Sedimenttexturen der Sohlbankfläche im Naturdenkmal "Saurierfährten Münchehagen" (Berrias), Rehburger Berge : Rippelmarken und Ichnofossilien als Grundlage einer Deutung des Ablagerungsraumes

Die Gesteine des bearbeiteten Aufschlusses, dem Naturdenkmal "Saurierfährten Münchehagen" bei Münchehagen (Rehburger Berge), liegen stratigraphisch in der Bückeberg-Formation des Berrias (Wealden). Aufgeschlossen ist der Hauptsandstein (Wealden 3) . Es werden die Sedimenttexturen der Sohlbankfläche des ehemaligen Steinbruchs analysiert und interpretiert. Vorherrschende Schichtungstypen sind Wellenrippelschichtung und Flaserschichtung. Die Sedimente sind stark bioturbat. Auf mehreren freiliegenden Flächenniveaus der Sohlbank sind Rip- pelmarken zu beobachten, die systematisch vermessen wurden. Danach handelt es sich uro Wellenrippeln und untergeordnet um strömungsüberformte Wellenrippeln durch ablaufendes Wasser. Zahlreiche Merkmale zeigen wiederholtes Auftauchen und Trok- kenfallen an. Tonlagen kennzeichnen zeitweilige Stillwasserbedingungen. Ein ehemals verzweigtes Rinnensystem ist in Relikten erhalten und beweist ebenfalls einen wechselnden Wasserstand (ablaufendes Wasser). Sporadisch kam es im Zuge hochenergetischer Ereignisse zu einem schichtflutartigen Abfließen des Wassers. Eine reiche Ichnofauna ist zu beobachten. Wenige Spurentypen sind vorhanden, die Spurendichte ist jedoch sehr hoch. Es dominieren horizontale oder wenig geneigte Gestaltungswühlgefüge, vertikale Bauten kommen nur untergeordnet vor. Als häufigste Spurentypen treten Thalassinoides, Muensteria, Plano- lites und Pelecypodichnus auf. Die Größe der Ichnofossilien ist meist gering. Die Spuren bilden eine Ichnocoenose aus Ichnofossilien der Cruziana- und untergeordnet der Skolithos- Fazies. Bivalven belegen Brackwasser-Verhältnisse. Dies alles sind Merkmale eines lagunären Ablagerungsraumes, gelegen am Rand eines gezeitenarmen bzw. -losen Nebenmeeres (Niedersächsisches Becken) im Übergang von der fluviatilen in die litorale Fazies im rückwärtigen Bereich eines Barrierensystems. Wahrscheinlich spielte Wind eine entscheidende Rolle als Ursache für Wasserspiegelschwankungen. Die maximale Wassertiefe bei auflandigem Sturm hat vermutlich nicht mehr als 3 - 4 m betragen. Sonst war sie wahrscheinlich deutlich geringer und ermöglichte Dinosauriern ein Durchwaten des Gewässers, wie Fährten auf der Sohlfläche beweisen.

ESR dating of pleistocene mammal teeth and its implications for the biostratigraphy and geological evolution of the coastal plain, Rio Grande do Sul, southern Brazil

The fossiliferous deposits in the coastal plain of the Rio Grande do Sul State, Southern Brazil, have been known since the late XIX century; however, the biostratigraphic and chronostratigraphic context is still poorly understood. The present work describes the results of electron spin resonance (ESR) dating in eleven fossil teeth of three extinct taxa (Toxodon platensis, Stegomastodon waringi and Hippidion principale) collected along Chui Creek and nearshore continental shelf, in an attempt to assess more accurately the ages of the fossils and its deposits. This method is based upon the analysis of paramagnetic defects found in biominerals, produced by ionizing radiation emitted by radioactive elements present in the surrounding sediment and by cosmic rays. Three fossils from Chui Creek, collected from the same stratigraphic horizon, exhibit ages between (42 +/- 3) Ka and (34 +/- 7) Ka, using the Combination Uptake model for radioisotopes uptake, while a incisor of Toxodon platensis collected from a stratigraphic level below is much older. Fossils from the shelf have ages ranging from (7 +/- 1) 10(5) Ka to (18 +/- 3) Ka, indicating the mixing of fossils of different epochs. The origin of the submarine fossiliferous deposits seems to be the result of multiple reworking and redeposition cycles by sea-level changes caused by the glacial-interglacial cycles during the Quaternary. The ages indicate that the fossiliferous outcrops at Chui Creek are much younger than previously thought, and that the fossiliferous deposits from the continental shelf encompass Ensenadan to late Lujanian ages (middle to late Pleistocene). (C) 2009 Elsevier Ltd and INQUA. All rights reserved.

