Taphonomy is the study of the fate of information in the fossil record. Information can be lost through the partial or complete destruction of fossils, or through the disruption of their original spatial relationships. Information can be "gained" if the alteration of fossils allows environmental information to be retrieved. In Bahia la Choya, northern Gulf of California, bioerosion, dissolution/maceration, and abrasion produce distinctive textures on the surfaces of shells in intertidal and shallow subtidal environments. Shells from different environments possess different surface textures, suggesting that textures on fossil shells could serve as paleoenvironmental indicators. Algal bioerosion is the chief mode of shell alteration and destruction in Bahia la Choya, though dissolution/maceration and abrasion are locally important. Algal bioerosion of shell surfaces is accelerated by the grazing activity of snails, and is most intense where snails are abundant. Microstratigraphic resolution is limited by vertical mixing of fossils and by the reworking of older fossils into younger deposits. Stratigraphic disorder is the departure from perfect chronological order of fossils in a stratigraphic sequence. I simulated mixing and reworking of fossils by simple computer models, and measured stratigraphic disorder using rank correlation statistics. As modeled, mixing produces disorder slowly, and its effects can be minimized by increasing sample size at each horizon and by increasing the vertical spacing between sampled horizons (though this reduces vertical resolution). Reworking generates disorder more efficiently, and its effects are not reduced by increasing sample size or spacing. The generation of stratigraphic disorder in fossiliferous sediments can also be modeled using M (depth of vertical mixing), I (thickness of sedimentary increments), and L (taphonomic loss rate) as parameters. Increasing M increases the disorder generated, and increasing I and L decreases disorder. For a worst case--high M and low I and L--the vertical spacing between samples must at least 3 times M to ensure a 5% temporal overlap between adjacent samples. A 1% temporal overlap requires a vertical spacing of 4.6 times M.

This dissertation explores geographic and diachronic variation in Great Plains and Rocky Mountain Paleoindian (12,500-7000 14C years before present) forager exploitation of animal resources in order to explore how use of different habitats influenced land-use and subsistence strategies. To accomplish this goal, this study documented the full range of variability in the Paleoindian record using a combination of published data and new data. These patterns were then compared to explicit predictions derived from behavioral ecology and animal ethology and biology studies. The results, presented in this dissertation, allow the testing of several, often contradictory, important subsistence-settlement hypotheses in current Paleoindian research, specifically the ongoing debate about Paleoindian diet breadth and human causes of megafaunal extinction. Overall, there appears to be a covariance between environmental zone and forager land use. Paleoindian foragers structured their land use according to the presence and nature of a number of important resources within major environmental zones. Specifically, this study finds sites in grassland settings with low diversity of resources have lower artifact densities and are often dominated by exotic lithic raw materials. In these same areas prehistoric groups made almost exclusive use of large fauna. Sites in foothill/mountain or alluvial valley settings with ecologically high density and high diversity have higher proportions of short-term camps than do other areas and those camps have higher artifact density than do other types of sites. These sites exhibit a mixed use of small- and medium-sized game. Overall this study shows Paleoindian hunters had only modest impact on prey species.

