, a lithosphere was sample where seismic P-wave velocity increases from approx. 3-4 km/s to 7.5 km/s. This velocity depth-distribution clearly shows profound similarities to serpentinized mantle and hence un-roofed mantle. Thus, seismic constrains support results from Ocean Drilling Program (ODP) hole 651A, which sample serpentinized peridotites in the Vavilov Basin. The transition between serpentinized mantle and continental crust is rather abrupt. Thus, within a ~10 km wide transitional domain, continental crust with a thickness of~ 9 km is juxtaposed against un-roofed mantle. All available data from the Tyrrhenian Sea support wide-spread mantle exhumation in the Vavilov Basin. Therefore, the Tyrrhenian Sea provides a rather different structure when compared to marginal basins in the Western Pacific and hence may not have supported a mid-ocean ridge-type spreading system opening the basin.</p>

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Seismic tomographic interpretation of Paleozoic sedimentary sequences in the southeastern North Sea

Geophysics ◽

10.1190/1.1996908 ◽

2005 ◽

Vol 70 (4) ◽

pp. R45-R56 ◽

Cited By ~ 10

Author(s):

Lars Nielsen ◽

Hans Thybo ◽

Martin Glendrup

Keyword(s):

North Sea ◽

Velocity Structure ◽

Seismic Velocity ◽

P Wave ◽

Wide Angle ◽

North German Basin ◽

Sedimentary Sequences ◽

The North ◽

Crystalline Crust ◽

German Basin

Seismic wide-angle data were recorded to more than 300-km offset from powerful airgun sources during the MONA LISA experiments in 1993 and 1995 to determine the seismic-velocity structure of the crust and uppermost mantle along three lines in the southeastern North Sea with a total length of 850 km. We use the first arrivals observed out to an offset of 90 km to obtain high-resolution models of the velocity structure of the sedimentary layers and the upper part of the crystalline crust. Seismic tomographic traveltime inversion reveals 2–8-km-thick Paleozoic sedimentary sequences with P-wave velocities of 4.5–5.2 km/s. These sedimentary rocks are situated below a Mesozoic-Cenozoic sequence with variable thickness: ∼2–3 km on the basement highs, ∼2–4 km in the Horn Graben and the North German Basin, and ∼6–7 km in the Central Graben. The thicknesses of the Paleozoic sedimentary sequences are ∼3–5 km in the Central Graben, more than 4 km in the Horn Graben, up to ∼4 km on the basement highs, and up to 8 km in the North German Basin. The Paleozoic strata are clearly separated from the shallower and younger sequences with velocities of ∼1.8–3.8 km/s and the deeper crystalline crust with velocities of more than 5.8–6.0 km/s in the tomographic P-wave velocity model. Resolution tests show that the existence of the Paleozoic sediments is well constrained by the data. Hence, our wide-angle seismic models document the presence of Paleozoic sediments throughout the southeastern North Sea, both in the graben structures and in deep basins on the basement highs.

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