A. C. López-Garrido

Nature and impact of the Neotectonic deformation in the western Sierra Nevada (Spain)

Abstract The current high relief of the western sector of the Sierra Nevada was practically nonexistent before the Tortonian, as attested by the marine Late Neogene outcrops that reach a height of 1830 m, which would easily surpass 2000 m if not for erosion. The significant uplift produced, over 3500 m, has caused considerable thinning, detachments and gravitational slides in the Alpujarride units. The general displacements of these movements are towards the WNW to SSW. On the whole, the morphology is fan-like, adapting itself to the border of the Sierra Nevada. This border contains normal conjugate NW–SE and N–S to NNE–SSW faults, the latter also with sinistral strike–slip character. These faults have accommodated the uplift of the Sierra Nevada within an almost N–S compressive context and linked E–W extension. This sector coincides with the western boundary of the Nevado-Filabride complex and, in its southern continuation, with the western limit of the lower Alpujarride units, seeming to indicate a fault (or faults) reaching deep into the basement. Uplift has taken place unevenly over the last few million years, with three noteworthy periods: during the deposition of the Block Formation in the Late Tortonian, towards the Early?–Middle Pleistocene, and in the Middle?–Late Pleistocene. This has resulted in considerable deepening of the fluvial net surrounding Sierra Nevada at the present time.

The Triassic palaeogeographic transition between the Alpujarride and Malaguide complexes. Betic–Rif Internal Zone (S Spain, N Morocco)

Abstract Various tectonic units situated between the Malaguide and Alpujarride complexes (in the Betic–Rif Internal Zone, S Spain and N Morocco) present Triassic successions sharing features of both complexes the presence of which indicates a transitional domain. These units (which we term Intermediate units) are situated preferentially near the external limit of the Betic–Rif Internal Zone, generally adapted to the shape of the Arc of Gibraltar. The palaeogeography of this area is reconstructed on the basis of the general geometric position of these units and their relationships with equivalent domains in the western Mediterranean, the scarce existing palaeomagnetic data and the directions of tectonic displacement. The most problematic reconstructions concern those units on the N border of the Betic–Rif Zone, as they have significant clockwise rotations (up to 200°), S and SE tectonic displacements, and a different geometric distribution from the rest of the units. We conclude that in general the transition between the Malaguide and Alpujarride complexes was gradual, the Malaguide domain located S of the Alpujarride, with the intermediate units lying, evidently, between the two complexes.

Ladinian carbonates of the Cabo Cope Unit (Betic Cordillera, SE Spain): a tethys-maláguide palaeogeographic gateway

SummaryThe Cabo Cope Unit, which outcrops east of Aguilas (Murcia), belongs to the Maláguide tectonic Complex (Betic Internal Zone) and displays stratigraphic characteristics of particular interest, including Triassic bioclastic carbonate beds which are not common in the Maláguide units. Biostratigrafic fossils have been found in these beds and may correlate with Triassic alpine biofacies. Alpine fauna fossils only appeared in those palaeogeographic units of the Internal Zone of the Cordillera referred to as Alpujárride units, while the influence of the Sephardic faunal province is evident in almost all the cordillera. For these reasons it is noteworthy that new alpine fauna fossils have been found in an Internal Zone unit in which relevant fossils rarely appear. The Triassic succession of the unit studied in this paper can be subdivided into two members: a lower one, which is clastic and contains thick gypsum beds, and an upper one, consisting of carbonate rocks. The lower member has been interpreted as a fluvial-coastal deposit. The upper member is interpreted as a sequence of carbonate ramp deposits. This ramp evolved into a shallow platform with tidal flats typical of a coastal zone. The bivalve fossilsDaonella cf.lommeli (Wissmann) and “Posidonia” sp. have been found in the carbonate member, along with the conodontSephardiella mungoensis (Diebel). These fossils are of the Late Ladinian age and have been found only in this outcroup of the Betic Cordillera. The presence of this fossil assemblage, which belongs to the alpine faunal province, indicates a connection during the Late Ladinian between the Tethys sea and this area of the Maláguide palaeogeographic domain. The palaeogeographic location of the Cabo Cope Unit during the Middle Triassic was at the south-easternmost part of the Betic Basin, implying that the connection between the Tethys and the Betic Basin was established in the easternmost domains of the basin.

