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<p>This study investigates the evolution of valley-type tufas in the Oued El Heddar Valley, south of Taza (Morocco), in relation to local geomorphological, hydrological, geological, and biological dynamics. These continental carbonate formations, produced through complex physico-chemical and biological processes, were analyzed in three representative stratigraphic sections: upstream near the main waterfall, at a meander, and downstream within the Echeqqa accumulation zone. Several tufa facies were identified, including laminated crusts, stromatolites, and deposits formed on vegetation and pebbles, exhibiting alternating layers of calcium carbonate (CaCO₃)-rich material and detrital sediments that reflect Holocene environmental fluctuations. The results highlight both lateral and vertical variations in crustal thickness across the valley. Upstream sectors, characterized by steep slopes and turbulent flow, favor rapid carbonate precipitation and thick accumulations reaching up to 2&#xa0;m with CaCO₃ contents of about 28.36%. At the meander, thickness averages 1.20&#xa0;m, while downstream, where slopes are gentler and detrital input increases, crusts thin to approximately 70&#xa0;cm, reflecting a progressive decline in carbonate saturation and hydraulic energy. Vegetation cover and organic substrates, such as roots and tree trunks, actively promote carbonate bioprecipitation, whereas increasing anthropogenic pressure, particularly water diversion for irrigation, currently inhibits active tufanization. Overall, valley-type tufas represent valuable archives for reconstructing the geomorphological and environmental evolution of the region.</p>

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Evolution of Fluvial Tufas of valley type in the centre of Ras Elma Sud Region, Taza (Morocco): case of the Oued El Heddar Valley

  • 期刊论文

  • 发表日期：

    2025年12月6日

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  • Kamal Lahrichi,
  • Hamid fattasse,
  • Marouane Laaraj,
  • Hicham El Asmi,
  • Abdelmonaim okacha,
  • Mohamed Makhchane

摘要

This study investigates the evolution of valley-type tufas in the Oued El Heddar Valley, south of Taza (Morocco), in relation to local geomorphological, hydrological, geological, and biological dynamics. These continental carbonate formations, produced through complex physico-chemical and biological processes, were analyzed in three representative stratigraphic sections: upstream near the main waterfall, at a meander, and downstream within the Echeqqa accumulation zone. Several tufa facies were identified, including laminated crusts, stromatolites, and deposits formed on vegetation and pebbles, exhibiting alternating layers of calcium carbonate (CaCO₃)-rich material and detrital sediments that reflect Holocene environmental fluctuations. The results highlight both lateral and vertical variations in crustal thickness across the valley. Upstream sectors, characterized by steep slopes and turbulent flow, favor rapid carbonate precipitation and thick accumulations reaching up to 2 m with CaCO₃ contents of about 28.36%. At the meander, thickness averages 1.20 m, while downstream, where slopes are gentler and detrital input increases, crusts thin to approximately 70 cm, reflecting a progressive decline in carbonate saturation and hydraulic energy. Vegetation cover and organic substrates, such as roots and tree trunks, actively promote carbonate bioprecipitation, whereas increasing anthropogenic pressure, particularly water diversion for irrigation, currently inhibits active tufanization. Overall, valley-type tufas represent valuable archives for reconstructing the geomorphological and environmental evolution of the region.