Alboran Sea Region Research Articles

Genomics reveals the role of admixture in the evolution of structure among sperm whale populations within the Mediterranean Sea.

In oceanic ecosystems, the nature of barriers to gene flow and the processes by which populations may become isolated are different from the terrestrial environment, and less well understood. In this study we investigate a highly mobile species (the sperm whale, Physeter macrocephalus) that is genetically differentiated between an open North Atlantic population and the populations in the Mediterranean Sea. We apply high-resolution single nucleotide polymorphism (SNP) analysis to study the nature of barriers to gene flow in this system, assessing the putative boundary into the Mediterranean (Strait of Gibraltar and Alboran Sea region), and including novel analyses on structuring among sperm whale populations within the Mediterranean basin. Our data support a recent founding of the Mediterranean population, around the time of the last glacial maximum, and show concerted historical demographic profiles in both the Atlantic and the Mediterranean. In each region there is evidence for a population decline around the time of the founder event. The largest decline was seen within the Mediterranean Sea where effective population size is substantially lower (especially in the eastern basin). While differentiation is strongest at the Atlantic/Mediterranean boundary, there is also weaker but significant differentiation between the eastern and western basins of the Mediterranean Sea. We propose, however, that the mechanisms are different. While post-founding gene flow was reduced between the Mediterranean and Atlantic populations, within the Mediterranean an important factor differentiating the basins is probably a greater degree of admixture between the western basin and the North Atlantic and some level of isolation between the western and eastern Mediterranean basins. Subdivision within the Mediterranean Sea exacerbates conservation concerns and will require consideration of what distinct impacts may affect populations in the two basins.

Shellfish collection on the westernmost Mediterranean, Bajondillo cave (∼160-35 cal kyr BP): A case of behavioral convergence?

The Middle (MP) and Early Upper Paleolithic (EUP) evidences of shellfish collection on the southern Iberian site of Bajondillo cave are presented and compared with Westernmost Mediterranean archaeological sites. The main feature is stasis for Mytilus galloprovincialis represents the dominant taxon during a ∼120kyr temporal sequence. The second feature is the decrease of the shellfishing signal when site distance to the coast increases. The data reveal that shellfish collection was practiced during Marine Isotopic Stage 4, a poorly documented stage in terms of aquatic adaptations. Striking is also that mollusc assemblages evidence an uninterrupted decreasing trend in terms of remains from the earliest to the latest levels, in particular when H. sapiens replaced H. neanderthalensis. Although taxa of secondary importance are too scarce to make reliable inferences, another difference between the MP and EUP collections is the substantial increase of infaunal bivalves in the latter cultural period. Warm and cold water mollusc records match temperature rises and drops although the scarcity of data do not allow one to proceed beyond qualitative statements. Likewise, the prevalence of fresh and brackish water mollusc hint at a permanent presence of freshwater around the site at all times. When compared with assemblages from the Alboran sea region (Westernmost Mediterranean Sea), the Bajondillo cave collections are remarkable for their abundance of mussels. Comparison between Bajondillo cave and Pinnacle Point reveal that infaunal bivalve abundances in the South African site are far higher than those recorded in the MP levels, though not those from the EUP. Whether this feature hints at subtle differences existing between the collection of shellfish by H. sapiens and H. neanderthalensis, reflects a behavioral convergence between the two hominine lineages or represents an inherited cognitive trait from a common ancestor is an issue in need of further analysis.

The Al Hoceima earthquake sequence of 1994, 2004 and 2016: Stress transfer and poroelasticity in the Rif and Alboran Sea region

The Al Hoceima earthquake sequence of 1994, 2004 and 2016: Stress transfer and poroelasticity in the Rif and Alboran Sea region

A high-resolution hydrodynamic-biogeochemical coupled model of the Gulf of Cadiz – Alboran Sea region.