The Upper Paleolithic site of Vale Boi in coastal, southwestern Portugal currently represents the earliest known case of grease-rendering in Eurasia, with initial occupation occurring during the early Gravettian at ~ 27,000 BP. Long-term exploitation of marine resources is indicated by marine shellfish remains, mainly in the form of limpets (<italic>Patella</italic>), recovered from all three cultural periods (Gravettian, Solutrean and Magdalenian). High-level exploitation of rabbits (<italic>Oryctolagus</italic>) began with initial use of the site and continued throughout the occupations, with a possible increase in intensity at the onset of the Solutrean. Grease-rendering of red deer (<italic>Cervus elaphus</italic>), horse (<italic>Equus caballus</italic>), European ass (<italic>Equus hydruntinus</italic>) and aurochs (<italic>Bos primigenius</italic>) bones was identified through multi-dimensional taphonomic and zooarchaeological analyses. Ungulate remains demonstrated extensive fragmentation and abundant evidence of impact features such as cone fractures, crushing, denting and cracking. The intensity of fragmentation and impact damage to red deer remains is significantly correlated with quantities of marrow and bone grease within these portions. Lack of density-mediated attrition of either the leporid remains or the cranial bone of red deer and horse, demonstrates that the loss of low-density, grease-rich post-cranial skeletal portions is due to human subsistence activities. Balanced body-part representation of ungulates indicates that density-mediated attrition of post-cranial elements is not related to differential transport of carcass portions. Comparison of element portion frequencies to food utility indices further demonstrates that humans were systematically harvesting marrow and bone grease throughout the Gravettian, Solutrean and Magdalenian culture periods. The co-occurrence of fire-cracked rock, stone anvils and hammerstones corroborates this suggestion. Although grease rendering at Vale Boi pre-dates other known sites in Eurasia by several thousand years, faunal assemblages in southeastern Spain indicate that resource diversification and intensification appeared there coevally with Vale Boi. The persistence and continued intensification of subsistence practices throughout the Upper Paleolithic suggests a sustained depression of large game in relation to human populations. This was likely due to patchy, spatially-restricted resources, resulting in territorial circumscription. Only through technological innovation and novel approaches to resource harvesting, were foragers able to maintain and ultimately expand their populations in southern Iberia.

In this study diatom distribution within the lower Save River, Mozambique, has been identified from surface sediments, surface water, mangrove cortex and buried sediments. Sandy units, bracketing a geographically extensive clay layer, have been dated with optical stimulated luminescence (OSL). Diatom analysis has been used to interpret the spatial salinity gradient and to discuss taphonomic processes within the delta. Previously, one study has been performed in the investigated area and it is of great importance to continue to identify diatom distributions since siliceous microfossils are widely used for paleoenvironmental research. Two diatom taxa, which were not possible to classify to species level have been identified; Cyclotella sp. and Diploneis sp. It is suggested that these represent species not earlier described; however they are assigned a brackish water affinity. Diatom analysis from surface water, surface sediments and mangrove cortex indicate a transition from ocean water to a dominance of freshwater taxa c. 10 km upstream the delta front. Further, ratios between marine/brackish taxa for samples from surface water and surface sediments do not correspond. It is therefore suggested that diatoms in surface sediments underestimate prevailing salinity conditions in water. In the investigated area extensive taphonomic processes seem to have large impact on diatom frustules in sediments and may bias interpretations. Therefore it is recommended to carefully investigate geology, geomorphology and vegetation before diatom analysis is applied in studies of delta paleoenvironments.

The Ediacaran Period, stretching from 635–542 million years ago, is one of the most dynamic intervals in the history of life. It witnessed the rapid transition from a microbially-dominated world, which had existed undisturbed for almost three billion years, to a Phanerozoic biosphere that is greatly modified by the interactions between macro-organisms and Earth surface systems. Ediacaran successions worldwide contain enigmatic assemblages of fossilised soft-bodied organisms. Determining the biological affinities of these fossils represents one of the major challenges in modern palaeontology. This thesis addresses some of the fundamental questions surrounding the Ediacara biota of the Avalon region from taphonomic, ontogenetic and palaeoenvironmental perspectives. Up-to-date stratigraphic ranges are produced for Avalonian macro-organisms, documenting spatial and temporal trends in their occurrence. New fossil assemblages are described, which include populations of juvenile rangeomorphs, and one of the earliest examples of community succession in the fossil record. The previously unexplained fossil Ivesheadia Boynton and Ford 1996 is re-described as a taphomorph, preserving the remains of Ediacaran macro-organisms that had died and undergone microbial decay on the seafloor prior to burial. This hypothesis implies considerable time-averaging of Avalonian palaeocommunities, and consequently suggests that the preserved fossil assemblages do not represent census populations of living organisms at the time of burial. Microbial decay is experimentally demonstrated to replicate aspects of Ivesheadia-type morphology, supporting the arguments presented herein for the preservation of microbially-induced taphomorphs during the Ediacaran. Finally, the discovery of the oldest evidence for metazoan locomotion, from 565Ma horizons at Mistaken Point in Newfoundland, suggests that motile macro-organisms were present amongst the Ediacara biota, ~20Myrs before the Cambrian boundary. This portrayal of Ediacaran palaeobiology views the deep-marine Avalonian ecosystems as diverse assemblages of both macro- and micro-organisms. Such palaeoenvironments preserve rare evidence of organisms capable of locomotion, and are likely to have included metazoans.