The stratigraphic and tectonic relationships of the Alpujarride and Malaguide complexes in the western Betic Cordillera (Casares, prov. of Malaga, South Spain)

Abstract In the western Betic Cordillera, the Malaguide Complex does not constitute the stratigraphic cover of the Alpujarride Complex, as previously suggested by some authors. Instead, they form two separate complexes, although there is a palaeogeographic transition between the two complexes in the Casares area. The geological structure of this sector is formed by north-south tectonic sheets which originated during the thrusting of the Malaguide over the Alpujarride. They mainly verge to the east and show a gradual change in the stratigraphie series and metamorphic grade.

Regional correlations across the Internides-Externides front (northwestern Rif Belt, Morocco) during the Late Cretaceous-Early Burdigalian times: palaeogeographical and palaeotectonic implications

Abstract New insights into the palaeogeographical evolution of the Rifian Internides and their external surroundings are inferred from six key stratigraphic successions selected across the Internides-Externides front. These successions span a time interval ranging from the late Cretaceous to the early Burdigalian. The main results are: (1) important lost palaeogeographical domains should be located during the late Cretaceous-Eocene between the present-day Ghomarides and the Dorsale Calcaire, on one hand, and between the Predorsalian units and the Flysch Trough as isolated carbonate platforms, on the other hand; (2) during the late Eocene-early Oligocene an extensional tectonic event, well marked in the Dorsale Calcaire, caused the collapse of these platforms and resulted in olistostromes and coarse-grained breccias in both the Predorsalian and the Béni Ider areas; (3) by the beginning of mid-Oligocene, an overturning contractional event in the Ghomarides resulted in the regional onset of the siliciclastic depositional regime throughout these palaeogeographical areas; (4) during the Aquitanian-early Burdigalian, the stepwise return of pelagic deposition in the Ghomarides indicates extensional phases, whereas the homogenization of the same pelagic facies over the Dorsale Calcaire and its external surroundings may indicate that the previously distant palaeogeographical areas were brought nearer (i.e. just before large-scale thrusting).

Reply to the comment by A. G. Jones et al. on “Deep resistivity cross section of the intraplate Atlas Mountains (NW Africa): New evidence of anomalous mantle and related Quaternary volcanism”

[1] Scientific discussion and different points of view are a basis of the advancement of knowledge. We acknowledge the comments of Jones et al. [2012] as an opportunity to publicly discuss the structure and origin of the Atlas Mountains. Moreover, we welcome the opportunity to compare our results with those recently published by the group responsible for the comment [Ledo et al., 2011], although it is not pertinent to comment in detail on a paper published in another journal. We also wish to remark that the paper of Ledo et al. [2011] was reviewed and published during the revision period of our contribution [Anahnah et al., 2011]; therefore, they are two different approaches and data sets, measured in different sites and by different instruments for the same region, lending readers the chance to compare different interpretations. The main differences on the data sets are: the profile of Anahnah et al. [2011] compared with the profile of Ledo et al. [2011] is 170 km longer, vertical magnetic data were obtained and lower frequencies were recorded. [2] We regret the style and way used by Jones et al. [2012]. We shall answer only those comments of Jones et al. [2012] related to objective issues. [3] One of the final conclusions of Jones et al. [2012] might serve as the starting point of our reply:

Présence du complexe tectonique Malaguide à l'est de Carthagène (zone interne Bétique, Espagne)

Triassic materials belonging to the Malaguide Complex east of Cartagena are described for the first time. This is the easternmost Malaguide outcrop known and it overlies the Portman Alpujarride unit. Knowledge of this outcrop contributes to the palaeogeographic reconstruction of the Betic Internal Zone in an area where the Alpujarride Complex is considerably thinned due to stratigraphic and tectonic reasons.