21,727 research outputs found

    Late Miocene to early Pliocene biofacies of Wanganui and Taranaki Basins, New Zealand: Applications to paleoenvironmental and sequence stratigraphic analysis

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    The Matemateaonga Formation is late Miocene to early Pliocene (upper Tongaporutuan to lower Opoitian New Zealand Stages) in age. The formation comprises chiefly shellbeds, siliciclastic sandstone, and siltstone units and to a lesser extent non-marine and shallow marine conglomerate and rare paralic facies. The Matemateaonga Formation accumulated chiefly in shelf paleoenvironments during basement onlap and progradation of a late Miocene to early Pliocene continental margin wedge in the Wanganui and Taranaki Basins. The formation is strongly cyclothemic, being characterised by recurrent vertically stacked facies successions, bounded by sequence boundaries. These facies accumulated in a range of shoreface to mid-outer shelf paleoenvironments during conditions of successively oscillating sea level. This sequential repetition of facies and the biofacies they enclose are the result of sixth-order glacio-eustatic cyclicity. Macrofaunal associations have been identified from statistical analysis of macrofossil occurrences collected from multiple sequences. Each association is restricted to particular lithofacies and stratal positions and shows a consistent order and/or position within the sequences. This pattern of temporal paleoecologic change appears to be the result of lateral, facies-related shifting of broad biofacies belts, or habitat-tracking, in response to fluctuations of relative sea level, sediment flux, and other associated paleoenvironmental variables. The associations also show strong similarity in terms of their generic composition to biofacies identified in younger sedimentary strata and the modern marine benthic environment in New Zealand

    Solving the woolly mammoth conundrum: amino acid 15N-enrichment suggests a distinct forage or habitat

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    Understanding woolly mammoth ecology is key to understanding Pleistocene community dynamics and evaluating the roles of human hunting and climate change in late Quaternary megafaunal extinctions. Previous isotopic studies of mammoths’ diet and physiology have been hampered by the ‘mammoth conundrum’: woolly mammoths have anomalously high collagen δ15N values, which are more similar to coeval carnivores than herbivores and which could imply a distinct diet and (or) habitat, or a physiological adaptation. We analyzed individual amino acids from collagen of adult woolly mammoths and coeval species and discovered greater  15N enrichment in source amino acids of woolly mammoths than in most other herbivores or carnivores. Woolly mammoths consumed an isotopically distinct food source, reflective of extreme aridity, dung fertilization and (or) plant selection. This dietary signal suggests that woolly mammoths occupied a distinct habitat or forage niche relative to other Pleistocene herbivores

    The Triassic-Jurassic boundary in the Andes of Argentina

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    The Arroyo Malo Formation at Alumbre Creek, on the northern bank of the Atuel River, west central Argentina, comprises a c. 300 m thick continuous marine succession across the Triassic-Jurassic System boundary, consisting of massive and laminated pelites indicative of a slope depositional environment. Late Triassic invertebrates, including ammonoids, nautiloids, bivalves, gastropods, brachiopods and corals are restricted to the lower 150 m. Beds between 125-135 m from the bottom yield Choristoceras cf. marshi Hauer, a species found in the Marshi/Crickmayi Zone of Europe and North America, together with loose fragments of Psiloceras cf. pressum Hillebrandt, coeval with the lower to middle part of the Hettangian Planorbis Zone. About 80 m higher are beds yielding Psiloceras cf. rectocostatum Hillebrandt, a species that gives name to an Andean biozone partially coeval with the Johnstoni and Plicatulum Subzones, upper Planorbis Zone. Other fossils recorded in the Rhaetian strata of this section are foraminifers, ostracods and plant remains identified as Zuberia cf. zuberi (Szaj.) Freng. and Clathropteris sp. The section was also sampled for conodonts and radiolarians, thus far with negative results. A palaeomagnetic study is underway.La Formazione Arroyo Malo ad Alumbre creek, sulla sponda settentrionale del fiume Atuel, Argentina centro-occidentale, comprende una successione marina continua spessa circa 300 m attraverso i! limite Triassico-Giurassico, ed e costituita da peliti massive e laminate indicative di un ambiente deposizionale di scarpata. Gli inverttfjrati del Ttiassico superiore, che includono ammonoidi, nautiloidi, bivalvi, gasteropodi, brachiopodi e coralli sono limitati ai primi 150 m. Gli strati fra i 125-135 m dalla base hanno dato Choristoceras cf. marshi Hauer, una specie trovata nella Zona a Marshi/Crickmayi di Europa e Nord America, insieme con frammenti sparsi di Psiloceras cf. pressum Hillebrandt, coeva con la parte mediana della Zona a Planorbis dell'Hettangiano. Circa. 80 m piu in alto ci sono strati contenenti Psiloceras cf. rectocostatum Hlllebrandt, una specie che da i! no me ad una biozona andina parzialmente coeva con le Sottózone a Johnstoni e Plicatulum, Zona a Planorbis superiore. Altri fossili documentati negli strati del Retico di questa sezione sono foraminiferi, ostracodi e resti di piante identificati come Zuberia cf. zuberi (Szaj.) Freng. e Clathropteris sp. La sezione e stata anche campionata per quanto riguarda conodonti e radiolari, finora con risultati negativi. Uno studio paleomagnetico e in corso.Fil: Riccardi, Alberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento de Paleontología Invertebrados; ArgentinaFil: Damborenea, Susana Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento de Paleontología Invertebrados; ArgentinaFil: Manceñido, Miguel Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento de Paleontología Invertebrados; ArgentinaFil: Iglesia Llanos, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentin

