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Palaeoenvironmental evolution of Lake Gacko (Southern Bosnia and Herzegovina): Impact of the Middle Miocene Climatic Optimum on the Dinaride Lake System

Palaeogeography Palaeoclimatology Palaeoecology, 2011 Jan 15, Vol.299(3-4), pp.475-492 [Peer Reviewed Journal]

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  • Title:
    Palaeoenvironmental evolution of Lake Gacko (Southern Bosnia and Herzegovina): Impact of the Middle Miocene Climatic Optimum on the Dinaride Lake System
  • Author: Mandic, O ; de Leeuw, A ; Vukovic, B ; Krijgsman, W ; Harzhauser, M ; Kuiper, Kf
  • Found In: Palaeogeography Palaeoclimatology Palaeoecology, 2011 Jan 15, Vol.299(3-4), pp.475-492 [Peer Reviewed Journal]
  • Subjects: Stratigraphy ; Absolute Age ; Alps ; Ar/Ar ; Biostratigraphy ; Bosnia-Herzegovina ; Breccia ; Cenozoic ; Climate Forcing ; Cyclostratigraphy ; Dates ; Dinaric Alps ; Dinaride Lake System ; Eastern Alps ; Europe ; Eutrophication ; Extinct Lakes ; Gacko Lake ; Invertebrata ; Karst ; Lacustrine Environment ; Lake Sediments ; Lake-Level Changes ; Lithofacies ; Magnetostratigraphy ; Middle Miocene ; Miocene ; Mollusca ; Neogene ; Paleoclimatology ; Paleoecology ; Paleoenvironment ; Paleogeography ; Paleolakes ; Paleolimnology ; Paleomagnetism ; Poljes ; Reversals ; Sediments ; Solution Features ; Southern Bosnia-Herzegovina ; Southern Europe ; Tephrochronology ; Tertiary ; Well Logs
  • Language: English
  • Description: In the Early to Middle Miocene, a series of lakes, collectively termed the Dinaride Lake System (DLS), spread out across the north-western part of the Dinaride-Anatolian continental block. Its deposits, preserved in numerous intra-montane basins, allow a glimpse into the palaeoenvironmental, palaeobiogeographic and geodynamic evolution of the region. Lake Gacko, situated in southern Bosnia and Herzegovina, is one of the constituent lakes of the DLS, and its deposits are excellently exposed in the Gracanica open-cast coal-mine. A detailed study of the sedimentary succession that addresses facies, sediment petrography, geophysical properties, and fossil mollusc palaeoecology reveals repetitive changes in lake level. These are interpreted to reflect changes in the regional water budget. First-order chronologic constraints arise from the integration of radio-isotopic and palaeomagnetic data. (super 40) Ar/ (super 39) Ar measurements on feldspar crystals from a tephra bed in the upper part of the sedimentary succession indicate a 15.31+ or -0.16 Ma age for this level. The reversed magnetic polarity signal that characterises the larger part of the investigated section correlates to chron C5Br of the Astronomically Tuned Neogene Timescale. Guided by these chronologic data and a detailed cyclostratigraphic analysis, the observed variations in lake-level, evident as two approximately 40-m and seven approximately 10-m scale transgression-regression cycles, are tuned to approximately 400-kyr and approximately 100-kyr eccentricity cycles. From the tuning, it can be inferred that the sediments in the Gacko Basin accumulated between approximately 15.8 and approximately 15.2 Ma. The economically valuable lignite accumulations in the lower part of the succession are interpreted to indicate the development of swamp forests in conjunction with lake-level falls corresponding to approximately 100-kyr eccentricity minima. Pedogenesis, rhizoliths and palustrine carbonate breccias in the upper part of the section reveal long-term aridity coinciding with a approximately 400-kyr eccentricity minimum. Eccentricity maxima are interpreted to trigger lake-level high-stands. These are accompanied by eutrophication events caused by enhanced denudation of the surrounding basement and increased detrital input into the basin. The presented age model proves that Lake Gacko arose during the Middle Miocene Climatic Optimum and that the optimum climatic conditions triggered the formation of this long-lived lake.
  • Identifier: ISSN: 0031-0182 ; DOI: 10.1016/j.palaeo.2010.11.024

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