Structural evolution of the '41st parallel zone': Tyrrhenian Sea

The present study is based on the interpretation of more than 1300 km of 16 kJ sparker seismic profiles recorded in July 1990, during the Cruise T-41 of the Geological Institute of Urbino. The investigated area extends along the 41st parallel in the central Tyrrhenian Sea between the northern Sardinian margin to the west and the Latium–Campanian margin to the east. This zone, situated on continental crust, marks the boundary between the northern Tyrrhenian and the southern Tyrrhenian domains. A kinematic reconstruction is presented, based on the age-dating of the recognized structures (i.e. normal faults, reverse faults, anticline and flower structures). The evolution of the ‘41st parallel zone’ can be described in terms of polyphase tectonics characterized by different orientations of the stress field during time. The direction of the normal fault-trends, turned clockwise, striking NE–SW in the late Tortonian–Messinian, E–W in the early Pliocene, NNW–SSE in the late Pliocene and N–S during the Quaternary. The concurrence of compressional and strike-slip deformations suggests oblique shear motions across the 41st parallel. The occurrence of late Pliocene–Quaternary tectonic activity in the northern Tyrrhenian Sea, locally characterized by inversion tectonics, suggests active mechanisms (intraplate compression?) superimposed on the post-rift subsidence.     

Mantle source heterogeneity in subduction zones: constraints from elemental and isotope (Sr,Nd, and Pb) data on Vulcano Island,Aeolian Archipelago,Italy

Mineralogy and Petrology - Vulcano is part of the Aeolian volcanic arc in the southern Tyrrhenian Sea. Its products were emplaced through multiple episodes of edifice building and collapse since...     

Growth of the Afanasy Nikitin seamount and its relationship with the 85°E Ridge,northeastern Indian Ocean

The Afanasy Nikitin seamount (ANS) is a major structural feature (400 km-long and 150 km-wide) in the Central Indian Basin, situated at the southern end of the so-called 85°E Ridge. Combined analyses of new multibeam bathymetric, seismic reflection and geochronological data together with previously described magnetic data provide new insights into the growth of the ANS through time, and its relationship with the 85°E Ridge. The ANS comprises a main plateau, rising 1200 m above the surrounding ocean floor (4800 m), and secondary elevated seamount highs, two of which (lie at 1600 and 2050 m water depths) have the morphology of a guyot, suggesting that they were formed above or close to sea-level. An unbroken sequence of spreading anomalies 34 through 32n.1 identified over the ANS reveal that the main plateau of the ANS was formed at 80–73 Ma, at around the same time as that of the underlying oceanic crust. The ⁴⁰Ar/³⁹Ar dates for two basalt samples dredged from the seamount highs are consistent, within error, at 67 Ma. These results, together with published results of late Cretaceous to early Cenozoic Indian Ocean plate reconstructions, indicate that the Conrad Rise hotspot emplaced both the main plateau of the ANS and Conrad Rise (including the Marion Dufresne, Ob and Lena seamounts) at 80–73 Ma, close to the India–Antarctica Ridge system. Subsequently, the seamount highs were formed by late-stage volcanism c. 6–13 Myr after the main constructional phase of the seamount plateau. Flexural analysis indicates that the main plateau and seamount highs of the ANS are consistent with Airy-type isostatic compensation, which suggest emplacement of the entire seamount in a near spreading-center setting. This is contrary to the flexural compensation of the 85°E Ridge further north, which is interpreted as being emplaced in an intraplate setting, i.e., 25–35 Myr later than the underlying oceanic crust. Therefore, we suggest that the ANS and the 85°E Ridge appear to be unrelated as they were formed by different mantle sources, and that the proximity of the southern end of the 85°E Ridge to the ANS is coincidental.     

SHRIMP U–Pb zircon dating of a metagabbro and eclogites from western Dabieshan (Hong''an Block), China, and its tectonic implications

