Early Priabonian Research Articles

Stratigraphy and biostratigraphy (charophytes) of the marine-terrestrial transition in the Upper Eocene of the NE Ebro Basin (Catalonia, Spain)

The onset of endorheic sedimentation in the Ebro Basin is a prominent feature of the basin’s evolution and has recently been characterized as a rapid event occurring in the Early Priabonian. In the north-eastern part of the basin this event coincides with the deposition of the Artes Formation (Fm.), mainly built up by red beds of alluvial origin. The marine-continental boundary has been poorly studied up to now in the so-called Llucanes area, and what was previously thought to be the base of the Artes Fm. is actually a transitional unit, which we define as the Sant Boi Formation, which covers the underlying marine Milany Depositional Sequence and passes laterally to the Terminal Complex, extending over 15km along the eastern margin of the Ebro Basin. The Sant Boi Fm. is formed by up to 15-20m of alternating siltstones and lutite, grading upwards to brackish and lacustrine marls and lignite, and represents deposition in a brackish to freshwater floodplain. It is characterized biostratigraphically by the fossil charophyte assemblage Harrisichara lineata, Harrisichara vasiformis-tuberculata and Nodosochara jorbae, from the middle part of the Priabonian. In contrast, the overlying red beds of the Artes Fm. are characterized by assemblages containing Harrisichara tuberculata, Nodosochara jorbae and Lychnothamnus longus from the Late Priabonian. These results are largely consistent with recent magnetostratigraphic studies performed south of the studied area, and have enabled us to refine the stratigraphy of the marine-continental transition in the north-eastern Ebro Basin.

Stratigraphy and Larger Foraminifera of the Middle Eocene to Lower Oligocene Shallow-Marine Units in the Northern and Eastern Parts of the Thrace Basin, NW Turkey

The shallow-marine Eocene Soğucak Limestone and Oligocene Ceylan Formation were studied in the northern and eastern parts of the Thrace Basin with detailed biometric analysis of the full spectrum of larger benthic foraminifera (mainly nummulitids and orthophragmines). This allows us to establish a high-resolution biostratigraphy in the context of the shallow benthic zonation (with SBZ zones) of the Tethyan Palaeogene since larger foraminiferal assemblages show a very strong Western Tethyan affinity. Only two species (Heterostegina armenica and Orbitoclypeus haynesi) are unknown so far to the west of the Thrace Basin. The age of particular larger foraminiferal sites is determined based on (i) the occurrence and developmental stage of different species of Heterostegina (H. armenica hacimasliensis n. ssp. is introduced here), (ii) the presence/absence of giant Nummulites, (iii) the presence/absence of Spiroclypeus, (iv) the developmental stage of reticulate Nummulites, (v) the occurrence and developmental stage of orthophragmines, (vi) the occurrence of particular Operculina and radiate Nummulites. Six larger foraminiferal horizons could be established. They correspond to (i) the vicinity of the early/late Bartonian boundary (SBZ 17/18), (ii) the middle late Bartonian (SBZ 18B), (iii) the latest Bartonian (SBZ 18C), (iv) the early Priabonian (SBZ 19), (v) the late Priabonian (SBZ 20) and (vi) the early Rupelian (SBZ 21). Three main shallow-water depositional environments could be recognized in both the late Bartonian and Priabonian: two of them took place in the middle shelf; one with low and another with high water-energy (back-bank and Nummulites-bank facies) whereas the third one refers to the outer shelf (fore-bank facies). Biostratigraphical and palaeoenvironmental observations allow us to reconstruct three subregions in the northern and eastern parts of the Thrace Basin with different depositional histories: (i) The eastern part of the territory, with an İstanbul Zone basement was flooded at the beginning of the middle late Bartonian (SBZ 18B), but the carbonate platform was drowned in the latest Bartonian (SBZ 18C). (ii) The Çatalca block, lying on the Istranca Massif, formed a palaeohigh in whose peripheries a similar depositional history to for the former sub-region can be reconstructed, although the central part was transgressed only in the late Priabonian and was not drowned at all. (iii) The northern margin of the recent Thrace Basin (also lying on the Istranca Massif) was flooded only in the latest Bartonian (SBZ 18C) or in the early Priabonian (SBZ 19) and the Priabonian carbonate platform had only partly and shallowly been