The southern Iberia regional seas comprise the Gulf of Cadiz and the Alboran Sea sub-basins connected by the narrow Strait of Gibraltar. Both basins are very different in their hydrological and biological characteristics but are, also, tightly connected to each other. Integrative studies of the whole regional oceanic system are scarce and difficult to perform due to the relative large area to cover and the different relevant time-scales of the main forcings in each sub-basin. Here we propose, for the first time, a fully coupled, 3D, hydrodynamic-biogeochemical model that covers, in a single domain (~2km resolution) both marine basins for a 20 years simulation (1989-2008). Model performance is assessed against available data in terms of spatial and temporal distributions of biological variables. In general, the proposed model is able to represent the climatological distributions of primary and secondary producers and also the main seasonality of primary production in the different sub-regions of the analyzed basins. Potential causes of the observed mismatches between model and data are identified and some solutions are proposed for future model development. We conclude that most of these mismatches could be attributed to the missing tidal forcing in the actual model configuration. This model is a first step to obtain a meaningful tool to study past and future oceanographic conditions in this important marine region constituting the unique connection of the Mediterranean Sea with the open world’s ocean.

Multiple-frequency tomography of the upper mantle beneath the African/Iberian collision zone

During the Cenozoic, the geodynamics of the western Mediterranean domain has been characterized by a complex history of subduction of Mesozoic oceanic lithosphere. The final stage of these processes is proposed to have led to the development of the Calabria and Gibraltar arcs, whose formation is still under debate. In this study, we take advantage of the dense broad-band station networks now available in the Alboran Sea region, to develop a high-resolution 3-D tomographic P velocity model of the upper mantle beneath the African/Iberian collision zone that will better constraint the past dynamics of this zone. The model is based on 13200 teleseismic arrival times recorded between 2008 and 2012 at 279 stations for which cross-correlation delays are measured with a new technique in different frequency bands centred between 0.03 and 1.0 Hz, and for the first time interpreted using multiple frequency tomography. Our model shows, beneath the Alboran Sea, a strong (4 per cent) fast vertically dipping anomaly observed to at least 650 km depth. The arched shape of this anomaly, and its extent at depth, are coherent with a lithospheric slab, thus favouring the hypothesis of a westward consumption of the Ligurian ocean slab by roll-back during Cenozoic. In addition to this fast anomaly in the deep upper mantle, high intensity slow anomalies are widespread in the lithosphere and asthenosphere beneath Morocco and southern Spain. These anomalies are correlated at the surface with the position of the Rif and Atlas orogens and with Cenozoic volcanic fields. We thus confirm the presence, beneath Morocco, of an anomalous (hot?) upper mantle, but without clear indication for a lateral spreading of the Canary plume to the east.

New evidence of delamination in the Western Alboran Sea: Geodynamic evolution of the Alboran domain and its margins

The presence of continuous upper crustal blocks between the Iberian Betics and Moroccan Rif in the western and middle Alboran Sea, detected with tomography, can add new information about the lithosphere structure and geodynamic evolution in this region. A large volume of seismic data (P and S wave arrival times) has been collected for the period between 1 December 1988 and 31 December 2008 by 57 stations located in northern Morocco (National Institute of Geophysics, CNRST, Rabat), southern Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) and used to investigate the lithosphere in the western Alboran Sea region. We use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocenters and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure imaged at 5km depth for the Tanger peninsula, the Alhoceima region and southern Spain. At 15, 30 and 45km depth we observe a near true structure imaged in northern Morocco, and southern Spain. At 60 and 100km, southern Spain and the SW region of the Alboran Sea give a near true structure. The resulting tomographic image shows the presence of two upper crustal bodies (velocity 6.5km/s) at 5–10km depth between the Betics, Rif, western and central Alboran Sea. Low velocities at the base of these two bodies favor the presence of melt. This new evidence proves that the Tethysian ocean upper crust was not totally collapsed or broken down during the late Oligocene–early Miocene. These two blocks of upper crust were initially one block. The geodynamic process in the eastern of the Mediterranean is driven by slab rollback. The delamination process of the lithospheric mantle terminates with the proposed slab rollback in the western part of the Mediterranean. This can be explained by the removal of the major part of the lithosphere beneath the area, except in the SW part of the Alboran Sea where a small part of the lithospheric mantle is still attached and is extends and dips to SE beneath the Rif, slowly peeled back to the west. A second detached lithospheric mantle is located and extends to eastern part of the Rif and dips to the SE. The removal of lithosphere mantle from the base of the crust was replaced and heated by extrusion of asthenospheric material coming from depth to replace the part of crust detached. A combination of isostatic surface/topographic uplift and erosion induced a rapid exhumation and cooling of deep crustal rocks.

