Palomagnetism of Mesoproterozoic Lavas in the Barby Formation of the Sinclair Region, Southern Namibia

Southern Namibia is part of the Kalahari Craton, which is speculated to have occupied a central location the Rodinia supercontinent. The Sinclair region, along the western margin of the Kalahari Craton, comprises several low-grade volcano-sedimentary sequences that are amenable to paleomagnetic study. With a stratigraphic thickness of between 3000m and 5000m, low metamorphic grade, and gentle deformation, the Barby lavas provide ample opportunity for generating a robust paleomagnetic pole. The goal of this project is to combine newly collected field data of the Barby formation with previously published paleomagnetic results from the Sinclair region, to obtain a fuller understanding of the motion of the Kalahari craton as global paleogeography transitioned between the Nuna and Rodinia supercontinents. Paleomagnetic results from previous sampling campaigns demonstrate a North to Northeast shallow characteristic remanent magnetization, bolstered by positive inverse baked-contact tests on ca. 1100-Ma dikes that intrude the Barby lavas. Here we present initial results from the latest field season, sampling five different structural panels of different bedding attitudes (younging directions as follows): Vergenoeg (NE), Klein Haremub (SE), Naus (N), Aruab (SW), and Osis (W; the Osis panel is isolated and is only tenuously correlated with the other Barby sections). Our sampling includes regional fold tests, more inverse baked-contact tests, and intraformational conglomerate tests on the age of magnetization. New zircon U-Pb geochronology via laser-ablation ICP-MS dates the nonconformably underlying Haremub granite at ca. 1335 Ma, providing a maximum age for the Barby succession. The combination of geochronologic and paleomagnetic results will help to constrain the location of the Kalahari Craton in mid-Mesoproterozoic time

Osteotomia em Chevron modificada: análise preliminar do comportamento baropodométrico Modified Chevron osteotomy: preliminary analysis of baropodometric behavior

OBJETIVO: Avaliar as características clínicas e baropodométricas da marcha de indivíduos com Hálux Valgo após a osteotomia em Chevron modificada, isolada ou em associação com a osteotomia de Weil. MÉTODOS: FORAM avaliados, antes e três meses após a cirurgia, 27 pés com deformidade leve e moderada. A avaliação clínica incluiu a pontuação da AOFAS e medidas radiográficas. A avaliação baropodométrica foi realizada através da Plataforma Emed-at. As variáveis Pico de Pressão, Integral Pressão-Tempo e Carga Relativa foram calculadas em 10 regiões: calcanhar, mediopé, 1-5º metatársicos, hálux, 2º, 3-5º dedos. RESULTADOS: Após a cirurgia houve aumento na pontuação da AOFAS e redução dos parâmetros radiográficos. A avaliação baropodométrica, após osteotomia em Chevron isolada, demonstrou redução da pressão e da força sob o 1º metatársico e hálux, assim como, aumento dessas variáveis nos metatársicos centrais e laterais. Após a osteotomia em Chevron/Weil ocorreram alterações significativas apenas na região do hálux e dos dedos. CONCLUSÃO: Em curto prazo, a técnica em Chevron modificada promoveu melhora das condições clínicas e dos parâmetros radiográficos. Em relação a avaliação baropodométrica constatou-se uma transferência de cargas da região medial para lateral do antepé, possivelmente pelo curto período de pós-operatório.<br>OBJECTIVE: To evaluate the clinical and baropodometric characteristics of the gaits of individuals with a hallux valgus deformity after modified Chevron osteotomy, in isolation or in association with the Weil osteotomy. METHODS: Foot evaluation happened before and three months after surgery analyzing 27 mildly and moderately deformed feet. The clinical evaluation included the AOFAS score and radiographic measurements. The baropodometric evaluation was done with the Emed-at platform. Peak of Pressure, Pressure-Time Integral and Relative Load were calculated in 10 different regions of the feet: calcaneous, midfoot, first to fifth metatarsal regions, hallux, second and third to fifth toes. RESULTS: After the surgical procedure, an increase in AOFAS scores and a decrease of radiographic parameters were seen. The baropodometric evaluation, after isolated Chevron osteotomy, showed a reduction in pressure and strength under the first metatarsal and hallux, as well as an increase in the same variables on central and lateral metatarsals. After Chevron/Weil osteotomy significant alterations had only occurred in the region of the hallux and toes. CONCLUSION: In the short-term, the modified Chevron technique promoted improvements in clinical conditions and radiographic parameters. The baropodometric evaluation evidenced a load transference from medial to lateral regions of the forefoot, possibly due to the short postoperative period