Late Eocene sea retreat from the Tarim Basin (west China) and concomitant Asian paleoenvironmental change

The Paleogene sediments of the southwest Tarim Basin along the West Kunlun Shan in western China include the remnants of the easternmost extent of a large epicontinental sea. This shallow sea once extended across the Eurasian continent before it retreated westward and eventually separated as the Paratethys Sea. Climate modeling results suggest that this sea retreat is an equally important forcing mechanism as the Tibetan plateau uplift in the aridification of the Asian continental interior and the intensification of the Asian monsoon system. The age and paleogeography of the retreat are poorly constrained, hindering the understanding of its cause and paleoenvironmental impacts. This study reports litho- and biostratigraphic results from two sections recording the last major regression out of the Tarim Basin that is expressed by a regional transition from marine clastics and limestones to continental red-beds. Rich micro- and macrofossil assemblages, including benthic foraminifera, ostracods, bivalves, calcareous nannofossils and organic walled dinoflagellate cysts (dinocysts), indicate a shallow, proximal and marine environment. Strong similarity to assemblages known from Central Asia and Europe confirms that surface–ocean connections extended across Eurasia from the Tarim Basin to the western Tethys during the latest Eocene. Moreover, the recovered fossil associations date the last marine sediments as earliest Priabonian in age (~37Ma; overlap between dinoflagellate Mps Interval Zone and calcareous nannofossil Zone CP 14). The retreat of the sea from the Tarim Basin is time-equivalent with the sea level lowstand at the Bartonian–Priabonian boundary but pre-dates both the Oligocene–Miocene regional uplift of the Pamir mountains and Kunlun Shan and the major eustatic sea-level falls of the Eocene–Oligocene Transition (~34Ma) and mid-Oligocene (~30Ma), which are usually held responsible for the sea retreat. Furthermore, a concomitant and significant aridification step occurs at ~36.6Ma (top of chron C17n.1n) as recorded by regional sedimentary records of the Xining Basin along the northeastern Tibetan Plateau, suggesting that the Tarim Sea served as a significant moisture contributor for the Asian interior.

A primitive hyracoid (Mammalia, Paenungulata) from the early Priabonian (Late Eocene) of Egypt

A new hyracoid genus and species, Dimaitherium patnaiki from the early Late Eocene (early Priabonian) Birket Qarun Formation in the Fayum Depression, Egypt, is described. The material is approximately 37 million years old and three million years older than any other hyracoid known from the Fayum area. A partial cranium preserves features that are likely primitive within Paenungulata, such as a postorbital process made up solely of the frontals (without a parietal contribution), a restricted jugal contribution to the anterior orbital margin, and an anteriorly positioned orbit. The internal mandibular fenestra, a peculiar feature seen in many younger Fayum hyracoids, is primitively absent in Dimaitherium, but a coronoid canal is present at the base of the ascending ramus as in later hyracoids. The dentition of Dimaitherium shows several primitive characteristics, such as poorly molarised premolars, but otherwise differs little from many younger hyracoids. Phylogenetic analysis consistently places younger hyracoids, including procaviids, in a clade to the exclusion of Dimaitherium and the much older Seggeurius and Microhyrax. Given the phylogenetic hypotheses proposed here, the presence of ‘broken’ hypocristids on the lower molars is likely to have evolved more than once during hyracoid evolution. Evidence from the humerus, astragalus and calcaneum indicate that Dimaitherium may have been an agile climber, and was likely capable of rapid movement but was not cursorially adapted. Of the other two small Fayum hyracoids, Dimaitherium was more similar to Thyrohyrax than to Saghatherium. The presence of only this single genus and species in the Birket Qarun localities cannot be explained by depositional biases, and makes an ancient origin for the Fayum hyracoid lineages unlikely. The poorly known large-bodied Early Eocene hyracoids ‘Megalohyrax’ gevini and ‘Titanohyrax’ mongereaui and tantulus from Algeria and Tunisia were not placed with Fayum species of Megalohyrax or Titanohyrax in our phylogenetic analyses. It is unlikely that these species belong to those genera and provide no compelling evidence for an Early Eocene or Paleocene divergence of the Fayum hyracoid lineages.

