Microfauna close to the Eocene-Oligocene boundary in the boring at Kallo

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The punctuation in the evolution of orbitoides in the campanian of South-West France

For the Orbitoides assemblages analyzed from a number of closely sampled sections of Campanian calcarenites in south-west France there is a sudden change in the means of several parameters of the internal embryonicnepionic stage. The direction of the change is in accordance with the nepionic acceleration principle, known to be valid for all lineages of orbitoidallarger foraminifera. Below and above the level of the morphological break we seem to be dealing with two longer periods without any systematic change in the morphology. In two of the sections the abrupt shift could be narrowed down to a lithostratigraphic distance of about ten centimetres, an interval which is thought to correspond to a time duration of less than a few thousand years. In none of the sections could any evidence be found that might point to a hiatus in the sedimentation or to a notable change in the open-marine, shallow-water environment. Since the discontinuity was found in sections about 90 km apart (Aubeterre and Meschers) the change must have occurred simultaneously throughout the entire Aquitaine basin. If we take into account that bioturbation must have had an obliterating effect on our data, it seems safe to conclude that the modal morphological change was very large and geologically instantaneous. Because no comparable change in internal morphology could be detected in the accompanying Lepidorbitoides lineage it is thought likely that the fundamental change in the population composition of the Orbitoides was an autonomous happening fitting into the evolutional theory of homeostasis and punctuation. The pulsating pattern in the stasis parts of our data sets is rather weak; phyletic gradualism is still thought to be an acceptable theory to explain the gain of more advanced morphotypes and the loss of conservative ones in our Orbitoides sequence. At the end of our paper it is argued that the concept of sympatric speciation passing through low-frequency bottlenecks in the suites of populations is the one that would fit best to the evolutional history of the lineages of orbitoidal foraminifera. This model would combine the random character and the directional aspect of evolution, which are expressed in various ways in all better known lineages

Smaller radiate Nummulites of Northwestern Europe

After the completion of J. P. H. KAASSCHIETER's monograph on the "Eocene Foraminifera of Belgium" (1961), an extensive collection of smaller radiate Nummulites from the Belgian Eocene remained without specific determination in the collections of the Utrecht Geological Institute. KAASSCHIETERhad found that naming these fossils on the basis of the existing literature would lead to very unsatisfactory results. He felt that a tremendous lot of work in measuring and counting should be needed to arrive at a still dubious ultimate result, for which reason he preferred to leave his collections as an heritage to a later generation. Since a rapid survey of the material shows no clear pattern of development within this group of Nummulites, no single student dared undertake the work. It was not until early 1963, while A. PAPP stayed in Utrecht for three months, that he and P. MARKSdeveloped a working scheme and put everybody available, some fifteen people altogether, to worL. At the end of these three months the results confirmed the previous opinion that the Eocene and Early Oligocene smaller Nummulites of the North Sea basin showed a peculiar evolutionary pattern and that they were of dubious stratigraphic value. Because of these rather disappointing conclusions the work slowed down, although at various time intervals additional data were gathered. Eventually, however, the evolution pattern and the stratigraphic results were considered to be certainly worth publishing in the context of renewed interest and activities around the Nordic Paleogene

Problems of detailed biostratigraphic and magnetostratigraphic correlation in the Potamidha and Apostoli sections of the Cretan Neogene