The Tyrrhenian Sea is a Neogene back-arc basin formed by continental extension at the rear of the eastward migrating Apennine subduction system. Its central part, generated from Tortonian to Pliocene, includes the Sardinia rifted margin to the west, an area with large volcanoes in the deep central sector, and the Campania rifted margin to the east. A reprocessing of some 2000 km of MCS lines, a new swath bathymetric map, and a review of previous geological and geophysical data allow to analyse the nature and distribution of continental vs. oceanic crust in this area, which evolved in a short time span.The central portion of the southern Tyrrhenian Sea is characterized by MOHO at about 10 km depth. North of Magnghi and Vavilov Smts, this thinned crustal domain include a wide continent–ocean transition, with the occurrence of extensional allochthons and of serpenitinzed sub-continental mantle, recalling other well known rifted margins, as the Iberia one. Sectors floored by oceanic crust should occur, mainly in the southern part of the study area, but they do not appear related to discrete spreading ridges. The continent–ocean boundary cannot be drawn unequivocally in the area, due also to the occurrence of widespread and huge magmatic manifestations not related to oceanic spreading. These portions of the southern Tyrrhenian Sea represents therefore a complex oceanic back-arc basin surrounded by magma-rich rifted continental margins.The abundant igneous manifestations and the very high stretching rates observed in the area may be related to the fact that the present Tyrrhenian area was occupied by an orogenic domain affected by shortening until middle Miocene times, which is just before the Late Miocene onset of back-arc extension. The lithosphere in the region had then to be rheologically weak. Abundant generation and ascent of magmas, mostly of Ocean Island Basalt type, was favoured by the large lithospheric permeability induced by strong extensional deformations.     

Chronology of the transition from a spreading ridge to an accretional seamount in the Marsili backarc basin (Tyrrhenian Sea)

Inversion of new high-resolution magnetic data from the Marsili seamount and the surrounding basin in the Tyrrhenian Sea reveals NNE–SSW magnetization stripes ranging from the Matuyama chron to the Brunhes chron, including the short positive Jaramillo subchron. The detailed magnetic chronology shows that from the late Matuyama (1.77 Ma), the average half spreading rate was about 1.5 cm yr⁻¹, with a slight decrease between the Jaramillo and the Brunhes events, when the growth of the volcanic edifice overcame lateral spreading. Analysis of spreading rate and volume of erupted lava indicates that at the beginning of the Jaramillo subchron (1.07 Ma), the Marsili basin evolved from pure horizontal spreading to a superinflated seamount as a consequence of tearing of the Ionian slab. Our data give us a snapshot of the geodynamic transition from an active backarc spreading phase to the vertical accretion of the seafloor because of a radical change in the subduction dynamics.     

Structural features in the Dead Sea-Jordan rift zone, interpreted from a combined magnetic-gravity study

The results of a combined analysis of aeromagnetic and gravity data covering the rift and adjacent areas show two different deep structural models: (a) Across the northern and central portions of the rift zone the crustal thickness and the character of the upper mantle remain unchanged. On the other hand, the lithology of the upper crust varies laterally so that the mafic composition of the rock type probably increases from east to west. (b) The southern portion of the rift may be underlain by an anomalous, low-density upper mantle.

Local negative gravity anomalies within the rift zone delineate deep depressions, separated by structural highs. The Dead Sea depression is interpreted to be filled by 7.5 km of young, low-density sediments.

Local magnetic anomalies which cover the northern portion only are interpreted as basalt flows. This approach enables delineation of fault patterns which support the classic view of sinistral strike slip movement along a complicated fault system.     

Stress modeling to determine the through-going active fault geometry of the Western North Anatolian Fault,Turkey

The North Anatolian Fault (NAF) is a 1200 km long dextral strike-slip fault which is part of an east-west trending dextral shear zone (NAF system) between the Anatolian and Eurasian plates. The North Anatolian shear zone widens to the west, complicating potential earthquake rupture paths and highlighting the importance of understanding the geometry of active fault systems. In the central portion of the NAF system, just west of the town of Bolu, the NAF bifurcates into the northern and southern strands, which converge, then diverge to border the Marmara Sea. At their convergence east of the Marmara Sea, these two faults are linked through the Mudurnu Valley. The westward continuation of these two fault traces is marked by further complexities in potential active fault geometry, particularly in the Marmara Sea for the northern strand, and towards the Biga Peninsula for the southern strand. Potential active fault geometries for both strands of the NAF are evaluated by comparing stress models of various fault geometries in these regions to a record of focal mechanisms and inferred paleostress from a lineament analysis. For the Marmara region, the best-fit active fault geometry consists of the northern and southern bounding faults of the Marmara basin, as the model representing this geometry better replicated primary stress orientations seen in focal mechanism data and stress field interpretations. In the Biga Peninsula region, the active geometry of the southern strand has the southern fault merging with the northern fault through a linking fault in a narrow topographic valley. This geometry was selected over the other two as it best replicated the maximum horizontal stresses determined from focal mechanism data and a lineament analysis.     

