José Enrique Tent-Manclús

Paleoenvironmental changes during the late Miocene (Messinian)–Pliocene transition (Bajo Segura Basin, southeastern Spain): Sedimentological and ichnological evidence

ABSTRACT A detailed sedimentological and paleontological analysis of the uppermost Miocene (Messinian)–Pliocene boundary at the northern border of the Bajo Segura Basin, southeastern Spain, was carried out in order to describe the evolution of the regional paleocoastline during the Pliocene reflooding of the Mediterranean immediately after the sea-level fall related to the Messinian Salinity Crisis. Multiple trace fossils typical of firm- and hardgrounds were recognized, allowing identification of Glossifungites (two different types), Entobia, and Gnathichnus ichnofacies. Trace-fossil analysis showed that lithology and media consistency exerted considerable control on the development of the different ichnocoenoses and that there was a clear decrease in hydrodynamic energy from a coastal to a shallow-water shelf environment related to progressive sea-level rise. Ichnological and sedimentological data provide evidence that the definitive flooding of the Mediterranean was rapid and synchronous throughout the northern margin of the Bajo Segura Basin. The following model for the Pliocene transgression in the study area is therefore proposed: (1) the marine ingression penetrated along the incised paleovalleys carved as a consequence of the fall in sea level, where the first two Pliocene systems were deposited (P0–P1); (2) during the maximum flooding surface of the transgression, the sea overflowed the margins of the paleovalleys and extended throughout the entire northern margin of the basin; and (3) the third Pliocene system was deposited, forming the lower part of a highstand systems tract (P2).

Lower Jurassic brachiopods from the Ibero-Levantine Sector (Iberian Range): Faunal turnovers and critical bioevents

Brachiopod fauna from the peri-Iberian platform system is well-known in the Late Pliensbachian-Toarcian interval. However, the diversity dynamics and the stratigraphical distribution of this group in the Ibero-Levantine Sector of the Iberian Range require more accurate analysis due to the patchy distribution of the outcrops. The abovementioned timespan involved a period of changes in long-term environmental conditions which led to a severe extinction and critical turnovers on the brachiopod fauna (ETMEE). The Ibero-Levantine sector has notable palaeobiogeographical significance as it represents the south-easternmost outcrops of the Iberian Range connecting with the Betic Domain positioned in the South-Iberian Palaeomargin. In this region, the brachiopod fauna has been arranged into six assemblages, showing a discontinuous stratigraphic distribution since its diversity dynamics is markedly conditioned by the extinction phases linked to the ETMEE: Ass. 1, recorded in the Spinatum-lower Tenuicostatum chronozones; Ass. 2, mainly recorded in the Tenuicostatum chronozone; Ass. 3, typifying the lower Serpentinum chronozone; Ass. 4, documented in the Serpentinum-lowermost Bifrons chronozones; Ass. 5, recorded in the Bifrons-Variabilis chronozones, and Ass. 6, distinctive of the Pseudoradiosa-Aalensis chronozones. The faunal succession shows strong affinities with the Euro-Boreal province, what rules out the transitional or even Mediterranean palaeogeographical affinity previously attributed to the southernmost part of this area. Amidst the main brachiopod-based bioevents must be considered the predominance of the genus Lobothyris in the pre-ETMEE assemblages, the conspicuous record of Liospiriferina? undulata , distinctive taxon of the north-African margin and, especially, the first record in the Iberian Peninsula of thecideid marker beds prior to the ETMEE. After the opportunistic strategy conducted by Soaresirhynchia bouchardi the distribution of the post-ETMEE brachiopod assemblages is markedly influenced by the depositional sequences, entailing premature turnovers and involving the earlier record of homeomorphic morphotypes of younger terebratulides and rhynchonellides

Evaluating Taphonomic Bias in a Storm-Disturbed Carbonate Platform: Effects of Compositional and Environmental Factors in Lower Jurassic Brachiopod Accumulations (Eastern Subbetic Basin, Spain)

