Vallesium
The Vallesium is a regional level in the terrestrial Neogene . It corresponds to zones MN 9 and 10 of the European land mammal chronology ( ELMMZ = "European Land Mammal Mega-Zones"). The Vallesium is underlain by the Astaracium and overlaid by the Turolium .
History and type locality
The step was proposed by Miquel Crusafont i Pairó (1950) and named after the Vallès-Penedès basin in Catalonia , where the type locality is also located.
definition
The lower limit is defined by the onset of the large mammal genera Hippotherium , Decennatherium and Machairodus . In small mammals, the first appearance of the genus Cricetulodon represents the basis. The end of the stage (and the beginning of the turolium ) is marked by the first appearance of the species Hyaenictis almerai , Adcrocuta eximia , Microstonyx major , Tragoportax gaufryi . In the case of small mammals, these are the species and genera Rotundomys , Pliopetaurista , Schreuderia and Progonomys cathalai . The Vallesium is currently correlated with a large part of the Lower and Middle Tortonian , the lower chronostratigraphic stage of the Upper Miocene . Geochronologically, this corresponds roughly to the period of 2.4 million years (from 11.1 to 8.7 million years ago).
Breakdown
The stage is divided into two biozones MN 9 and MN 10. Occasionally the stage is also divided into a lower and an upper Vallesium, the lower Vallesium of the Biozone MN 9 and the upper Vallesium of the Biozone 10.
Vallesium crisis
The Vallesium Crisis ( English : Vallesian Crisis ) is an abrupt change in flora and fauna around 9.6 million years ago, which is documented among other things for mammals. The change in species composition was first detected in the Vallès-Penedès Basin and was the result of a significant change in the climate in Europe and in northern and eastern Africa. Starting from the Spanish Mediterranean region, the subtropical , evergreen forests in western and central Europe disappeared as a result of gradual cooling; in their place followed deciduous trees and, in some southern regions, steppes . One of the consequences of this was that most of the human species that had lived in Europe up to that point - including Dryopithecus , Ankarapithecus and Graecopithecus - became extinct. The cause of climate change is a change in ocean currents, which in turn is associated with the folding of the Himalayas and the Tibetan highlands .
literature
- J. Agustí, L. Cabrera, M. Garcés, W. Krijgsman, O. Oms, JM Parés: A calibrated mammal scale for the Neogene of Western Europe. State of the art. Earth Science Reviews, 52: 247-260, Amsterdam 2001 ISSN 0012-8252
- Miguel Crusafont Pairó : La cuestion del llamado Meotico espanol. Arrahona (Sabadell) 1: 3-9, 1950.
- Everett Lindsay: Eurasian mammal biochronology: an overview. Palaeogeography, Palaeoclimatology, Palaeoecology, 133: 117-128, Amsterdam 1997 ISSN 0031-0182
Individual evidence
- ^ Jordi Agusti, Salvador Moyà-Solà: Mammal extinctions in the Vallesian (Upper Miocene). In: Lecture Notes in Earth Sciences , Volume 30, 1990, pp. 425-432, doi : 10.1007 / BFb0011163
- ^ Jordi Agusti: The biotic environments of the late Miocene hominids. In: Winfried Henke , Ian Tattersall (Eds.): Handbook of Paleoanthropology. Springer Verlag, Berlin 2007, pp. 979-1010, ISBN 978-3-540-32474-4