Andrea Baucon

Organism-substrate interactions and their products – biogenic structures – are important biosignatures on Earth. This study discusses the application of ichnology – the study of organism-substrate interactions – to the search for present and past life beyond Earth. Three main questions are addressed: (1) Why to look for biogenic structures (i.e. traces and ichnofabrics) beyond Earth? (2) What biogenic structures to expect on other planets, moons and asteroids? (3) How to study extraterrestrial biogenic structures? Review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life: trace fossils preserve the activity of soft-bodied organisms; biogenic structures are resilient to processes that obliterate other biosignatures (i.e. mechanical and chemical degradation , diagenesis, tectonism and metamorphism); traces are very visible biosignatures; traces indicate environment and behaviour; traces can be universal biosignatures, i.e., biosignatures ideally suited for detecting any type of life. A model of organism-substrate interactions beyond Earth is here proposed. Expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis: excavations, meandering traces and biodeposition structures. Most of the existing rovers and orbiters provide basic instruments for searching these traces. It is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting, GPR, LiDAR, and drilling equipment with optical televiewer. In this study, open-access databases of rover and orbiter imagery have been searched for traces and ichno-fabrics, but no unquestionable evidence of biogenic structures beyond Earth has been found besides those produced by humans. This sounds along the lines of the famous Fermi Paradox: if the universe is teeming with aliens, where are their traces? Results of this search show that habitable environments are not the only place to look for biogenic structures; non-habitable environments such as moons without atmosphere can favour the preservation of shallow-tier traces. The better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection, including the interaction between astronauts or vehicles and the substrate may produce disturbances. Although this study highlights a new direction of study with the tools and concepts of ichnology, dialogue MARK between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science: Does life exist beyond Earth?

Traces – burrows, borings, footprints – are important evidences of biological behaviour on Earth, yet they received relatively little attention in the field of astrobiology. This study aims to discuss the application of ichnology (i.e. the study of life activity traces) to the search for past and modern life beyond Earth (i.e. herein called Astroichnology). Organisms apparently represent a more direct evidence of life than traces. Consequently, why to look for traces (and trace fossils) is a central question. The reason is fourfold: 1) the Earth's ichnological record shows that traces record accurately the activity of soft-bodied organisms – from annelids to prokaryotes – that are comparatively underrepresented in the fossil record but that constitute the most part of the benthic biomass. 2) trace fossils are commonly the only preserved evidence of life in sediments that are otherwise unfossiliferous. 3) bioturbation and bioerosion change the physico-chemical properties of the substrate and leave (bio-)geochemical, petrographic and geotechnical signals that enable to relate with the presence of life. 4) the bioturbating activity of organisms commonly results in structures that are far more abundant and more visible/detectable than their tracemakers (e.g. several arthropods produce km-scale mounded topographies in aquatic and continental environments; cm-sized organisms shaped the geochemistry of the Earth's benthic ecosystem during the Cambrian Agronomic revolution). With increasing availability of high-resolution imagery, the search for past and modern traces is possible for several terrestrial bodies, such as the Moon, Mars, Venus, Titan and Mercury. Nevertheless, finding ichnological evidences beyond Earth is still a significant challenge because of (a) resolution issues, (b) relative paucity of bedding-plane imagery, (c) lack of core data, (d) lack of method-specific instrumentation. For these reasons, there is a great potential for developing tools that incorporate ichnology into an astrobiological framework. Specifically, tools for the analysis of sediment and/or rock cores are needed for observing biogenically-produced sedimentary fabrics (ichnofabrics) beyond Earth. Applied ichnology provides a vast set of practical tools (i.e. CT-scanning, borehole imagery) for studying ichnofabrics. Finally, a question might arise: What to expect? Models of bioturbation beyond Earth are extremely complex and variable due to the variety of geodynamical conditions existing on solar and exo-planets. Nevertheless, burrowing and boring behaviours are expected to be a general pattern for life because they allow to face harsh surficial physico-chemical conditions (e.g. cosmic rays) and/or evolutionary pressures, both for mineralized or soft-bodied organisms. Identifying more precisely the forms and variation of Earth's traces in extreme environments and their evolutionary paths is likely to provide a more robust predictive model for bioturbation beyond Earth.

