Discovery of a Charophyte locality and Biostratigraphy of the continental Eocene deposits of Oued Méridja (southwestern Algeria)

The continental deposits of Oued Méridja area (west of Bechar, southwestern Algeria) have been assigned by previous authors to the early Eocene on the basis of lacustrine gastropod fauna (Pseudoceratodes). This study reports new paleontological and biostratigraphic data from the Oued Méridja section. Recent field investigations resulted in the discovery of an important charophyte assemblage, composed of five species belonging to four genera: Maedleriella cristellata, Maedleriella aff. cristellata, Harrisichara aff. leptocera, Peckichara disermas and? Gyrogona sp. This association allows to suggest a late Thanetian to early Ypresian age for this locality.     

Wilkes Land Late Pleistocene diatom age model: From bio-events to quantitative biostratigraphy

A new method merges conventional and quantitative biostratigraphic approaches, supported by magnetic polarity data, to develop a chronological framework for sediment core MD03-2595 retrieved on the continental rise off Wilkes Land, East Antarctica before proceeding to paleoceanographic and paleoclimatic analysis. This combined method helped to identify climatic cycles, highlight stratigraphic discontinuities and reworking, and assess regional sedimentological and diatom biostratigraphic evolution. Core MD03-2595 spans the last 0.8 Ma, from the Mid Pleistocene Transition (MPT) to the Early Holocene. A hiatus including Marine Isotope Stages (MIS) 19, 18 and 17 was identified, and a decreasing trend in sediment accumulation rates from MIS 16 to the Holocene was observed. This quantitative diatom biostratigraphic dataset, placed in its own sedimentological and paleomagnetic context, provides new information regarding the paleobiogeographic distribution and ecological responses of biostratigraphically significant diatom species, such as Thalassiosira elliptipora and T. fasciculata, for the Matuyama–Brunhes (M–B) transition, and Actinocyclus ingens, Hemidiscus karstenii and Rouxia spp. for the middle and late Pleistocene diatom biozonation.     

The Miocene mammal record of the Vallès-Penedès Basin (Catalonia)

The land mammal record of the Vallès-Penedès Basin (Catalonia, NE Spain) ranges from the early Miocene (Ramblian) to the late Miocene (Turolian), that is from about 20 to 7 Ma. Here we present an updated review of the mammal succession focusing on biochronology as well as on environmental and faunal changes. Based on faunal similarities with central Europe, we interpret this basin as a transitional zone between the forested environments of northern regions and the more arid landscapes of the inner Iberian Peninsula. The quality of the Vallès-Penedès record and its chronostratigraphic control is clearly better for the late Aragonian and the Vallesian (between 12.6–9.0 Ma), especially for small mammals. Therefore, we analyze small mammal diversity dynamics during this interval. Contrary to previous analyses, which found an abrupt extinction event coinciding with the early/late Vallesian boundary (the Vallesian Crisis), our results show that this pattern is due to uneven sampling. Instead, taxonomic richness slowly decreased since the late Vallesian as a result of a series of extinctions that mostly affected forest-dwelling taxa.     

The marine paleogene of the tremp region (NE Spain)-depositional sequences,facies history,biostratigraphy and controlling factors

Summary The marine Paleogene of the Tremp Basin in the Central Southern Pyrenees corresponds to four depositional sequences which are related to global eustatic third order cycles (Tejas A 2.3–2.6). Associated transgressive and downlap surfaces coincide with boundaries of biozones. Lowstand systems tracts consist of estuarine and braid delta systems. Transgressive and highstand systems tracts are composed of carbonate banks and reefs. Slow thrust-induced changes of the basin topography conditioned the basic type and the areal distribution of carbonate highstand and clastic lowstand systems. Rapid relative sea level changes controlled the activity and internal dynamic of the depositional systems. E-W directed blind thrust anticlines are covered during highstand periods by carbonate fringing banks withNummulites bars. N-S orientation of thrust anticlines leads to the evolution of reef-dominated barrier banks and shelf lagoonal homoclinal ramps. On-bank transport of carbonate sands dominates during transgressions, off-bank transport during highstand periods. Continuous thrusting during the Ilerdian caused angular unconformities only in combination with relative sea level fall. Sequence-internal onlap configurations result from contemporaneous tectonic tilting. Fourth order carbonate bank margin cycles contain well developed lowstand tracts due to increased subsidence rates. Fourth order flooding surfaces are marked by paleosoil horizons at their landward continuation.     