Stratigraphy and Larger Foraminifera of the Eocene Shallow-marine and Olistostromal Units of the Southern Part of the Thrace Basin, NW Turkey

The Eocene marine sequence in the southern part of the Thrace Basin (NW Turkey) involves a variety of platform and deep-marine olistostromal units, the stratigraphy of which have been vigorously debated in the past. A detailed analysis of larger foraminifera in these either foraminifera or foraminifera-coral-coralline algae-dominated platform and associated comparatively deeper-marine units permits us to establish a high-resolution biostratigraphy in the context of shallow benthic zonation (with SBZ zones) of Tethyan Paleogene. The oldest zone (SBZ 5, corresponding to the basal Ypresian) was observed only in olistoliths. An old erosional remnant of a transgressive shallow-marine to basinal sequence (Dişbudak series; late Ypresian−? middle Eocene) was recognized below the regionally most widespread carbonate platform unit, the Soğucak Formation. The Dişbudak sequence, previously considered to belong to the Soğucak Formation and formally introduced recently, contains larger foraminifera, such as orthophragmines, nummulitids and alveolinids in its shallow-marine package referred to SBZ 10 (late Ypresian). The Soğucak Formation, which often exhibits patch reef developments, contains a rich and diverse assemblage of orthophragmines (Discocyclina, Orbitoclypeus and Asterocyclina), nummulitids (reticulate and other Nummulites, Assilina, Operculina, Heterostegina and Spiroclypeus), and other benthic taxa (Silvestriella, Pellatispira, Chapmanina, Orbitolina, Linderina, Gyroidinella, Fabiania, Halkyardia, Eoannularia, Sphaerogypsina, Asterigerina, Planorbulina and Peneroplis). Their assemblages, referred to SBZ 15/16, 17, 18, 19 and 20 Zones, provide a precise tool for recording the history of marine events which resulted in the deposition of the Soğucak Formation during four main periods. Their spatial distribution, recorded as late Lutetian, early Bartonian, late Bartonian and Priabonian, suggests a marine transgression from WSW to ENE. The Çengelli flysch sequence overlying the Soğucak Formation in a limited area to the east of the Gelibolu Peninsula, contains benthic foraminifera, mainly from limestone olistoliths mostly derived from the Soğucak Formation, and also in the turbiditic strata. The assemblages in the olistoliths reveal the existence of various shallow marine limestone sequences ranging in age from late Bartonian to early Priabonian.

Biometric analysis of middle and upper Eocene Discocyclinidae and Orbitoclypeidae (Foraminifera) from Turkey and updated orthophragmine zonation in the Western Tethys

