RT Journal Article
T1 Sedimentary evolution of the continental Early–Middle Triassic Cañizar Formation(Central Spain): Implications for life recovery after the Permian–Triassic crisis
A1 López Gómez, José
A1 Galán Abellán, Ana Belén
A1 Horra Del Barco, Raúl De La
A1 Fernández Barrenechea, José María
A1 Arche, Alfredo
A1 Bourquin, Sylvie
A1 Marzo Carpio, Mariano
A1 Durand, Marc
AB The Permian–Triassic transition (P–T) was marked by important geochemical perturbations and the largestknown life crisis. Consequences of this event, as oxygen-depleted conditions and the unusual behavior ofthe carbon cycle, were prolonged during the Early Triassic interval delaying the recovery of life in both terrestrialand marine ecosystems. Studies on Lower Triassic sediments of continental origin, as in the case ofWestern Europe, are especially problematic due to the scarcity of fossils and absence of precise dating. TheCañizar Fm. is an Early–Middle Triassic unit of continental origin of the SE Iberian Ranges, E Spain. A detailedsedimentary study of this unit allows a shedding of light on some unresolved problems of the continental depositsof this age.The top of this unit is dated as early Anisian by means of a pollen association, while the age of its base is hereestimated as late Smithian or Smithian–Spathian transition. Different facies associations and architectural elementshave been defined in this unit. In the western and central parts of the basin, this unit shows sedimentarycharacteristics of fluvial deposits with locally intercalated aeolian sediments, while in the eastern partthere is an alternation of both aeolian and fluvial deposits. Sedimentary structures also indicate changes inthe climate conditions, mainly from arid to semiarid. Two marked arid periods when well-preserved aeoliansediments developed during early–middle Spathian and Spathian–Anisian transition. They alternated withtwo semiarid but more humid periods during the late Spathian and early Anisian. These conditions basicallycorrespond with the general arid and very arid conditions described for central–western European plate duringthe same period of time. The Ateca–Montalbán High, in the northern border of the study basin, must haverepresented an important topographic barrier in the western Tethys separating aeolian dominated areas tothe N and NE from fluvial dominated areas to the south.The Cañizar Fm. has been subdivided into six members (A–F) separated by seven (1–7) major boundingsurfaces (MBS). These surfaces are well recognized laterally over hundred of km and they represent104–105 My. MBS-5 is considered to be of late Spathian age and it is a clear indication of tectonic activity,represented by a mild unconformity. This event represents a change in the sedimentary characteristics(reactivation) of the unit and from here to the top of the unit are found the first signals of biotic recovery,represented by tetrapod footprints, plants, roots and bioturbation. All of these characteristics and the estimatedage represented by the MBS-5 event permit this surface to be related to the coeval Hardegsen unconformityof Central–Western Europe. These first signals of biotic recovery can thus be related to anincreased oxygen supply due to the new created paleogeographical corridors in the context of this tectonicactivity. These biotic signals occurred 5 My after the Permian–Triassic limit crisis; a similar delay as occurredin other coeval and neighboring basins.
PB Elsevier
SN 0037-0738
YR 2012
FD 2012
LK https://hdl.handle.net/20.500.14352/42460
UL https://hdl.handle.net/20.500.14352/42460
LA eng
DS Docta Complutense
RD 27 jul 2024