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

Abstract

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.

Sedimentary evolution of the continental Early–Middle Triassic Cañizar Formation (Central Spain): Implications for life recovery after the Permian–Triassic crisis

“…16), but it is not until the early Anisian, during deposition of the Eslida Fm., about 1 My later, that diversity showed a clear increase in this area, as shown by the presence of different paleontological groups (Bethoux et al, 2009;Gand et al, 2010;Ga l. in-AbeUan, 2011). Therefore, the first signals of recovery of life in the SE Iberian Basin started just after the unconformity represented by MBS-S, a 7th order surface that we have been related to the coeval tectonic event in Western and Central Europe mirrored by the so-called Hardegsen unconformi ty.…”

“…there is no evidence of any biotic remains below member E, all the fossil remains found are only in the upper part of this unit, just above MBS-S, the 7th order surface separating members E and D. The fossil content is restricted to one pollen association (Doubinger et al, 1990), some fragments of plants, and some pre served ichnofossils: a few tetrapod traces (Gand et al, 2010) and bio turbation (Figs. 4, 16).…”

“…The change in fluvial style of the Cafiizar Fm. with respect to these two for mations L6pez-G6mez et al, 2010), the absence of fine-fraction, and the braided nature of the fluvial chan nels with frequent abandonment and re-occupation can be explained by the absence of vegetation, especially riparian assodations that cover (Mac Na.ughton et al, 1997;Ashworth et al, 2000), as observed in some of the described elementary sequences, especially in sector W. Clear changes in the vertical evolution of the system are observed when the subunits are compared. The most important differences are related to the MBS-S (Fig.…”

Sources of Sr and S In Aluminum-Phosphate-Sulfate Minerals In Early-Middle Triassic Sandstones (Iberian Ranges, Spain) and Paleoenvironmental Implications for the West Tethys

“…Biodiversity is enhanced in the Eslida Formation (Fig. 3) with the presence of tetrapod traces and plant and invertebrate fossils (Bèthoux et al 2009;Gand et al 2010;Galán-Abellán 2011). It is also divided into six members whose ages range from Pelsonian (middle Anisian) for the upper part to Bithynian-Aegian (early Anisian) for the lowest members (Boulouard and Viallard 1982;Doubinger et al 1990;López-Gó mez et al 2012).…”

“…1C;Ló pez-Gómez and Arche 1993b). The lower part of Cañ izar Formation is devoid of any fossils, however, carbonized organic matter, a palynological assemblage, incipient paleosols, and the oldest Triassic tetrapod footprints of the Iberian Peninsula occur in the uppermost part (Gand et al 2010;López-Gó mez et al 2012). The age of the upper part is Aegian (lower Anisian) based on pollen and spore assemblages (Doubinger et al 1990), and although the base of this unit has not been dated yet, an early Olenekian (Smithian) age has been inferred based on correlations with equivalent sediments in the Catalonian Ranges and other European basins (Dinarès-Turrel et al 2005;Bourquin et al 2011;Ló pez-Gómez et al 2012).…”