Receiver function images of the base of the lithosphere in the Alboran Sea region

We analyse data from seismic stations surrounding the Alboran Sea between Spain and North Africa to constrain variations of the lithosphere-asthenosphere boundary (LAB) in the region. The technique used is the receiver function technique, which uses S-to-P converted teleseismic waves at the LAB below the seismic stations. We confirm previous data suggesting a shallow (60-90 km) LAB beneath the Iberian Peninsula and we observe a similarly shallow LAB beneath the Alboran Sea where the lithosphere becomes progressively thinner towards the east. A deeper LAB (90-100 km) is observed beneath the Betics, the south of Portugal and Morocco. The structure of the LAB in the entire region does not seem to show any indication of subduction related features. We also observe good P receiver function signals from the seismic discontinuities at 410 and 660 km depth which do not indicate any upper-mantle anomaly beneath the entire region. This is in agreement with the sparse seismic activity in the mantle transition zone suggesting the presence of only weak and regionally confined anomalies.

Active surface deformation and sub-lithospheric processes in the western Mediterranean constrained by numerical models

Research Article| September 01, 2010 Active surface deformation and sub-lithospheric processes in the western Mediterranean constrained by numerical models Eugénie Pérouse; Eugénie Pérouse 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Search for other works by this author on: GSW Google Scholar Philippe Vernant; Philippe Vernant 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Search for other works by this author on: GSW Google Scholar Jean Chéry; Jean Chéry 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Search for other works by this author on: GSW Google Scholar Robert Reilinger; Robert Reilinger 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Simon McClusky Simon McClusky 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Eugénie Pérouse 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Philippe Vernant 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Jean Chéry 1Laboratoire Géosciences Montpellier CNRS (Centre National de la Recherche Scientifique)-Université Montpellier 2, 34095 Montpellier, France Robert Reilinger 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Simon McClusky 2Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Publisher: Geological Society of America Received: 14 Dec 2009 Revision Received: 20 Apr 2010 Accepted: 27 Apr 2010 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2010 Geological Society of America Geology (2010) 38 (9): 823–826. https://doi.org/10.1130/G30963.1 Article history Received: 14 Dec 2009 Revision Received: 20 Apr 2010 Accepted: 27 Apr 2010 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Eugénie Pérouse, Philippe Vernant, Jean Chéry, Robert Reilinger, Simon McClusky; Active surface deformation and sub-lithospheric processes in the western Mediterranean constrained by numerical models. Geology 2010;; 38 (9): 823–826. doi: https://doi.org/10.1130/G30963.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We present the results of dynamic modeling of the western Mediterranean that accounts for observed global positioning system (GPS) surface deformation of the Alboran Sea and surrounding Rif and Betic Mountains as the result of the combined effects of relative motion of the Eurasian and Nubian plates, low strength in the Alboran Sea region and sub-lithospheric processes occurring beneath the External Rif domain. Assuming that the lithosphere behaves elastically over the short time period of the GPS observations, an elastic plate model is considered in our study, including an area of weak lithosphere (factor of 10) centered on the Alboran Sea and in which lateral boundary conditions consist of the Nubia-Eurasia oblique convergence. Sub-crustal processes are modeled by application of a horizontal traction on a small area (patch) at the base of the elastic plate. Our modeling studies demonstrate the need for sub-crustal or sub-lithospheric, southwestward-directed forcing to account for observed southwestward motion of the Rif and Betic domains. Based on the location, orientation, and small area of the traction patch, we hypothesize that forcing is associated with delamination and rollback of the subducted African continental lithospheric mantle beneath the External Rif zone, due to the pull of the oceanic part of the Western Mediterranean slab, a dynamic process that may be similar to that where the over-riding plate is driven toward the subduction zone during slab rollback. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Asymmetric Delamination and Convective Removal Numerical Modeling: Comparison with Evolutionary Models for the Alboran Sea Region

Convective removal and mantle delamination are geodynamical mechanisms proposed to explain the presence of extension in the Alboran Sea within a regional context of compression. Using a new thermomechanical algorithm, we present here a quantitative evaluation and comparison of conceptual models based on these geodynamical mechanisms. In contrast to the in situ convective removal process, the laterally propagating delamination mechanism is shown here to be consistent with first-order features of the Alboran Sea such as the thinning/thickening distribution, intermediate-depth seismicity and upper mantle structure imaged by seismic tomography. The lower crust is predicted to reach depths of 100–150 km in some areas, due to mechanically-driven viscous drag of the downwelling mantle.

