The Segmented Zambezi Sedimentary System from Source to Sink: 1. Sand Petrology and Heavy Minerals

The Zambezi River rises at the center of southern Africa, flows across low-relief Kalahari Plateau, meets Karoo basalt, plunges into Victoria Falls, follows along rifts, and pierces through Precambrian basement to eventually deliver its load onto Mozambican passive margin. Reflecting polyphase evolution, river is subdivided segments with different geological geomorphological character, a subdivision finally fixed by man’s construction large reservoirs faithfully testified sharp changes in sediment composition. Pure quartzose sand recycled from desert dunes uppermost tract next progressively enriched basaltic rock fragments clinopyroxene. Sediment renewed first downstream Lake Kariba Cahora Bassa, documenting stepwise decrease quartz durable heavy minerals. Composition becomes quartzo-feldspathic lower tract, where most supplied high-grade basements rejuvenated southward propagation East African rift. Feldspar abundance Lower has no equivalent among big rivers on Earth far exceeds that sediments northern delta, shelf, slope, revealing provenance signals upper reaches have ceased be transmitted routing system after closure dams. This high-resolution petrologic study allows us critically reconsider several dogmas, such as supposed increase mineralogical “maturity” during long-distance fluvial transport, forges key unlock rich information stored sedimentary archives, ultimate goal accurately reconstruct evolution this mighty flowing changing landscapes since late Mesozoic.