    Potential natural vegetation and pre-anthropic pollen records on the Azores Islands in a Macaronesian context

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    This paper discusses the concept of potential natural vegetation (PNV) in the light of the pollen records available to date for the Macaronesian biogeographical region, with emphasis on the Azores Islands. The classical debate on the convenience or not of the PNV concept has been recently revived in the Canary Islands, where pollen records of pre-anthropic vegetation seemed to strongly disagree with the existing PNV reconstructions. Contrastingly, more recent PNV model outputs from the Azores Islands show outstanding parallelisms with pre-anthropic pollen records, at least in qualitative terms. We suggest the development of more detailed quantitative studies to compare these methodologies as an opportunity for improving the performance of both. PNV modelling may benefit by incorporating empirical data on past vegetation useful for calibration and validation purposes, whereas palynology may improve past reconstructions by minimizing interpretative biases linked to differential pollen production, dispersal and preservation.Spanish Ministry of Economy and Competititvity, project PaleoNAO [CGL2010-15767]Spanish Ministry of Economy and Competititvity, project RapidNAO [CGL2013-40608-R]Spanish Ministry of Economy and Competititvity, project PaleoMODES [CGL2016-75281-C2-1-R]info:eu-repo/semantics/publishedVersio

    Complex belemnites of the Puaroan (lower-? middle Tithonian) stage in the Port Waikato Region of New Zealand

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    Belemnite guards range through 2700 feet of Puaroan strata in the Port Waikato region. All are Belemnopsis of the uhligi-complex. Belemnopsis aucklandica aucklandica (Hochstetter) in its most typical form may be restricted to the lower 700 feet of the sequence. Three species are described, together with what may be transitional forms. The morphology of juvenile guards is in marked contrast with that of mature specimens, and development of the adult guard is revealed by examination of internal sections. Some aspects of belemnite paleoecology are discussed. Belemnite biostratigraphy of the area is outlined and the more important fossil localities are described

    Mollusk species at a Pliocene shelf whale fall (Orciano Pisano, Tuscany)

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    The recovery of an intact, 10 m long fossil baleen whale from the Pliocene of Tuscany (Italy) offers the first opportunity to study the paleoecology of a fully developed, natural whale-fall community at outer shelf depth. Quantitative data on mollusk species from the whale fall have been compared with data from the sediments below and around the bones, representing the fauna living in the muddy bottom before and during the sinking of the carcass, but at a distance from it. Although the bulk of the fauna associated with the fossil bones is dominated by the same heterotrophs as found in the surrounding community, whale-fall samples are distinguishable primarily by the presence of chemosymbiotic bivalves and a greater species richness of carnivores and parasites. Large lucinid clams (Megaxinus incrassatus) and very rare small mussels (Idas sp.) testify to the occurrence of a sulphophilic stage, but specialized, chemosymbiotic vesicomyid clams common at deep-sea whale falls are absent. The whale-fall community is at the threshold between the nutrient-poor deep sea and the shallow-water shelf, where communities are shaped around photosynthetic trophic pathways and chemosymbiotic specialists are excluded by competition. © SEPM (Society for Sedimentary Geology)