Mantle structure under Gibraltar constrained by dispersion of body waves

We study the Africa‐Iberia plate boundary in the vicinity of Gibraltar. Numerous models have been proposed for that region throughout the last decades, proposing mechanisms that range widely from continental delamination, convective removal, to subduction of oceanic lithosphere. To better constrain upper‐mantle structure under the region, we study waveforms of P‐waves that traverse the Alboran Sea region between Spain and Morocco. These show dispersive behavior, which, together with early arrival times, confirms the presence of an anomalous upper mantle structure under the Alboran Sea. The dispersion is consistent with that expected from subducted lithosphere. Waveforms of body waves therefore provide a way to better constrain the elusive mantle structure and dynamics of the Alboran Sea region.

Active tectonics of the western Mediterranean: Geodetic evidence for rollback of a delaminated subcontinental lithospheric slab beneath the Rif Mountains, Morocco

Surface deformation in Morocco, derived from five years of global positioning system (GPS) survey observations of a 22-station network, four continuously recording GPS (CGPS) stations, and four International GNSS Service (IGS) stations in Iberia, indicates roughly southward motion (∼3 mm/yr) of the Rif Mountains, Morocco, relative to stable Africa. Motion of the Rif is approximately normal to the direction of Africa-Eurasia relative motion, which is predominantly strike slip, and results in shortening of the Rif and subsequent crustal extension of the adjacent Alboran Sea region. The sense, and the N-S asymmetry of the observed deformation (i.e., no evidence for north-directed shortening in the Betic Mountains north of the Alboran Sea) cannot be easily explained in terms of crustal plate interactions, suggesting that dynamic processes below the crust are driving the recent geologic evolution of the western Mediterranean. The model that best fits the observations involves delamination and southward rollback of the African lithospheric mantle under the Alboran and Rif domains.

Seismic tomography of the crust and lithospheric mantle in the Betic Cordillera and Alboran Sea

The Alboran Domain lies between the South of Spain and the North of Morocco and contains a Miocene extensional basin which formed during continuous compression between the African and Eurasian plates. We have performed a 1-D and 3-D passive velocity tomography study of the structure of the crust and lithospheric mantle of the Betic Cordillera and Alboran Sea region. An important drawback encountered in most passive seismic tomography studies is that the quality of the data set used is inhomogeneous and it is often impossible to measure the error. This occurs as the data set needs to be very large which implies using several years’ worth of data from different seismic networks with different station noise levels and phase travel time picking accuracy. We present a simple method to quantitatively determine the errors in the travel time data typically used in passive seismic tomography studies. We use this method to determine the standard error of our data set and present the tomography results with quantitatively determined error bars. An additional advantage of performing the error analysis is that the data can be weighted in terms of its standard error, and hence the contribution of noisy data can be reduced in the inversion, resulting in substantially enhanced tomography images. The main structural results obtained in the 1-D inversion of the data are: (1) the average velocity of the crust in the Betic Cordillera is V p=6.0±0.05 km/s and V s=3.5±0.05 km/s, indicating an average V p/ V s ratio of 1.71 for the crust. (2) The average Moho depth in the Betic Cordillera is less than 36 km. (3) The average crustal velocity in the Alboran Sea is V p=6.4±0.1 km/s and V s=3.4±0.2 km/s, indicating an average V p/ V s ratio of 1.88 for the crust. (4) The average depth of the Moho in the Alboran Sea is greater than 20 km. The 3-D inversion provides new structural information of the Alboran basin over the depth range 24–60 km. For the depth range 24–31 km we image the centre and north western margin of the basin and observe velocities of the order of 7.2–7.5±0.45 km/s, which could correspond to lower crust material or else anomalous low velocity mantle material. For the depth range 31–40 km we image the centre and the southern margin of the basin and observe P phase velocities of 8.0–8.2±0.55 km/s which we interpret as normal mantle material. Below this layer, in the depth range 40–60 km we image the centre and northern margin of the basin and observe low P velocities ( V p=7.8±0.55 km/s). At present the preferred model used to explain the formation of the Alboran Sea Basin makes use of the process of Lithospheric Delamination. The low velocity layer observed in the mantle starting at approximately 40 km depth could be interpreted to be hot mantle material or the asthenosphere, however, the normal mantle velocities observed in the 31–40 km layer above it do not support replacement of the lithosphere by hot asthenospheric material in the lower crust or immediately beneath the crust. If this is so, then delamination must have occurred within the lithospheric mantle at an approximate depth of 40 km, or else not occurred at all.

