THE MIOCENE FROM BUZĂU AREA A GEOLOGICAL AND GEOCONSERVATION PERSPECTIVE Marius Stoica Alexandru Andrășanu Dan Palcu Răzvan Gabriel Popa The 11th Romanian Symposium on Palaeontology Bucharest, September 25-30, 2017 Marius Stoica Alexandru Andrășanu Dan Palcu Răzvan Gabriel Popa THE MIOCENE FROM BUZĂU AREA A GEOLOGICAL AND GEOCONSERVATION PERSPECTIVE 2017 Descrierea CIP a Bibliotecii Naţionale a României The Miocene from Buzău area : a geological and geoconservation perspective / Marius Stoica, Alexandru Andrăşanu, Dan Palcu, Răzvan Gabriel Popa. - Bucureşti : Editura Universităţii din Bucureşti, 2017 Conţine bibliografie ISBN 978-606-16-0913-0 I. Stoica, Marius II. Andrăşanu, Alexandru III. Palcu, Dan IV. Popa, Răzvan-Gabriel 55 Copyright © Marius Stoica, Alexandru Andrășanu, Dan Palcu, Răzvan Gabriel Popa, 2017 Tiparit la S.C. MRT Marketing Research and Training S.R.L Printed in Romania THE MIOCENE FROM BUZĂU AREA A GEOLOGICAL AND GEOCONSERVATION PERSPECTIVE Marius Stoica Alexandru Andrășanu Dan Palcu Răzvan Gabriel Popa Revised version with supplementary data of the “Neogene deposits in the South-Eastern Carpathians- Field Trip Guide”, by Marius Stoica, Mihaela C. Melinte-Dobrinescu and Dan Palcu, 2012 2017 Table of Contents Geology of the Carpathians ................................................................................................ 7 The Eastern Carpathians .................................................................................................... 9 The Dacian Basin ................................................................................................................. 10 Description of the Field Trip Stops .................................................................................... 14 Day 1. Slănic Prahova area and Mud Volcaneous ............................................................ 14 Stop 1. Middle Badenian evaporitic formation in the Salt Mountain ....................... 16 Stop 2. Middle Badenian salt mine ........................................................................... 17 Stop 3. Lower to Middle Badenian tuff and ”Globigerina marls” in the ”Piatra Verde” (The Green Stone) hill ................................................................................... 19 Stop 4. The Middle Badenian Evaporitic Formation north of Slănic Prahova ......... 20 Stop 5. Lower Miocene gypsum at the Slon Valley .................................................. 22 Stop 6. Mud Volcanoes at Pâclele ............................................................................. 23 Day 2. Slănicul de Buzău Valley.......................................................................................... 25 Stop 7. Lower Miocene Lopătari – Meledic salt diapir ............................................ 26 Stops 8, 9. Geological profile along Slănicul de Buzău Valley at Mȃnzăleşti ......... 27 Stops 10, 11. Geological profile along Slănic Valley between Beşli and Vintilă Vodă Villages ............................................................................................................ 30 Stop 12. The stratotype of Dacian / Romanian boundary, Upper Dacian rich fossiliferous cycles of reddish sandstones ................................................................. 37 Buzau Land Aspiring UNESCO Global Geopark ......................................................... 38 References.............................................................................................................................. 41 OVERVIEW E S N W Fig. 1. A different look on the Carpathians. South-eastern Europe seen from an unusual perspective. Greece on the upper right with the Mediterranean Sea behind. On the upper left the Black Sea and Turkey. In the center of this view the bow of the Carpathian Mountains can be seen. Copyright © Cristoph Herman, http://earth.imagico.de/. GEOLOGY OF THE CARPATHIANS The Mesozoic deformations of the Carpathians are characterized by strong basement involved The Carpathians are an Alpine Orogen, the thrusting (e.g. Dacia, East Vardar, Ceahlău- eastward continuation of the Northern Alps Severin). These basement nappes outcrop in (Fig. 2). Similar to the Alps, the Carpathians the western part of the Eastern Carpathians record the closure of the Alpine Tethys. In the (Bucovinian nappes), the South Carpathians case of the Carpathians, this spans from the (Getic nappes), and from the basement of the Latest Jurassic to Middle Miocene. Transylvania Basin (Fig. 2, 3). 