Algerian licensing round may offer opportunity for exploration plays in deep offshore frontier

Cope, M. J.

doi:10.3997/1365-2397.21.7.25550

Cited by 19 publications

(10 citation statements)

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“…The additional multichannel seismic lines L1 to L4 of Fig. 2a were acquired and processed in 2000 by Western-Geco (Cope 2003) for Sonatrach. The seismic source consisted of a tuned first peak from a sleeve airgun array of 3000 ci (45 l) shot at a pressure of ∼2000 psi and towed at 6 m in depth (Arab et al 2014;Medaouri et al 2014).…”

Section: Multichannel Seismic Datamentioning

confidence: 99%

Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

Bouyahiaoui¹,

Sage²,

Abtout³

et al. 2015

Geophysical Journal International

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We determine the deep structure of the eastern Algerian basin and its southern margin in the Annaba region (easternmost Algeria), to better constrain the plate kinematic reconstruction in this region. This study is based on new geophysical data collected during the SPIRAL cruise in 2009, which included a wide-angle, 240-km-long, onshore-offshore seismic profile, multichannel seismic reflection lines and gravity and magnetic data, complemented by the available geophysical data for the study area. The analysis and modelling of the wide-angle seismic data including refracted and reflected arrival travel times, and integrated with the multichannel seismic reflection lines, reveal the detailed structure of an ocean-to-continent transition. In the deep basin, there is an ∼5.5-km-thick oceanic crust that is composed of two layers. The upper layer of the crust is defined by a high velocity gradient and P-wave velocities between 4.8 and 6.0 km s −1 , from the top to the bottom. The lower crust is defined by a lower velocity gradient and P-wave velocity between 6.0 and 7.1 km s −1 . The Poisson ratio in the lower crust deduced from S-wave modelling is 0.28, which indicates that the lower crust is composed mainly of gabbros. Below the continental edge, a typical continental crust with P-wave velocities between 5.2 and 7.0 km s −1 , from the top to the bottom, shows a gradual seaward thinning of ∼15 km over an ∼35-km distance. This thinning is regularly distributed between the upper and lower crusts, and it characterizes a rifted margin, which has resulted from backarc extension at the rear of the Kabylian block, here represented by the Edough Massif at the shoreline. Above the continental basement, an ∼2-km-thick, pre-Messinian sediment layer with a complex internal structure is interpreted as allochthonous nappes of flysch backthrusted on the margin during the collision of Kabylia with the African margin. The crustal structure, moreover, provides evidence for Miocene emplacement of magmatic intrusions in both the deep basin and the continental margin. Based on the crustal structure, we propose that the eastern Algerian basin opened during the southeastward migration of the European forearc before the collision, along a NW-SE elongated spreading centre that ran perpendicular to the subduction trend. Such an atypical geometry is explained by the diverging directions of the subduction rollback during the backarc opening: eastward for the Corsica-Sardinia block, and southward for the Kabylian blocks. This geometry of the forearc can be interpreted as the surface expression of a slab tear at depth, which is responsible for atypical magmatism in the overlying backarc oceanic basin.

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Section: Multichannel Seismic Datamentioning

confidence: 99%

Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

Bouyahiaoui¹,

Sage²,

Abtout³

et al. 2015

Geophysical Journal International

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“… Location map of the eastern Algerian margin and basin displaying the seismic lines used in this work. “L”: acquired by WesternGeco (2000‐2002; Cope, 2003); “SPI”: acquired during the SPIRAL Project (Graindorge et al., 2009), including five wide‐angle seismic profiles with positions of OBS; “ALE”: acquired by Total Company; “MS”: acquired by OGS (1972–1979 R/V Marsili, Finetti & Morelli, 1972) (see Data Repository for more details). …”

Section: Data Set and Methodsmentioning

confidence: 99%

“…Various datasets for this research are included in these papers and their supplementary information files: Datasets for this research are described in these papers: (Cope, 2003;https://doi.org/10.3997/1365-2397Finetti & Morelli, 1972;Graindorge et al, 2009;…”

