Disentangling the Hettangian carbon isotope record: Implications for the aftermath of the end-Triassic mass extinction

This study provides an organic carbon stable isotope (delta(13)C(org)) record calibrated with detailed ammonite biostratigraphy, following the end-Triassic biological crisis. Precise correlation between this crucial fossil group and the delta(13)C(org) record is key to understanding feedbacks between biological and environmental events following mass extinction. The latest Triassic and Hettangian delta(13)C(org) record shows several negative and positive excursions. The end-Triassic negative shift coinciding with the mass extinction interval is followed by a positive excursion in the earliest Hettangian Psiloceras spelae beds, which marks the onset of recovery in the marine ecosystem. This positive trend is interrupted by a second negative delta(13)C(org) excursion in the P. pacificum beds related to a minor ammonite extinction event. This pattern of the delta(13)C(org) curve culminates in the uppermost Hettangian Angulata Zone major positive excursion. This indicates that both the ecosystem and the carbon cycle remained in a state of perturbation for at least 2 Ma, although the recovery of some pelagic taxa already began at the base of Jurassic. The early and late Hettangian positive delta(13)C(org) excursions have been confused in several recent papers. Here, we show that during the Hettangian there are indeed two distinct positive delta(13)C(org) excursions. Phases of anoxia and further pulses of Central Atlantic Magmatic Province volcanism during the Hettangian might have inhibited the full recovery for that interval of time. The main Liasicus-Angulata organic positive CIE (carbon isotope excursion) during the Late Hettangian might be related to gradual decreasing of pCO(2) due to protracted high organic burial, and coincides with a second phase of recovery, as indicated by a pulse of ammonoid diversification.

Dating human skeletal remains using a radiometric method: Biogenic versus diagenetic (90)Sr and (210)Pb in vertebrae.

In forensic science, there is a strong interest in determining the post-mortem interval (PMI) of human skeletal remains up to 50 years after death. Currently, there are no reliable methods to resolve PMI, the determination of which relies almost exclusively on the experience of the investigating expert. Here we measured (90)Sr and (210)Pb ((210)Po) incorporated into bones through a biogenic process as indicators of the time elapsed since death. We hypothesised that the activity of radionuclides incorporated into trabecular bone will more accurately match the activity in the environment and the food chain at the time of death than the activity in cortical bone because of a higher remodelling rate. We found that determining (90)Sr can yield reliable PMI estimates as long as a calibration curve exists for (90)Sr covering the studied area and the last 50 years. We also found that adding the activity of (210)Po, a proxy for naturally occurring (210)Pb incorporated through ingestion, to the (90)Sr dating increases the reliability of the PMI value. Our results also show that trabecular bone is subject to both (90)Sr and (210)Po diagenesis. Accordingly, we used a solubility profile method to determine the biogenic radionuclide only, and we are proposing a new method of bone decontamination to be used prior to (90)Sr and (210)Pb dating.

