Resumen de Tesis Doctoral: Magnetoestratigrafía de las sucesiones del Mioceno medio y superior del Vallès occidental (Depresión del Vallès-Penedès, NE de España): Implicaciones biocronológicas y cronoestratigráficas

• Autores: Miguel Garcés Crespo
• Localización: Acta geológica hispánica, ISSN 0567-7505, Vol. 32, Nº 3-4, 1997, págs. 257-261
• Idioma: español
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• Dialnet Métricas: 1 Cita
• Resumen

  • The magnetostratigraphic analysis of the middle to late Miocene continental deposits trom the Vallés-Penedés basin, combined with its well-documented fossil mammal record, provides a well-resoluted chronology for the upper basin infill. It is based on the biostrat graphic and magnetostratigraphic cross-correlation of 18 sections throughout the alluvial and transitional / shallow marine sequences the Western Vallés area. The biostratigraphic framework consists of 24 mammal localities of upper Aragonian and Vallesian age. Correlation of the studied sections to the geomagnetic polarity time scale (GPTS) is based on the distinctive pattern of local magne tozones, as weIl as the radiometric age of the late Vallesian fauna from the Bicorp Basin (9.6 ± 0.3 Ma) and the known relationship of th, late Vallesian assemblages with marine beds belonging to the planktonic foraminifera N16 zone. It has led to an absolute dating of th faunal events and a precise chronostratigraphy of the Vallesian mammal stage in its type area. The Hipparion First Appearance Datum (FAD) defines the lower Vallesian boundary and is dated at 11. 1 Ma, at the base of chron C5r. In. It is in good agreement with radiometric ages from the early Hipparion bearing sites in the Vienna Basin (11. 1 ± 0.5 Ma) and the classic Hówenegg locality in Germany (108 ± 0.3 Ma). It also agrees with the age of the turkish localities of Yailacilar (11.6 ± 0.25 Ma) and Yenieskihisar-2 (11.1 ± 0.2 Ma) with absence of Hipparion. All these support the isochrony of the dispersal of Hipparion throughout: the Mediterranean region. A possible isoch rony at a larger geographical scale (Old World, Mesogea) must await more reliable ages of the Hipparion FAD in Asia and Africa. The Cricetulodon FAD that defines the MN9a / MN9b boundary occurs at the middle part of C5n. Assuming an on average constant sedimentation rate, this datum has an age of approximately 10.4 Ma..