Caractérisation de l’occupation des sites de la région de Témara (Maroc) au Pléistocène supérieur et nouvelles données sur la subsistance des Hommes du Paléolithique moyen d’Afrique du Nord : exemples des approches taphonomiques et archéozoologiques menées sur les faunes d’El Harhoura 2 et d’El Mnasra » Ce travail en taphonomie et en archéozoologie se concentre sur les faunes pléistocènes de la région de Témara où deux sites fouillés récemment, El Harhoura 2 et El Mnasra, ont retenu notre attention. Il porte principalement sur l’Atérien (Paléolithique moyen/MSA), faciès culturel du Pléistocène supérieur propre à l’Afrique du Nord, dont l’aspect comportemental - en particulier les pratiques cynégétiques, la fonction des sites, l’organisation spatiale du territoire - est peu documenté. Le croisement des résultats obtenus sur les restes osseux de grands Mammifères avec les rares données régionales a permis de proposer un modèle hypothétique d’occupation des sites. Les occupations pérennes de courte durée au cours desquelles les Hommes ont effectué de multiples activités sont datées du stade 5. L’exemple d’El Mnasra montre que les Hommes ont consommé des Ongulés de toutes tailles (Gazelles, Suidés, Alcelaphinés, Équidés, grands Bovinés…) et que les différentes étapes de la chaîne opératoire du traitement des carcasses ont été effectuées in situ. Outre la grande faune, leur régime alimentaire était composé également de Tortues et de Mollusques marins. Comme l’indique l’exemple d’El Harhoura 2, aux stades isotopiques 4 et 3, en concomitance avec une dégradation climatique et une baisse du niveau marin, les occupants principaux des cavités étaient les Carnivores qui ont consommé principalement des Gazelles. Il semble que les Hommes n’ont effectué que de brefs passages dans les grottes. À l’Ibéromaurusien (Paléolithique supérieur final/LSA), le seul exemple d’El Harhoura 2 témoigne que, malgré le changement culturel observé au sein de l’industrie lithique et l’utilisation de la cavité à des fins sépulcrales, les accumulateurs majoritaires des faunes restent les Carnivores alors que les proportions d’Ongulés de tailles supérieures aux Gazelles augmentent. Comparés à plus large échelle, ces résultats mettent en exergue des similitudes dans les stratégies de subsistance qui s’ajoutent à d’autres convergences telles que l’utilisation de pigments, de Nassarius sp. … Au stade isotopique 5, le milieu littoral est exploité en association avec la consommation d’Ongulés d’assez grande taille et de Tortues aussi bien en Afrique du Nord qu’en Afrique du Sud par les Hommes Anatomiquement Modernes (HAM). La diversification des ressources n’est pas le seul fait des HAM, puisque les Néandertaliens de la péninsule ibérique et d’Italie ont également exploité le milieu littoral. Ainsi, cette période semble cruciale pour l’appréhension des dynamiques évolutives et comportementales des Hommes du MSA/HAM, non seulement en Afrique du Nord, mais également dans d’autres régions. / The Upper Pleistocene occupation of the Témara Region (Morocco) and new data concerning Middle Palaeolithic subsistence behaviour in North Africa: A taphonomic and zooarchaeological approach to the fauna from El Harhoura 2 and El Mnasra”This work presents a taphonomic and zooarchaeological analysis focused on Pleistocene fauna from the Temara region of Morroco with particular emphasis on the recently excavated sites of El Harhoura 2 and El Mnasra. Particular attention is paid to the Aterian (Middle Palaeolithic, MSA), a techno-complex specific to Upper Pleistocene North Africa and whose behavioural aspects remain poorly documented. This is especially the case for hunting practices, site function and the spatial organization of the territory. This work proposes an interpretative model based on large mammal faunas considered in conjunction with the little regional information that is currently available. The results suggest short occupations involving multiple activities during MIS 5. The example of El Mnasra indicates that Aterian groups consumed ungulates of various sizes (Gazelles, Equidae, Suidae, Bovinae, etc.) with the entire chaîne opératoire related to the butchery of carcasses carried out on-site. In addition to large game, these groups also integrated tortoise and shellfish in their diet. The example of El Harhoura 2 demonstrates carnivores who preyed mainly on gazelle to be the site’s main occupants