Tafonomia e paleoicnologia do neogénico superior do sector Cacela-Huelva (SE da Ibéria)

Tese de doutoramento em Paleontologia. Faculdade de Ciências do Mar e do Ambiente, Univ. do Algarve, 2005

Pleistocene mammals from the southern Brazilian continental shelf

Fossils of terrestrial mammals preserved in submarine environment have been recorded in several places around the world. In Brazil such fossils are rather abundant in the southernmost portion of the coast, associated to fossiliferous concentrations at depths up to 10 m. Here is presented a review of such occurrences and the first record of fossils in deeper areas of the continental shelf. The fossils encompass several groups of both extinct and extant mammals, and exhibit several distinct taphonomic features, related to the marine environment. Those from the inner continental shelf are removed and transported from the submarine deposits to the coast during storm events, thus forming large konzentrat-lagerstatte on the beach, called "Concheiros". The only fossils from deeper zones of the shelf known so far are a portion of a skull, a left humerus and of a femur of Toxodon sp. and a lower right molar of a Stegomastodon waringi, all collected by fishermen at depths around 20 m. The presence of fossils at great depths and distances from the present coastline, without signs of abrasion and far from areas of fluvial discharges does indicate that these remains have not been transported from the continent to the shelf, but have been preserved directly on the area that today correspond to the continental shelf. These remains indicate the existence of large fossiliferous deposits that have developed during periods of sea-level lowstand (glacial maxima) and have been submerged and reworked by the sea-level rise at the end of the last glaciation. (C) 2010 Elsevier Ltd. All rights reserved.

Lower Aptian Comparative Stratigraphy of the Basco-Cantabrian Region (Spain) and Eastern Cordillera (Colombia): implications for local factors in the depositional record of Oceanic Anoxic Event 1a (OAE-1a)

An important episode of carbon sequestration, Oceanic Anoxic Event 1a (OAE-1a), characterizes the Lower Aptian worldwide, and is mostly known from deeper-water settings. The present work of two Lower Aptian deposits, Madotz (N Spain) and Curití Quarry (Colombia), is a multiproxy study that includes fossil assemblages, microfacies, X-ray diffraction bulk and clay mineralogy, elemental analyses (major, minor, trace elements), Rock-Eval pyrolysis, biomarkers, inorganic and organic carbon content, and stable carbon isotopes. The results provide baseline evidence of the local and global controlling environmental factors influencing OAE-1a in shallow-water settings. The data also improve our general understanding of the conditions under which organic-carbon-rich deposits accumulate. The sequence at Madotz includes four intervals (Unit 1; Subunits 2a, 2b and 2c) that overlap the times prior to, during and after the occurrence of OAE-1a. The Lower Unit 1(3m thick) is essentially siliciclastic, and Subunit 2a (20m) contains Urgonian carbonate facies that document abruptly changing platform conditions prior to OAE-1a. Subunit 2b (24.4 m) is a mixed carbonate-siliciclastic facies with orbitolinid-rich levels that coincides with OAE-1a δ13C stages C4-C6, and is coeval with the upper part of the Deshayesites forbesi ammonite zone. Levels with pyrite and the highest TOC values (0.4-0.97%), interpreted as accumulating under suboxic conditions, and are restricted to δ13C stages C4 and C5. The best development of the suboxic facies is at the level representing the peak of the transgression. Subunit 2c, within δ13C stage C7, shows a return of the Urgonian facies. The 23.35-m section at Curití includes a 6.3-m interval at the base of the Paja Formation dominated by organic-rich marlstones and shales lacking benthic fossils and bioturbation, with TOC values as high as 8.84%. The interval overlies a level containing reworked and phosphatized assemblages of middle Barremian to lowest Aptian ammonites. The range of values and the overall pattern of the δ13Corg (-22.05‰ to -20.47‰) in the 6.3m-interval is comparable with Lower Aptian δ13C stage C7. Thus, conditions of oxygen depletion at this site also occurred after Oceanic Anoxic Event-1a, which developed between carbon isotope stages C3 and C6. Both sites, Madotz and Curití, attest to the importance of terrigenous and nutrient fluxes in increasing OM productivity that led to episodic oxygen deficiency.

