Francisco J. García-Tortosa

Seismically induced slump on an extremely gentle slope (<1°) of the Pleistocene Tecopa paleolake (California)

A superbly exposed ∼5 km 2 slump is developed in middle Pleistocene lacustrine deposits of the Tecopa Basin (California, United States). A subhorizontal detachment (

Tectonic units from the Sierra Espuña-Mula area (SE Spain): implication on the triassic paleogeography and the geodynamic evolution for the Betic-Rif Internal Zone.

Tectonic units of the Sierra Espuña-Mula area are described in order to characterize the palaeogeographic passage from the Alpujarride to the Malaguide Complexes through the “intermediate units”. Moreover, the Meso-Cenozoic cover of the Malaguide units in this area show the transition from the Malaguide to the “Internal Dorsal”. Both features are relevant for the palaeogeographic reconstruction and geodynamic evolution of the Betic-Rif Internal Zone (BRIZ) in the framework of the Alpine Perimediterranean Chains. These data, together with others from other sectors of the Betic-Rif Cordillera enable us to propose a palaeogeography during the Triassic rifting with two subsident areas related to two oceanic branches (the Nevadofilabride-Alpujarride to the north, and the Maghrebian, to the south) separated by a continent or shallow marine area (the Malaguide). These branches were closed during post-rifting geodynamic evolution including two different piling phases: a first top-to-the-north in the northern branch (Alpine tectogenesis, Latest Cretaceous-Middle Oligocene); a second top-to-the-south in the southern branch (Maghrebian tectogenesis, Late Oligocene-Early Miocene). The opposite arrangement of units in the Betic with respect to the Rif required clockwise rotations to form the Gibraltar Arc, confirmed by data from the literature. These rotations are related to the westward displacement and subsequent collision of the BRIZ against the African and Iberian palaeomargins.

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.

Seismic-Induced Landslides: Lessons Learned from Recent Earthquakes in Spain

On February 23, 2015, an earthquake of magnitude Mw 4.7 (Imax = V, scale EMS) struck the center of the Spain, triggering dozens of instabilities in taluses and natural slopes of an area characterized by low relief. These instabilities were characterized by: (1) very small size, most of them with volumes lower than 1 m3, and (2) to occur in rock masses affected by multiple discontinuities, which pre-defined blocks that fell down during the shaking. The inventory of instabilities of this earthquake has shown that most of the instabilities occurred on the slopes of the road network, although the larger instabilities were observed in natural slopes. The comparative analysis of this inventory with those made for other recent earthquakes occurred in the SE of Spain (1999, 2002, 2005 and 2011), all of them of similar magnitude Mw (between 4.7 and 5.1), allow to recognize that the vast majority of instabilities induced by these earthquakes were rock/soil falls, being other typologies of landslides very rare. In all cases, the size of instabilities triggered were small, usually with volumes of 1 m3 or less, reaching the larger volumes up to 500–1000 m3. Data available from these events point out that large landslides, as known in relation with historical earthquakes in Spain, cannot be induced by moderate to low magnitude earthquakes. Besides, slope morphology seems to control the location of induced instabilities. Thus, when the terrain is steep, as in the area affected by the earthquake in Lorca (2011, Mw 5.1), most of instabilities occur in natural slopes and affect the upper part of slopes. As the relief is less rugged, natural slopes instabilities are progressively less frequent until the extreme case of the 2015 event, when instabilities were located mostly on slopes of the road network.

New data from Orihuela and Callosa Mountains (Betic Internal Zone, Alicante, SE Spain). Implications for the “Almágride Complex” controversy

En este trabajo presentamos los resultados del estudio estratigrafi co y estructural de las sierras de Orihuela y Callosa (provincia de Alicante, SE de Espana), pertenecientes ambas a la Zona Interna Betica. Estas sierras fueron asignadas por autores precedentes al Complejo Ballabona-Cucharon, mas tarde redefi nido como Almagride. Los datos presentados en este trabajo nos llevan a proponer una nueva serie estratigrafi ca, division tectonica y evolucion geodinamica del sector estudiado. Asi mismo, asignamos las unidades reconocidas a la parte inferior del Complejo Alpujarride, confi rmando que el Complejo Almagride no debe ser considerado como elemento singular de la Zona Interna Betica.