Propagation of regional seismic phases (Lg and Sn) and Pn velocity structure along the Africa-Iberia plate boundary zone: tectonic implications

We used over 1000 regional waveforms recorded by 60 seismic stations located in northwest Africa and Iberia to map the efficiency of L g and Sn wave propagation beneath the Gulf of Cadiz, Alboran Sea and bounding Betic, Rif and Atlas mountain belts. Crustal attenuation is inferred from the tomographic inversion of L g/Pg amplitude ratios. Upper mantle attenuation is inferred from maps of Sn propagation efficiency derived by inversion of well-defined qualitative efficiency assignments based on waveform characteristics. Regions of L g attenuation correlate well with areas of thinned continental or oceanic crust, significant sedimentary basins, and lateral crustal variations. Comparison of the Sn efficiency results with velocities obtained from an anisotropic Pn traveltime inversion shows a fairly good correlation between regions of poor Sn efficiency and low Pn velocity. A low Pn velocity (7.6–7.8 km s−1 ) and significant Sn attenuation in the uppermost mantle is imaged beneath the Betics in southern Spain, in sharp contrast to the relatively normal Pn velocity (8.0–8.1 km s−1 ) and efficient Sn imaged beneath the Alboran Sea. Slow Pn velocity anomalies are also imaged beneath the Rif and Middle Atlas in Morocco. We do not identify any conclusive evidence of lithospheric-scale upper mantle attenuation beneath the Rif, although the crust in the Gibraltar region appears highly attenuating, making observations at stations in this region ambiguous. Paths crossing the Gulf of Cadiz, eastern Atlantic and the Moroccan and Iberian mesetas show very efficient Sn propagation and are imaged with high Pn velocities (8.1–8.2 km s−1 ). The spatial distribution of attenuation and velocity anomalies lead us to conclude that some recovery of the mantle lid beneath the Alboran Sea must have occurred since the early Miocene episode of extension and volcanism. We interpret the low-velocity and attenuating regions beneath the Betics and possibly the Rif as indicating the presence of partial melt in the uppermost mantle which may be underlain by faster less attenuating mantle. In the light of observations from other geophysical and geological studies, the presence of melt at the base of the Betic crust may be an indication that delamination of continental lithosphere has played a role in the Neogene evolution of the Alboran Sea region.

Geodynamic evolution of the lithosphere and upper mantle beneath the Alboran region of the western Mediterranean: Constraints from travel time tomography

A number of different geodynamic models have been proposed to explain the extension that occurred during the Miocene in the Alboran Sea region of the western Mediterranean despite the continued convergence and shortening of northern Africa and southern Iberia. In an effort to provide additional geophysical constraints on these models, we performed a local, regional, and teleseismic tomographic travel time inversion for the lithospheric and upper mantle velocity structure and earthquake locations beneath the Alboran region in an area of 800×800 km2. We picked P and S arrival times from digital and analog seismograms recorded by 96 seismic stations in Morocco and Spain between 1989 and 1996 and combined them with arrivals carefully selected from local and global catalogs (1964–1998) to generate a starting data set containing over 100,000 arrival times. Our results indicate that a N‐S line of intermediate‐depth earthquakes extending from crustal depths significantly inland from the southern Iberian coast to depths of over 100 km beneath the center of the Alboran Sea coincides with a W to E transition from high to low velocities imaged in the uppermost mantle. A high‐velocity body, striking approximately NE‐SW, is imaged to dip southeastwards from lithospheric depths beneath the low‐velocity region to depths of ∼350 km. Between 350 and 500 km the imaged velocity anomalies become more diffuse. However, pronounced high‐velocity anomalies are again imaged at 600 km near an isolated cluster of deep earthquakes. In addition to standard tomographic methods of error assessment, the effects of systematic and random errors were assessed using block shifting and bootstrap resampling techniques, respectively. We interpret the upper mantle high‐velocity anomalies as regions of colder mantle that originate from lithospheric depths. These observations, when combined with results from other studies, suggest that delamination of a continental lithosphere played an important role in the Neogene and Quaternary evolution of the region.