Section: Data Availability Statementmentioning

confidence: 99%

“…For this study, we use mainly a set of deep penetrating seismic reflection lines (10 s TWT) designed to image the sedimentary units below the widespread Messinian salt including crust and Moho reflectors. These 2D multi-channel sections labeled "L" (Figure 5) have been recorded in the Algerian offshore by WesternGeco in -2002(Cope, 2003 using a sleeve tuned air gun array (3000 inch3) as a seismic source towed at 6 m depth. The shot points were spaced by 25 m, the processing sample interval is 4 ms and the processing record length is 10,000 ms.…”

Section: Seismic Datamentioning

confidence: 99%

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Back‐Arc Dynamics Controlled by Slab Rollback and Tearing: A Reappraisal of Seafloor Spreading and Kinematic Evolution of the Eastern Algero‐Balearic Basin (Western Mediterranean) in the Middle‐Late Miocene

et al. 2022

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“…The resulting seismic sections have a low resolution and high penetration owing to the low frequencies of the airguns tuned for combined wide-angle data (Figure 4A). We also use some industrial lines published in the last years, designed to image below the Messinian salt layer and the deepest layers of the crust and offering a relatively good lateral and vertical resolution (Figure 4B; Cope, 2003). Finally, some older seismic lines from the 1970s are used to improve the coverage of the margin and to tie the main reflectors from one line to another.…”

Section: Seismic Data Setsmentioning

confidence: 99%

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

Leffondré¹,

Déverchère²,

Medaouri

et al. 2021

Front. Earth Sci.

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Subduction initiation is an important but still poorly documented process on Earth. Here, we document one of a few cases of ongoing transition between passive and active continental margins by identifying the geometrical and structural signatures that witness the tectonic inversion of the Algerian continental margin and the deep oceanic domain, located at the northern edge of the slow-rate, diffuse plate boundary between Africa and Eurasia. We have analyzed and tied 7900 km of deep seismic reflection post-stacked data over an area of ∼1200 km long and ∼120 km wide. The two-way traveltime lines were converted into depth sections in order to reconstruct and map realistic geometries of seismic horizons and faults from the seafloor down to the acoustic basement. Along the whole length of this young transitional domain, we identify a clear margin segmentation and significant changes in the tectonic signature at the margin toe and in the deep basement. While the central margin depicts a typical thick- and thin-skinned tectonic style with frontal propagation of crustal thrust ramps, the central-eastern margin (Jijel segment) reveals a higher strain focusing at the margin toe together with the largest flexural response of the oceanic lithosphere. Conversely, strain at the margin toe is limited in the western margin but displays a clear buckling of the oceanic crust up to the Spanish margin. We interpret these contrasting, segmented behavior as resulting from inherited heterogeneities in (1) the geometry of the Algerian continental margin from West to East (wrench faulting in the west, stretched margin elsewhere) and (2) the Miocene thermal state related to the diachronous opening of the Algerian basin and to the magmatic imprint of the Tethyan slab tearing at deep crustal levels. The narrow oceanic lithosphere of the Western Algerian basin is assumed to favor buckling against flexure. From the dimension and continuity of the main south-dipping blind thrusts identified at the margin toe, we reassess seismic hazards by defining potential lengths for ruptures zones leading to potential magnitudes up to 8.0 off the central and eastern Algerian margins.

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Algerian licensing round may offer opportunity for exploration plays in deep offshore frontier

Cited by 19 publications

References 0 publications

Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

Crustal structure of the eastern Algerian continental margin and adjacent deep basin: implications for late Cenozoic geodynamic evolution of the western Mediterranean

Back‐Arc Dynamics Controlled by Slab Rollback and Tearing: A Reappraisal of Seafloor Spreading and Kinematic Evolution of the Eastern Algero‐Balearic Basin (Western Mediterranean) in the Middle‐Late Miocene

Ongoing Inversion of a Passive Margin: Spatial Variability of Strain Markers Along the Algerian Margin and Basin (Mediterranean Sea) and Seismotectonic Implications

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