Fluid evolution at the Variscan front in the vicinity of the Aachen thrust

Quartz-carbonate-chlorite veins were studied in borehole samples of the RWTH-1 well in Aachen. Veins formed in Devonian rocks in the footwall of the Aachen thrust during Variscan deformation and associated fluid flow. Primary fluid inclusions indicate subsolvus unmixing of a homogenous H(2)O-CO(2)-CH(4)-(N(2))-Na-(K)-Cl fluid into a H(2)O-Na-(K)-Cl solution and a vapour-rich CO(2)-(H(2)O, CH(4), N(2)) fluid. The aqueous end-member composition resembles that of metamorphic fluids of the Variscan front zone with salinities ranging from 4 to 7% NaCl equiv. and maximum homogenisation temperatures of close to 400A degrees C. Pressure estimates indicate a burial depth between 4,500 and 8,000 m at geothermal gradients between 50 and 75A degrees C/26 MPa, but pressure decrease to sublithostatic conditions is also indicated, probably as a consequence of fracture opening during episodic seismic activity. A second fluid system, mainly preserved in pseudo-secondary and secondary fluid inclusions, is characterised by fluid temperatures between 200 and 250A degrees C and salinities of < 5% NaCl equiv. Bulk stable isotope analyses of fluids released from vein quartz, calcite, and dolomite by decrepitation yielded delta D(H2O) values from -89 to -113 aEuro degrees, delta(13)C(CH4) from -26.9 to -28.9aEuro degrees (VPDB) and delta(13)C(CO2) from -12.8 to -23.3aEuro degrees (VPDB). The low delta D and delta(13)C range of the fluids is considered to be due to interaction with cracked hydrocarbons. The second fluid influx caused partial isotope exchange and disequilibrium. It is envisaged that an initial short lived flux of hot metamorphic fluids expelled from the epizonal metamorphic domains of the Stavelot-Venn massif. The metamorphic fluid was focused along major thrust faults of the Variscan front zone such as the Aachen thrust. A second fluid influx was introduced from formation waters in the footwall of the Aachen thrust as a consequence of progressive deformation. Mixing of the cooler and lower salinity formation water with the hot metamorphic fluid during episodic fluid trapping resulted in an evolving range of physicochemical fluid inclusion characteristics.

A contribution to the study of post-depositional alterations of pottery using TL dating analysis

In luminescence dating, the potassium concentration significantly contributes to the dose rate value in the age estimation. Within this study, fine-grain thermoluminescence dating has been applied on sherds of calcareous pottery of known age, excavated at a Roman site in Mallorca, Spain. For those of the samples that showed signs of severe potassium leaching, according to chemical and mineralogical examination, the thermoluminescence analysis provided overestimated dates. By using the known archaeological age of the samples, a corrected dose rate value can be estimated which provides the potassium concentration averaged for the burial period. Finally, a step-like model can then be used to estimate the fraction of the burial period after which most of the alteration effects took place.

Constructive micritic envelope developed in the vadose continental environment in the Pleistocene eoliantes of Mallorca (Spain)

In this study we analyze and explain the formation of the constructive micrite envelope in the vadose continental environment. This constructive micrite envelope shows a wide variety of textural components. The principal textural components are: microorganisms, micritic and microspar LMC cement, whisker crystals, microfibres and aggregates of LMC acicular crystals. The main microorganisms are hyphae fungi, although actynomicetes and bacteries also occur. The constructive micrite envelope is due to the action of calcified filaments (hyphae fungi) which collapse and coalesce forming an intertwined mesh as well as due to the precipitation of micritic and microspar cement. The whisker crystals, microfibres and aggregates of LMC acicular crystals are secondary microtextures. Constructive micrite envelopes does not indicate a specific diagenetic environment. The constructive micrite envelopes present irregularities or bumps at the outer surface of the grains, and the destructive micrite envelopes present irregularities towards the grain interior. This morphologic criterion is useful to differenciate the micrite envelope origin, constructive or destructive, in the fossil record.

The biogenic origin of needle fibre calcite

Needle fibre calcite is one of the most ubiquitous habits of calcite in vadose environments (caves deposits, soil pores, etc.). Its origin, either through inorganic, indirect or direct biological processes, has long been debated. In this study, investigations at 11 sites in Europe, Africa and Central America support arguments for its biogenic origin. The wide range of needle morphologies is the result of a gradual evolution of the simplest type, a rod. This rod is the elementary brick which, by aggregation and welding, builds more complex needles. The absence of cross-welded needles implies that they are welded in a mould, or under a longitudinal and unidirectional constraint, before being released inside the soil pores. The difference between the lengthening of the needles and the c axis can be explained by the existence of needles observed under a scanning electron microscope in organic sleeves, which can act as a mould during rod growth. Complex morphologies with epitaxial outgrowths on straight rods cannot have grown entirely inside organic microtubes; they must result from soil diagenesis after the release of straight rods in a soil-free medium. Whisker crystals are interpreted as the result of growth and coalescence of euhedral crystals on a rod. Rhomb chains are considered to be the consequence of successive epitaxial growth steps on a needle during variations in growth conditions. Isotopic signatures for needle fibre calcite vary from -16.63[per mille] to +1.10[per mille] and from -8.63[per mille] to -2.25[per mille] for Delta13C and Delta18O, respectively. The absence of high Delta18O values for needle fibre calcite precludes a purely physicochemical origin (evaporative) for this particular habit of calcite. As epitaxial growth cannot precipitate in the same conditions as initial needles, needle fibre calcite stable isotopic signatures should be used with caution as a proxy for palaeoenvironmental reconstructions. In addition, it is suggested that the term needle fibre calcite should be kept for the original biogenic form. The other habit should be referred to as epitaxial forms of needle fibre calcite.