during OIS 3-4, a period which can be correlated with more rigorous climatic conditions and lower sea levels. Aterian groups probably occupied the rockshelter only during brief stopovers. Despite culture changes evident in the lithic industry and the site being used as a burial ground during the ensuing Iberomaurusian period (Late Upper Palaeolithic/LSA), the accumulators of the fauna at El Harhoura 2 remain carnivores and the proportion of species larger than gazelle increases. On a larger scale, these results highlight similarities in subsistence strategies that can be added to other convergent behavioural features such as the use of pigments and the presence of Nassarius sp. beads. During OIS 5, anatomically modern humans (AMH) exploited coastal areas as well as fairly large ungulates and tortoise in both North and South Africa. However, this diversification of resources is not unique to AMH as Neanderthals are known to have exploited coastal environments in the Iberian Peninsula and Italy. This period is therefore crucial for understanding Middle Palaeolithic/ MSA evolutionary dynamics and related behavioural traits not only in North Africa, but also in a broader geographical perspective.

La thèse s'intéresse à l'enregistrement des propriétés de la biodiversité dans les archives sédimentaires. Elle s'appuie sur l'analyse d'une faune contemporaine de milieu tropical, collectée dans le Lagon de Touho, Nouvelle-Calédonie lors de l'expédition Montrouzier en 1993. Les différences de diversité entre les assemblages de bivalves vivants et de coquilles mortes d'un même site sont quantifiées à l'aide de plusieurs descripteurs (richesse taxonomique, indice PIE d'eveness, courbes de raréfactions, indices de fidélité) et d'outils de classification (analyses Cluster, NMDS). Les associations d'espèces vivantes varient dans l'espace en fonction de paramètres environnementaux comme le type du substrat ou la profondeur. La composition des assemblages morts diffère des écosystèmes vivants, mais ils conservent globalement les informations environnementales. Les assemblages morts sont en général plus diversifiés que les communautés vivantes associées, à cause de l'accumulation de nombreuses espèces rares. Cet enrichissement s'explique par : 1) la préservation des coquilles autochtones, 2) l'apport de coquilles allochtones et 3) la condensation du temps. Des différences de fidélité entre les communautés biologiques et les assemblages de coquilles mortes apparaissent en fonction des environnements. Par exemple, les environnements à substrat induré sont associés à une mauvaise préservation des communautés vivantes, contrairement aux environnements profonds qui conservent bien les espèces autochtones mais accumulent beaucoup d'espèces allochtones. / The thesis explores how the properties of biodiversity are preserved in the sedimentary archives. Discussions are supported by the analysis of the modern tropical fauna of the Touho Lagoon (New Caledonia), collected during the Montrouzier expedition in 1993. The differences between live bivalve assemblages and dead shell assemblages are quantified with various indices (taxonomic richness, PIE index of evenness, rarefaction curves, fidelity indices) and classification tools (Cluster analyses, NMDS).Environmental parameters, such as the type of substrate or the water-depth, are responsible for variations among live species associations. The composition of dead shell assemblages differs from the living communities but environmental informations arepreserved. Generally, the dead shell assemblages are more diversified than live fauna of the same sites because of the accumulation of rare species. The higher diversity of dead shell assemblages can be explained by 1) the preservation of autochthonous bivalve shells, 2) the input of allochthonous shells and 3) the time-averaging. The fidelity of dead shell assemblages to the biological communities varies according to the environmental conditions. For example, dead shell assemblages found on hard substrate environments may be very different from the living communities. Allochthonous species tend to accumulate in deep outer shelf environments... Salinity, substrate or water-depth are main perturbation factors, as they imply loss or gain of taxa.The preservation of living communities varies according to the biological caracteristics, such as ecology, population structure or shells mineralogy.

