Development of Lower Cretaceous deposits from Bihor-Pădurea Craiului unit (Apuseni Mountains, Romania): Comparisons with Villany region in Hungary

The Lower Cretaceous deposits from Bihor-Pădurea Craiului unit follow a sedimentary gap due to the uplift of the region at the end of the Late Jurassic, when bauxitic rocks were formed. The succession consists of the following lithostratigraphic units: (1) Blid Formation, comprising two members: (1a) Dobreşti Member (Valanginian-Hauterivian) known in the old literature as “Limestone with characeans and gastropods”), and (1b) Coposeni Member (Barremian), the old “Lower Pachyodont limestone”; (2) Ecleja Formation, consisting mainly of marls, but containing also two lithologically different members: (2a) Gugu Breccia Member (Upper Barremian), and (2b) Valea Bobdei Limestone Member (Lower Bedoulian), corresponding partly to the old “Middle Pachyodont limestone”; (3) Valea Măgurii Limestone Formation (Upper Bedoulian), also corresponding partly to the old “Middle Pachiodont limestone”, and (4) Vârciorog Formation (mainly marls and sandstones, with limestone intercalations) (Gargasian-Albian) that correspond to the old “Formation of glauconitic sandstones and Upper Pachyodont limestone”. Of these lithostratigraphic units Dobreşti Member and Ecleja Marls have been often a subject of controversy. The age of Dobreşti Member proved to be Valanginian-Hauterivian. Regarding the Ecleja Marls, recent researches revealed that the succession of the startotype is younger as considered before (Late Aptian-Albian, instead of Late Barremian-Early Aptian). Other recent researches have shown the development of a large pile of Upper Aptian-Albian platform limestones, equivalent of limestone intercalations within the Vârciorog Formation. These new data change our understanding of the Bihor-Pădurea Craiului basin evolution during the Aptian-Albian time interval. At the biginning of Aptian, a deeper basin was formed. On local highs within the basin isolated carbonate platforms developed (Valea Bobdei, Valea Magurii, and Subpiatra Limestones). Material from these platforms can be found as debris flows (allodapic limestones) intercalated in the terrigenous succession of the basin. Within the Villany Hills (Hungary) the Nagyharsány Limestone formed also on the Upper Jurassic Szársomlyó Limestone Fm revealing bauxite lenses (Harsányhegy Bauxite Fm) at its base. The age of the Nagyharsany Limestone wich consists of four lithologic (calcareaous) members is considered as Valanginian-Early Albian. It is covered by the Bisse Marls of Late Albian-Cenomanian age. No other marl intercalations were reported from the Nagyharsany Limestone.
   The Bisse Marl is replaced at a marked contact by flysch type succession of the Bóly Sandstone Formation in the Late Albian. Based mainly on micropaleontological association the lower part of the Villány succession could be compared with the Dobreşti and Coposeni members of the Blid Formation, while its middle and upper parts of the Nagyharsány Limestone could be correlated with Valea Bobdei-Valea Măgurii, and Subpiatră Limestones, respectively. The Vârciorog Fm is equivalent to the Bisse and Bóly Formations.
   Acknowlegdments: The study was partly financed by CNCSIS (grant ID_95, Ioan Cociuba), and by Alexander von Humboldt Fountation (Ioan I. Bucur).