Structural development of the Neogene Radicondoli–Volterra and adjoining hinterland basins in Western Tuscany (Northern Apennines,Italy)

This paper presents a geological–structural study of some Neogene hinterland basins of the Northern Apennines, located on the Tyrrhenian side of the chain. These basins developed on the already delineated thrust-fold belt from middle–late Tortonian times. Their evolution has been commonly referred to an extensional tectonic regime, related to the opening of the Tyrrhenian Sea. New data have allowed us to hypothesize a different tectonic evolution for the chain, where compressive tectonics plays a major role both in the external and in the hinterland area. In this frame, the hinterland area located west of a major outcropping crustal thrust (Mid-Tuscany Metamorphic Ridge) has been the target of a geological–structural investigation. The field mapping and structural analysis has been focused on the syntectonic sediments of the Radicondoli–Volterra basin as well as on adjoining minor basins. These basins commonly display a synclinal structure and are generally located in between basement culminations, probably corresponding to thrust anticlines. Sediments of the hinterland basins have been affected by compressive deformation and regional unconformities separate stratigraphic units due to the activity of basement thrusts. In the study area, normal faulting either accommodates the thrusting processes or post-dates compressive deformation. A chronology of faulting and a six-stage evolution of this area are presented, providing further insights for the Neogene tectonic evolution of the Northern Apennines. Copyright © 1998 John Wiley & Sons, Ltd.     

Analyses of Aeromagnetic Data to Delineate Basement Structures and Reveal Buried Igneous Bodies in Kaladgi Basin,Karnataka

Aeromagnetic data overcome constrain of inadequate exposures and provide signatures of bodies beneath sediment cover. Present work on analysis of aeromagnetic data over western part of Kaladgi basin provided insight into the basement structures and their role in basin evolution. In the study area, the NW-SE and NE-SW are the major trends of magnetic lineament followed by E-W and N-S trends.Archean to Paleoproterozoic basement is manifested by two structural zones, NW-SE trends related to major lineaments within the basement and the NE-SW trends presumed intra-basinal fault systems which controlled the local depressions. The basin configuration deduced from depth to basement show that the Kaladgi basin is an open deep basin and divided into several sub-basins, separated by fault-controlled NE-SW and NW-SE oriented basement ridges. An intriguing find in the western part are the numerous scattered smaller-scale, circular or semicircular, distinct magnetic anomalies of moderate to strong magnetic signal with strong remenance. Analyses coupled with 3D inversions in combination with sub-surface probing reveal in-homogeneities within basement gneisses and supracrustal rocks of the Kaladgi basin, Dharwar craton. 3D inversions of these circular bodies, suggest that they are apophyses of the intrusions or alternatively as younger intrusive stocks. Sub-surface probing by boreholes over circular bodies revealed leucocratic granite with porphyritic texture emplaced as intrusive within the Chitradurga metasediments. This implies that these intrusives are post-Chitradurga schist and pre Badami sediments as they have not affected the latter. However, they can be presumed to be coeval to potassic granites, which intrude the eastern part of the western Dharwar craton in southern India, until geochronological data are available.     

Pre-Quaternary orogen-parallel extension in the Southern Apennine belt, Italy

The Southern Apennine fold and thrust belt differs from other parts of the peri-Tyrrhenian orogen. In most of the peri-Tyrrhenian belt, hinterland extension is oriented at a high-angle to the orogen axis and appears to be related to rifting and formation of oceanic crust within the Tyrrhenian basin. The Southern Apennines share the late-stage development of normal faults related to the opening of the Tyrrhenian Sea, but also experienced an episode of extension parallel to the strike of the tectonic belt. The orogen-parallel extension was apparently formed in response to the increase in length of the deformed belt during arcuation. Arcuation ostensibly was related to asymmetrical rifting in the hinterland, which was greater in the Southern Tyrrhenian Sea than in areas to the north, and proportionately greater shortening in the frontal parts of the southern belt as compared to regions in the north. During arcuation, extension was spatially concentrated within structural domains and was accomplished by displacement on low-angle detachment faults cutting through a previously imbricated thrust stack. During the Miocene-Pliocene, NNW-SSE extension in the interior of the Southern Appennine belt formed coveally with ENE-WSW shortening in the foreland. Longitudinal extension ceased in the Pleistocene, when younger high-angle normal faults formed in response to the easterly migration of Tyrrhenian Sea rifting and NE-SW extension associated with lithospheric stretching.     