Rochas mesozóicas do Brasil contêm registros relativamente abundantes de tetrápodes fósseis continentais, particularmente triássicos e cretáceos, alguns de importância internacional. Embora estudos paleontológicos de caráter taxonômico sejam relativamente comuns, são ainda escassos os estudos tafonômicos de alta resolução, especialmente das ocorrências com dinossauros cretáceos. Entretanto, a Tafonomia e a Estratigrafia constituem ferramentas indispensáveis para a determinação dos processos deposicionais, dos paleoambientes e das relações ecológicas entre os fósseis. A presente contribuição fornece a primeira análise estratigráfica e tafonômica de detalhe, de três bone-beds de dinossauros que ocorrem no Alto de Paracatu, Bacia Sanfransiscana, na região de Montes Claros, município de Coração de Jesus, MG. A sucessão sedimentar portadora das ocorrências fósseis é, provavelmente, coeva às rochas do Grupo Areado (Formação Abaeté, Barremiano-Aptiano). Entretanto, tanto a sucessão sedimentar, quanto a ocorrência de dinossauros são novas para a Bacia Sanfranciscana e aqui descritas pela primeira vez. Para estudar as ocorrências fossilíferas acima, procedimentos padrão para mapeamento geológico e levantamentos estratigráficos foram empregados, culminando com a análise de fácies e determinação da arquitetura dos depósitos. Arenitos e siltitos, dentre outros litótipos, forneceram amostras para as análises petrográficas. As análises tafonômicas incluíram a exposição e o mapeamento das ocorrências. A direção e o mergulho dos elementos ósseos alongados foi plotada em estereogramas. As feições tafonômicas dos ossos e as evidências de deformação litostática, composição mineral e alteração da textura superficial dos ossos foram analisadas tanto no campo, como no laboratório. Os dados obtidos indicam que as três acumulações estudadas ocorrem em sedimentos de leques aluviais, em ambiente lacustre marginal, representando concentrações parautóctones/autóctones, de ossos de poucos indivíduos saurópodes e terópodes, com mistura temporal. Na sucessão sedimentar, as concentrações apresentam distribuição vertical e horizontal restrita. De acordo com os dados disponíveis de momento, a história tafonômica dos restos de dinossauros de Coração de Jesus pode ser sumariada da seguinte forma: Fase bioestratinômica incluiu (1) biodegradação subaérea de carcaças de saurópodes, às margens do sistema lacustre, (2) desarticulação parcial ou total dos esqueletos de alguns indivíduos, (3) necrofagia de algumas carcaças de saurópodes, provavelmente por terópodes, e (4) pré-soterramento (recobrimento) e reorientação dos ossos, por fluxos de detritos atingindo o sistema lacustre. Os processos relativos à diagênese dos fósseis incluíram: (1) deformação plástica dos ossos, devido à pressão litostática, (2) perminaralização inicial, (3) fraturamento dos ossos devido ao rearranjo dos depósitos, pela deposição final das cunhas clásticas, associadas aos fluxos de detritos distais, e (4) exposição natural, subaérea, de alguns espécimes e intemperismo em ambiente atual. Finalmente, o tipo de concentração acima descrito e a sucessão sedimentar sugerem que as fácies sedimentares associadas às porções distais dos leques aluviais podem acumular carcaças de grandes saurópodes, titanossaurídeos, em