Ichnology is a powerful tool for understanding the evolutionary paths of animal clades, through the paleobiology of behavior preserved in Lagerstätten such as the Cabeço da Ladeira (Portugal) site. Here, the peritidal carbonates of the Chão das Pias Formation (Middle Jurassic, upper Bajocian) record the development of microbial mats in a tidal flat. Episodically, the flat was expanded during periods of equinoctial spring tides that may have been responsible for the in situ killing of several members of echinoderm clades, and the fine preservation of their endoskeleton, in addition to the behavior of an arthropod-dominated endo-and epifauna. Mat-preserved shallow tiers with a moderate ichnodiversity attributed to the Cruziana ichnofacies include trackways of crabs (Laterigradus lusitanica igen. nov., isp. nov.) and shrimps (Diplopodichnus isp.); trails of fishes (?Undichna), gastropods (Archaeonassa fossulata), isocrinid crinoids (Krinodromos bentou igen. nov., isp. nov.) and insects (Haplotichnus indianensis); and burrows of shrimps or lobsters (Thalassinoides suevicus) and other arthropods (Asterosoma ludwigae, Gyrochorte comosa), or polychaetes (Rhizocorallium commune). This is implied already above (igen. nov., etc.) and seems not needed. The crab trackways and gastropod bulldozing trails, extending up to 12.3 m, are among the longest invertebrate cursorial traces ever found in the fossil record. The mortichnial crawling trail of a crinoid is the first evidence of locomotion for this group in the fossil record, and a rare unambiguous example of this ethology. Extensive continuous trackways attributed to amphibious crabs record, with great detail, typical gaits of underwater punting and walking sideways on dry land. The earliest evidences of sidewalking behavior may also be evidence for the development of the crab form during their rise in the Jurassic.

Thick quartzite beds with large bedding planes exposures thoroughly bioturbated with Deadalus desglandi, that can be followed for several kilometers, were discovered in the Lower Ordovician (Floian) of the Armorican Quartzite Formation at Muradal Mountain, UNESCO Naturtejo Geopark (Central Portugal). The complex architecture of this form of Daedalus is discussed and the model of " subtidal pumping " , based on the presence of a draft-fill channel in each one of the burrows, is introduced to explain the feeding pattern in " clean " quartzites. Extremely crowded monoichnospecific levels show that they were strongly controlled by shifting substrate conditions but mostly limited in time, pointing to the colonization of event beds by soft-bodied populations in very shallow marine and very dynamic settings. The magnitude of the Daedalus ichnofabric fluctuations shows that sandflat substrate colonization by the Daedalus producer after each event was intense, mostly sequential, with an exclusive and almost total occupation of the emptied ecospace. The presence of only one preserved behavioral strategy, the substrate depth affected by these structures, the high density of burrows and passive patchiness rates are characteristics of r-selected populations. Such large-scale and frequent disturbance events as storms, extreme on a gradient of disturbance intensities, were responsible for some of the earliest opportunistic behaviours in the fossil record. Daedalus was among the most resilient of them in the Early Paleozoic of this part of the world. Resumo: Níveis de quartzitos maciços com larga exposição dos planos de estratificação intensamente bioturbados com Deadalus desglandi, que podem ser seguidos ao longo de vários quilómetros, foram descobertos no Ordovícico Inferior (Floiano) da Formação do Quartzito Armoricano na Serra do Muradal, Geopark Naturtejo da UNESCO (Portugal Central). A complexa arquitectura desta forma de Daedalus é discutida e o modelo de " bombagem subtidal " , baseado na existência de um fino canal axial em cada uma das galerias, é introduzido para explicar o padrão de alimentação em areias aparentemente sem evidências da presença de matéria orgânica. Os níveis monoicnoespecíficos extremamente povoados mostram que estes seriam fortemente condicionados pelas condições do substrato móvel e fundamentalmente limitados no tempo, apontando para uma colonização episódica de populações de organismos de corpo mole em ambientes marinhos muito pouco profundos e dinâmicos. A magnitude da flutuação dos icnofábricas de Daedalus mostra que a colonização do substrato da planície de maré arenosa pelo produtor de Daedalus após cada um destes eventos seria intensa, na sua maioria multigeracional, com uma ocupação exclusiva e quase total do ecospaço entretanto deixado vago. A presença de apenas uma estratégia comportamental preservada, a profundidade do substrato afectada por estas estruturas, a elevada densidade de icnofósseis e os níveis de agregação passiva são características de populações que apresentam selecção-r. Eventos que afectam espacialmente grandes áreas e causam frequentes perturbações extremas dos substratos, como as tempestades, terão sido responsáveis por alguns dos mais antigos comportamentos oportunísticos encontrados no registo fóssil. Daedalus encontra-se entre os mais resilientes destes durante o Paleozóico Inferior, nesta parte do planeta. Palavras-chave: Deadalus desglandi, eventos de colonização, bioturbação densa, bombagem de nutrientes, Ordovícico Inferior.

