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Nummulitids, Lepidocyclinids and strontium isotope stratigraphy of the Porto Badisco Calcarenite (Salento Peninsula, southern Italy). Implications for the biostratigraphy and paleobiogeography of Oligocene Larger Benthic Foraminifera
No full textThe Oligocene Porto Badisco Calcarenite (Apulian Carbonate Platform, southern Italy) contains very rich and diverse assemblages of larger benthic foraminifera. In this paper we provide the first comprehensive taxonomic study of Nummulitids and Lepidocyclinids, based on a biometric approach to species identification. The larger foraminiferal assemblage is dominated by Eulepidina, Heterostegina and Spiroclypeus. Nummulites, Operculina and Nephrolepidina make a subordinate but significant contribution. The concurrent range of the larger foraminiferal species present in the Porto Badisco Calcarenite, and in particular the presence of Spiroclypeus margaritatus and of Miogypsinoides complanatus-formosensis, indicates the late Oligocene Shallow Benthic Zone (SBZ) 23. The taxonomic composition of the larger foraminiferal assemblage of the Apulian Carbonate Platform is very similar to coeval assemblages of other localities of the western Tethyan realm (southern France, southern Spain, Malta, Greece), while some typical components of the SBZ 23 assemblages, like Heterostegina assilinoides and Eulepidina dilatata, are missing in more eastern areas (Turkey, India). Strontium isotope stratigraphy gives an age of 23.6 ± 0.5 Ma for the lower part of the Porto Badisco Calcarenite, constraining the chronostratigraphic calibration of the SBZ 23 within the latest Chattian. This calibration further supports the correlation between the SBZ 23 of the European Basins biozonal scheme with the Te 4 stage of the East Indian Letter Classification
Comment on “Singh R, Vadlamani R, Bajpai S, Maurya AS (2024) Strontium Isotope Stratigraphy of Marine Oligocene–Miocene Sedimentary Successions of Kutch Basin, Western India. Geological Journal, 1–20. DOI: 10.1002/gj.4961”
No full textThis is a comment on the paper of Singh et al. (Geological Journal, 2024:1–20) on Strontium isotope stratigraphy of marine Oligocene–Miocene sedimentary successions of Kutch Basin, western India. Kutch hosts stratotypes of some lithostratigraphic and chronostratigraphic units of India. In this study, the Sr-isotope estimated ages of the studied formations deviate significantly from their known ages based on biostratigraphy. The authors have not validated the interpreted ages with biostratigraphy. We believe a scrupulous screening of samples and validation of Sr-isotope data with biostratigraphy are two essential requirements of Sr-isotope stratigraphy. Unfortunately, Singh et al. made a new contribution to Kutch stratigraphy that falls short of meeting both conditions, leading to incorrect ages of the regional chronostratigraphic units of India
Paleobiological Applications of Three-Dimensional Biometry on Larger Benthic Foraminifera: A New Route of Discoveries
No full textFour specimens of larger benthic foraminifera (the Recent Palaeonummulites venosus and Operculina ammonoides, and the phylogenetically related Paleogene Nummulites fabianii and N. fichteli) were investigated by X-ray tomography. The resulting three-dimensional measurements enabled a comprehensive, quantitative study of shell morphology to interpret cell growth without specific shell preparation and/or destruction. After segmentation and extraction of all scanned lumina, the following characters were measured on all chambers of each specimen: chamber volume, septal distance, chamber height, and chamber width. The sequence of chamber lumina follows either a logistic function Palaeonummulites, Operculina), where the deceleration in growth rate of the latest chambers could mark the onset of reproduction, or it can be modeled by a series of stepwise functions with differing constants Nummulites). Variations around the growth model are either periodic, following external cycles, or random as expressed by abrupt deviations. Therefore, they may reflect the response of the cell to environmental changes in terms of cyclic changes (e.g., seasonality) or single events (e.g., predator attack). Correlations between chamber volume and the other chamber parameters show that septal distance always matches the sequence in chamber volume and can therefore be used as a proxy for environmental analyses in both growth models. Chamber height and width often remain constant around their function and rarely deviate drastically to accommodate the needed lumen for retaining test size and shape. Chamber width may vary according to chamber volume in involute specimens, whereas both chamber height and width correlate with volume in those tests following an Archimedean spiral. X-ray-tomography shows particular promise in determining which parameters that can be assessed routinely in two dimensions primarily reflect environmental conditions vs. parameters best used for taxonomie identification and for systematic lineage reconstruction
Supposed trans-Atlantic migration of Heterostegina around the Eocene/Oligocene boundary
Get PDFAccording to our hypothesis, Heterostegina ocalana migrated eastward through the previously much narrower Atlantic Ocean around the Eocene/Oligocene boundary. Sporadic populations of H. n. sp., its phylogenetic successor, survived in the western part of the Neotethys until the end of the Rupelian, when they became extinct
Heterostegina matteuccii sp. nov. (Foraminiferida: Nummulitidae) from the lower Oligocene of Sicily and Aquitaine: a possible transatlantic immigrant
No full textThe systematics and phylogenetic relations of the Oligocene species of Heterostegina (Nummulitidae) are poorly known
compared to those of Eocene and Miocene species. The new species Heterostegina matteuccii sp. nov., characterized by
the combination of an advanced nepionic stage (i.e. very few operculine chambers) and a relatively small proloculus, is
here described from the lower Oligocene Caltavuturo Formation of Portella Colla (Madonie Mts, Sicily, Italy). The same
species is recorded also in the ‘Calcaire a asteries’ Formation of Illats (Northern Aquitaine, near Bordeaux, France).
Biometrically, H. matteuccii sp. nov. does not fit within any known Neo-Tethyan lineage of Heterostegina from the
Eocene to the Miocene, and hence is considered to be a member of a distinct phyletic lineage. The advanced nepionic stage
of H. matteuccii sp. nov., however, calls for the existence of predecessors. The Priabonian (and possibly also earliest
Oligocene) H. ocalana Cushman, 1921 from the American-Caribbean realm is here interpreted as the most probable
ancestral form for the H. matteuccii lineage. Thus, an early Oligocene eastward transatlantic migration of this lineage may
be inferred. New results of strontium isotope stratigraphy from both sides of the Atlantic Ocean are consistent with this
hypothesis
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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