excelente estado de preservação. Essas ocorrências chamam a atenção para o potencial dos depósitos de leques aluviais, em sistemas de lagos tectônicos, como repositório de importantes dados paleontológicos do Mesozóico. / The Mesozoic rocks from Brazil exhibit a particularly abundant record of Triassic and Cretaceous tetrapod fossils, some with worldwide relevance. Although paleontological studies are relatively numerous, high resolution taphonomic information about the Cretaceous dinosaur occurrences are normally missing. However, both taphonomy and stratigraphy are necessary for reconstructing paleoenvironments and original ecological relationships among fossil organisms. The present contribution provides the first detailed stratigraphical and taphonomical analyses of three dinosaur bone-beds from the Montes Claros region, Coração de Jesus County, State of Minas Gerais. The fossiliferous sedimentary succession at the Paracatu-High, Sanfranciscana Basin, is probably coeval to rocks of the Areado Group (Abaeté Formation, Barremian-Aptian). Both the sedimentary deposits and the bone concentrations are entirely new to the stratigraphic record of the Sanfranciscana Basin. To study these occurrences conventional stratigraphic sections were measured and detailed logs taken after field-based facies analysis. Lateral mapping and photographs indicate the lateral continuity of beds and sedimentary architecture. Sandstones and mudstones, among others provided samples for petrographical analysis. Taphonomical methods included bone deposit mapping using grid squares and photographs. The strike and dip of long axes of appendicular bones were plotted in stereoplots. Taphonomic signatures of bones and evidence of pre-burial disturbance, lithostatic deformation, mineral composition, and bone surficial texture were analyzed in the field and laboratory. Data gathered indicate that the three bone-beds are localized (stratigraphically and geographically) time-averaged, parautochthonous/autochthonous accumulations of articulated, disarticulated/associated, and disarticulated bones that represent a few sauropod and teropod individuals. The bone concentrations are found in alluvial fan sediments within a lake system. The taphonomic history can be briefly summarized, as follow: Biostratinomic processes included (1) subaerial biodegradation of sauropod carcasses on lake margins, (2) partial or total skeletal disarticulation of some specimens, (3) scavenging or necrophagy of sauropod carcasses by teropod dinosaurs, and (4) pre-burial and reorientation of all bones by sporadic debris flows. Fossil-diagenetic processes included: (1) plastic deformation of bones due to lithostatic pressure, (2) initial permineralization, (3) fracturing during the final burial and deposition of clastic edges associated to debris flows, and (4) exposure of some individuals, and postfossilization, subaerial bone weathering. The type of bone concentrations and the sedimentary succession, herein described, suggests that debritic facies in distal-fan environments can accumulate large titanosaur bones, some in excellent preservational state. This taphonomic mode outlines the potential of alluvial fans as important sources of paleontological data in Mesozoic tectonic controlled lake systems.