Palaeogene marine stratigraphy in China

Palaeogene deposits are widespread in China and are potential sequences for locating stage boundaries. Most strata are non‐marine origin, but marine sediments are well exposed in Tibet, the Tarim Basin of Xinjiang, and the continental margin of East China Sea. Among them, the Tibetan Tethys can be recognized as a dominant marine area, including the Indian‐margin strata of the northern Tethys Himalaya and Asian‐margin strata of the Gangdese forearc basin. Continuous sequences are preserved in the Gamba–Tingri Basin of the north margin of the Indian Plate, where the Palaeogene sequence is divided into the Jidula, Zongpu, Zhepure and Zongpubei formations. Here, the marine sequence ranges from Danian to middle Priabonian (66–35 ma), and the stage boundaries are identified mostly by larger foraminiferal assemblages. The Paleocene/Eocene boundary is found between the Zongpu and Zhepure formations. The uppermost marine beds are from the top of the Zongpubei Formation (~35 ma), marking the end of Indian and Asian collision. In addition, the marine beds crop out along both sides of the Yarlong Zangbo Suture, where they show a deeper marine facies, yielding rich radiolarian fossils of Paleocene and Eocene. The Tarim Basin of Xinjiang is another important area of marine deposition. Here, marine Palaeogene strata are well exposed in the Southwest Tarim Depression and Kuqa Depression. They comprise mostly neritic and coastal lagoon facies of the Tethyan realm. Palaeontological evidence suggests that the Paleocene/Eocene boundary here is in middle of the Qimugen Formation. The Tarim Basin was largely drained by Late Oligocene. To the east, the marine offshore Palaeogene strata are widespread in the North Taiwan and East Zhejiang depressions of the continental shelf basin of East China Sea. Abundant fossils including foraminifera, calcareous nannofossils, ostracods, pollen and bivalves occur in the marine environment. Biostratigraphically, the sequence is well correlated with the international planktonic foraminiferal and nannofossil zonations.     

The North China Steptoean positive carbon isotope excursion and its global correlation with the base of the Paibian Stage (early Furongian Series), Cambrian

The use of carbon isotope excursion in Cambrian stratigraphical correlation is a standard practice at both the intercontinental and intracontinental scales. The Steptoean positive carbon isotope excursion (SPICE) is one of the prime examples in this regard in correlating the base of the Paibian Stage and Furongian Series. A lack of definite SPICE evidence in the North China craton has been a challenge in precision correlation between North China and other palaeo‐continents. This study provides new carbonates carbon isotope data from the type locality of the Changshan Formation in Hebei Province, North China. Our new δ13C_carb data provide new objective evidence for the presence of the SPICE in North China. The sampling section is relatively condensed, and the interval of the SPICE curve is less than one and half‐metres after analysing 64 samples (the sampling interval within the SPICE is less than 10 cm). The onset of the SPICE curve in Tangshan, Hebei, occurs in the barren interval between the Neodrepanura and Chuangia trilobite zones. Based on this study and previous work, this could imply the middle part of the Prochuangia‐Paracoosia trilobite Zone in North China and can be correlated with the base of the Paibian Stage and Furongian Series.     

