Raúl de la Horra

New ichnites from the Middle Triassic of the Iberian Ranges (Spain): paleoenvironmental and paleogeographical implications

The Iberian Basin or its present-day expression, the Iberian Ranges, was refilled with red bed sediments of alluvial origin during the late Olenekian–Anisian period represented by the Cañizar (Olenekian–Anisian) and Eslida (Anisian) Formations, both commonly known as Buntsandstein facies. In the late part of the Anisian, the Tethys Sea reached the eastern side of the Iberian microplate, represented by the shallow marine facies of the Landete and Cañete Formations, also called Muschelkalk facies. The ichnites studied in this paper belong to the Anisian continental-marine transition in the SE Iberian Ranges. The Cañizar Formation shows the oldest Triassic footprints found in the Iberian Peninsula, consisting in swimming, uncomplete lacertoid three digit Rhynchosauroides traces with possibly resting (cubichnia) and furrowing (pascichnia) Cruziana/Rusophycus due to large triopsids. Specimens from Lacertoïd and Crocodiloïd groups have been collected in the Eslida Formation. Rhynchosauroides sp. is the most representative ichnospecies of the first group, while in the Crocodiloïd group, the presence of Chirotherium barthii Kaup 1835 and Isochirotherium cf coureli (Demathieu 1970) are distinctive. In the Landete Formation specimens are found from Crocodiloïd and Dinosauroïd groups. Brachychirotherium gallicum Willruth 1917, Brachychirotherium sp. and Chirotherium sp. are characteristic of the first one, and ‘Coelurosaurichnus’ perriauxi and cf Paratrisauropus latus as the most representative of the second group. Some of the specimens described here present ancestors in the Early Triassic and have been described in the Triassic of North America, Italy and France. Possible paleogeographical connections with faunas of SE France can be inferred. Based on different sedimentary structures and plant remains, the footprints are related to fluvial systems within huge flood plains, playa and shallow marine environments, with alternating dry and wet periods. The vertical ichnites distribution during the Anisian shows that the fauna modification was weak at a high clade level. In the Triassic of the Iberian microplate, there are no findings of traces prior to the Anisian, and the footprint content for the Middle Triassic is less diversified than in other neighbouring regions. By comparison with other western Pangea areas, there was a later appearance of the forms after the end-Permian mass extinction event in the studied area.

The Karstic Habitat of Spelaeogriphaceans from the Las Hoyas Fossil Site (Upper Barremian, Serranía de Cuenca, Spain)

Fossil remains of spelaeogriphaceans (Family Acadiocarididae) are common in Las Hoyas Konservat-Lagerstatte (upper Barremian, La Huerguina Formation, southwestern Iberian Basin), although they belong to an extremely rare group in the fossil record. They have been interpreted as having inhabited karstic environments as do their contemporaneous equivalents; however, this interpretation has not been clearly proven. Based on tectonic, sedimentological, geochemical, and palaeontological data, the aim of this work is to explore the evidence for active karst processes contemporaneous with Barremian sedimentation in order to support the palaeoecological hypothesis, and to shed further light on the reconstruction of the palaeogeographical evolution of the basin.

Palynostratigraphy of the Middle Triassic (Anisian) Eslida Formation, SE Iberian Ranges, Spain

ABSTRACT The Triassic record in the SE Iberian Ranges starts with two tecto-sedimentary units of continental origin in Buntsandstein facies: and Cañizar and Eslida Formations. The Eslida Formation always lies conformably on top of the Cañizar Formation and it grades upwards into overlying coastal mud flats, traditionally assigned to the Röt facies. In the past, accurate dating of the Eslida Formation was problematic because of its continental character, absence of datable fossil remains, and lithological similarities with Middle—Upper Permian rocks. Macroflora and fossilised vertebrate footprints in the Eslida Formation indicate an Anisian age (Middle Triassic). In this work, we date the Eslida Formation on the basis of a palynological assemblage. The precise dating of the Eslida Formation is essential in order to establish stratigraphical correlations with other units in the Iberian Ranges and to obtain palaeogeographical considerations on the rapid subsidence represented by the sedimentary record of this unit in the new NNE—SSE Middle Triassic rift developed in eastern Iberia.

