231 research outputs found
Paleozoic ages and excess 40Ar in garnets from the Bixiling Peclogite in Dabieshan, China: New insights from 40Ar/39Ar dating by stepwise crushing
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Pressure-temperature-time evolution of the high pressure metamorphic complex of Sifnos, Greece
Integrated stratigraphy and 40Ar/39Ar chronology of the Early to Middle Miocene Upper Freshwater Molasse in eastern Bavaria (Germany)
A detailed integrated stratigraphic study was carried out on middle Miocene fluvial successions of the Upper Freshwater Molasse (OSM) from the North Alpine Foreland Basin, in eastern Bavaria, Germany. The biostratigraphic investigations yielded six new localities thereby refining the OSM biostratigraphy for units C to E (sensu; Heissig, Actes du Congres BiochroM'1997) and further improving biostratigraphic correlations between the different sections throughout eastern Bavaria. Radioisotopic ages of 14.55 Β± 0.19 and 14.88 Β± 0.11 Ma have been obtained for glass shards from the main bentonite horizon and the Ries impactite: two important stratigraphic marker beds used for confirming our magnetostratigraphic calibration to the Astronomical Tuned Neogene Time Scale (ATNTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). Paleomagnetic analysis was performed using alternating field (AF) and thermal (TH) demagnetization methods. The AF method revealed both normal and reverse polarities but proofs to yield unreliable ChRM directions for the Puttenhausen section. Using the biostratigraphic information and radioisotopic ages, the magnetostratigraphic records of the different sections are tentatively correlated to the Astronomical Tuned Neogene Time Scale (ATNTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). This correlation implies that the main bentonite horizon coincides to chron C5ADn, which is corroborated by its radioisotopic age of 14.55 Ma, whereas the new fossil locality Furth 460, belonging to OSM unit E, probably correlates to chron C5Bn.1r. The latter correlation agrees well with the Swiss Molasse locality Frohberg. Correlations of the older sections are not straightforward. The Brock horizon, which comprises limestone ejecta from the Ries impact, possibly correlates to C5ADr (14.581 Β± 14.784 Ma), implying that, although within error, the radioisotopic age of 14.88 Β± 0.11 Ma is somewhat too old. The fossil localities in Puttenhausen, belonging to the older part of OSM unit C, probably coincide with chron C5Cn.2n or older, which is older than the correlations established for the Swiss Molasse. Β© Springer-Verlag 2007
The Gediz River fluvial archive: A benchmark for Quaternary research in Western Anatolia
The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River Project (2001β2010) and present new data which leads to a revised stratigraphical model for the Early Pleistocene development of this fluvial system. In previous work we confirmed the preservation of eleven buried Early Pleistocene fluvial terraces of the Gediz River (designated GT11, the oldest and highest, to GT1, the youngest and lowest) which lie beneath the basalt-covered plateaux of the Kula Volcanic Province. Deciphering the information locked in this fluvial archive requires the construction of a robust geochronology. Fortunately, the Gediz archive provides ample opportunity for age-constraint based upon age estimates derived from basaltic lava flows that repeatedly entered the palaeo-Gediz valley floors. In this paper we present, for the first time, our