Types of crust beneath the Ligurian Sea

The structural setting beneath the Ligurian Sea resuJts from several tectonic events reflected in the nature of the crust. The central-western sector, called the Ligurian basin, is part of the northwestern Mediterranean. It is a marginal basin that was generated in Oligocene-Miocene time by subduction of the Adriatic plate beneath the European plate and by the eastward drift of the Corsica-Sardinia block. The eastern sector belongs to the Tyrrhenian basin system and is characterized by extensional activity which since Tortonian time superimposed an earlier compressional regime. Our effort has been addressed in particular towards simplifying the complex nature of the crust of the Ligurian basin by modelling its genesis using uniform extension and sea-floor depth variation with age. In the rift stage of the basin's evolution, the initial subsidence reaches the isostatic equilibrium level of the asthenosphere by a thinning factor of 3.15. The additional passive process, corresponding to the cooling of the lithosphere since 21 Ma, leads to a total tectonic subsidence of 3.4 km, representing the boundary of the extended continental crust. For values up to 4.1 km a transitional-type crust is expected, whereas for higher tectonic subsidence values a typical oceanic crust should exist. After setting these constraints, the boundaries of the different crust types have been drawn based on total tectonic subsidence observations deduced from bathymetry and post-rift sediment thickness. Although there is a general agreement with the previous reconstructions deduced from other experimental data, the oceanic realm has wider extent and more complex shape. The northernmost part of this realm shows crust of sub-oceanic type altemating basement highs with lower subsidence values. The observed surface heat flux is consistent with the predicted geothermal held in the Alpine-Provençal continental margin and in the oceanic domain. However, a characteristic thermal asymmetry is clearly visible astride the basin, due to the enhanced heat flux of the Corsica margin. Even if the uniform extension model accounts well at a regional level for the present basement depth, a remarkable tectonic subsidence excess has been found in the Alpine-Provençal continental margin. This evidence agrees with the reprise in compression of the margin; the direction of the greatest principal stress is N120°E on average.     

The Tyrrhenian back－arc basin and subduction of the Ionian lithosphere

A deep, narrow, and distorted Benioff zone, plunging from the Ionian Sea towards the southern Tyrrhenian basin, is the remnant of a long and eastward migrating subduction of eastern Mediterranean lithosphere. From Oligocene to Recent, subduction generated the Western Mediterranean and the Tyrrhenian back-arc basins, as well as an accretionary wedge constituting the SouthernAoenninic Arc.In the Tyrrhenian Sea, stretching started in late Miocene and eventually produced two small oceanic areas: the Vavilov Plain during Pliocene (in the centralsector) and the Marsili Plain during Quaternary (in the southeastern sector). They are separated by a thicker crustal sector, called the Issel Bridge. Back-arc exten-sion was rapid and discontinuous, and affected a land locked area where continental elements of various sizesoccurred. Discontinuities in extension were mirrored bychanges in nature of the lithosphere scraped off to form the Southern Apenninic Arc. Part of the tectonic units of the southern Apennines, accreted into the wedge from late Miocene to Pliocene, had originally been laid down on thinned conti-nental lithosphere, which should constitute the deep portion of the present slab. After Plio-cene, only Ionian oceanic lithosphere wassubducted, because the large buoyancy of thewide and not thinned continental lithosphere of Apulia and Africa (Sicily) preserved the seelements from roll back of subduction. After Pliocene, the passively retreating oceanic slabhad to adjust and distort according to the geometry of these continental elements.The late onset of arc volcanism in respect to the duration of extension in the Tyrrhenian-Ionian system may find an expla-nation considering an initial stage of subduc-tion of thinned continental lithosphere. The strong Pleistocene vertical movements that occurred in the whole southeastern system(subsidence in the back-arc basin and upliftin the orogenic arc) may instead be related to the distortion of the oceanic slab.     

Heat flow and geodynamics in the Tyrrhenian Sea

The present heat flow in the southern Tyrrhenian Sea appears as a transient thermal wave that has migrated eastward in time. The higher heat flow in the south‐eastern side of the basin confirms the suggestion of an eastward‐migrating rift. Punctuation of the Tyrrhenian backarc extension in lithospheric boudins is accompanied by a concentrated increase in heat flow generated by asthenospheric intrusions and related magmatism progressively moving eastward. The migration of the asthenosphere in the same direction could explain these phenomena.     

