Interpreting the Cenozoic tectonic and topographic history of Africa in the context of the evolution of the East African Rift System is a major current question, with implications for fundamental hypotheses related to continental mantle dynamics, climate, and faunal evolution, including human origins. Key to deciphering these links is accurate determination of the chronology of uplift, volcanism, rifting and sedimentation patterns between the volcanically active, older [Paleogene] Eastern Branch, and the putatively younger (~12-7 Ma), less volcanic Western Branch. Here we show that landscape development and initiation of the Western Branch began >14 million years earlier than previous estimates, contemporaneously with the Eastern Branch. We combine detrital zircon geochronology, tephro-and magnetostratigraphy, and palaeocurrent analysis of the Rukwa Rift Basin, Tanzania, to constrain the timing of rifting, magmatism, drainage development, and landform dynamics in part of the Western Branch. Our findings demonstrate that riftrelated volcanism and lake development began by ~26-25 Ma, preceded by pediment development and major fluvial drainage reversal recording the onset of the African Superswell. This suggests that the uplift of eastern Africa was more widespread and synchronous than previously recognized. These data are integral to interpreting the connections between African Cenozoic climate change and faunal evolution.

Stable-isotopic analyses of h u m a n bone, n o w an established aid to dietary reconstruction in archaeology, represent the diet as averaged over m a n y years. Separate analysis of different skeletal components enables changes in diet and place of residence to be tracked, giving a fuller life-history for long-dead individuals.

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Trace elements diffuse negligible distances through the pristine crystal lattice in minerals: this is a fundamental assumption when using them to decipher geological processes. For example, the reliable use of the mineral zircon (ZrSiO4) as a U-Th-Pb geochronometer and trace element monitor requires minimal radiogenic isotope and trace element mobility. Here, using atom probe tomography, we document the effects of crystal–plastic deformation on atomic-scale elemental distributions in zircon revealing sub-micrometre-scale mechanisms of trace element mobility. Dislocations that move through the lattice accumulate U and other trace elements. Pipe diffusion along dislocation arrays connected to a chemical or structural sink results in continuous removal of selected elements (for example, Pb), even after deformation has ceased. However, in disconnected dislocations, trace elements remain locked. Our findings have important implications for the use of zircon as a geochronometer, and highlight the importance of deformation on trace element redistribution in minerals and engineering materials.

The geology of the northern segment of the Itabuna-Salvador -Curaçá orogen, São Francisco craton, is reviewed, and new U-Pb ages, and Nd isotope and major and trace element data are combined to improve understanding of its tectonic evolution. The results indicate that oceanic crust and island arc sequences accreted at about 3.

ABSTRACT:The Cabo Frio Tectonic Domain is composed of a Paleoproterozoic basement tectonically interleaved with Neoproterozoic supracrustal rocks (Buzios-Palmital successions). It is in contact with the Neoproterozoic-Cambrian Ribeira Orogen along the SE Brazilian coast. The basement was part of at least three continental margins: (a) 1.97 Ga; (b) 0.59 -0.53 Ga; (c) 0.14 Ga to today. It consists of continental magmatic arc rocks of 1.99 to 1.94 Ga. Zircon cores show a 2.5 -2.6 Ga inheritance from the ancient margin of the Congo Craton. During the Ediacaran, this domain was thinned and intruded by tholeiitic mafic dykes during the development of an oceanic basin at ca. 0.59 Ma. After the tectonic inversion, these basin deposits reached high P-T metamorphic conditions, by subduction of the oceanic lithosphere, and were later exhumed as nappes over the basement. The Cabo Frio Tectonic Domain collided with the arc domain of the Ribeira Orogen at ca. 0.54 Ga. It is not an exotic block, but the eastern transition between this orogen and the Congo Craton. Almost 400 m.y. later, the South Atlantic rift zone followed roughly this suture, not coincidently. It shows how the Cabo Frio Tectonic Domain was reactivated as a continental margin in successive extensional and convergent events through geological time.KEYWORDS: Ribeira Orogen; sutures; Orosirian; Cambrian; South Atlantic. RESUMO: O Domínio Tectônico do Cabo Frio é formado essencialmente por um embasamento paleoproterozoico tectonicamente intercalado com rochas supracrustais do Neoproterozoico (Sucessões Buzios e Palmital). Está em contato com o orógeno neoproterozoico-cambriano Ribeira na costa SE do Brazil. O embasamento já fez parte de pelo menos três margens continentais: (a) a 1,97 Ga

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