complete dataset of 40Ar/39Ar age estimates and associated palaeomagnetic measurements. These data, which can be directly related to the underlying fluvial deposits, provide age constraints critical to our understanding of this sequence. The new chronology establishes the onset of Quaternary volcanism at βΌ1320ka (MIS42). This volcanism, which is associated with GT6, confirms a pre-MIS42 age for terraces GT11-GT7. Evidence from the colluvial sequences directly overlying these early terraces suggests that they formed in response to hydrological and sediment budget changes forced by climate-driven vegetation change. The cyclic formation of terraces and their timing suggests they represent the obliquity-driven climate changes of the Early Pleistocene. By way of contrast the GT5-GT1 terrace sequence, constrained by a lava flow with an age estimate of βΌ1247ka, span the time-interval MIS42 β MIS38 and therefore do not match the frequency of climate change as previously suggested. The onset of volcanism breaks the simple linkage of terracing to climate-driven change. These younger terraces more likely reflect a localized terracing process triggered by base level changes forced by volcanic eruptions and associated reactivation of pre-existing faults, lava dam construction, landsliding and subsequent lava-dammed lake drainage. Establishing a firm stratigraphy and geochronology for the Early Pleistocene archive provides a secure framework for future exploitation of this part of the archive and sets the standard as we begin our work on the Middle-Late Pleistocene sequence. We believe this work forms a benchmark study for detailed Quaternary research in Turkey
ΠΠ΅ΡΠΎΠ΄ ΠΈΠ½ΡΠ΅Π³ΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ Π΄ΠΈΡΡΠ΅ΡΠ΅Π½ΡΠΈΠ°Π»ΡΠ½ΡΡ ΡΡΠ°Π²Π½Π΅Π½ΠΈΠΉ Π΄ΠΈΠ½Π°ΠΌΠΈΠΊΠΈ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΡ ΠΌΠ°ΡΠΈΠ½ Ρ Π²ΡΠ°ΡΠ°ΡΡΠΈΠΌΡΡ ΡΠΎΡΠΎΡΠΎΠΌ
ΠΠ»Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΏΠ΅ΡΠ΅Ρ
ΠΎΠ΄Π½ΡΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² Π² ΡΠ»Π΅ΠΊΡΡΠΎΡΠ΅Ρ
Π½ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠΈΡΡΠ΅ΠΌΠ°Ρ
, ΡΠΎΠ΄Π΅ΡΠΆΠ°ΡΠΈΡ
ΡΡΠ°ΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠ»Π΅ΠΊΡΡΠΎΠΌΠ°Π³Π½ΠΈΡΠ½ΡΠ΅ ΡΡΡΡΠΎΠΉΡΡΠ²Π°, Π²ΠΊΠ»ΡΡΠ΅Π½Π½ΡΠ΅ Π² ΡΠ»ΠΎΠΆΠ½ΡΠ΅ ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΡ
Π΅ΠΌΡ, ΡΠ°Π·ΡΠ°Π±ΠΎΡΠ°Π½ ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΡΠΉ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡ Colo, ΡΡΠ½ΠΊΡΠΈΠΎΠ½ΠΈΡΡΡΡΠΈΠΉ Π½Π° ΠΎΡΠ½ΠΎΠ²Π΅ ΠΌΠ°Π³Π½ΠΈΡΠΎΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΡ
Π΅ΠΌ Π·Π°ΠΌΠ΅ΡΠ΅Π½ΠΈΡ Π² ΠΌΠ°ΡΡΠΈΡΠ½ΠΎΠΉ ΡΠΎΡΠΌΠ΅. ΠΠ»Π°Π²Π½Π°Ρ ΠΌΠ°ΡΡΠΈΡΠ° ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ° Colo ΡΠΎΠ΄Π΅ΡΠΆΠΈΡ ΠΊΠΎΡΡΡΠΈΡΠΈΠ΅Π½ΡΡ ΠΏΡΠΈ ΠΈΡΠΊΠΎΠΌΡΡ
ΡΠΎΠΊΠ°Ρ
ΠΈΠ»ΠΈ ΠΌΠ°Π³Π½ΠΈΡΠ½ΡΡ
ΠΏΠΎΡΠΎΠΊΠ°Ρ
. ΠΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΏΡΠΎΡΠ΅ΡΡΠΎΠ² Π² ΡΠ»Π΅ΠΊΡΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΠΌΠ°ΡΠΈΠ½Π°Ρ
Ρ Π²ΡΠ°ΡΠ°ΡΡΠΈΠΌΡΡ ΡΠΎΡΠΎΡΠΎΠΌ ΡΠ²ΡΠ·Π°Π½ΠΎ Ρ ΠΈΠ½ΡΠ΅Π³ΡΠΈΡΠΎΠ²Π°Π½ΠΈΠ΅ΠΌ Π΄ΠΈΡΡΠ΅ΡΠ΅Π½ΡΠΈΠ°Π»ΡΠ½ΡΡ
ΡΡΠ°Π²Π½Π΅Π½ΠΈΠΉ, Π² ΠΊΠΎΡΠΎΡΡΠ΅ Π²Ρ
ΠΎΠ΄ΡΡ ΠΏΡΠΎΠΈΠ·Π²Π΅Π΄Π΅Π½ΠΈΡ ΠΈΡΠΊΠΎΠΌΡΡ
Π²Π΅Π»ΠΈΡΠΈΠ½, ΠΏΠΎΡΡΠΎΠΌΡ Π½Π΅ΠΏΠΎΡΡΠ΅Π΄ΡΡΠ²Π΅Π½Π½ΠΎ ΡΡΠΈ ΡΡΠ°Π²Π½Π΅Π½ΠΈΡ Π½Π΅ ΠΌΠΎΠ³ΡΡ ΡΠ΅ΡΠ°ΡΡΡΡ Π² ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌΠ½ΠΎΠΌ ΠΊΠΎΠΌΠΏΠ»Π΅ΠΊΡΠ΅ Colo
Ar/Ar geochronology of the Balaton Highlands volcanic field: timing of volcanic events and its bearing on the Plio-Miocene environment in the western Pannonian basin
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