Nd and Sr isotope compositions in modern and fossil bones - Proxies for vertebrate provenance and taphonomy

Rare earth elements (REE), while not essential for the physiologic functions of animals, are ingested and incorporated in ppb concentrations in bones and teeth. Nd isotope compositions of modern bones of animals from isotopically distinct habitats demonstrate that the (143)Nd/(144)Nd of the apatite can be used as a fingerprint for bedrock geology or ambient water mass. This potentially allows the provenance and migration of extant vertebrates to be traced, similar to the use of Sr isotopes. Although REE may be enriched by up to 5 orders of magnitude during diagenesis and recrystallization of bone apatite, in vivo (143)Nd/(144)Nd may be preserved in the inner cortex of fossil bones or enamel. However, tracking the provenance of ancient or extinct vertebrates is possible only for well-preserved archeological and paleontological skeletal remains with in vivo-like Nd contents at the ppb-level. Intra-bone and -tooth REE analysis can be used to screen for appropriate areas. Large intra-bone Nd concentration gradients of 10(1)-10(3) are often measured. Nd concentrations in the inner bone cortex increase over timescales of millions of years, while bone rims may be enriched over millenial timescales. Nevertheless, epsilon(Nd) values are often similar within one epsilon(Nd) unit within a single bone. Larger intra-bone differences in specimens may either reflect a partial preservation of in vivo values or changing epsilon(Nd) values of the diagenetic fluid during fossilization. However, most fossil specimens and the outer rims of bones will record taphonomic (143)Nd/(144)Nd incorporated post mortem during diagenesis. Unlike REE patterns, (143)Nd/(144)Nd are not biased by fractionation processes during REE-uptake into the apatite crystal lattice, hence the epsilon(Nd) value is an important tracer for taphonomy and reworking. Bones and teeth from autochthonous fossil assemblages have small variations of +/- 1 epsilon(Nd) unit only. In contrast, fossil bones and teeth from over 20 different marine and terrestrial fossil sites have a total range of epsilon(Nd) values from -13.0 to 4.9 (n = 80), often matching the composition of the embedding sediment. This implies that the surrounding sediment is the source of Nd in the fossil bones and that the specimens of this study seem not to have been reworked. Differences in epsilon(Nd) values between skeletal remains and embedding sediment may either indicate reworking of fossils and/or a REE-uptake from a diagenetic fluid with non-sediment derived epsilon(Nd) values. The latter often applies to fossil shark teeth, which may preserve paleo-seawater values. Complementary to epsilon(Nd) values, (87)Sr/(86)Sr can help to further constrain the fossil provenance and reworking. (C) 2011 Elsevier Ltd. All rights reserved.

Hibernia: An Irish Immigrant Neighborhood in Burlington, Iowa, 2000

Hibernia is mostly a memory today as is so many immigrant neighborhoods. However, there are several guideposts to the past that still witness to the history of years gone by, such as St. Patrick's Church, a beacon reflecting the Irish Catholic heritage. Murray Iron Works and the Embalming Burial Case Company and the worker's homes on the surrounding streets witness to the industrial/employee relationship of the past.

