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Recognition of large biogenic sedimentary structures (burrows, nests), their differentiation from physical structures (small storm-surge channels, synsedimentary deformation, buried objects), as well as imaging bioturbation in real time remain key challenges in sedimentology and ichnology. To address these issues, this study focused on laboratory and field ground-penetrating radar (GPR) experiments using both traditional time-lapse mode (TLM) and a time-triggered mode (TTM). In three sets of laboratory experiments, substrate consisted of dry, well-mixed, moderately sorted, medium sand common for upper beach (berm/foredune) and aeolian settings. Targets simulating burrowing organisms were placed on a basal layer (L1) buried by ~20-cm-thick cover horizon (L2), both with near identical mean grain size (1.69 and 1.65 ϕ, respectively). Improvements were made to the experimental design, including an experiment with a saline balloon (vertical pull) and a ground-coupled antenna, at varied moisture levels (0%, 3.7%, and 29.5%). High-frequency (2300 MHz) surveys were captured in TTM while manually extracting the target (variable deformation rate; total time window: 20 seconds). Velocities of simulated deformation calculated from time-triggered radargrams have the potential to be used in the field and laboratory to quantify rates of subsurface bioturbation not available by direct observation. Sediment disruption was quantified using standard ImageJ-aided grayscale analysis to detect truncations (breaks in reflection continuity), with an increase of 10-28% relative to undeformed substrate. Similarly, area-based mean grayscale values increased between 8-16% for damp and saturated TLM surveys, respectively. Complementing the laboratory experiments, this research produced one of the first GPR databases of post-emergence sea turtle nests, ichnologically understudied and relatively complex biogenic structures. A simulated structure (Deauville Beach, DE) and two in situ post-emergence sea turtle nests (Sandbridge Beach, VA) were imaged with an 800 MHz antenna, complemented with sediment texture and magnetic susceptibility analyses. The Delaware experiment provided a reference dataset for a full ethological sequence of nesting and emergence, for comparison with few available studies. At Sandbridge, a clear anomaly was identified at the recent Kemp’s Ridley (Lepidochelys kempii) nesting site, including a V-shaped truncation (width: 0.3-0.5 m; depth: ~0.75-0.9 m). At another location, an older (2020) loggerhead (Caretta caretta) nest was imaged and characterized in a similar aeolian ramp setting, which is characterized by a unique combination of upper berm and aeolian granulometric statistics. Numerous ghost crab burrows, with some imaged during surveys, place sea turtle nests into the Psilonichnus ichnofacies, with overprinting representing a contemporary ichnocoenosis rather than a facies shift. This research has wide-ranging implications for: 1) nest recognition in ancient sequences through identification of diagnostic aeolian ramp packages with diagnostic deformation structures; 2) distinguishing nests from morphologically similar paleo-channels based on overall metrics (tiered components) and fill structure, and 3) conservation of endangered species, with novel applications for nest characterization and potential hatchling emergence monitoring. / Geology

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Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-04T19:08:31Z No. of bitstreams: 1 DissRMAS.pdf: 2567370 bytes, checksum: 878fab5581b7d1cab72a62b808602d5a (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T18:17:46Z (GMT) No. of bitstreams: 1 DissRMAS.pdf: 2567370 bytes, checksum: 878fab5581b7d1cab72a62b808602d5a (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T18:17:53Z (GMT) No. of bitstreams: 1 DissRMAS.pdf: 2567370 bytes, checksum: 878fab5581b7d1cab72a62b808602d5a (MD5) / Made available in DSpace on 2016-10-20T18:18:00Z (GMT). No. of bitstreams: 1 DissRMAS.pdf: 2567370 bytes, checksum: 878fab5581b7d1cab72a62b808602d5a (MD5) Previous issue date: 2016-05-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Ichnofossils are abundant in the sandstones of the Botucatu Formation, Paraná Basin, of Neocomian age. This formation covers much of the Midwest, Southeast and South of Brazil, and other countries in South America. Several sandstone samples containing trace fossils were collected and deposited in the paleontological collection of the Departmento de Ecologia e Biologia Evolutiva (DEBE) of the Universidade Federal de São Carlos (UFSCar). In this work, trace fossils attributed to arachnids, i.e. ichnogenera Paleohelcura Gilmore, 1926 and Octopodichnus Gilmore, 1927, were studied and their presence is recorded for the first time in Brazil. The aim of this study was to infer how different environmental conditions such as moisture, texture, substrate inclination and even behavioral aspects of the organisms can affect the structure of the traces left by different arthropods. To do this, several neoichnological experiments were made, with six arachnids (two Tityus serrulatus, one Lycosa sp., one Loxosceles sp., and two individuals of the family Gonyleptidae) and five individuals of other invertebrate classes (three insects, one isopod and one diplopod). The experiments consisted on making the animals walk on a tray with sand of different grain sizes, different inclinations and different moisture levels. The results of these experiments, which showed different trace morphologies, according to each imposed condition, proved the influence of these conditions on the morphology of the footprints and on the behavior of the studied animals. In addition, these results showed how, in some situations, for example, in an uphill movement in a slope of 30° of inclination, it’s possible that animals with highly different track’s shapes leave very similar tracks, thus making much more difficult the identification of the track’s producer animal through the analysis of the ichnofossils. It was also possible to prove how the moisture level and the substrate inclination are important for the tracks’ preservation. / Icnofósseis são abundantes nos arenitos da Formação Botucatu, Bacia do Paraná, de idade Neocomiana. Esta formação abrange grande parte do Centro-oeste, Sudeste e Sul do Brasil, além de outros países da América do Sul. Várias amostras de arenito contendo icnofósseis foram coletadas e depositadas na coleção paleontológica do Departamento de Ecologia e Biologia Evolutiva (DEBE) da UFSCar. Neste trabalho foram estudados os icnofósseis atribuídos a aracnídeos, ou seja, os icnogêneros Paleohelcura Gilmore, 1926 e Octopodichnus Gilmore, 1927, registrados pela primeira vez no Brasil. O principal objetivo deste estudo foi identificar como diferentes condições do ambiente, como umidade, textura, inclinação do substrato e até mesmo aspectos comportamentais podem afetar a estrutura dos rastros deixados por diferentes artrópodes. Para isso foram realizados diversos experimentos neoicnológicos com seis aracnídeos (dois Tityus serrulatus, uma Lycosa sp., uma Loxosceles sp., e dois indivíduos da família Gonyleptidae) e cinco indivíduos de outras classes de invertebrados (três insetos, um isópode e um diplópode). Os experimentos consistiram em fazer os animais caminharem sobre uma bandeja com diferentes granulometrias de areia em diferentes inclinações e com diferentes níveis de umidade. Os resultados desses experimentos, que mostraram diferentes formatos dos rastros de acordo com cada condição imposta, comprovaram a influência dessas condições na morfologia das pegadas e no comportamento dos animais estudados. Além disso, esses resultados mostraram como em algumas situações, por exemplo, em um movimento de subida em relevos de 30° de inclinação, é possível que animais com morfologias acentuadamente diferentes deixem rastros muito semelhantes, o que dificulta a identificação do animal produtor por meio da análise de icnofósseis. Também foi possível comprovar como a umidade e a inclinação do substrato são importantes na conservação dos rastros.

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