ABSTRACT In order to evaluate taxonomic and environmental control on the preservation pattern of brachiopod accumulations, sedimentologic and taphonomic data have been integrated with those inferred from the structure of brachiopod accumulations from the easternmost Lower Jurassic Subbetic deposits in Spain. Two brachiopod communities (Praesphaeroidothyris and Securina communities) were distinguished showing a mainly free-lying way of life in soft-bottom habitats. Three taphofacies are discriminated based on proportion of disarticulation, fragmentation, packing, and shell filling. Taphofacies 1 is represented by thinly fragmented, dispersed brachiopod shells in wackestone beds. Taphofacies 2 is spatially restricted to small lenses where shells are poorly fragmented, rarely disarticulated, usually void filled, and highly packed. Taphofacies 3 is represented by mud or cement filled, loosely packed, articulated brachiopods forming large pocket-like structures. Temporal and spatial averaging were minimally involved in taphofacies 2 and 3. It is interpreted that patchy preservation implies preservation of primary original patchiness of brachiopod communities on the seafloor. The origin of shell-rich taphofacies (2 and 3) is related to rapid burial due to episodic storm activity, while shell-poor taphofacies 1 records background conditions. The nature and comparative diversity of these taphofacies underscores the importance of rapid burial for shell beds preservation. Differences in preservation between taphofacies 2 and 3 are mainly related to environmental criteria, most importantly storm energy and water depth. In contrast, the taxonomic-specific pattern of the communities is a subordinate element of control, controlling only minor within-taphofacies differences in preservation.

New evidence of nearshore Mid-Triassic Zoophycos : morphological and paleoenvironmental characterization

Zoophycos is a well-known trace fossil common throughout the Phanerozoic. Paleozoic forms show important differences in morphology and habitat distribution with respect to the Jurassic, Cretaceous, and Cenozoic ones. Therefore, Early–Middle Triassic is considered a crucial time-span for the understanding of the evolution of this trace fossil. So far, Early Triassic Zoophycos is unknown and Middle Triassic forms were recorded only in deposits from Thuringia. The morphology and paleoenvironment of Zoophycos from the middle–upper Muschelkalk of the Iberian Range is herein described. The best-preserved trace fossils occur in a dolomicritic bed Ladinian in age, and are represented by small forms with a subcircular, slightly lobed outline and very little penetration depth. They were deposited in a very shallow, quiet-water environment with transition to supratidal/emerged areas. The low diversity of both trace fossils and skeletal remains point to stressful conditions related to strong salinity variations and/or poor water circulation. A comparison was made with Zoophycos from Anisian deposits of the Muschelkalk in Germany. This showed that both forms are quite simple and penetrate only the shallowest tiers, although they are different in whorl outline and lobe shape. This confirms that, notwithstanding the morphological variability of this group, Zoophycos still maintained a quite simple structure in the Triassic. A shallow-water environment was deduced for both localities, confirming that at least until the Early Jurassic Zoophycos had not definitively migrated toward deep-water areas.

Brachiopod assemblages from the Early-Middle Jurassic transition in the Eastern Subbetic (SE Spain): Systematic and palaeobiogeographic implications and palaeoenvironmental significance

This research has been supported by the Synthesys Project (HU-TAF 3036) of the European Union and the Project CGL2009-07830 of MCI (Spain). A. Dulai was supported by the Hungarian Scientific Research Fund (OTKA K77451).

New paleobiogeographical and paleoenvironmental insight through the Tortonian brachiopod and ichnofauna assemblages from the Mediterranean-Atlantic seaway (Guadix Basin, SE Spain)

The paleogeography of the Late Neogene Atlantic-Mediterranean seaway via the Betic-Rifean Domain is quite complex due to the presence of several marine corridors. The study of transitional basins in these seaways is crucial to understand the configuration and evolution of the Mediterranean-Atlantic inter-connection. A mixed skeletal-siliciclastic sandstone succession located in one of these transitional areas (Guadix Basin, Southern Spain) was studied from a comprehensive paleontological standpoint focused on the main benthic assemblages (foraminifera, brachiopods, and trace fossils), integrating the data with the study of planktic foraminifera for an accurate biostratigraphic framework. Brachiopods are mostly represented by the Aphelesia-Gryphus assemblage. Two trace fossil assemblages were observed, dominated by Ophiomorpha with Bichordites (1) and Macaronichnus (2), respectively. The benthic foraminiferal assemblage is mostly represented by Planulina and Cibicides. The data gathered from the benthic communities reveal habitats with high-energy and turbulent conditions in an outer neritic-upper bathyal bathymetric range. Brachiopods from the Alicún section show a Mediterranean paleobiogeographic affinity. They were constrained in the Late Tortonian to the restricted basins of the Betic-Rifean Seaway and after the Messinian Salinity Crisis proliferated in both Mediterranean- and Atlantic-type basins of the Betic-Rifean Domain. The Guadix Basin contributed to the Mediterranean-Atlantic faunal inter-connection through the Betic-Rifean Seaway during the Late Tortonian and facilitated the earliest Pliocene expansion of brachiopods in the Mediterranean.