Biostratigraphy and paleoceanographical significance of the Neogene planktonic foraminifera from the Pelotas Basin, southernmost Brazil

Analysis of the planktonic foraminifers recovered from 1-SCS-2 drill-hole, Florianópolis platform (Pelotas Basin, southern Brazilian Atlantic Margin), allowed recognition of the Catapsydrax dissimilis, Catapsydrax stainforthi, Globorotalia fohsi robusta, Globorotalia mayeri, Globorotalia margaritae evoluta and Globigerinoides trilobus fistulosus Miocene and Pliocene zones and four important hiatuses. Correlation with well 1-SCS-3B and other zonal schemes, as well as recognition of early diagenesis instead of a reworking process, allowed confident age assignment. The Miocene foraminifers constitute a tropical/sub-tropical assemblage, whereas in the Pliocene, the presence of scarce species associated to subantarctic water masses suggests that the Malvinas Current reaches the area but it was not a controlling factor in the paleoenvironmental conditions.     

Spatial and temporal development of siliceous basin and shallow-water carbonate sedimentation in Oxfordian Northern Calcareous Alps

The Late Jurassic succession of Mount Rettenstein (central Northern Calcareous Alps, Austria) is unique in comparison to all other sections known in the Northern Calcareous Alps because it provides the oldest coexistence of radiolarite basin sedimentation with contemporaneous shallow-water carbonate intercalations. An up to 3.5-m-thick debris flow made up of shallow-water carbonate detritus with a radiolaritic matrix is overlain by thin (calcareous) radiolarite, followed by several hundreds of meters of shallow-water carbonates of the Plassen Formation. Benthic foraminifers (Labyrinthia mirabilis Weynschenk and Alveosepta aff. jaccardi) and the radiolarian associations indicate a depositional age of both the debris flow and the basal Plassen Formation around the boundary of Middle/Late Oxfordian resp. in the Late Oxfordian. This is as yet the first unambiguous evidence of Oxfordian shallow-water sedimentation in the Northern Calcareous Alps. This early neritic stage with the settlement of ooid bars and coral-stromatoporoid-reefs, evidenced by the debris flow resediments in siliceous basin sedimentation, is followed by the definite, rapid progradation of the actual Late Oxfordian/Kimmeridgian–Berriasian Plassen Carbonate Platform with its steep slope configuration. Assumably, this evolution was steered by a mixture of both global environmental and regional tectonic constraints.     

Cambrian high-resolution biostratigraphy and carbon isotope chemostratigraphy in Scania, Sweden: first record of the SPICE and DICE excursions in Scandinavia

A core drilling (Andrarum‐3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90‐m‐thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts (s. l.), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone (P. spinulosa Subzone). Carbon isotopic analyses (δ¹³C_org) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt. atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus (Homagnostus) obesus Zone. The DICE displays a peak value, in the samples at hand, of –30.45‰δ¹³C_org in the lower part of the P. atavus Zone. The δ¹³C_org values increase through the overlying L. laevigata and A. pisiformis zones and display peak values of c. –28.00‰δ¹³C_org in the lowermost Furongian Olenus wahlenbergi and O. attenuatus subzones. Thereafter the values decrease significantly through the O. scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50–2.00‰δ¹³C_org is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed.     

Late Paleozoic and Triassic bryozoans from the Tethys Himalaya (N India, Nepal and S Tibet)

New findings of Late Paleozoic and Triassic bryozoans from the Tethys Himalaya are reported. Fifteen species, including three undetermined, were described, while determinations at order, family or genus level were obtained on fragmentary material. The studied bryozoans were framed in a solid lithostratigraphic scheme spanning across the Tethys Himalaya for over 1500 km, from NW India (Zanskar and Spiti) through Nepal (Dolpo and Manang) to South Tibet; they are concentrated in correlatable stratigraphic intervals corresponding to the Upper Devonian-Tournaisian, Bashkirian, Sakmarian, Midian and Lower Norian. This study allowed us to integrate bryozoan occurrences reported from the literature, mostly referring to the Tournaisian, Bashkirian and Early Norian, and to refine the available biostratigraphic dates. Bryozoan-rich intervals are interpreted as associated to long-term transgressions, in turn driven by major climatic and/or tectonic events. Cosmopolitan genera which prevail in the Paleozoic, are replaced by provincial forms after the Triassic crisis.