Quantitative subsidence-uplift analysis of the Bajo Segura Basin (eastern Betic Cordillera, Spain): tectonic control on the stratigraphic architecture

The Bajo Segura Basin is located in the eastern Betic Cordillera, at present connected with the Mediterranean Sea to the east. It has a complete stratigraphic record from the Tortonian to the Quaternary, which has been separated into six units bounded by unconformities. This paper is concerned with the northern edge of the basin, controlled by a major strike–slip fault (the Crevillente Fault Zone, CFZ), where the most complete stratigraphic successions are found. The results obtained (summarised below) are based on an integrated analysis of the sedimentary evolution and the subsidence-uplift movements. Unit I (Early Tortonian) is transgressive on the basin basement and is represented by ramp-type platform facies, organised in a shallowing-upward sequence related to tectonic uplift during the first stages of movement along the CFZ. Unit II (lower Late Tortonian) consists of shallow platform facies at bottom and pelagic basin facies at top, forming a deepening-upward sequence associated with tectonic subsidence due to sinistral motion along the CFZ. Unit III (middle Late Tortonian) is made up of exotic turbiditic facies related to a stage of uplift and erosion of the southern edge of the basin. Unit IV (upper Late Tortonian) consists of pelagic basin facies at bottom and shallow platform facies at top, defining a shallowing-upward sequence related to tectonic uplift during continued sinistral movement on the basin-bounding fault. Units V (latest Tortonian–Messinian) and VI (Pliocene–Pleistocene p.p.) consist of shallowing-upward sequences deposited during folding and uplift of the northern margin of the basin. No definitive evidence of any major eustatic sea-level fall, associated with the ‘Messinian salinity crisis’, has been recorded in the stratigraphic sections studied.     

Expansion of the South China Sea basin: Constraints from magnetic anomaly stripes,sea floor topography,satellite gravity and submarine geothermics

The widely distributed E–W-trending magnetic anomaly stripes in the central basin and the N–E-trending magnetic anomaly stripes in the southwest sub-basin provide the most important evidence for Neogene expansion of the South China Sea. The expansion mechanism remains, however, controversial because of the lack of direct drilling data, non-systematic marine magnetic survey data, and irregular magnetic anomaly stripes with two obvious directions. For example, researchers have inferred different ages and episodes of expansion for the central basin and southwest sub-basin. Major controversy centers on the order of basinal expansion and the mechanism of expansion for the entire South China Sea basin. This study attempts to constrain these problems from a comprehensive analysis of the seafloor topography, magnetic anomaly stripes, regional aeromagnetic data, satellite gravity, and submarine geothermics. The mapped seafloor terrain shows that the central basin is a north-south rectangle that is relatively shallow with many seamounts, whereas the southwest sub-basin is wide in northeast, gradually narrows to the southwest, and is relatively deeper with fewer seamounts. Many magnetic anomaly stripes are present in the central basin with variable dimensions and directions that are dominantly EW-trending, followed by the NE-, NW- and NS-trending. Conversely such stripes are few in the southwest sub-basin and mainly NE-trending. Regional magnetic data suggest that the NW-trending Ailaoshan-Red River fault extends into the South China Sea, links with the central fault zone in the South China Sea, which extends further southward to Reed Tablemount. Satellite gravity data show that both the central basin and southwest sub-basin are composed of oceanic crust. The Changlong seamount is particularly visible in the southwest sub-basin and extends eastward to the Zhenbei seamount. Also a low gravity anomaly zone coincides with the central fault zone in the sub-basin. The submarine geothermic distribution demonstrates that the southwest sub-basin has a higher geothermal value than the central basin, and that the central fault zone is defined by a low thermal anomaly. This study suggests that NW–SE expansion of the southwest subbasin is later than the N–S expansion of the central basin with the sub-basin extending into the central basin and with both expansions ending at the same time. The expansion of southwestern sub-basin, similar to the Japanese Sea, is likely caused by left-lateral strike slip on the central fault zone in the South China Sea, which may have significance for finding oil and gas in this region.     

http://www.sciencedirect.com/science/article/pii/S1674987114001133

A chronological study of seamount rocks in the South China Sea basin provides a great opportunity to understand the expansion and evolution history of the sea basin. In this paper, we analyzed the 40Ar...     