Active continental subduction beneath the Betic Cordillera and the Alborán Sea

P- and S-wave seismic tomography detect a low-velocity anomaly in the upper mantle beneath the Betic Cordillera and the Alboran Sea region. The anomaly is associated with the intermediate-depth seismicity (h

P‐wave tomographic images in the Central Betics‐Alborán Sea (South Spain) using local earthquakes: Contribution for a continental collision

To investigate the relationship between shallow and intermediate‐depth earthquakes and the crust and upper mantle structure beneath the Betic‐Cordillera and Alborán sea region, we have applied seismic tomography to 2569 P‐wave arrival times from 367 microearthquakes recorded by both permanent and temporary seismic stations deployed in the region. These earthquakes occurred in the depth range of 0 to 110 km beneath the Central Betic Cordilleras and Alborán sea. Our results have revealed significant structural heterogeneities in the crust and upper mantle beneath the study area. In the upper crust there is a high‐velocity anomaly at Sierra Gorda (western boundary of the Granada basin) penetrating to 15 km depth, which is in good agreement with the aeromagnetic anomaly. In the Granada basin, a low‐velocity anomaly is located in the middle crust, which coincides with a previously detected greater cutoff depth of seismicity, and are considered to be associated with a highly fractured zone generated by an intracrustal detachment. The northern boundary of the Alborán sea (Málaga coast) is well imaged as low velocities from 50 to 90 km depths. This low‐velocity zone in the upper mantle is associated with the intermediate‐depth seismicity, which outline a section of continental crust related to the collision/subduction beneath the northern part of the Alborán sea‐southern part of the Central Betics.

Three‐dimensional upper mantle structure beneath the intraplate Atlas and interplate Rif mountains of Morocco

We integrate observations based on teleseismic P wave travel times and available geologic data to infer that the lithosphere beneath the intraplate Atlas mountains is thin and/or it is characterized by lower P wave velocities, while beneath the interplate Rif mountains and the adjacent Alboran Sea a previously thickened lithosphere has been delaminated into the upper mantle. Using surface geology and geochronology data, previous studies have proposed that lithospheric delamination took place in this region. In this study we show through analysis of teleseismic P wave residuals the existence of a high‐velocity (>3%) upper mantle body, which is interpreted to be the delaminated, rigid lithosphere. This high‐velocity layer is overlain by a very low velocity uppermost mantle material (Pn velocities of about 7.6–7.7 km s−1) interpreted to be asthenospheric material replacing the delaminated lithosphere. Teleseismic P waves recorded by a recently installed digital seismic network and an older analog network in Morocco provide the residuals database. A total of 734 P wave residuals from 92 selected teleseismic earthquakes are used to document the spatial pattern of upper mantle velocity structure beneath northern Morocco and the Alboran Sea. Subsequent use of these residuals in a tomographic inversion scheme produced a three‐dimensional velocity image of the upper mantle. We infer from the P residuals that strong upper mantle velocity anomalies exist beneath both the Rif and Atlas regions. The Rif stations show negative residuals (∼1–1.5 s) for ray paths from the east and northeast and show positive residuals (∼1–1.5 s) for ray paths from the northwest and southwest. Tomographic results indicate the existence of a high‐velocity body (∼3% higher velocities) in the upper mantle beneath the eastern Rif and Alboran Sea, extending approximately from subcrustal depths down to a depth of at least 350 km. In the western Rif, however, 1–2% lower velocity material is imaged in the upper mantle. The residuals of the Atlas stations also show azimuthal variations. In general, most of the P waves that travel beneath the High and Middle Atlas have about 0.5–1.0 s delays. In contrast, the rays that travel beneath the northwestern margin of the Atlas mountains and the adjacent Moroccan Meseta area show negative residuals (∼1 s), suggesting that higher velocity material exists beneath the platform area adjacent to the Atlas mountains. Tomographic results indicate that beneath most of the Atlas system the uppermost mantle has about 1% lower velocities. Beneath the Alboran Sea region, however, reported low uppermost mantle Pn velocities contrast strongly with higher velocity upper mantle velocities obtained by our analysis. Low‐velocity uppermost mantle beneath the Alboran Sea underlain by a high‐velocity upper mantle material is used to support earlier interpretations of lithospheric delamination beneath the Rif and Alboran Sea regions. The enigmatic occurrence of subcrustal earthquakes in these regions is also consistent with this active delamination mechanism.