Large gypsum nodules in the Paleogene and Neogene evaporites of Spain: distribution and palaeogeographic significance

Sabkha and deep burial set tings are the most com mon sites where diagenetic anhydrite forms. In a sabkha setting, displacive facies (iso lated nodules, bed ded nodules, enterolithic levels) of early diagenetic or primary anhydrite are generated (Shearman, 1966; Hardie, 1967). These anhydrite facies are commonly foundat the top of shoal ing cycles representing the evolution from subaqueous depositional conditions at the base (carbonates, lutites) to exposure conditions at the top where in ter stitially-grown gypsum/anhydrite de velops ( sabkha cy cles). In a deep burial setting, gypsum transforms to tally to anhydrite with in creas ing temperature and lithostatic pressure (Murray, 1964). Al though this mineral transformation usually preserves the depositional gypsum facies, a significant textural change is in volved in other cases, resulting in replacive anhydrite with a nodular-mosaic or"chicken-wire" fabric (Warren, 2006). In the two settings, how ever, the size of the individual anhydrite nodules is relatively small, rarely reaching some tens of centimetres across. More over, bedding is preserved or little disturbed, al though minor de formation is caused by the displacive sabkha nodules.

Las necrópolis protohistóricas tumulares de Cataluña meridional: el ejemplo de Sebes (Flix, Tarragona)

Se presentan los resultados de las recientes intervenciones arqueológicas realizadas en la necrópolis del Hierro I de Sebes (Flix, Tarragona). Se ha precisado la extensión de la necrópolis, su duración, los rituales funerarios y la estructura social de la población mediante técnicas y métodos de carácter interdisciplinar (antropología, carbono 14, prospecciones geofísicas…). Se ha constatado la coexistencia de túmulos y urnas y la agrupación de las estructuras en dos áreas. Sobre esta base se pretende mejorar el conocimiento de las necrópolis de cremación en un territorio de contacto entre diferentes tradiciones de enterramiento. Se dan a conocer datos inéditos procedentes del estudio antropológico de los huesos cremados de Sebes y de las dataciones radiocarbónicas de algunos de ellos. Estos datos, considerados en conjunto con los del resto de la necrópolis, permiten relacionarla más con las necrópolis tumulares leridanas que con las del Bajo Aragón - Terra Alta.

Novedades sobre el mundo funerario en la Ribera d’Ebre

La excavación de las necrópolis de incineración de Santa Madrona (Riba-roja d’Ebre) y Sebes (Flix) aportan nuevos datos sobre el estudio del mundo funerario en esta zona. Ambas presentan una fase de utilización durante la Primera Edad del Hierro (siglos vii-vi a.C.), caracterizada por un predominio de estructuras tumulares, junto a las que se documentan otras variantes (urnas funerarias sin túmulo, deposiciones de huesos sin urna, ofrendas funerarias, estructuras empedradas sin urna, etc.). En ambas necrópolis, los estudios antropológicos muestran que todos los grupos de edad estaban representados. Los materiales cerámicos y ajuares presentan gran similitud entre las diferentes sepulturas, lo que sugiere una cierta igualdad en el tratamiento de los difuntos. La existencia, en ambos casos, de dos áreas diferenciadas, podría indicar una separación en función de grupos familiares.

La necròpolis protohistòrica de Sebes (Flix, Ribera d'Ebre)

The archaeological research carried out between 2005 and 2008 at the site of Sebes (Flix, Tarragona) has identified an habitat of the early Iron Age and a contemporary burial site. In general the interrements are secondary cremations buried under circular tumuli. We focus on the first results of these interventions, as well as on the paleoanthropological analyses, the radiocarbon datings and the geophysical surveys.