    Benthic foraminifers and siliceous sponge spicules assemblages in the Quaternary rhodolith rich sediments from Pontine Archipelago shelf

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    The bottom samples (Quaternary in age) of two cores (CS1 and Caro1) collected at 60 and 122 m water depth in the marine area near Ponza Island (Pontine Archipelago, Tyrrhenian Sea) are investigated. In particular, benthic foraminifers and siliceous sponge spicules are considered. The coralline red algae (pralines, boxworks and unattached branches) are abundant in both samples and, particularly, in the CS1 bottom as well as the benthic foraminifers. The siliceous sponge spicules also are very diversified and abundant in the CS1 bottom sample, while in the Caro1 bottom they are rare and fragmented. Benthic foraminiferal assemblage of two samples is dominated by Asterigerinata mamilla and Lobatula lobatula, typical epiphytic species but also able to live on circalittoral detrital seafloors, adapting to an epifaunal lifestyle. Based on these data the bottom of the studied cores represents the upper circalittoral zone, within the present-day depth limit distribution of coralline red algae in the Pontine Archipelago (shallower than 100 m water depth)

    Dietary Adaptations and Intra- and Interspecific Variation in Dental Occlusal Shape in Hominin and Non-hominin Primates

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    Dental morphology and tooth shape have been used to recreate the dietary adaptations for extinct species, and thus dental variation can provide information on the relationship between fossil species and their paleoenvironments. Variation in living species with known behaviors can provide a baseline for interpreting morphology, and behavior, in the fossil record. Tooth occlusal surface outlines in hominins and non-hominin primates, and other mammals, have been used for assessments of taxonomic significance, with variability often considered as being primarily phylogenetic. Few studies have attempted to assess how diet might influence the pattern of variability in closely related species. Here the occlusal surface shape variability in anterior and postcanine maxillary dentition in primates is measured to assess whether the relationship between diet and variability is consistent. Data were collected from five non-hominin primates in a range of dietary categories, as well as two hominin species, including the derived Paranthropus robustus and a gracile australopith. Mapping a series of 50 sliding semilandmarks based on 2-D photographs using tpsDig software, occlusal surfaces were outlined. Thereafter, outline shapes were quantified using Elliptical Fourier Functional Analysis, and principle components and multivariate analyses were preformed to explore the pattern of intra and interspecific variability in occlusal outlines.These results suggest that there is not a clear relationship between dietary feeding adaptations for all categories examined and selection for larger premolars and molars, as well as smaller incisors, led to less variation in both anterior and post-canine teeth of the fossil hominin Paranthropus robustus

    Paleoecology of the Maastrichtian and Danian sediment at North of Central Alborz, Iran, based on Planktonic foraminifera

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    In order to study the fossil contents of the Ziarat-kola section for biostratigraphical purposes the 212 meters was sampled at Central Alborz. The sequence is mainly made up of monotonous grey- green to light grey marl. Based on Planktonic foraminifera age of Maastrichtian-Danian is determined to the section.

Four zones were determined by the benthic foraminifera morphogroup for showing oxygen and productivity change. The approximate low oxygen and high food supply has been indicates zone of one that increase infauna to epifauna morphotype percent is low (nearness 60% infouna, 40% epifauna). In zone two, with due attention to equal percent of Epifauna ratio to infauna, intermediate oxygen and food supply is anticipated. The decrasing epifauna foraminifera and increasing infauna demonstrates low oxygen and high food supply condition at zone of three. In zone four, increasing epifauna (approximate 90 percent) that are indicated high oxygen condition and low food supply. Analysis of planktonic foraminifera assemblage at this section with Cretaceous biostratigraphical provinces is indicating a close similarity with Tethyan provinces
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