ACTA PALaEONTOLOGICA ROMANIAE V. 7 (2011), P. 335-342 REASSESSMENT OF THE SPATIAL EXTENT OF THE MIDDLE MEMBER, DENSUŞ-CIULA FORMATION (MAASTRICHTIAN), HAŢEG BASIN, ROMANIA 1 1 1 ŞTEFAN VASILE , ZOLTÁN CSIKI , DAN GRIGORESCU Abstract. The fossil-bearing Maastrichtian continental deposits of the Haţeg Basin have been assigned to different lithostratigraphic units and subunits based on their lithology and fossil content; among these, the vertebrate fossil- and volcanoclast-bearing beds from the north–western part of the basin were referred to the Middle Member of the Densuş- Ciula Formation. Continuing fieldwork in this area allows a reconsideration of the spatial extent of the previously- separated units. Based on their lithology and fossil remains, deposits cropping out near General Berthelot locality can be also included into the Middle Member of the Densuş-Ciula Formation. Accordingly, the eastern boundary of this subunit has to be moved eastwards than it was previously considered. Keywords: Haţeg Basin; Maastrichtian; Densuş-Ciula Formation; eggshells; microvertebrates. INTRODUCTION The vertebrate-bearing continental deposits of Haţeg Nopcsa considered most of the coarser-grained Basin, well-known for the remains of dwarf dinosaurs they sediments (sandstones and conglomerates with thin silty yielded, cover the north–western and central–eastern mudstone intercalations) cropping out at Sânpetru, parts of the basin. While in the central–eastern part the Sântămăria-Orlea, Nălaţ-Vad, Haţeg, Crăguiş, deposits occur extremely patchy, along several of the main Fărcădinul de Jos (today General Berthelot) and river courses (see Codrea et al., 2009 for a review), at the Fărcădinul de Sus (today Fărcădin) to represent the north–western margin these deposits are distributed as an same type of freshwater deposits, generically-named elongated belt extending eastward from Ciula Mică and “the Sânpetru Sandstone”. In the area between Densuş, Densuş localities, towards the town of Haţeg. Ciula Mică, Răchitova and Stei, Nopcsa described tuff- Nevertheless, the outcrops here are also discontinuous, rich deposits, associated with porphyric rock due to the extensive cover of soil and vegetation in this intercalations, considering them to be a local facies hilly area. Due to this setting, as well as to the absence of variation of the Sânpetru Sandstone. Nopcsa (1905) also traceable marker-beds in the dominantly siliciclastic noted the constant increase in the size and the quantity sequence, dating of the deposits and establishment of a of the volcanogenic clasts proceeding from Sânpetru well-defined lithostratigraphic framework had proven to be towards Densuş, a good hint to where the source difficult. One of the main controversial points concerns the supplying this volcanogenic material was located. spatial extent of the Maastrichtian deposits and the Laufer (1925) recognized the same distinction position of the Cretaceous/Tertiary boundary (K-TB), as it between the tuffaceous and the fluvio-lacustrine facies of was often assumed (see below) that continental deposition the “Danian” deposits, while also mentioning leaf in this area was continuous into the Paleogene. Lacking impressions from Densuş area. However, he raised other means of dating, the presence and, respectively, some doubts about the Cretaceous age of the absence of clearly-identifiable Cretaceous fossils was conglomerates cropping out around Crăguiş, considering used as the main argument to draw the possible position them to represent a “problematic Paleogene”, based on of the K-TB. This limit is considered to mark the boundary the lack of fossil remains in this area. between two subunits of the lithostratigraphic unit that To the contrary, Mamulea (1953) assigned the groups the continental deposits from the north-western continental deposits lying east of a Ciula Mică–Densuş part of the Haţeg Basin. line to the Paleogene–Lower Miocene (Aquitanian), Recent discovery of fossil remains, including mainly based on a perceived colour difference (i.e., dinosaurian eggshells, suggests that the area covered by dominantly gray deposits in the Răchitova-Ştei-Densuş- Maastrichtian continental beds extends probably farther Ciula perimeter, as opposed to dominantly red deposits eastward along the northern border of the basin than east of it) and the purported presence of in situ dinosaur previously considered. bones in this area. Although not expressed straightforward, the bones reported previously by LITHOSTRATIGRAPHY OF THE MAASTRICHTIAN Nopcsa (e.g., 1905) from the Vălioara area were CONTINENTAL DEPOSITS – A HISTORICAL considered as being reworked from the underlying OVERVIEW tuffaceous deposits of the “Danian”. This line of reasoning was followed subsequently by other workers Nopcsa (1905) was the first to describe the Cretaceous as well (e.g., Iliescu et al., 1972, unpublished report); deposits of the Haţeg Basin in detail, trying to fit the accordingly, the Geological Map of Romania also shows dinosaur-bearing deposits into the general geological these deposits as being of Paleogene age (Codarcea et framework. Nopcsa outlined the lithological features of the al., 1968). fossiliferous deposits, which he considered to be Danian in age, the Danian representing at that time the last stage of the Cretaceous. 