Modélisation par automate cellulaire des phénomènes diagénétiques des plateformes carbonatées : calibration et paramétrage à partir de deux cas d'études : l'Urgonien du Vercors (Crétacé inférieur, SE France) et les Calcaires Gris du Mont Compomolon (Lias, NE Italie)

Une fois déposé, un sédiment est affecté au cours de son enfouissement par un ensemble de processus, regroupé sous le terme diagenèse, le transformant parfois légèrement ou bien suffisamment pour le rendre méconnaissable. Ces modifications ont des conséquences sur les propriétés pétrophysiques qui peuvent être positives ou négatives, c'est-à-dire les améliorer ou bien les détériorer. Une voie alternative de représentation numérique des processus, affranchie de l'utilisation des réactions physico-chimiques, a été adoptée et développée en mimant le déplacement du ou des fluides diagénétiques. Cette méthode s'appuie sur le principe d'un automate cellulaire et permet de simplifier les phénomènes sans sacrifier le résultat et permet de représenter les phénomènes diagénétiques à une échelle fine. Les paramètres sont essentiellement numériques ou mathématiques et nécessitent d'être mieux compris et renseignés à partir de données réelles issues d'études d'affleurements et du travail analytique effectué. La représentation des phénomènes de dolomitisation de faible profondeur suivie d'une phase de dédolomitisation a été dans un premier temps effectuée. Le secteur concerne une portion de la série carbonatée de l'Urgonien (Barrémien-Aptien), localisée dans le massif du Vercors en France. Ce travail a été réalisé à l'échelle de la section afin de reproduire les géométries complexes associées aux phénomènes diagénétiques et de respecter les proportions mesurées en dolomite. De plus, la dolomitisation a été simulée selon trois modèles d'écoulement. En effet, la dédolomitisation étant omniprésente, plusieurs hypothèses sur le mécanisme de dolomitisation ont été énoncées et testées. Plusieurs phases de dolomitisation per ascensum ont été également simulées sur des séries du Lias appartenant aux formations du groupe des Calcaire Gris, localisées au nord-est de l'Italie. Ces fluides diagénétiques empruntent le réseau de fracturation comme vecteur et affectent préférentiellement les lithologies les plus micritisées. Cette étude a permis de mettre en évidence la propagation des phénomènes à l'échelle de l'affleurement. - Once deposited, sediment is affected by diagenetic processes during their burial history. These diagenetic processes are able to affect the petrophysical properties of the sedimentary rocks and also improve as such their reservoir capacity. The modelling of diagenetic processes in carbonate reservoirs is still a challenge as far as neither stochastic nor physicochemical simulations can correctly reproduce the complexity of features and the reservoir heterogeneity generated by these processes. An alternative way to reach this objective deals with process-like methods, which simplify the algorithms while preserving all geological concepts in the modelling process. The aim of the methodology is to conceive a consistent and realistic 3D model of diagenetic overprints on initial facies resulting in petrophysical properties at a reservoir scale. The principle of the method used here is related to a lattice gas automata used to mimic diagenetic fluid flows and to reproduce the diagenetic effects through the evolution of mineralogical composition and petrophysical properties. This method developed in a research group is well adapted to handle dolomite reservoirs through the propagation of dolomitising fluids and has been applied on two case studies. The first study concerns a mid-Cretaceous rudist and granular platform of carbonate succession (Urgonian Fm., Les Gorges du Nan, Vercors, SE France), in which several main diagenetic stages have been identified. The modelling in 2D is focused on dolomitisation followed by a dédolomitisation stage. For the second study, data collected from outcrops on the Venetian platform (Lias, Mont Compomolon NE Italy), in which several diagenetic stages have been identified. The main one is related to per ascensum dolomitisation along fractures. In both examples, the evolution of the effects of the mimetic diagenetic fluid on mineralogical composition can be followed through space and numerical time and help to understand the heterogeneity in reservoir properties. Carbonates, dolomitisation, dédolomitisation, process-like modelling, lattice gas automata, random walk, memory effect.

Detection of Body Dump Sites and Clandestine Burials: a GIS-Based Landscape Approach

Forensic archaeology has been of inestimable help in the location and excavation of clandestine burials (Hunter 1996a:16-17, 1996b; Killam 2004; Levine et al. 1984). Landscape archaeology techniques have been adapted and widely applied for such purposes. In this article, an adaptation of one of the most common applications of archaeological GIS, that is predictive site location, is applied to the detection of body dump sites and clandestine burial sites, bringing together in the process the fields of landscape archaeology, forensic sciences, and GIS.