Carlos Neto de Carvalho

A History of Ideas in Ichnology

Abstract Although the concept of ichnology as a single coherent field arose in the nineteenth century, the endeavor of understanding traces is old as civilization and involved cultural areas worldwide. In fact, fossil and recent traces were recognized since prehistoric times and their study emerged from the European Renaissance. This progression, from empirical knowledge toward the modern concepts of ichnology, formed a major research field which developed on a global scale. This report outlines the history of ichnology by (1) exploring the individual cultural areas, (2) tracing a comprehensive bibliographic database, and (3) analyzing the evolution of ichnology semiquantitatively and in a graphical form (“tree of ichnology”). The results form a review and synthesis of the history of ichnology, establishing the individual and integrated importance of the different ichnological schools in the world.

STARS OF THE AFTERMATH: ASTERIACITES BEDS FROM THE LOWER TRIASSIC OF THE CARNIC ALPS (WERFEN FORMATION, SAURIS DI SOPRA), ITALY

Abstract Trace fossils are important evidence of benthic activity, but they have received less study than body fossils for investigating the aftermath of the end-Permian extinction. There is therefore a need to document Lower Triassic ichnofaunas to understand their significance with respect to the end-Permian crisis. In light of this need, this paper describes a novel Lower Triassic ichnosite at Mount Pallone (Carnic Alps, Italy), where the Campil Member (Smithian) of the Werfen Formation (Griesbachian–Spathian) presents an abundant ichnofauna characterized by excellent preservation and low diversity. Documented ichnogenera include Asteriacites lumbricalis, Gyrochorte comosa, Diplocraterion habichi and Planolites beverleyensis. The ichnofaunal composition and the bioturbation style suggest a marginal marine paleoenvironment ranging from intertidal to shallow subtidal settings. Storm influence, hydrodynamic energy, sedimentation rate, freshwater input and/or water temperature played an important role in structuring the benthic ecosystem. Dense (300 specimens/m2) aggregations of the trace fossil Asteriacites lumbricalis reveals social behavior of their inferred brittlestar producers (Echinodermata, Ophiuroidea). In line with modern brittlestar beds, social behavior provided significant advantage because raised arms of brittlestars dampened hydrodynamic energy. This study suggests that Asteriacites beds may be considered ichnological proxies for marine settings, low bioturbation intensity, shallow tiering, high sedimentation rate and/or event-bed deposition, significant levels of hydrodynamic energy, and low predation pressure. The studied ichnofauna reflects stressed environmental conditions, but it is unclear whether this reflects local brackish conditions (‘Gazpacho model’) or global hot temperatures (‘Hot Soup model’).

Behaviors mapped by new geographies: Ichnonetwork analysis of the Val Dolce Formation (lower Permian; Italy-Austria)

The Pramollo Basin (Italy-Austria) is one of the richest body and trace fossil sites of the Alps, and exhibits a well-preserved Permian–Carboniferous fluvio-deltaic to marginal-marine sedimentary succession. Despite the exceptionally abundant and well-preserved ichnological heritage, the trace fossils of the Pramollo Basin are not well studied, particularly those of Permian units. This study focuses on the ichnofauna of the Val Dolce Formation (Permian; partly Asselian to partly Sakmarian), with the goal of documenting its ichnological heritage and reconstructing its paleoenvironment. These research questions are addressed by applying network theory, an emerging field of complexity science that focuses on web-like systems made of interconnected entities. An ichnological system can be seen as a set of interlinked ichnotaxa, the topology of which depends on the organism-environment interactions. In addition, traditional paleontological and sedimentological observations are used to reconstruct the paleoenvironment. The following ichnotaxa are documented from the Val Dolce Formation: Archaeonassa isp., Curvolithus simplex , Cylindrichnus isp., Helminthoidichnites tenuis , Nereites missouriensis , Planolites isp., Phymatoderma isp., Pramollichnus pastae , Psammichnites plummeri , Taenidium isp., and Zoophycos isp. Network analysis indicates that the Val Dolce ichnological system is structured, with ichnotaxa organized in environment-driven ichnoassociations: Cylindrichnus - Planolites (proximal delta front), Phymatoderma - Zoophycos (prodelta with dysoxic porewaters), Cylindrichnus - Helminthoidichnites - Curvolithus - Zoophycos (distal delta front–proximal prodelta), and Helminthoidichnites - Taenidium - Curvolithus - Nereites - Zoophycos (prodelta). Furthermore, the delta front–prodelta gradient is accompanied by increasing bioturbation intensity and diversity, reflecting the decreasing intensity of major environmental stressors (hydrodynamics, freshwater input, turbidity). Centrality measures of network analysis allow the topological position of traces to be discerned within the studied system, detecting the paleoenvironmental resolution of individual ichnotaxa. As intersections of sets can be described by networks, the studied ichnoassociations can be considered as occupying intersecting behavioral niches. In analogy with the concept of a Hutchinsonian niche, an ichnotaxon’s niche exists in a multidimensional abstract space defined by environmental parameters, which are expressed as spatial variables in the paleolandscape. Consequently, ichnoassociations are not just association patterns, but represent spatial, environmental, and topological entities. This approach allows the reconstitution of spatial relationships between the geographical ranges of ichnotaxa and ichnoassociations, providing information on the physical arrangement of different subenvironments, that is, the structure of the paleoenvironment.

