Oxygen-related facies in Lake Pannon deposits (Upper Miocene) at Budapest-Köbánya

• Published in: Facies 2006-05, Vol.52 (2), p.209-220
• Main Authors: Magyar, Imre, Müller, Pál Mihály, Sztanó, Orsolya, Babinszki, Edit, Lantos, Miklós
• Format: Article
• Language: English
• Subjects: Bioturbation; Clay; Lakes; Miocene; Mollusks; Organic loading; Oxygen; Oxygenation; Sand; Shellfish; Trace fossils
• ISSN: 0172-9179; 1612-4820
• DOI: 10.1007/s10347-005-0036-y

Oxygen availability is considered to have been a major factor in shaping the sedimentary facies and biofacies of a Late Miocene (8-8.5 Ma old) Lake Pannon sequence studied in the Kozma-street outcrop in Budapest-Köbánya. The sequence contains blue clays deposited in low-oxygen conditions between the storm and the fair-weather wave bases and thin intercalations of laminated fine sand interpreted as tempestites. The storms caused temporary oxygenation of the bottom and thus promoted bioturbation, as indicated by the presence of trace fossils belonging to the Arenicolites ichnofacies or a lacustrine equivalent of the marine Skolithos ichnofacies. Fully bioturbated sand layers with the infaunal Dreissenomya and other littoral molluscs indicate longer periods of bottom ventilation. The blue clays immediately above these sand layers also contain abundant and diverse mollusc fauna. Oxygen deficiency on the "shelf" of Lake Pannon was a local phenomenon probably caused by a high organic loading and/or a salinity-induced stratification.[PUBLICATION ABSTRACT]