Neogene patterns of relative plate motion for Africa-Europe: some implications for recent central Mediterranean tectonics

A detailed relative motion picture for the Neogene Africa-Europe plate kinematics is presented. The kinematic reconstruction was carried out using the finite difference solution between the rotation parameters determined for Anomalies 7 to 2 in the Africa-North America-Europe plate motion circuit. The analysis shows a motion of Africa with respect to Europe which is NNE directed during Late Oligocene to Burdigalian times, becoming NNW trending from the Langhian to the early Tortonian; from upper Tortonian times onward, the motion changes to a clear north-west directed convergence. Major Late Neogene tectonic features of the central Mediterranean region can, to a large extent, be explained within the context of the reconstructed major plate motions. Late Tortonian to Recent Africa-Europe slip vectors are compatible with a variety of geological phenomenoa such as north-west directed subduction beneath Calabria, south-east translation of Calabria and extension in the Tyrrhenian Sea, north-west trending slip vectors from thrust earthquakes between Gibraltar and Sicily, and dextral strike-slip across the North African margin.     

http://www.sciencedirect.com/science/article/pii/S1674987111001009

The North Yellow Sea Basin is a Mesozoic and Cenozoic basin.Based on basin-margin facies,sedimentary thinning,size and shape of the basin and vitrinite reflectance.North Yellow Sea Basin is not a residual basin.Analysis of the development of the basin’s three structural layers,self-contained petroleum systems,boundary fault activity,migration of the Mesozoie—Cenozoic sedimentation centers, different basin structures formed during different periods,and superposition of a two-stage extended basin and one-stage depression basin,the North Yellow Sea Basin is recognized as a superimposed basin.     

Magmatism of the Weddell Sea rift system in Antarctica: Implications for the age and mechanism of rifting and early stage Gondwana breakup

Thick (∼800 m) basaltic successions from the eastern Antarctic Peninsula have been dated in the interval 180–177 Ma and preserve a transition from a continental margin arc to a back-arc extensional setting. Amygdaloidal basalts from the Black Coast region of the eastern margin of the Antarctic Peninsula represent a rare onshore example of magmatism associated with back-arc extension that defines the early phase of Weddell Sea rifting and magmatism, and Gondwana breakup. The early phase of extension in the Weddell Sea rift system has previously been interpreted to be related to back-arc basin development with associated magnetic anomalies attributed to mafic-intermediate magmatism, but with no clearly defined evidence of back-arc magmatism. The analysis provided here identifies the first geochemical evidence of a transition from arc-like basalts to the development of depleted back-arc basin basalts in the interval 180–177 Ma. The exposed Black Coast basaltic successions are interpreted to form a minor component of magmatism that is also defined by onshore sub-ice magnetic anomalies, as well as the extensive magnetic anomalies of the southern Weddell Sea. Back-arc magmatism is also preserved on the Falkland Plateau where intrusions postdating 180 Ma are associated with early phase rifting in the Weddell Sea rift system. Back-arc extension was probably short-lived and had ceased by the time the northern Weddell Sea magmatism was emplaced (<175 Ma) and certainly by 171 Ma, when an episode of silicic magmatism was widespread along the eastern Antarctic Peninsula. Previous attempts to correlate mafic magmatism from the eastern Antarctic Peninsula to the Ferrar large igneous province, or, as part of a bimodal association with the Chon Aike silicic province are both dismissed based on age and geochemical criteria.     

Magnetostratigraphy of the Ouarzazate Basin: Implications for the timing of deformation and mountain building in the High Atlas Mountains of Morocco.

Two magnetostratigraphic profiles (450 samples) have been carried out to constrain the age of synorogenic formations in the southern foreland of the High Atlas of Morocco. The Amekchoud profile covers the Aït Ouglif and Aït Kandoula alluvial formations that form the bulk of the Ouarzazate basin fill, indicating an age between the upper Langhian and the Messinian (Miocene). Data obtained in the previously unexplored Hadida formation profile covers the oldest terms of the foreland basin succession, but the low quality of the magnetic record only allows proposing a tentative age between the middle Lutetian and an undetermined middle to late Eocene. The correlation of the Amekchoud profile is based on the recognition of the long C5n chron (Tortonian) in the middle part of the section studied and a new vertebrate locality of upper Tortonian age found in the upper part. These results indicate a discontinuous record of foreland basin development in the southern Atlas domain from mid Eocene to late Miocene times, punctuated by an intermediate large hiatus of 20-25 ma (late Eocene to mid Miocene). Thrusting in the Sub-Atlas frontal thrust belt began before the Aït Ouglif and Kandoula formations, probably during the Oligocene, and extends up to recent times. The alternation of periods of deposition with others of no sedimentary record, which does not coincide with specific tectonic events, results probably from the interference of orogenic deformation and the mantle-related thermal uplift events that have been described for the Moroccan Atlas.