1 Laboratory of Paleontology, Faculty of Geology and Geophysics, University of Bucharest; 1 N. Bălcescu Ave., 010041, Bucharest, Romania; e-mail: [email protected] 335 ŞTEFAN VASILE, ZOLTÁN CSIKI & DAN GRIGORESCU Fig. 1 - Simplified geological map of the Haţeg Basin, showing the location of the main egg and eggshell localities. Abbreviations: Bd – Badenian; J1 – Lower–Middle Jurassic; J3 – Upper Jurassic; K1 – Lower Cretaceous; K2m – marine Upper Cretaceous; K2c – continental Upper Cretaceous (the Densuş-Ciula and Sânpetru Formations); Pc – crystalline basement, mainly Precambrian; Pg – Paleogene; Q – Quaternary; Sm – Sarmatian (redrawn after Grigorescu & Csiki, 2008). Dincă et al. (1972) assigned the “Danian” deposits to represents an important component of the rocks. No the Maastrichtian, according to the conclusions of the significant vertebrate remains have been reported from Copenhagen International Geological Congress (1970), this member, the most important paleontological which included the Danian stage into the Paleocene discoveries concern those of Late Cretaceous fossil Series, the Maastrichtian becoming the uppermost stage plant impressions (Mărgărit & Mărgărit, 1967). of the Cretaceous. The deposits forming the Middle Member comprise The revival of fossil vertebrate research in the Haţeg silty mudstones, sandstones and conglomerates Basin that started in the late 1970’s, brought new containing volcanogenic clasts in significantly-smaller information on the stratigraphic context of the continental quantities than those of the lower member, as well as deposits, whose Maastrichtian age was reinforced by typical latest Cretaceous vertebrate remains. palynological studies (Antonescu et al., 1983). The Upper Member was described to consist of Two lithostratigraphical units have been recognized coarse deposits, mainly matrix-supported, massive red- within the Maastrichtian continental deposits (Grigorescu & colored conglomerates, devoid of volcanogenic clasts or Anastasiu, 1990; Grigorescu, 1992; Fig. 1). The typical vertebrate remains, distributed from west of Fărcădin to “Sânpetru Sandstone” facies deposits along the Sibişel east of Haţeg. The age of this member was not very well and Râul Mare valleys have been assigned to the constrained: it may be as old as the Maastrichtian, as it Sânpetru Formation, together with the sandstones and red overlays the Maastrichtian deposits of the Middle silty mudstones exposed along the Bărbat River valley, at Member, but, because of the absence of vertebrate Pui. The more recently-identified uppermost Cretaceous fossil remains, it may also partially correspond to the deposits along the Ruşor and Râul Mare rivers have also Lower Paleogene. These deposits correspond to been attributed to the Sânpetru Formation (Codrea et al., Laufer’s above-mentioned “problematic Paleogene”. 2009). The Sânpetru Formation deposits are characterized by the absence of volcanogenic material among the clasts THE MIDDLE MEMBER OF THE DENSUŞ-CIULA of the coarser deposits (sandstones and conglomerates) FORMATION and the common occurrence of vertebrate fossil remains. The Maastrichtian continental deposits placed west of As already mentioned, the Middle Member of the Haţeg and north of the Galbena River valley were grouped Densuş-Ciula Formation is exposed in different valleys as the Densuş-Ciula Formation, and have been separated and escarpments in the area bounded by a line crossing into three members, based on their fossil content and Densuş, Ciula Mare and Tuştea along the Galbena River lithological features (see Grigorescu, 1992). The Lower to the south, the Poiana Ruscă crystalline basement to Member, best exposed along Densuş Valley, is the north and north-west, and the Upper Cretaceous represented by deposits corresponding to the “tuff facies” marine Răchitova Formation and the Lower Member of as described by Nopcsa, where the volcanogenic material the same Densuş-Ciula Formation, to the west. 336 REASSESSMENT OF THE MIDDLE MEMBER OF THE DENSUŞ-CIULA FORMATION All types of detritic rocks are reported to occur within been reported from Livezi (Grigorescu & Csiki, 2008). this member, the inferred depositional environment being Newly discovered limited outcrops