Mesozoic and Cenozoic Vertebrates and Paleoenvironments Tributes to the career of Prof. Dan Grigorescu p. 43-55 EARLY CRETACEOUS PALAEOENVIRONMENTAL CHANGES IN THE BUCEGI MOUNTAINS (ROMANIA) Victor BARBU 1 and Mihaela Carmen MELINTE 2 Abstract. The litho- and biostratigraphical investigations, focused on the Lower Cretaceous deposits from the Bucegi Mountain area, allow the identification of significant palaeoenvironmental changes. Based on the calpionellid, foraminiferal and calcareous nannofossil content, the age of the studied deposits was assigned to the Late Berriasian-Late Valanginian interval. The calcareous nannofloral fluctuations in diversity and abundance identified in the study area of the Southern Carpathians indicate oligotrophic conditions in the late Berriasian-earliest Valanginian, replaced by an eutrophic palaeoenvironment within the late Early Valanginian (including also the Early/Late Valanginian boundary), and by a mesotrophic setting in the Late Valanginian. Keywords: Late Berriasian - Late Valanginian; calpionellids; calcareous nannofossils; benthic foraminifera; palaeoenvironment; Romanian Carpathians. Rezumat. Investigaţiile lito- şi biostratigrafice asupra depozitelor cretacic inferioare din zona Munţilor Bucegi au pus în evidenţă modificări paleoambientale semnificative în intervalul studiat. Pe baza asociaţiilor de calpionele, foraminifere bentonice şi nannofosile calcaroase, vârsta depozitelor pelagice studiate a fost atribuită intervalului Berriasian superior-Valanginian superior. Fluctuaţiile în abundenţă şi diversitate ale nannoplanctonului calcaros indică, pentru arealul studiat, un palaeomediu oligotrofic în intervalul Berriasian superior-partea inferioară a Valanginianului inferior, urmat de instaurarea unor condiţii mesotrofice, la partea superioară a Valanginianului inferior (incluzând şi limita Valanginian inferior/superior). În Valangininul superior, paleomediul eutrofic este înlocuit de unul mesotrofic. Cuvinte cheie: Berriasian târziu – Valanginian târziu; calpionellide; nannofosile calcaroase; foraminifere bentonice; paleomedii; Carpaţii româneşti. 1 Exploration & Reservoir Department, Petrom S.A., Member of OMV Group, E & P Headquarter, 1 Piata Eroilor, Ploiesti, 100316 Romania, e-mail: victor.barbu@petrom.com 2 National Institute of Marine Geology and Geo-ecology, Dimitrie Onciul Street, No. 23-25, 024053 Bucharest, Romania, e-mail: melinte@geoecomar.ro INTRODUCTION The Bucegi Mountains, the investigated area, is situated at the eastern end of the Southern Carpathians. The sedimentary rock- sequence of the studied area, overlying the metamorphic basement is represented by Middle Jurassic siliciclastic rocks and Upper Jurassic - Lower Cretaceous carbonate sediments. These deposits belong to the sedimentary cover of the Getic Nappe (Fig. 1), which is included in the Median Dacidian tectonical units (sensu Sǎndulescu, 1984). According to Patrulius et al. (1976), the Upper Jurassic to Lower Cretaceous carbonate rocks of the Southern Carpathians belong to several carbonate platforms, grouped under the name of the Getic Carbonate Platform. Mid-Cretaceous (Upper Aptian-Albian) silici- clastic rocks, representing the post-tectonic cover of the Getic Nappe, crop out also in the Bucegi Mountain area (Sǎndulescu, 1984). Geological investigations, focussed mainly on the litho- and biostratigraphical aspects of the Upper Jurassic - Lower Cretaceous Getic Carbonate Platform of the Bucegi Mountains and the adjacent area (Dâmbovicioara, Braşov, Codlea, and Carhaga – Perşani Mts.), were published since the mid 1900’s, by Patrulius (1969), Neagu (1975), Patrulius & Avram (1976; 2004), Manoliu et al. (1978), Avram & Grǎdinaru (1993), C.E. Panaiotu et al. (1997), Dragastan et al. (2000), Melinte & Mutterlose (2001), Barbu (2002; 2005 a, b), Barbu et al. (2002), and Barbu & Melinte (2005). The aim of this paper is to present the palaeoenvironmental changes which took place during the earliest Cretaceous in the area of Bucegi Mountains, based on lithological and palaeontological evidences. 2. MATERIAL AND METHODS The studied section, namely in this study P4, is situated in the north-western part of Bucegi Mountains, between the Gaura Valley to the south, and the “La Politzie” saddle to the north (GPS reading 45 0 26’69”N; 25 0 24’21”E, altitude of 1450 m) – Fig. 1.