The ontogeny of bipedalism: insights from the study of talar growth

The development of bipedal locomotion was gradual during evolution, and with the increase in discoveries of fossils and, in particular, in discoveries of pedal bones, the attention to this problematic has grown in the last decades. Moreover, the discoveries of juveniles fossil foot bones has led the attention to the evolution and the development of bipedal locomotion. The study of the development of human gait in children may help in shedding light to the development of human locomotion. The human talus plays a pivotal role, linking the leg to the foot and receiving and distributing the weight, while permitting a wide range of foot movements. It is also present at birth, and this makes a perfect bone to study to disentangle how the bone structure acts to cope with the changes in locomotion and body weight. Here, I analyze the external and internal morphology of the human talus from the perinatal period to adolescence, to investigate how the different phases of the acquisition of bipedal gait affect talar morphology, and how the bone copes with the weight gain during growth. Results show that the talar internal and external morphologies change in line with the different activities and loading of the foot. Initially, at around birth, the talus has a very globular and immature external shape, with a very dense trabecular architecture, composed of thin, numerous, and densely packed trabeculae, with a rather isotropic structure. External and internal morphologies change in relation to the different loading patterns which follow during growth, showing a more specialized structure, both in the external and internal morphology, linked to the maturation of bipedal locomotion, until the adult-like pattern is reached, during adolescence.

Ecological responses of Western Palearctic avian species to late Quaternary climate oscillations

This PhD thesis explores the ecological responses of bird species to glacial-interglacial transitions during the late Quaternary in the Western Palearctic, using multiple approaches and at different scales, enhancing the importance of the bird fossil record and quantitative methods to elucidate biotic trends in relation to long-term climate changes. The taxonomic and taphonomic analyses of the avian fossil assemblages from four Italian Middle and Upper Pleistocene sedimentary successions (Grotta del Cavallo, Grotta di Fumane, Grotta di Castelcivita, and Grotta di Uluzzo C) allowed us to reconstruct local-scale patterns in birds’ response to climate changes. These bird assemblages are characterized by the presence of temperate species and by the occasional presence of cold-dwelling species during glacials, related to range shifts. These local patterns are supported by those identified at the continental scale. In this respect, I mapped the present-day and LGM climatic envelopes of species with different climatic requirements. The results show a substantial stability in the range of temperate species and pronounced changes in the range of cold-dwelling species, supported by their fossil records. Therefore, the responses to climate oscillations are highly related to the thermal niches of investigated species. I also clarified the dynamics of the presence of boreal and arctic bird species in Mediterranean Europe, due to southern range shifts, during the glacial phases. After a reassessment of the reliability of the existing fossil evidence, I show that this phenomenon is not as common as previously thought, with important implications for the paleoclimatic and paleoenvironmental significance of the targeted species. I have also been able to explore the potential of multivariate and rarefaction methods in the analyses of avian fossils from Grotta del Cavallo. These approaches helped to delineate the main drivers of taphonomic damages and the dynamics of species diversity in relation to climate-driven paleoenvironmental changes.