Trabalhos objetivando a tafonomia de concentrações fossilíferas geradas em ambiente glacial ou periglacial são raros. Neste contexto, a presente dissertação realizou a caracterização tafonômica das concentrações fossilíferas da Formação Cape Melville, Grupo Moby Dick (Mioceno Inferior), Ilha Rei George, Antártica, tendo em vista a elucidação da gênese destes depósitos. Para tanto, dados relativos a um total de 534 espécimes foram obtidos nas camadas ricamente fossilíferas das quatro seções, denominadas Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) e Lava Crag (LCS), levantadas no topo da Península Melville entre Janeiro e Fevereiro de 2003. Destas, apenas a Seção PRS apresenta duas camadas fossilíferas distintas (PRS-C1 e PRS-C2). A fauna estudada é composta predominantemente por restos de moluscos bivalves. Restos menos abundantes de corais, caranguejos, gastrópodes e braquiópodes, além de icnofósseis, também estão presentes. A análise da composição taxonômica, ecológica e tafonômica permitiu identificar semelhanças entre as Seções PRS e HGS e entre as Seções CS e LCS. As seções PRS e HGS são compostas dominantemente por bivalves depositívoros da infauna rasa (Ennucula frigida, Enncula musculosa e Yoldia peninsularis), preservados preferencialmente com as valvas articuladas fechadas, porém fora da posição de vida, indicando remobilização da fauna pré-soterramento; a ausência de sinais de fragmentação, abrasão e incrustação indica que os bioclastos não foram afetados por processos bioestratinômicos químicos, físicos ou biológicos intensos. A ocorrência de bioclastos piritizados na Seção HGS é interpretada como resultante da decomposição dos organismos soterrados, ainda vivos, em ambiente anóxico. As assembléias das seções CS e LCS são constituídas dominantemente por bivalves suspensívoros da infauna profunda (Neilo (N.) rongelii), preservados preferencialmente com as valvas desarticuladas, indicando que os processos bioestratinômicos físicos foram mais atuantes, sendo, no entanto, raros os sinais de fragmentação e de outras assinaturas tafonômicas como incrustação e bioerosão. As valvas desarticuladas estão preservadas preferencialmente com a convexidade voltada para baixo indicando que os bioclastos foram colocados em suspensão e redepositados fora da posição de maior estabilidade hidrodinâmica; a orientação em planta destes bioclastos exibe direção preferencial, indicando atuação de correntes fracas e um maior tempo de exposição na interface água/sedimento; a ocorrência de raros restos de bivalves suspensívoros escavadores da infauna profunda (Panopea (P.) cf. P. regularis) e de caranguejos (Antarctidromia inflata) preservados em posição de vida é indicativa de que esta comunidade foi soterrada in situ por sedimentos em suspensão que trouxeram a tanatocenose de valvas desarticuladas. Os resultados obtidos no presente estudo reiteram a importância dos estudos tafonômicos e paleoecológicos no entendimento da dinâmica deposicional do passado, contribuindo com um grande conjunto de dados úteis na caracterização de ambientes glaciais e periglaciais. / Works focusing on the taphonomy of fossil concentrations generated in glacial or periglacial environment are rare. In this context, the present dissertation carried out the taphonomic characterization of the fossil concentrations of the Cape Melville Formation, Moby Dick Group (Lower Miocene), King George Island, Antarctica, in order to elucidate the genesis of these deposits. To this end, data relative to a total of 534 specimens were obtained in the richly fossil layers of the four sections, called Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) and Lava Crag (LCS), investigated at the top of the Melville Peninsula between January and February of 2003. Of these, only the PRS Section presents two distinct fossil layers (PRS-C1 and PRS-C2). The studied fauna is mainly composed of remains of bivalve clams. Less abundant remains of corals, crabs, gastropods and brachiopods, as well as trace fossils, also are present. Taxonomic, ecological and taphonomic analyses allowed similarities to be identified between PRS and HGS and CS and LCS. PRS and HGS Sections are dominantly composed by shallow infaunal deposit-feeding bivalves (Ennucula frigida, Enncula musculosa Yoldia peninsularis), preserved preferentially with closed articulated valves, however out of life position, indicating remobilized fauna; the absence of signs of spalling, abrasion and incrustation indicates that the bioclasts were not affected by intense chemical, physical or biological bioestratinomic processes. The occurrence of pyritized bioclasts in HGS is interpreted as the result of decomposition of the entombed organisms, still alive, in an anoxic environment. The assemblages of CS and LCS Sections are dominantly constituted by deep infaunal suspension-feeding bivalves (Neilo (N.) rongelii), preserved preferentially with disarticulated valves, indicating that the physical biostratinomic processes were more operative; however there are few signs of spalling or other taphonomic signatures such as incrustation and bioerosion. Disarticulated valves are preferentially preserved convex down indicating that bioclasts were placed in suspension and redeposited in a position other than that of greatest hydrodynamic stability; the orientation of these bioclasts in plan view shows a preferential direction, indicating weak currents and a longer time of exposition at the water/sediment interface; the occurrence of rare remains of deep infaunal suspension-feeding bivalves (Panopea (P.) cf. P. regularis) and crabs (Antarctidromia inflata) preserved in life position is indicative that this community was entombed in situ by sediments in suspension that brought the thanatocenosis of disarticulated valves. The results obtained in the present study reiterate the importance of taphonomic and paleoecological studies for the understanding of the depositional dynamics of the past and contribute a great number of data useful in the characterization of glacial and periglacial environments.

