A fossil shark tooh in early contexts of Cerro Casa de Piedra 7, southwest Patagonia, Argentina

Fil: Castro, Alicia Susana. División Arqueología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cione, Alberto Luis. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Civalero, María Teresa. INAPL. Ciudad Autónoma de Buenos Aires; ArgentinaFil: De Nigris, Mariana. INAPL. Ciudad Autónoma de Buenos Aires; Argentin

Taxonomy, Taphonomy, and Bioerosion of Lamniform and Carcharhiniform Shark Teeth from Onslow Bay, North Carolina and an Example Extension from the Gulf Coastal Plain of the U.S.A.

This dissertation is divided into four sections that feature assemblages of self-collected fossils recovered while SCUBA diving in Onslow Bay, North Carolina, and the Ouachita River near Malvern, Arkansas. Sections one through three focus on Cenozoic lamniform and carcharhiniform shark teeth, including those of large Otodus megalodon, collected from submerged, actively forming lag deposits adjacent to outcrops of the Miocene Pungo River and Pliocene Yorktown formations in Onslow Bay. Section one documents the submerged collecting localities and the taxonomy and biostratigraphic properties of the fossil shark teeth they contain. Section two documents bathymetric controls on the degree of taphonomic reworking and bioerosion of these shark teeth from shallower, intermediate, and deeper shelf localities in Onslow Bay. Section three identifies and utilizes bioerosion in megatoothed shark teeth in addition to radiocarbon dating of endolithic bivalves and corals to time the process of lag deposit formation. Section four consists of a research extension into the Gulf Coastal Plain of the USA and focuses on an assemblage of Teredolites-bored driftwood recovered from a fossiliferous lag deposit at the contact between the Arkadelphia Formation and Midway Group submerged in the Ouachita River near Malvern, Arkansas. This driftwood derives from a known Cretaceous-Paleogene (K-Pg) boundary section and features trace fossils similar to those occurring in megatoothed shark teeth from Onslow Bay. Although the Malvern lag deposit is geologically older than those actively forming in Onslow Bay, the processes of lag deposit formation are extremely similar. Lag deposits in both study areas contain diverse, time-averaged vertebrate fossil assemblages with a notable abundance of biostratigraphically significant and taphonomically distinct shark teeth, infrequent terrestrial elements, and accumulated in response to numerous storm events and sea level cyclicity. Moreover, the processes of lag deposit formation observed in the actively forming Onslow Bay lags provide a means to interpret and model the formation of similar deposits, including the Malvern K-Pg lag, preserved in the stratigraphic record. Results from this dissertation indicate that the process of vertebrate lag deposit formation: 1) occurs globally, 2) is independent of geologic age, and 3) is the product of numerous storm events, including impact generated tsunamis, and sea level cyclicity within shallow shelf stratigraphic sections

Unveiling the consequences of environmental variation and species abundances on beach taphofacies in Bahamas: The role of cementation and exhumation

Although environmental variability generates differences in the preservation of shell assemblages, intrinsic variations in shell characteristics can confound the effects of environment on preservation. However, several studies proposed that the composition of shell supply only affects the intensity of alteration but not its preservation trend along the environmental gradient and that environmental variability represents a major driver of taphofacies preservation. Here, we examine whether taphonomic differences among four infaunal and aragonitic bivalve species differing in shell thickness affect the definition of beach taphofacies in tropical carbonate environments on San Salvador Island (Bahamas). We show that (1) taphofacies can be discriminated with respect to (a) wave and storm activity as a function of exposure to Trade Winds, and (b) sandy beaches versus beaches with a mixture of sands and beach rock (representing a source of exhumed and cemented shells), and (2) species-specific bivalve assemblages show similar gradients in preservation, documenting that differences in preservation between species have minor effects on taphonomic discrimination of beach environments. Environments with a mixture of sands and beach rock are characterized by higher frequency of external cementation and abrasion than sandy beaches. Shells from low-energy beaches are more fragmented and discolored than shells from high-energy beaches. Previous studies showed that shells from San Salvador sandy beaches are more time-averaged than shells from rocky beaches. Differences in preservation between these two environments indicate two pathways: (1) assemblages on sandy beaches are degraded at higher rate but are enriched by old exhumed and lithified shells, and (2) assemblages on rocky beaches are cemented at higher rate. Old and lithified shells on sandy beaches are probably derived from submerged or exposed beach rock patches, leading to the mixture of young, well-preserved shells with old, poorly preserved shells. Shells on sandy beaches thus experience a complex history of burial and exhumation before their final deposition. Therefore, shell assemblages in lower energy carbonate environments from San Salvador Island are highly time-averaged, with the presence of old, poorly preserved shells. The depositional environment is thus the dominant factor controlling the structure of San Salvador beach taphofacies.Fil: Bayer, María Sol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Balseiro, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Muñoz, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Gordillo, Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Taphonomy of the vertebrate bone beds from the Klūnas fossil site, Upper Devonian Tērvete Formation of Latvia

