TY - JOUR T1 - The Segmented Zambezi Sedimentary System from Source to Sink: 1. Sand Petrology and Heavy Minerals A1 - Garzanti,Eduardo A1 - Pastore,Guido A1 - Resentini,Alberto A1 - Vezzoli,Giovanni A1 - Vermeesch,Pieter A1 - Ncube,Lindani A1 - Niekerk,Helena Johanna Van A1 - Jouet,Gwenael A1 - Dall’asta,Massimo AD - Laboratory for Provenance Studies, Department of Earth and Environmental Sciences, University of Milano-Bicocca, 20126 Milano, Italy AD - London Geochronology Centre, Department of Earth Sciences, University College London, London WC1E 6BT, United Kingdom AD - Department of Environmental Sciences, University of South Africa, Florida, South Africa AD - Unité de Recherche Geosciences Marines, IFREMER (Institut Français de Recherche pour l’Exploitation de la Mer), CS 10070, 29280 Plouzané, France AD - TOTAL Exploration and Production, CSTJF, Avenue Larribau, 64018 Pau Cedex Pau, France UR - https://doi.org/10.1086/715792 DO - 10.1086/715792 N2 - The Zambezi River rises at the center of southern Africa, flows across the low-relief Kalahari Plateau, meets Karoo basalt, plunges into Victoria Falls, follows along Karoo rifts, and pierces through Precambrian basement to eventually deliver its load onto the Mozambican passive margin. Reflecting its polyphase evolution, the river is subdivided into segments with different geological and geomorphological character, a subdivision finally fixed by man’s construction of large reservoirs and faithfully testified by sharp changes in sediment composition. Pure quartzose sand recycled from Kalahari desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed first downstream of Lake Kariba and next downstream of Lake Cahora Bassa, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract, where most sediment is supplied by high-grade basements rejuvenated by the southward propagation of the East African rift. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. This high-resolution petrologic study of Zambezi sand allows us to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance fluvial transport, and forges a key to unlock the rich information stored in sedimentary archives, with the ultimate goal to accurately reconstruct the evolution of this mighty river flowing across changing African landscapes since the late Mesozoic. Y1 - 2021/07 PB - University of Chicago Press JF - Journal Of Geology SN - 0022-1376 VL - 129 IS - 4 SP - 343 EP - 369 ID - 83467 ER -