Research Article| December 01, 2006 Biometric analysis of middle and upper Eocene Discocyclinidae and Orbitoclypeidae (Foraminifera) from Turkey and updated orthophragmine zonation in the Western Tethys Ercan Özcan; Ercan Özcan 1Department of Geology, Faculty of Mines, Istanbul Technical University, Ayazaga/Istanbul 34469, Turkey email: ozcanerc@itu.edu.tr Search for other works by this author on: GSW Google Scholar György Less; György Less 2Department of Geology and Mineral Resources, University of Miskolc, H-35 15, Miskolc-Egyetemváros, Hungary email: foldlgy@uni-miskolc.hu; geobot@freemail.hu Search for other works by this author on: GSW Google Scholar Mária Báldi-Beke; Mária Báldi-Beke 3Geological Institute of Hungary H-1143, Budapest, Stefánia út 14, Hungary email: bal5963@iif.hu; kollanyi@mafi.hu Search for other works by this author on: GSW Google Scholar Katalin Kollányi; Katalin Kollányi 3Geological Institute of Hungary H-1143, Budapest, Stefánia út 14, Hungary email: bal5963@iif.hu; kollanyi@mafi.hu Search for other works by this author on: GSW Google Scholar Botond Kertész Botond Kertész 2Department of Geology and Mineral Resources, University of Miskolc, H-35 15, Miskolc-Egyetemváros, Hungary email: foldlgy@uni-miskolc.hu; geobot@freemail.hu Search for other works by this author on: GSW Google Scholar Author and Article Information Ercan Özcan 1Department of Geology, Faculty of Mines, Istanbul Technical University, Ayazaga/Istanbul 34469, Turkey email: ozcanerc@itu.edu.tr György Less 2Department of Geology and Mineral Resources, University of Miskolc, H-35 15, Miskolc-Egyetemváros, Hungary email: foldlgy@uni-miskolc.hu; geobot@freemail.hu Mária Báldi-Beke 3Geological Institute of Hungary H-1143, Budapest, Stefánia út 14, Hungary email: bal5963@iif.hu; kollanyi@mafi.hu Katalin Kollányi 3Geological Institute of Hungary H-1143, Budapest, Stefánia út 14, Hungary email: bal5963@iif.hu; kollanyi@mafi.hu Botond Kertész 2Department of Geology and Mineral Resources, University of Miskolc, H-35 15, Miskolc-Egyetemváros, Hungary email: foldlgy@uni-miskolc.hu; geobot@freemail.hu Publisher: Micropaleontology Press Received: 26 Sep 2006 Accepted: 09 Feb 2007 First Online: 06 Mar 2017 Online ISSN: 0026-2803 Print ISSN: 1937-2795 © 2006 The Micropaleontology Project, Inc. Micropaleontology (2006) 52 (6): 485–520. https://doi.org/10.2113/gsmicropal.52.6.485 Article history Received: 26 Sep 2006 Accepted: 09 Feb 2007 First Online: 06 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ercan Özcan, György Less, Mária Báldi-Beke, Katalin Kollányi, Botond Kertész; Biometric analysis of middle and upper Eocene Discocyclinidae and Orbitoclypeidae (Foraminifera) from Turkey and updated orthophragmine zonation in the Western Tethys. Micropaleontology 2006;; 52 (6): 485–520. doi: https://doi.org/10.2113/gsmicropal.52.6.485 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyMicropaleontology Search Advanced Search Abstract Orthophragmines from late Lutetian (Alaman), Bartonian (Keçili) and early Priabonian (Sarköy) localities in Turkey are described and illustrated for the first time. Biometry of megalospheric individuals, based on a large number of free specimens sectioned mainly in the equatorial plane, contributes to our knowledge about the orthophragmines in several aspects. They are of western Tethyan affinity and belong to the evolutionary lineages of the genera Discocyclina, Nemkovella, Orbitoclypeus and Asterocyclina, known mainly from the European part of peri-Mediterranean region. Identified foraminifera are categorized into evolutionary lineages, different developmental stages of which are distinguished by biometrically defined subspecies. Two new species of Asterocyclina, A. sireli n. sp. and A. ferrandezi n. sp. from the late Lutetian and early Priabonian respectively, one subspecies of Discocyclina, D. trabayensis elazigensis n. ssp. and one of Orbitoclypeus, O. douvillei malatyaensis n. ssp., both from the Bartonian, are introduced. An emended description of Nemkovella daguini, the poorly known orthophragminid taxon (formerly ascribed to Orbitoclypeus), is given, with emphasis on equatorial development and generic position. Stratigraphic position of orthophragminid populations is ascertained from the calcareous nannoplankton, planktonic foraminifera and the assemblages of accompanying larger foraminifera, such as Heterostegina, Spiroclypeus and some lineages of Nummulites (especially of N. fabiani and N. perforatus). The stratigraphic distribution of some orthophragminid taxa is rearranged and a revision of late Lutetian to early Priabonian orthophragminid foraminiferal zones (marked by OZ), in the context of shallow benthic zonation of Tethyan early Paleogene, is proposed. In the updated zonation, OZ 12 corresponds to the latest Lutetian to earliest Bartonian interval, OZ 13 to the late early Bartonian, and OZ 14 to the late Bartonian to earliest Priabonian time-span. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A rapid clay-mineral change in the earliest Priabonian of the North Sea Basin?