Differentiation of delta and open marine deposits based on an integrated ichnological and sedimentological analysis of the Late Triassic Nayband Formation, Tabas Block, Central Iran

BackgroundThe palaeoenvironmental significance of trace fossil assemblages in the shallow marine deposits of the Late Triassic Nayband Formation of the Tabas Block, Central Iran has been assessed for the first time. The siliciclastic successions of the Nayband Formation, are highly bioturbated and allow relationships between changes in ichnoassemblages within a depositional system to be documented and placed in a palaeoenvironmental framework.PurposeThe main purposes of this paper are: (1) to describe and illustrate the trace fossils assemblages of the Nayband Formation; (2) integration of ichnologic and sedimentologic data to evaluate different stress factors on the infaunal communities; and (3) to briefly discuss paleoenvironmental distribution of various trace fossil assemblages in order to differentiate between deltaic and non-deltaic shoreface successions.MethodsThe Upper Triassic Nayband Formation has been studied and measured in one section, where the Nayband Formation is well accessible and continuously exposed. This section was logged and evaluated using physical sedimentology and ichnology in order to establish a basis for the interpretation of sedimentary processes (facies) and depositional systems. In this study, trace fossils (diversity, abundances, and ethologies) and the spatial arrangement of sedimentary structures are used to further refining the interpretation of environmental parameters such as hydrodynamic energy, water turbidity, substrate properties, food supply, temperature, oxygenation, salinity, and sedimentation rates.ResultsBased on facies characteristics and stratal geometries, the siliciclastic succession is divided into two facies associations, fluvial-dominated delta (FA), and open marine (FB). Twenty-eight ichnogenera have been identified in delta and open marine successions: The assemblage is dominated by Rhizocorallium, Thalassinoides, Ophiomorpha, Helminthopsis, Palaeophycus and Skolithos. Their distribution is clearly linked with lithofacies and depositional environments.ConclusionHigh rates of fluvial discharge, high water turbidity, seasonally high rates of deposition and phytodetrital pulses in river-dominated deltas may cause marked variations in the temperature, oxygenation and salinity of the fluvial-dominated delta successions. All of these factors in combination lead to impoverishment in trace diversity and reduction in burrow size but to rapid colonization of the substrate by single-layer colonizers of opportunistic deposit feeders. Low ichnodiversity, low bioturbation intensities with highly bioturbated clusters shown by single colonization events by opportunistic, simple feeding strategies of trophic generalists and a paucity of suspension-feeding structures elements represent a “stressed”, non-archetypal Cruziana ichnofacies. The changes of behavioural complexity and the tiering profiles in the offshore-shoreface complex of the Nayband Formation when compared with the river-dominated delta successions represent the transition from epifaunal life habits with simple tiering structures to infaunal life habits with complex tiering pattern. The occurrence of diverse trace fossil suites attributable to the Zoophycos ichnofacies, the archetypal Cruziana ichnofacies and the Skolithos ichnofacies in wave-dominated shoreface-offshore complex point to stress-free environmental conditions in open waters due to persistent wave agitation, and hence, a wide colonization window.ResumenAntecedentesSe ha evaluado por primera vez la importancia paleoambiental de las asociaciones de fósiles en los depósitos marinos poco profundos de la Formación Nayband del bloque de Tabas, Irán central, datada del Triásico tardío. Las sucesiones siliciclasticas de la Formación Nayband están altamente bioturbadas y permiten relacionar los cambios en asambleas de trazas fósiles dentro de un sistema deposicional para ser documentados y colocados en un marco paleoambiental.ObjetivosLos principales propósitos de este trabajo son: (1) describir e ilustrar las asociaciones de trazas fósiles de la Formación Nayband; (2) integración de datos icnológicos y sedimentológicos para evaluar diferentes factores de estrés en las comunidades endobentónicas; y (3) discutir brevemente la distribución paleoambiental de varios conjuntos de trazas fósiles con el fin de diferenciar entre las sucesiones shoreface deltaicas y no-deltaicas.MétodosLa Formación Nayband del Triásico Superior se ha estudiado y medido en una sección, donde la secuencia es bien accesible y permanentemente expuesta. Esta sección se registró y evaluó utilizando sedimentología física e icnología con el fin de establecer una base para la interpretación de los procesos sedimentarios (facies) y sistemas de deposición. En este estudio se usan trazas fósiles (diversidad, abundancias y etologías) y la disposición espacial de estructuras sedimentarias para refinar aún más la interpretación de parámetros ambientales tales como energía hidrodinámica, turbidez del agua, propiedades del sustrato, suministro de alimentos, temperatura, oxigenación, salinidad, y tasas de sedimentación.ResultadosA partir de las características faciales y geometrías estratales, la sucesión siliciclástica se divide en dos asociaciones de facies, delta fluvial (FA) y mar abierto (FB). Veintiocho icnogeneros han sido identificados en sucesiones de delta y marinas abiertas: El conjunto está dominado por Rhizocorallium, Thalassinoides, Ophiomorpha, Helminthopsis, Palaeophycus y Skolithos. Su distribución está claramente relacionada con las litofacies y los ambientes de deposición.ConclusionesLas altas tasas de descarga fluvial, alta turbidez del agua, estacionalmente altas tasas de deposición y pulsos de fitodetritos en deltas con influencia fluvial pueden causar marcadas variaciones en la temperatura, la oxigenación y la salinidad. Todos estos factores en combinación llevan al empobrecimiento en la diversidad de trazas y reducción en el tamaño de las madrigueras, así como a una rápida colonización del sustrato por los animales depositivoros oportunistas colonizadores de una sola capa. Icnodiversidad baja, bajas intensidades de bioturbación con concentraciones altamente bioturbados mostradas por eventos de colonización individuales mediante estrategias oportunistas y simples de alimentación de los generalistas tróficos y una escasez de estructuras de alimentación suspensivora representan icnofacies de Cruziana “estresantes” no arquetípicas. Los cambios de la complejidad del comportamiento y los perfiles de organización en niveles del complejo en alta mar-cara de playa de la Formación Nayband cuando se compara con las sucesiones de delta con influencia fluvial representan la transición de los hábitos de vida epifaunales con estructuras de organización en niveles sencillos para hábitos de vida infaunales con el patrón complejo de organización en niveles. La ocurrencia de suites de trazas fósiles diversas atribuible a la icnofacies de Zoophycos, a la icnofacies de Cruziana arquetípica y a la icnofacies de Skolithos en un complejo cara de playa-costa afuera dominada por la influencia de las olas apuntan para condiciones ambientales libres de estrés en aguas abiertas debido a la agitación de ola persistente, y por lo tanto, creando una amplia ventana para la colonización.