The Utrecht working group taking part in the I.G.C.P. project no. 1, "Accuracy in time", received its initial funds in the middle of 1975. The group hastened to collect a first series of samples with which it could begin its research. The marly clays of the selected sections Apostoli and Potamidha 1 cover the major part of the marine Middle-Upper Miocene of Crete (Freudenthal, 1969; Meulenkamp, 1969). The corresponding time span, estimated to be some five million years, was thought to be sufficiently long to permit a detailed study of the evolution of the benthonic foraminiferal lineages of Planorbulinella and Uvigerina and an evaluation of the entries of some planktonic marker species. Moreover, the facies of the deposits was considered suitable for magnetostratigraphic research. The biostratigraphers sampled both sections closely with equal spacing, each sample covering an interval of five to ten centimetres. The magnetostratigraphers had their own sampling method; the position of their cores was calibrated in the field with the sampling spots of the biostratigraphers. In some parallel sections layers with volcanic ash were sampled for radiometric dating. It soon appeared that the bentonite samples were unsuitable, at best they yielded untrustworthy results. Next, the entire Apostoli section was found to give normal polarity for all samples after demagnetization, evidently the sandy-silty character of the clays of this section had provided an opportunity for a subrecent destruction of the original magnetisation in the expected reversed polarity intervals. Since the Potamidha section appeared more suitable, efforts on the Apostoli section were stopped with the exception of the investigation of the Uvigerina lineage (Thomas, in preparation). The gathering of the faunal and floral composition data on the Potamidha samples was started and the usual Utrecht counting procedure was applied, i.e. counting up to 200 specimens for benthonic foraminifera, for planktonic foraminifera and for calcareous nannofossils. While this process of data collecting was nearing completion, the working group began to be dissatisfied with the method. Another partial project was inserted, in which different counting methods were tried and compared (Zachariasse et al., 1978). A variable approach to the collecting of quantitative data appears advisable. Some parts of the numerical composition of the Potamidha faunas and floras should have been tackled with techniques other than the standard 200- counting adopted in the beginning. In the meantime Raju had completed the observations of the Potamidha Planorbulinella and the magnetostratigraphic survey had yielded tangible results which called for a nearby comparison section. Section Potamidha 2 was sampled primarily for such a repetition of the polarity scale of Potamidha 1. The problems ensuing from this comparison necessitated the continuance of the investigation of the Potamidha 1section. A second major result emerged from Raju's Planorbulinella observations, and as a result a continuation of the research downward into the older samples from the Apostoli section was considered to be highly desirable. This research was carried out by P. H. Doeven in the course of 1977. The group which had made the 200-counts on the composition of the three groups of microfossils was not enthusiastic about repeating the timeconsuming counting with the more sophisticated methods that had become available. The group felt it would be more logical to include new problems and subjects into its programme. Hence, it was decided that we would present the "primitive" data on the benthonic foraminifera, the planktonic foraminifera and the calcareous nannoplankton as they were in 1976-77. These data are sufficiently detailed to serve as a backcloth for the account of the peculiar Planorbulinella evolution and the problems that originated from the magnetostratigraphic correlations

Depth-relations of recent larger foraminifera in the Gulf of Aqaba-Elat

Intensive research on the recent foraminifera in the Gulf of Aqaba- Elat and their physico-chemical environment is being carried out for the last decade by groups of specialists from the Universities of Jerusalem, Basel, and Copenhagen. The results obtained hitherto indicate that this part of the northern Red Sea may represent a model-area of prime interest for a better understanding of foraminiferal distribution and, therefore, for paleontological interpretations of fossil faunas. The involvement in the study of this model area of the Utrecht University group is based on the latter's participation in the International Geological Correlation Program, Project 73/1/1 "Accuracy in Time". Since many biostratigraphical correlations are based on the evolution of measurable parameters of larger foraminiferal species groups, an investigation of possibly environment-dependent morphological changes in living Foraminifera was urgently needed. A recently advanced theory that proloculus-size might increase at greater water-depth was one such topic. Since the thermo-, halo-, and pycnoclines in the Gulf of Elat are rather insignificant, changes with depth in morphology and distribution of foraminiferal species must be governed by depth-related factors other than temperature, salinity or density. Direct or indirect influence of light penetration and types of substrate are thought to control in the Gulf the depthdistribution of the Soritidae and of the investigated species of Borelis, Amphistegina, Planorbulinella, Operculina, Heterostegina, and Heterocylina. Light may equally influence the intraspecific variation in several of these groups. Major changes seem to take place in the uppermost 80 meters of the depth-profiles. For the LG.C.P. project satisfactory estimates can be made now of the range of variation that mean values of such "evolutionary" features as protoconch diameter and nepionic arrangement may show at one time level, as a consequence of environmental control. The volume summarizes the present-day knowledge on the distribution and morphology of the larger Foraminifera of the Gulf, on their reproduction cycles, symbionts, and their possibly symbiont- and depth-related variability in stable oxygen-isotope ratios