Combined sedimentological and taphonomical study of the siliciclastic sequence of the Tērvete Formation in the stratotypical area was aimed at revealing the formation of the three oryctocoenoses discovered and related structural and textural features of the deposits, as well as at detailed observation of the taphonomical peculiarities of the obtained palaeontological material. The fossil vertebrate assemblage is represented by 14 taxa comprising placoderms, acanthodians, sarcopterygians and actinopterygians. The three oryctocoenoses, first recognized in 2010, differ in the proportions of repeatedly buried material, in the number and degree of preservation of small and fragile skeletal elements, as well as in the evaluated current velocity and the transportation distance. Sedimentary concentrations of marine vertebrate remains, dominated by the antiarchs Bothriolepis ornata and B. jani, have been formed under the influence of fluvial and tidal processes in the shallow-water environment, deltaic or estuarine settings. Elongated placoderm and sarcopterygian bones are probably better indicators of the palaeoflow direction than acanthodian spines or sarcopterygian teeth

Late Quaternary environmental reconstruction of the Lacepede Shelf, southern Australia

The study of relative sea-level changes and ultimately glacio-eustatic sea-level for the Late Quaternary, is commonly addressed by analysing the ocean-land interface from continental shelves, which represent submerged former coastal plains established during periods of low sea-level. In Late Quaternary time, only during the last interglacial MIS 5e highstand (128 – 116 ka) and during the present, Holocene interglacial, has sea level been near or above present sea-level. The Lacepede Shelf is a large (30,000 km2), wide (180 km) and shallow (up to 120 m) embayment, which has been partly or entirely subaerially exposed during the Late Quaternary. The shelf is a far-field environment from Pleistocene ice sheets and is tectonically stable in a global context. The Lacepede Shelf is bordered to the north by the Murray Basin, a Paleogene–Quaternary epicratonic sedimentary basin. The high level of tectonic stability of the region implies that environmental changes experienced on the shelf were largely a function of sea-level changes. The Murray Basin and Coorong Coastal Plain, adjacent to the Lacepede Shelf, represent a sequence of Paleogene to Quaternary emergent interglacial barriers of international significance in the study of the Quaternary sea-level fluctuations. The Coorong Coastal Plain extends up to 100 km inland from the modern shoreline and its 20 barriers record their formation during interglacial and warm interstadial highstands. In contrast, the Lacepede Shelf preservers a record of Late Pleistocene lowstand deposition, and a rising-stage period of sea-level, associated with the post-Last Glacial Maximum transgression. Accordingly, the Lacepede Shelf is an ideal realm for the study of aspects of Late Quaternary sea-level changes. While Late Quaternary glacio-eustatic sea-levels are well established, controversies remain regarding the magnitude of highstands and lowstands, the timing of the Last Glacial Maximum (LGM) and the number of highstands during MIS 3 (North Greenland Ice Core Project, NGRIP, core vs. sedimentary record). To address some of these controversies at a regional scale, this thesis focuses on reconstructing palaeoenvironmental changes associated with sea-level oscillations on the Lacepede Shelf. The study is based on five sediment cores located broadly in a north-south transect across the depocenter of the continental platform. The core sites correspond with the location of the former courses of the River Murray, at the time of glacial low sea-level

Estudio tafonómico y espacial del yacimiento DS del Lecho I de la garganta de Olduvai (Tanzania)