7 OVERVIEW Fig. 2. Tectono-structural maps of the Carpathians Bend Zone from Merten et al. (2010). Solid black line marks the A-A’ cross section of Fig. 3. The red circle stands for the field trip area. 8 OVERVIEW The Cenozoic deformations of the Carpathians The most recent deformation stage of the are recorded by „thin-skinned“ nappes (Fig. 2) Carpathians, referred to as the Vallachian as the remnants of the Alpine Tethys and are stage, is Pliocene to Recent in age (Fig. 3). subducted under the Carpathians to the west. This deformation is not related to the The thin-skinned nappes comprise sediments subduction process, because it post-dates the scraped off from the subducting plate during orogen collision. Instead, the Vallachian stage several thrusting phases, as follows: has been interpreted as the result of intra- Cretaceous (Ceahlău nappe), Late Oligocene – Carpathian compressional forces evident also intra-Burdigalian (Black-Flysch, Audia, Macla, on the present-day stress measurements. This Tarcău nappes), and Middle Miocene (Tarcău, intra-plate compression was accommodated by Marginal Folds, and Subcarpathian nappes). lithospheric-scale folding due to the strong The total amount of shortening observed in the post-collisional foreland coupling between the „thin-skinned“ nappes and estimated based on upper and lower plates. In the SE Carpathians, balanced cross-sections varies from 150 to 500 the lithospheric-scale folding resulted in 2-3 km. km of uplift and erosion in the core of the orogen, out-of-sequence reactivation of older thrust planes, and inversion of Mesozoic grabens on the lower plate. Fig. 3. Transect A-A’ (shown on Fig. 1) across the Carpathians Bend Zone from Merten et al. (2010). The section illustrates the Cretaceous basement nappes of the internal Carpathians (“Dacia”, to the west) and the thin-skinned outer (external) Carpathians (to the east). THE EASTERN CARPATHIANS mountainous chain, with peaks higher than 2,000 m, rises. The Eastern Carpathians are The Eastern Carpathians represent an located between the Transylvanian Depression important segment of the Romanian (westwards), The Moldavian Plateau Carpathians that develop between the Tisa (eastwards) and the Romanian plain Valley to the North and Dâmboviţa Valley to (southwards). the South. On a distance as long as 600 km a 9 OVERVIEW From a geological point of view, the Eastern Within Palaeogene times, the turbiditic Carpathians chain consist of a nappe pile sedimentation reached the largest areal made up of basement nappes in the western development, showing also the most complex part, and Early Cretaceous pelitic marine lithological diversity. A peculiar facies deposits, Late Cretaceous to Palaeogene developed in the Oligocene-Early Miocene flysch deposits, as well as Miocene to interval in the outer part of the Molavid basin, Quaternary molasse deposits, in the central covering the West Tarcău Nappe, the Vrancea and eastern parts. Imbrication and internal Nappe and the Subcarpathian Nappe, made by deformation of the nappes took place in bituminous rocks and massive quartz several periods of deformation from the sandstones, namely the Kliwa Facies. This Late Cretaceous to Quaternary. facies coexists with innermost Outer Moldavide flysch sediments of the Fusaru- Based on the age of the main deformation and Pucioasa facies, supplied by an inner, the mutual areal position, the following Carpathian, source area (Ştefănescu and tectonical units were recognized (Săndulescu, Melinte, 1996). Additionally, transitional 1988): the Pienids, the Transylvanian Nappes, zones between the two above-mentioned facies the Median Dacides (Central East Carpathians could be observed. Nappes), the Outer Dacides, the Inner Moldavids and the Outer Moldavids (Fig. 3). In the Burdigalian, an evaporitic (salt and/or gypsum) event marks the end of the turbiditic The Moldavian realm developed in deposition in the inner part of the Moldavides Hauterivian-Albian times as Euxinic basin, and of the hemipelagic (bituminous facies) in characterised by the deposition of rich-organic outer structures. black shales (Roban and Melinte-Dobrinescu, 2012). The Mid-Cretaceous tectonic movement This event was followed, within the Late determined an important deepening in the Burdigalian-Early Badenian interval, by the Moldavid basin. Hence, sediments deposited in deposition of thick molasses and schlier the marine red bed facies (Melinte-Dobrinescu deposits in the Tarcău, Vrancea and and Roban, 2011) accumulate below or close Subcarpathian nappes. A second evaporitic the CCD. During the Late Cretaceous (i.e., event took place within the Middle Badenian, Senonian), the turbidite sedimentation covered followed by the sedimentation of Upper the main part of the Moldavid basin; hence, Miocene-Pliocene coarse grained and sandy different turbidite sequences, such as sandy molasses (Săndulescu, 1984), restricted to the flysch, shaly flysch or calcareous ones, were Subcarpathian Nappe and, mainly to the sedimented (Săndulescu et al., 1980; foredeep. Săndulescu, 1994). THE DACIAN