Application of shallow seismic profiling to study riverbed architectural facies: a case study of the Tocantins river (Pará - Brazil)

To date, the vast majority of river sedimentology study has relied on two main categories of observation: direct observation of shallow trenches, cut faces and cores or geophysical survey on dry and shallow regions of braid bars. In this study, a sub-bottom profiler was used to investigate the stratigraphy of the lower course of the Tocantins River in the Amazon region, between the city of Tucuruì and the village of Nazaré dos Patos. The interest in this specific region lies on the possible variation of the fluvial regime due to the installation of the dam of the Tucuruì hydroelectric plant and the perspective that such river would become navigable as soon as the canal lock will be completed. Collected data show a detailed variety and complexity of architectural elements, as well as internal structure of sandy macroforms. Furthermore, the results allowed the identification of three main environments linked to channel sedimentation processes: by-pass, transition and deposition environments, whose distribution is linked to channel dynamics and bedrock topography. The application of the study is manifold, once it provides not only an insight into sedimentary structure of alluvial forms and sedimentation history, but also elements demanded to plan eventual engineering works for river navigability.Até hoje, a maior parte dos estudos de sedimentologia fluvial tem adotado dois principais métodos de investigação: observação direta de trincheiras, faces expostas e testemunhos, ou levantamento geofísico nas regiões emersas ou rasas das barras fluviais. Neste estudo, um perfilador acústico de subfundo foi utilizado para investigar a estratigrafia do baixo curso do Rio Tocantins, na bacia Amazônica, entre a cidade de Tucuruí e a vila de Nazaré dos Patos. O interesse neste trecho do rio reside na possível variação do regime fluvial devido à instalação da barragem da usina hidrelétrica de Tucuruí e à perspectiva de que este rio se torne navegável após a conclusão da construção da eclusa. Os perfis coletados mostram detalhes da variedade e complexidade de elementos arquiteturais e a estrutura interna das macroformas arenosas. Além disso, os resultados permitiram a identificação de três ambientes correlacionados com os processos sedimentares ativos no canal: ambientes de by-pass, transição e deposição, que estão relacionados à dinâmica do canal e topografia do embasamento. A aplicação deste estudo é multíplice, uma vez que fornece informações sobre a estrutura sedimentar das formas aluvionais e histórico de deposição, mostra elementos necessários ao planejamento de eventuais intervenções para a navegabilidade do rio

Carcass characteristics and meat quality of sheep fed buffelgrass silage to replace corn silage

The aim of the study was to evaluate the carcass characteristics, proximate composition, and sensorial attributes of meat from sheep fed diets in which buffelgrass silage replaced corn silage. Thirty-two intact male crossbred Santa Inês sheep with an average live weight of 20.09 ± 2.0 kg were housed in individual stalls and allotted at random to four treatments in which corn silage was replaced by buffelgrass silage at the levels of 0 (control), 33.3%, 66.6%, and 100%. After an adaption period of 10 days, the sheep were fed for an additional 61 days. Feed was offered ad libitum and corn silage comprised 60% of the diet for the control group. Carcass characteristics, non-carcass components and meat quality were evaluated. Hot carcass yield, cold carcass yield, true carcass yield, trimmings, fat weight, and mesenteric and omental fat weight were highest for the control group (P <0.05). Loin eye area had a quadratic response (P =0.02), with the largest areas being observed in animals fed the diet containing 66.6% buffelgrass silage. Liver weight (P <0.01), luminosity of the meat (P <0.05), and cooking loss (P <0.05) likewise had nonlinear responses to the concentration of buffelgrass silage in the diet. The treatments did not have significant negative influence on the nutritional and organoleptic characteristics of the meat