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Geografía e Historia, leída el 16-12-2020Faunal remains recovered at early archaeological sites dated to around 2 million years (Ma) play a critical role in discussions about the evolution of early hominin behavior. Anthropogenic assemblages from this time period are scarce, however and, until recently, most of the available evidence on the behavior of early Homo has been almost exclusively obtained at the FLK Zinj site from Bed I in Olduvai Gorge (Tanzania). The recent discovery of DS (David’s Site, 1.84 Ma) and two additional hominin-made accumulations on the same paleosurface as the iconic site of FLK Zinj provides an invaluable opportunity to address key issues regarding early hominin lifestyles, particularly their subsistence behaviors and their foraging capabilities. The DS site has been extensively excavated and is exceptionally well preserved. Over the past years, significant advances in taphonomic and spatial statistical techniques have been made, which mainly involve the combination of several variables in multivariate approaches and the use of machine learning algorithms. The application of these methods to the faunal fossil record within extended frames of reference helps overcome equifinality when trying to detect the main agent of site formation and interpret site function...Los restos faunísticos recuperados en algunos de los yacimientos arqueológicos más antiguos, que datan de alrededor de dos millones de años (Ma), desempeñan un papel muy importante en las discusiones sobre la evolución del comportamiento de los homininos. Sin embargo, los conjuntos arqueológicos de origen antrópico de ese periodo son escasos y, hasta hace poco, la mayor parte de los datos disponibles sobre el comportamiento de los primeros miembros del género Homo han sido obtenidos casi exclusivamente del yacimiento FLK Zinj del Lecho I de la Garganta de Olduvai (Tanzania). El reciente descubrimiento de DS (David’s Site, 1.84 Ma) y de otras dos acumulaciones generadas por homininos sobre la misma paleosuperficie que el emblemático yacimiento de FLK Zinj, brinda una valiosa oportunidad para abordar cuestiones clave relacionadas con la forma de vida de los primeros Homo con nuevos datos, en particular sus comportamientos de subsistencia y sus capacidades depredadoras. El yacimiento se ha excavado en extensión y se encuentra excepcionalmente bien preservado. A lo largo de los últimos años, se han realizado avances significativos en las herramientas tafonómicas y espaciales estadísticas disponibles, que ahora comprenden principalmente la combinación de varias variables en aproximaciones multivariantes y el uso de algoritmos de máquinas de aprendizaje automático. La aplicación de estos métodos al registro faunístico fósil y la utilización de marcos referenciales ampliados permite superar problemas de equifinalidad a la hora de detectar el agente principal de formación del yacimiento e interpretar la funcionalidad de la localidad...Fac. de Geografía e HistoriaTRUEunpu

Déjà vu: a reappraisal of the taphonomy of quarry VM4 of the Early Pleistocene site of Venta Micena (Baza Basin, SE Spain)

Venta Micena, an Early Pleistocene site of the Baza Basin (SE Spain), preserves a rich and diverse assemblage of large mammals. VM3, the main excavation quarry of the site, has been interpreted as a den of the giant hyaena Pachycrocuta brevirostris in the plain that surrounded the Baza palaeolake. Taphonomic analysis of VM3 has shown that the hyaenas scavenged the prey previously hunted by the hypercarnivores, transported their remains to the communal den, and consumed the skeletal parts according to their marrow contents and mineral density. In a recent paper (Luzón et al. in Sci Rep 11:13977, https://doi.org/10.1038/s41598-021-93261-1, 2021), a small sample of remains unearthed from VM4, an excavation quarry ~ 350 m distant from VM3, is analysed. The authors indicate several differences in the taphonomic features of this assemblage with VM3, and even suggest that a different carnivore could have been the agent involved in the bone accumulation process. Here, we make a comparative analysis of both quarries and analyse more skeletal remains from VM4. Our results indicate that the assemblages are broadly similar in composition, except for slight differences in the frequency of megaherbivores, carnivores and equids according to NISP values (but not to MNI counts), the degree of bone weathering, and the intensity of bone processing by the hyaenas. Given that VM4 and VM3 were not coeval denning areas of P. brevirostris, these differences suggest that during the years when the skeletal remains were accumulated by the hyaenas at VM3, the rise of the water table of the Baza palaeolake that capped with limestone the bones was delayed compared to VM4, which resulted in their more in-depth consumption by the hyaenas