The updated orthophragminid zonation and main turnovers based on the late Paleocene to Priabonian record from Turkey

Abstrac

Late Eocene evolution of Spiroclypeus in Europe

Abstrac

Bartonian to end-Rupelian reticulate Nummulites of the Western Tethys

Abstrac

Evolution of western Tethyan involute Heterostegina from late Bartonian to the end-Priabonian

Abstrac

Paleobiological applications of three-dimensional biometry on larger benthic foraminifera: A new route of discoveries

Four 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

Integrated biostratigraphy of the middle to upper Eocene Kırkgeçit Formation (Baskil section, Elazığ, eastern Turkey): larger benthic foraminiferal perspective

The Baskil section, located to the west of Elazığ in eastern Turkey, represents deep-marine facies of the Eocene Kırkgeçit Formation, deposited in a wide spectrum of environmental conditions ranging from shelf to basin. The 390-m-thick sequence was deposited at bathyal depths in the Tethys, at the edge of the subsiding Anatolide–Tauride plate and is highly promising for an integrated study of Bartonian to earliest Priabonian mid-latitude neritic and deep-marine biota. The section contains numerous allochthonous limestone beds, characterized either by turbidites or debris flows with resedimented larger benthic foraminifera (LBF). The section spans the planktonic foraminiferal Zones E10/11 to E14, the calcareous nannofossil zones NP15–NP18, shallow benthic zones (SBZ) SBZ16/17 to SBZ18A, including orthophragminid (OZ) zones OZ12–OZ14. The Bartonian–Priabonian boundary is placed at NP17/18 boundary by the lowest occurrence of Chiasmolithus oamaruensis, which lies within Subchron C17n.1n and Zone SBZ18A. The LBF, obtained as loose specimens from 17 turbiditic and debris flow beds, are characterized predominantly by 21 orthophragminid lineages and 13 nummulitid species as well as some other stratigraphically diagnostic genera. Most of the orthophragminid lineages straddle the Bartonian–Priabonian boundary, whereas Orbitoclypeus douvillei and Discocyclina pulcra appear to be the only orthophragminids confined to SBZ17 at its upper range. The Nummulites fabianii-lineage first appearing in zones E12 and NP16 in the Bartonian shows a well-documented evolution of the embryon, and is referred to Nummulites garganicus in the Bartonian, whereas its successor Nummulites hormoensis straddles the Bartonian/Priabonian boundary. The first appearances of N. hormoensis and Heterostegina armenica as well as the last occurrences of Nummulites ptukhiani and Assilina exponens in the section are almost coeval and are utilized to mark SBZ17–18 boundary. The first appearance of the H. armenica-lineage is recorded in zones E14 and upper part of NP17. Two important species, Chapmanina gassinensis and Silvestriella tetraedra, have been first recorded in SBZ18A just above the Bartonian–Priabonian boundary. Thus, the transition of N. garganicus to N. hormoensis, the first appearances of H. armenica, C. gassinensis and S. tetraedra as well as the last occurrences of N. ptukhiani, Assilina exponens, Discocyclina pulcra and Orbitoclypeus douvillei, all across the SBZ17–18 boundary or within the SBZ18A, appear to be the most useful bioevents in the transition from the Bartonian to the Priabonian in shallow-marine realms

High-resolution integrated magnetobiostratigraphy of a new middle Eocene section from the Neotethys (ElaziÄ\u9d Basin, eastern Turkey)

The progressive closure of the Neotethys Ocean had a profound impact on the oceanclimate system during the Cenozoic. In this perspective, Turkey represents a key area for studying the climate evolution during the Eocene, because it was located at the gateway between the Neotethys and the Atlantic Ocean. Here, we present a high-resolution integrated magnetobiostratigraphic record of a new middle Eocene sedimentary section from the ElaziÄ\u9d Province, eastern Turkey. The continuous, undisturbed, and undeformed sedimentary record, together with preserved geomagnetic signal and fossil assemblages, allows the establishment of a detailed age model, which spans from the upper part of chron C19n.1r to the base of chron C17n.1n (42.4-37.8 Ma). Field observations and paleontological and paleomagnetic data show that the section has not been affected by the widespread tectonic deformation that characterizes the region. We suggest that the magnetostratigraphically and biostratigraphically calibrated Baskil section represents a new, outstanding shallow- to deep-marine sequence where paleoceanographic and paleogeographic studies can be conducted to understand the middle Eocene climate evolution