A resolução temporal é uma questão-chave em Paleontologia, uma vez que a sua magnitude define a precisão dos estudos não somente paleoecológicos como também evolutivos. A resolução temporal é estimada pela magnitude de time-averaging (mistura de gerações em uma camada, uma amostra). Tais estimativas têm sido amplamente conduzidas em ambientes marinhos recentes. A plataforma continental do sul do Brasil (PSB; 22°S – 34°S) tem sido um laboratório natural para estudos desta natureza desde o início do século XXI. Consequentemente, possui um amplo acervo de dados disponíveis para comparação. Neste contexto, esta tese visou responder (i) qual a magnitude do time-averaging em acumulações de bivalves da PSB? (ii) como este processo varia ao longo de gradientes espaciais? e (iii) como o time-averaging reflete na informação biológica preservada no registro fóssil? Para isto, mais de 140 espécimes de bivalves foram datados integrando racemização de aminoácidos e 14C AMS. Além disto, análises tafonômicas foram realizadas em todas as amostras datadas, incluindo mais sete amostras em sedimentos lamosos. A resolução temporal (time-averaging) e a variabilidade total de idades (mistura temporal) basearam-se em uma nova abordagem numérica, a estatística bayesiana, que integra os erros e as incertezas derivadas da distribuição posterior dos resíduos associados com os modelos resultantes das calibrações das idades. As tendências onshore-offshore — aumento da mediana e da uniformidade das curvas de frequência de distribuição de idades, redução da variabilidade tafonômica, ainda que a escala do time-averaging seja invariante — provavelmente refletem a interação entre as mudanças do nível relativo do mar e da bioprodutividade mais elevada em águas menos profundas. / The temporal resolution of the fossil record plays a key role in paleontology because it determines the scale and the precision of paleoecological and evolutionary studies. The temporal resolution of the fossil record is estimated by the magnitude of time-averaging (non-contemporaneous generations preserved in a single layer, a bulk-sample). Quantitative estimates of time-averaging have been conducted primarily on mollusk shells from modern shallow-water marine settings. Most of them have been addressed in the Southern Brazilian continental shelf (SBS; 22°S up to 34°S), which is considered a natural laboratory for several similar studies since the earlier of current century (XXI). Consequently, the SBS has several available datasets that allow comparisons of the new results displayed here with those previous data. Thus, this thesis aimed answer (i) what is the magnitude of time-averaging on SBS mollusk death assemblages? (ii) how does time-averaging vary across spatial gradients? and (iii) how does time-averaging can reflect on the preservation of the fossil record? Here, >140 specimens were individually dated using amino acid racemization calibrated using radiocarbon ages (14C). In addition, taphonomic analyses were conducted in all samples, including more seven muddy sites. The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the 14C–AAR calibration average model. The onshore-offshore trends — increased median age, decreased skewness of age distributions, decreased taphonomic variation, yet the invariant scale of time-averaging — likely reflect the interplay between sea-level changes and elevated bioproductivity in shallower water settings.