Mihaela Carmen Melinte et al. – Upper Cretaceous Oceanic Red Beds in the Romanian Carpathians GEO-ECO-MARINA 9-10/2003-2004 National Institute of Marine Geology and Geo-ecology Modern and Ancient Fluvial, Deltaic and Marine Environments and Processes Proceedings of Euro-EcoGeoCentre-Romania TURBIDITIC AND PELAGIC UPPER CRETACEOUS OCEANIC RED BEDS IN THE ROMANIAN CARPATHIANS WORKSHOP OF IGCP 463, ROMANIA, AUGUST 15-18, 2004 Mihaela Carmen MELINTE, Titus BRUSTUR, Dan JIPA, Stefan SZOBOTKA, Cristina ANGHELUŢĂ National Institute of Marine Geology and Geo-ecology (GEOECOMAR), 23-25 Dimitrie Onciul Str., 024053 Bucharest Abstract. Upper Cretaceous Red Beds are widely distributed in the former Tethyan Realm, in the European, Asian and Central North Atlantic regions. This type of sedimentation followed in many regions the Lower Cretaceous Black Shales, indicating the replacement of an anoxic regime with an oxic one. For a better understanding of causes which produced such changes in deposition, the Upper Cretaceous Red Beds were intensively studied since 2002, by the participants in the IGCP-UNESCO Project 463-Upper Cretaceous Oceanic Red Beds: Response to Ocean/Climate Change (CORB). The Third Workshop of this Project was held in Romania in 2004, the one-day conference being followed by a three-day field trip in the Romanian Carpathians. Most of the investigated sections in the field are situated in the Bend Area of the Romanian Carpathians. Upper Cretaceous Red Beds from the above-mentioned region display various facies (pelagic/hemipelagic, turbiditic), covering the interval Cenomanian-Maastrichtian (including the K/T boundary interval). The causes which produce this type of sedimentation are various. Changes in geoechemical regime, in palaeoproductivity of surface waters as well as in palaeogeography were assumed to interact. Key words: Upper Cretaceous, red beds, Romanian Carpathians. INTRODUCTION A major change in the world oceans from disoxic sediment deposition to an oxic depositional regime took place within the Upper Cretaceous. Such change, in the western Tethys and Central North Atlantic oceanic basin, occurred shortly after deposition of the Bonarelli horizon (Cenomanian/Turonian boundary interval), which is marked by a significant change in the δ13C carbon isotope. The deep sea red pelagic deposition of clays and marls continues into early Cenozoic (Paleo-cene/early Eocene). This change resulted in major modification in the location of the organic carbon reservoir, therefore it has a direct economic impact, as it affected location of source rocks for oil hydrocarbon generation, and it may also indicate changes in the climate and atmospheric conditions. Several Earth processes, such as paleoceano-graphic (e.g., changes in global ocean chemistry, paleocirculation), tectonic (opening and closing of the seaways, migration of the continent plates), climatic (change from greenhouse to icehouse conditions) and eustatic (major sea-level rise), could contribute to this change. Another possibility is that this dramatic change in Late Cretaceous sediment deposition may signal a change in paleoproductivity, which could alter the balance between carbon sources and sinks in the oceans. Some scientists suggested that the increase in organic carbon in deep sea sediments during the middle Cretaceous was, in part, related to an increase in organic productivity in the oceans. Therefore, does the lack of organic carbon in deep ocean sediments during the Late Cretaceous represent a major change in bioproductivity in the ocean? If it does, what caused such a major change? If no carbon was buried under the oceans, what was the carbon cycle during this time period and what was its effect on the paleoclimate? Global change from deposition of pelagic “black shale” to deposition of oxic sediments may indicate more fundamental changes in long-term carbon cycling on Earth. The above-mentioned issues constitute the subject of IGCP UNESCO 463-Upper Cretaceous Oceanic Red Beds: Response to Ocean/Climate Change (CORB) -, which was approved to be funded between 2002-2006. The first two meetings (during the summer of 2002 and 2003) were held in Italy (Ancona) and respectively in Turkey (Bartin, on the coast of the Black Sea). ROMANIAN WORKSHOP As Cretaceous Oceanic Red Beds are widely distributed in the Romanian Carpathians, made by different facies (turbiditic and pelagic) as well as covering different stages, the members of the IGCP-UNESCO 463 planned the Third meeting of this project in Romania. Consequently, the Third Meeting of IGCP UNESCO Project 463 was held in Romania, between 15 th -18 th The workshop was organized by the National Institute of Marine Geology and Geo-ecology (GEOECOMAR Bucharest) and sponsored by National Institute of Marine of August 2004.