TAPHONOMIC TOOLS TO EVALUATE SEDIMENTATION RATES AND STRATIGRAPHIC COMPLETENESS IN ROSSO AMMONITICO FACIES (EPIOCEANIC TETHYAN JURASSIC)

A combined multidisciplinary approach has been applied to calculate minimum values of the stratigraphic completeness and, secondarily, sedimentation rates in 9.2 m thick Rosso Ammonitico facies from central Apennines (Italy) and 11 m thick deposits of the same facies in Southern Spain. Middle - Upper Toarcian expanded sedimentation in Valdorbia section (Umbria-Marche Apennines) and extremely condensed Oxfordian-Tithonian sedimentation at Puerto Escaño section (External Subbetic) have been investigated using combined taphonomic, ichnologic and sedimentologic data and analyses. At Valdorbia, infaunal tiering is largely preserved and 27 horizons of infaunal-tiering truncation and casting reveal strong erosional activity forced by tempestite/turbidite events. Therefore, microstratigraphic gaps could be evaluated without biostratigraphic control. In this expanded section, 13 horizons of firm- and hardgrounds have been recorded showing simple or gradational tiering. Conversely, in the condensed Puerto Escaño section, taphonomic analysis reveals 25 horizons of bioclasts truncation (mainly in ammonites), and 56 horizons of firm-hardgrounds intensively bioturbated. In Valdorbia rather than in Puerto Escaño section, the evaluation of flattening in burrows and spherical bioclasts reveal a measurable mechanical compaction and dissolution. In addition, Rosso Ammonitico at Valdorbia section favoured the calculation of decompaction coefficients (nd) for each lithology easier than in Puerto Escaño section. In condensed and essentially hiatal Rosso Ammonitico, mottled deposits due to intense bioturbation dominate and tiering cannot be recognizable. This fact is accentuated by usual overprinting of elementary depositional events, which in turn hampered the accurate calculation of missing deposits. Therefore, in condensed Rosso Ammonitico the latter was only available in terms of minimal missing-record trough the analysis of truncated bioclasts.&nbsp

Itinerario paleontológico por el Cerro de la Cruz (Sierra del Reclot).

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Rasgos geológicos del Jurásico de la Sierra de Reclot (Alicante)

Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUEpu

Rasgos morfológicos e icnológicos de la superficie erosiva del límite Messiniense-Plioceno (Sierra del Colmenar, Alicante). Relación con la crisis de salinidad del Mediterráneo

The Messinian/Pliocene boundary in the Sierra del Colmenar (Alicante) is represented by an erosional surface called the end-Messinian unconformity. This erosional surface cuts the coastal and lagoonal deposits of the late Messinian (Terminal Complex) as a result of the sea-level fall related to the salinity crisis in the centre of the Mediterranean. The beginning of the subsequent transgresion during the lower Pliocene is registered by an erosive surface that carved the underlying Messinian deposits. This surface morphology and trace fossil colonization is controlled by the substrate characteristics. Thus, onto consistent calcareous substrates it is developed coastal palaeocliffs colonized by Trypanites icnofacies, meanwhile on the marly substrates there is no abrupt palaeocliffs with icnofacies of Skolithos colonization. The enhancing Pliocene reflooding was recorded by the sedimentation of coastal and shallow marine deposits over the erosive surface

Asociaciones de foraminíferos bentónicos y evolución paleoambiental del Plioceno inferior en el sector de Elche-Crevillente (Cuenca del Bajo Segura, Alicante): Resultados preliminares

Benthic foraminifer assemblages of two Early Pliocene sections located between Elche and Crevillente are studied. In both sucessions three stratigraphic units are distinguished: P0 Unit, littoral conglomerates (transgressive lag); P1 Unit, pelagic marl-dominated interval; and P2 Unit, shallow marine calcarenites. Benthic foraminifers in the P1 and P2 Units are grouped in three main paleoecological categories: shallow water euryhaline (A), intermediate water (B), and deep water stenohaline (C). Distribution trends in these paleoecological groups, planctonic/benthonic ratios, and sedimentological data permit the reconstruction of the Early Pliocene paleoenvironmental evolution of this area. End-Messinian unconformity corresponds to an incissed valley, subsequently filled with Early Pliocene marls (P1). The acommodation space reduction determined the progressive decrease of the planctonic and the deep water stenohaline benthic foraminifers

Tectonic framework and extensional pattern of the Malaguide Complex from Sierra Espuña (Internal Betic Zone) during Jurassic-Cretaceus: implications for the Westernmost Tethys geodynamic evolution.

Mapping, lithostratigraphic, biostratigraphic and structural detailed analyses in Sierra Espuña area (Internal Betic Zone, SE Spain) have allowed us to reconstruct the Jurassic–Cretaceous evolution of the Westernmost Mesomediterranean Microplate palaeomargin and, by correlation with other sectors (Northern Rift, central and western Internal Betic Zone), to propose a geodynamic evolution for the Westernmost Tethys. Extension began from Late Toarcian, when listric normal faults activated; these faults are arranged in three categories: large-scale faults, separating hectometric cortical blocks; main faults, dividing the former blocks into some kilometre-length blocks; and secondary faults, affecting the kilometric blocks. This fault ensemble, actually outcropping, in the Sierra Espuña area, broke the palaeomargin allowing the westerly Tethyan Oceanic aperture with an extension at about 17.2%. Extension was not homogeneous in time, being the Late Toarcian to the Dogger–Malm boundary the period when blocks underwent the greatest movement (rifting phase), leading to the drowning of the area (8.2% extension). During the Malm (drifting phase) extension followed (5.7%), while during the Cretaceous a change to pelagic facies is recorded with an extension of about 3.3% ( post-drift stage). This evolution in the Westernmost Tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low-angle fault of the rifting.Peer reviewe