Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 21. 2003. (Budapest, 2003)
Some of these are of tectonic nature. There is considerable evidence to the occurrence of movements (of varying intensity) during the Lutetian s. 1. Such are: gravel interbeds in profiles of the Farkasgyepű and Bakonyjákó areas, oscillatory sedimentation in the so-called Upper Lutetian coal bearing sequence (KOPEK 1980), fluviatile Tokod Sandstone. All these can be connected with the praepyreneic movements (DUDICH & MÉSZÁROS 1963), more recendy called the "terminal Middle Eocene event". At the Lutetian/Bartonian boundary considerable sea deepening can be recognized in the Bakony region. The corresponding sediments are hemipelagic, bathyal (Padrag Marl Formation). This seems to coincide with the number 36 third order cycle of the TA 3 Eocene superq r cle of eustatic sea level changes (HAQ, HARDENBOL & VAIL 1987). Climatic reasons may eventually explain the appearance of JV. aff. prestwichianus in the Priabonian of the Balinka Basin, namely boreal influence. With regard to the thattime subtropical to tropical climate of the Tethyan realm, this would correspond to Mediterranean climate. This assumption is supported by the presence of the equally "boreal" species N. rectus in the Nagyegyháza Basin. An interesting observation refers to the part played by the physical chemistry of seawater. In the larger interval of the andesitic and dacitic tuffs produced by Eocene volcanic activity, in some horizons of the Bartonian and the Priabonian the number of theratologically anomalous specimens is conspicuously high (reversal of growth direction, uni- and bivalent double shells, accessorial chambers etc.). In this respect, the Nummulites of the Halimba Basin, and even more those coming from the tufaceous-tuffitic beds of the Dorog Basin, are the most significant. A starting point for the explanation of this phenomenon may be found a paper published by VlTÁLIS-ZlLAHY (1963). She found unexpectedly high strontium contents in some Eocene samples from the Dorog Basin that contains larger foraminifera. This prompted the author of the present paper to inquire into the physiological effects of strontium. According to the relevant physiological literature, strontium is not only a mutagenic element, but it may also bring about the formation of neoplasma, and, consequendy, irregular shell building. The forthcoming geochemical studies will have to decide whether this hypothesis is true or not. The next observation concerns salinity. In several pro files, Alveolina, Orbitolites and Miliolina constitute characteristic communities. It is conspicuous that Nummulites species are almost totally absent. This extremely subordinate role of the stricdy stenohaline Nummulites may be due to a slight decrease from the normal 35 permil salinity, which is somewhat better tolerated by Alveolines and Orbitolites, and is even very favourable for Miliolina. However, other kinds of competition are also possible. To reach an unambiguous solution, further studies are needed. Beyond doubt the external factors contributed to the almost monospecific occurrence of N. perforatus and N. millecaput in the representative profiles (boreholes Sv. Land Balinka 219.). This phenomenon is known in other regions as well: in Lybia (ARNI 1965), Egypt (AIGNER 1983, 1985), Spain (SERRA-KlEL «SC REGUANT 1984), SW Slovenia (PAVLOVEC 1984) and Switzerland (HERB 1986). The massive accumulation of foraminifera shells, baptized "biofabric" by AIGNER (1985), can be approached by two different ways. Namely by analysing (1) the ratio of the microspheric (B) and the megaspheric (A) generations, and (2) the arrangement of the shells. On this basis, four types can be distinguished: 1 — autochtonous (undisturbed) arrangement, 2 — parautochtonous arrangement, 3 — residual arrangement, 4 — allochtonous arrangement (AIGNER 1985). In the investigated profiles type 1 (JV. perforatus, N. millecaput in borehole Sv. 1.) and type 3 (N. millecaput in borehole Ba. 219.) could be identified. In type 1 the generation A is dominating (A:B ratio = 10:1), while in type 3 the generation B is dominating. In the latter type the B forms make up fascicles, eventually tile-on-tile structures intercalated by A forms. In some intervals of the Balinka samples, Form A has been almost completely removed hydrodynamically, leaving behind a residual "package", consisting only of Form B. In the case of type 1, the energy level of the medium was low, while in that of type 3 the water must have been rather agitated. The depth distribution was dealt with in a previous paper (KECSKEMÉTI 1989), so there is no need to elaborate on it here. Role of the evolutive factors in the development of palaeocommunities The test of the larger Foraminifera, just as the test of any other fossil, reflects the process of ontogeny and phylogeny, their level and trend. Consequendy, its morphogenetic study provides us with valuable information about the process of evolution. The general evolutionary trend of Nummulites and other larger Foraminifera, which display an alternation of gene, can be best traced on the ontogeny of the microspheric (B) generation. Three statements may serve as a starting point. — The spire of the microspheric generation consists of three successive sectors: the inner or embryonal one (core with the diameter of the initial chamber in the megaspheric generation), the middle one (corresponding with the full test diameter of the adult megaspheric generation), and the outer one, exceeding the shell diameter of the megaspheric generation. — In ontogeny, the changes of the shape of the chamber are of particular importance. These are also relevant for phylogeny: the primitive taxa are characterized by high (operculinoid) or isometric (assilinoid) chambers, while the more evolved ones by long (nummulitoid) chambers. — The middle spire sector of the microspheric generation is characteristic for each taxon, while the features of the three sectors combined provide information about the general evolutionary level of the taxa, which defines the place of a given taxon in the phylogenetic lineage.