Barrier-islands are common landforms and biodiverse habitats, yet they received scarce neoichnological attention. This gap is tackled by studying the Mula di Muggia barrier-island system (Grado lagoon, Italy), focus-ing on morphology, ecology and ethology of individual traces. The following incipient ichnotaxa are Thalassinoides and 'squat burrows'. Vertebrate (Avipeda-/Ardeipeda-like, Canipeda) and invertebrate tracks ('parallel furrows') are also described. For each ichnotaxon, tracemaker and behavior are discussed, together with their position with respect to sediment barriers. Results suggest that sediment barriers impose a sharp contrast in terms of ichnological composition. Back-barrier is dominated by branched burrows (i.e. Thalassinoides, Parmaichnus), while the fore-barrier presents vertical and U-shaped burrows (Arenicolites, Skolithos). The environmental conditions of the back-barrier show that low-oxygen substrates favor intense bioturbation, provided that the water column is sufficiently oxygenated.

The largest ever described Cruziana, more than 200 mm wide, are not uncommon in the Lower-to-Middle Ordovician Armorican Quartzite Formation, at the Ichnological Park of Penha Garcia, central Portugal. They are the most visible trace fossils of ichnocoenoses dominated by classic arthropod intrastratal burrows, tunnels, and trackways, and Skolithos piperocks in a shallow marine, transgressive siliciclastic succession. The typical " Armorican Quartzite " of the Skolithos Ichnofacies is overlaid by a sequence of alternating storm-related quartzites and pelites of the Cruziana Ichnofacies, where the Cruziana rugosa Group is far abundant and shows a unique diversity of behaviors. A quantitative comparison of the Cruziana ichnospecies from Penha Garcia with the trilobite communities from the Middle Ordovician of Canelas, where large body clusters of asaphids are common, was preliminarily performed with the aim of establishing a genetic relationship and eventual trophic migratory paths across trilobite ontogenesis. The gregarious behavior commonly found in discrete beds totally covered by Cruziana is explained under the trilobite clustering paleobiology, as detritus feeding congregations where the opportunity for scavenging cannot be ruled out. The large body size inferred for some of the Cruziana rugosa trilobite producers may be correlated with the high latitude position of Penha Garcia in the shores of Gondwana during the Ordovician times, the diversification of food resources and abundance, and the capacity to explore them and thrive in oxygen-depleted substrates, that may have resulted in " polar gigantism " among them.

ABSTRACT 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.

ABSTRACT 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.

600 million years,
21 paintings,
9 meters long and 4 meters tall.
These are the record numbers of Andrea Baucon’s Paleobiologica, a series of large-sized artworks celebrating the evocative power of Paleontology. It is not a case that Paleobiologica accompanied Dinoexpo, world’s largest traveling exhibition about dinosaurs, hosted by the UNESCO Geopark Naturtejo (Portugal).
This symbiotic relationship between science and esthetics makes Paleobiologica more than simply an art exhibit. Intended as a visual narration of biological evolution, Paleobiologica traverses deep time through the diversity of life. Each painting corresponds either to a fossil site or a moment in geological time; past ecosystems have been reconstituted through a meticulous scientific approach. This book features full-color illustrations of works in Paleobiologica, along with texts that explore the scientific research behind the exhibition. A short foreword by Andrea Baucon explains the history and ideas behind this event. This is followed by a lavish full-colour portfolio of the paleontologic visions, ranging from Ediacaran underwater scenarios to a 36-metre-square Mesozoic landscape and a snow-covered panorama with mammoth.

Since the days of Leonardo da Vinci, art has been a passionate way to express geology.
Geology in Art is the first book to document the artistic phenomena in which geology brings its own aesthetic and conceptual heritage. From painting to music, literature to sculpture, comics to photography, Geology in Art leads you on a journey through Geologic Art in a delightful and informative way.
Accompanied by beautiful reproductions, the book crosses centuries and genres, from Leonardo to Conan Doyle.
The contemporary art world is analyzed through interviews, in the belief that artists’ opinions and statements are valid source materials for the study of Geologic Art.
With its large format and more than 100 illustrations of art works, this is both a coff ee-table book and an educational experience that informs, inspires and entertains art and geology enthusiasts alike.