Abstract In the Eocene to Oligocene transitional strata in Belgium, clay mineral associations vary in response to the climatic evolution and to tectonic pulses. Decreasing smectite to illite ratios and the systematic occurrence of illite-smectite irregular interlayers are consequences of a cooling climate. A marked increase in kaolinite content occurs just after a major unconformity formed at the Bartonian/Priabonian boundary and consequently is interpreted as resulting from the breakdown of uplifted saprolites.

The Szolnok unit and its probable paleogeographic position

In the Szolnok unit, a flysch trough, beneath the Great Hungarian Plain, a more than 1000 m thick clastic sedimentary series has been penetrated by drilling activity in the last few decades. Refering to the non-continous core material this sequence is built up by rhythmic, turbidite-dominated sandstones and shales. Earlier, the flysch series was thought to have been continuously deposited during the Cretaceous and the Paleogene. The detailed study of the available drilling cores proved that only a few Late Cretaceous and Paleogene nannoplankton zones are present in the sequence and there is no positive evidence for the others. Evidence was found for the presence of Campanian-early Maastrichtian, latest Paleocene-Early Eocene, Middle Eocene (Bartonian) and early Priabonian, as well as for most Oligocene nannoplankton zones. The Szolnok unit is thrust and folded into imbricated structures. Micropaleontological investigations suggest evidence for post-Oligocene compressional deformation. This non-continuous stratigraphic built up of the Szolnok sedimentary sequence suggests that it can be correlated with some of the Central (“Inner”) Carpathian flysches and strata correlation with the Outer Carpathian flysch units can be excluded. Taking into account all the lithological and paleontological features of the Szolnok unit succession a gradual change of the depositional environment is proposed from deep-water pelagic to shallower environment during the time of its formation.

Relationship of Clay Minerals to Depositional Environment in the Non-Marine Eocene Pontils Group, Se Ebro Basin (Spain)

ABSTRACT The Eocene sequence along the central part of the SE margin of the Tertiary Ebro Basin (Igualada area) consists of alternating marine and non-marine deposits up to 2000 m thick. Non-marine conditions persisted through the Cuisian--early Bartonian (early-middle Eocene) and resulted in the deposition of the Pontils Group (up to 900 m thick). During the late Bartonian--early Priabonian (late Eocene), marine environments prevailed in this area, leading to the deposition of the Santa Maria Group. Paleoenvironmental interpretations of the Pontils Group were obtained from sedimentology data of an earlier study. The nonmarine environments recorded in this group are: alluvial fans, flood plains, mudflats, playa-lakes, and shallow freshwater lakes. X-ray diffraction, TEM, SEM, EDX, and chemical analyses of mudstones and marls from the Pontils Group indicate that the diverse environments also can be distinguished from one another on the basis of the clay-mineral content. Illite is present in all samples of the Pontils Group. Palygorskite, with minor amounts of illite and sometimes chlorite, is the dominant clay mineral in flood plain and mud flat sediments. Palygorskite is also predominant in sabkha, playa-lake and carbonate-lagoonal sediments. This clay mineral is absent in sediments from fresh, organic-rich lakes. Kaolinite is relatively abundant in mudstones from the organic-rich lakes. Smectite is relatively abundant in the sediments from subaqueous environments but is almost always absent from the sediments which were subjected to subaerial exposure and water-table oscillations such as flood plain and mudflat deposits. According to these clay-mineral distribution trends, the organic-rich lacustrine, lagoonal, and marine sediments preserve the detrital clay-minerals. The original detrital assemblages were mostly formed by illite, associated with chlorite, kaolinite and subordinate smectite. In the environments which underwent repeated flooding and desiccation, chlorite and smectite were eventually eliminated and palygorskite was formed. Microscopic observation suggests that palygorskite was formed in mudflats and flood-plains mainly by the transformation of smectite and/or illite in a Mg-rich environment. In the sabkha facies, the abundance of palygorskite, frequently associated with smectite, dolomite, and chert, suggests palygorskite neoformation in a Si- and Mg-rich environment.