Alluvial-eolian interaction in a Cambrian rift margin: the Pedra das Torrinhas and Pedra Pintada formations (Guaritas Group, RS)

This work presents a study of selected outcrops from the Pedra das Torrinhas Formation of the Guaritas Group (Cambrian, Camaquã Basin), near the basin bordering Encantadas Fault Zone. The studied succession includes alluvial fan deposits that pass laterally into eolian deposits. Sedimentary facies and architectural element analysis were performed, followed by sedimentary petrography and microscopic porosity analysis, aiming to characterize the porosity of the deposits and its spatial distribution. The main objective was to contribute to a better understanding of the porosity spatial distribution in depositional systems characterized by the interaction between alluvial and eolian processes, with special reference to deposits formed prior to the development of terrestrial plants. Porosity values are related to depositional processes, with higher porosities associated to eolian dune deposits (mean of 8.4%), and lower porosity related to interdunes (mean of 3.4%) and alluvial fans (mean of 4.3%). Architectural elements analysis revealed the spatial relationships of these deposits, a response to the interplay of the eolian and alluvial processes. The integration of porosity data reveals that the interaction of alluvial and eolian processes results in heterogeneous distribution of porosity at the facies association scale. Eolian reworking of alluvial facies increases porosity whereas sheet-flood and other alluvial processes in the interdune areas reduce porosity.<br>O presente trabalho consiste no estudo de afloramentos da Formação Pedra das Torrinhas do Grupo Guaritas (Cambriano, Bacia Camaquã), próximo à Zona de Falha das Encantadas. As sucessões estudadas incluem depósitos de leques aluviais que passam lateralmente para depósitos eólicos. Foram realizadas análises de fácies e de elementos arquiteturais, seguidos de petrografia sedimentar e análise microscópica de porosidade, com o objetivo de caracterizar a porosidade da unidade e sua distribuição espacial. o principal objetivo foi contribuir para uma melhor compreensão da distribuição espacial de porosidade em sistemas deposicionais caracterizados pela interação aluvial-eólica, com atenção especial à sistemas deposicionais pré-vegetação. A porosidade é controlada principalmente pelos processos deposicionais, com os valores maiores associados a depósitos de dunas eólicas (média de 8,4%) e os menores a facies de interdunas (média de 3,4%) e de leques aluviais (média de 4,3%). A análise dos elementos arquiteturais mostra a relação espacial destes depósitos, provocada por interações entre sistemas deposicionais aluviais e eólicos. A integração de dados revela que a interação de processos aluviais e eólicos resultou em uma complexa heterogeneidades na escala de associação de facies. o retrabalhamento eólico de fácies aluviais provocou aumento de porosidade enquanto que a ocorrência de enchentes-em-lençol em áreas de interduna e o aporte de sedimentos aluviais em interdunas inundadas formaram corpos sedimentares com porosidade reduzida

Carnivoran remains from the Malapa hominin site, South Africa

Recent discoveries at the new hominin-bearing deposits of Malapa, South Africa, have yielded a rich faunal assemblage associated with the newly described hominin taxon Australopithecus sediba. Dating of this deposit using U-Pb and palaeomagnetic methods has provided an age of 1.977 Ma, being one of the most accurately dated, time constrained deposits in the Plio-Pleistocene of southern Africa. To date, 81 carnivoran specimens have been identified at this site including members of the families Canidae, Viverridae, Herpestidae, Hyaenidae and Felidae. Of note is the presence of the extinct taxon Dinofelis cf. D. barlowi that may represent the last appearance date for this species. Extant large carnivores are represented by specimens of leopard (Panthera pardus) and brown hyaena (Parahyaena brunnea). Smaller carnivores are also represented, and include the genera Atilax and Genetta, as well as Vulpes cf. V. chama. Malapa may also represent the first appearance date for Felis nigripes (Black-footed cat). The geochronological age of Malapa and the associated hominin taxa and carnivoran remains provide a window of research into mammalian evolution during a relatively unknown period in South Africa and elsewhere. In particular, the fauna represented at Malapa has the potential to elucidate aspects of the evolution of Dinofelis and may help resolve competing hypotheses about faunal exchange between East and Southern Africa during the late Pliocene or early Pleistocene

A history of British seismology

The work of John Milne, the centenary of whose death is marked in 2013, has had a large impact in the development in global seismology. On his return from Japan to England in 1895, he established for the first time a global earthquake recording network, centred on his observatory at Shide, Isle of Wight. His composite bulletins, the “Shide Circulars” developed, in the twentieth century, into the world earthquake bulletins of the International Seismological Summary and eventually the International Seismological Centre, which continues to publish the definitive earthquake parameters of world earthquakes on a monthly basis. In fact, seismology has a long tradition in Britain, stretching back to early investigations by members of the Royal Society after 1660. Investigations in Scotland in the early 1840s led to a number of firsts, including the first network of instruments, the first seismic bulletin, and indeed, the first use of the word “seismometer”, from which words like “seismology” are a back-formation. This paper will present a chronological survey of the development of seismology in the British Isles, from the first written observations of local earthquakes in the seventh century, and the first theoretical writing on earthquakes in the twelfth century, up to the monitoring of earthquakes in Britain in the present day

Spinal Pathologies in Fossil Hominins

Back disorders are often conjectured to be a trade-off to the evolution of upright bipedalism. Yet, this association has not been substantiated so far. This chapter presents an overview of the known spinal pathologies in the hominin fossil record. Apart from a benign primary bone tumour in MH1 (Australopithecus sediba) and developmental defects in the Middle Pleistocene Pelvis 1 individual from Sima de los Huesos, the Kebara 2 Neanderthal and two individuals from El Sidrón, they include pathologies related to the biomechanical failure of the growing spine and degenerative osteoarthritis. While the latter is particularly common in Neanderthals, biomechanical failure of the growing spine seems to have affected all hominin species. This includes spondylolisthesis in the Pelvis 1 individual from Sima de los Huesos, traumatic juvenile disc herniation in KNM-WT 15000 (Homo erectus), anterior disc herniation (limbus vertebra) in StW 431 (A. africanus), and Scheuermann’s disease in A.L. 288-1 (A. afarensis) and three isolated thoracic vertebrae from Hadar, Sts 14 (A. africanus), SKX 3342 (Paranthropus robustus), the Pelvis 1 individual from Sima de los Huesos and perhaps Kebara 2 and Shanidar 3. Juvenile disc herniation, traumatic anterior disc herniation and Scheuermann’s disease all involve displacement of disc material and have a higher incidence following strains and trauma to the spine during the increased vulnerability phase of the pubertal growth spurt. The remarkably high prevalence of this kind of disorders in our ancestors might suggest that our spine has become less vulnerable during the course of human evolution