Dynamic adaptation of byzantine consensus protocols

The problem of distributed consensus in the presence of Byzantine faults has received particular attention in recent decades. Today a variety of solution to this problem exist, each optimized for particular execution conditions. Given that, in most cases, real systems operate under dynamic conditions, it is important to develop mechanisms that allow the algorithms to be adapted or changed at runtime to optimize the system to the current conditions. The problem of dynamic adaptation of consensus algorithms is not new, but the literature is scarce for the Byzantine case and there is no comprehensive comparison of existing solutions. This work has two complementary objectives. First, it studies how the different dynamic adaptation techniques proposed for the crash failure model can be applied in the presence of Byzantine faults. Second, it presents a comparative study of the performance of these switching algorithms in practice. For that purpose, we have implemented the switching algorithms in a common software framework, based on the open source BFT-SMaRt library. Using this framework we have performed an extensive evaluation that offers useful insights on the practical effects of different mechanisms used to support the run-time switching among Byzantine protocols.

Multifractals and Capacity Dimension as Measures of Disturbance Patch Dynamics in Daedalus Ichnofabrics

An ichnofabric includes all structure and textural changes of the sediment resulting from bioturbation (and bioerosion) at all scales. Abundance and distribution of burrows reflects the non-linear sorting effects of physical and biological parameters, resulting in a disturbance regime which generates patchiness. To analyze the patch dynamics of trace fossils as a result of environmental disturbance, this study quantifies bioturbation rates and spatial and temporal variation based on fractal geometry. Multifractal spectrum is used as a measure of spatial ichnofabric heterogeneities. The magnitude of the Daedalus ichnofabric fluctuations for the two stratigraphic sequences sampled shows that sandflat substrate colonization by the Daedalus halli worm producer after each storm event was opportunistic, mostly multigenerational, with an exclusive and significant occupation of emptied ecospace, for the purpose of meiofauna harvesting in clean sands.