Sedimentology, clay mineralogy and palaeosols of the Mid-Carnian Pluvial Episode in E Spain: insights into humidity and sea-level variations

This study examines rainfall variations of the Mid-Carnian Pluvial Episode (CPE) based on the continental fluvial sedimentology, palaeosol and clay mineralogy records of the Stable Meseta (eastern Spain). In the formation examined, the Manuel Fm or K2 Fm, the CPE is represented by three regressive–transgressive sequences, or subunits K2.1, K2.2 and K2.3, from base to top. Each subunit broadly consists of a genetic stratigraphic sequence bearing well-developed highstand, lowstand and transgressive systems tracts. Hydromorphic features in the palaeosols suggest changes in the activity of both groundwater and surface water. The clay mineral assemblage is dominated by illite, with a minor presence of kaolinite and traces of smectite in some samples. After ruling out tectonism in the study area, climate and eustatism emerge as the main allogenic controls in the sedimentary record. Differentiated sedimentary facies and architectural elements in the K2.2 subunit were probably controlled by both a more humid climate and source area, whereas K2.1 and K2.3 were more related to base-level changes and eustatic control. The presence of more waterlogged pedotypes and of kaolinite and traces of smectite in the clay mineral assemblage of K2.2 also indicates increased humidity. Notwithstanding, our data do not point to intense rainfall periods for the CPE in eastern Spain.

Palynostratigraphic Data for the Buntsandstein and Muschelkalk Facies from the Iberian Ranges (Spain)

This work presents results of a compilation of all published palynological data as well as other unpublished data, on the basis of which a unified palynological biozonation is proposed for the Buntsandstein and Muschelkalk facies from the Iberian Ranges (Spain).

The Stratigraphy and Rifting Evolution of the Oxfordian–Barremian (Upper Jurassic–Lower Cretaceous) in the Serranía de Cuenca (Southwestern Iberian Ranges, Spain)

The Oxfordian to late Barremian geological history of the Serrania de Cuenca Basin is very different from that of other domains of the Iberian Basin. A rifting-related phase of thermal uplift of the area prompted the emersion of the Jurassic marine platforms during the Oxfordian. For almost 30 Myr, the Jurassic carbonates were covered by thick tropical soils and preserved from true erosion. The onset of extension in this area initiated karst processes and progressively generated small and complex half-graben-like basins that were filled by a continental subtropical system of wetlands (the La Huerguina Formation). This unit shows a complex internal architecture that has been separated into six different stratigraphic units, some of them defined for the first time.

Early Triassic Fluvial–Aeolian Interaction in the Catalan Ranges (Northeastern Spain) and Its Palaeogeographical Significance for the Western Tethys

The Early Triassic was still marked by the general perturbations related to the drastic palaeoenvironmental changes that occurred around the Permian–Triassic transition. These perturbations affected both marine and continental environments and were caused by events such as massive volcanism from the Siberian Traps and the consequent general geochemical anomalies that caused a widespread episode of mass mortality. When compared with the marine record, studies of continental rocks are scarce due to the decimated fossil record and important hiatuses. Some of these studies have been conducted in Central Europe series and in isolated areas of Antarctica, the Urals, and South Africa. During the late Early Triassic (Spathian), Central Europe was dominated by significantly dry conditions that allowed aeolian dune fields to develop. Southwards of this vast area, conditions were changing towards the more humid conditions that affected northern Africa. This chapter focuses on the Catalan Ranges, northeastern Spain, where exceptional outcrops of continental rocks of Early–Middle Triassic age allow detailed sedimentary and palaeoenvironmental studies to be made. These studies offer new information about the palaeogeography of the western Tethys area, the climatic variations south of Central Europe, and the first steps of life recovery in this area after the Permian–Triassic boundary crisis. Data in this chapter provide the basis for a sedimentological interpretation of the Lower Triassic sediments of the Catalan Ranges, where aeolian deposits are more important than previously thought. In addition, a new palaeogeography of the northeastern Iberian Peninsula is presented, which shows that fluvial deposits were dominant in the Iberian Ranges, but in the Ebro and Catalan Basin, aeolian deposits predominated in depressions among topographic highs of Palaeozoic rocks, receiving far less fluvial input and probably of local origin. This arrangement of facies is well known in Early Triassic basins of Western and Central Europe, but until now has been overlooked in the Iberian Peninsula.

Palaeoenvironmental Interpretation of Palaeosols and Palustrine Carbonates of the Earliest Cretaceous Terrestrial Ecosystems in the Serranía de Cuenca, Iberian Ranges, Spain

Bauxitic materials redeposited on top of the karstified Jurassic carbonates in the Serrania de Cuenca, Iberian Ranges, display palaeosols and palustrine carbonates that were deposited coevally with the sedimentation of the Rambla de las Cruces I Sequence (upper Barremian; La Huerguina Formation). This sequence contains rich micro- and macrovertebrate assemblages in the Buenache and Las Hoyas basins, to the south of the study area. Different palaeodrainage and palaeotopographic locations are responsible for the different types of palaeosols, some of which preserve vertebrate remains. This study clarifies various palaeoenvironmental aspects of the sedimentation of the La Huerguina Formation, and evaluates upper Barremian terrestrial settings as potential fossil sites.