The Valanginian history of the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania): Evidence for emergence and drowning of the platform


Grădinaru, Mihaela
Lazar, Iuliana
Bucur, Ioan I.
Grădinaru, Eugen
Săsăran, Emanoil; Ducea, Mihai N. and Andrăşanu; Alexandru

Lower Cretaceous successions that crop out in the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania) preserve records of the Valanginian events in different settings of the platform.
The integrated sedimentological, biostratigraphical, geochemical and mineralogical analysis of the upper BerriasianeValanginian successions reveal successive stages in the evolution of the carbonate platform:
(a) pre-drowning stage of the shallow-shelf and slope settings of the platform; (b) subaerial exposure and karstification; and (c) incipient flooding and drowning of the carbonate platform. Following the subaerial exposure, starting in the middle early Valanginian, the eastern part of the Getic Carbonate Platform experienced a drowning phase documented by iron oxyhydroxides, phosphate and glaucony mineralized discontinuity surface and glaucony-rich sediments disposed on the discontinuity surface. Recognition of the diachronous intra-Valanginian discontinuity surface within the studied successions is based on clear evidences (facies contrast, depositional and diagenetic features, biostratigraphic and taphonomic data, and geometrical relations). The negativeepositive carbon isotope excursion is correlated with the global perturbations of the carbon cycle related to the Valanginian “Weissert” episode, and it is documented for the first time in the shallowest parts of the Getic Carbonate Platform. Tectonic activity and eustatic sea-level fluctuations were most probably the main factors that led to fault-block tilting, local emersion and subsequent drowning of the eastern part of the Getic Carbonate Platform during the Early Cretaceous. We infer that the eastern part of the Getic Carbonate Platform was affected by late Berriasianeearly Hauterivian extensional tectonics that could be related to the Neo-Cimmerian movements with effects generally recognized in the northern peri-Tethyan areas.

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Fig. 1. Location of the studied sections: A General location of the studied zones within the Southern Carpathians (based on the geotectonic map of Romania, Sandulescu, 1984). BeD Locations of the studied sections on the geological outline maps: B Bras¸ ov-Codlea zone (modified from Sandulescu et al., 1972), C D^ambovicioara zone (modified from Dimitrescu et al., 1971), D Southern part of the Bucegi Mountains (modified from Patrulius, 1969).

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Cretaceous Research 66 (2016) 11e42 © 2016 Elsevier Ltd. All rights reserved.