Tracing the abundance and distribution of geochemical elements and plant waxes in terrestrial and marine deposits of southern and central Morocco

ABSTRACT Terrigenous materials are delivered to the oceans via fluvial and aeolian pathways; the interpretation of terrigenous signals in marine sediments needs an accurate understanding of initial source regions for different terrestrial components. This work aims to evaluate the relative contributions of these transport mechanisms by conducting a source-to-sink analysis of geochemical elements and plant-wax lipids from terrestrial and marine surface samples collected across southern and central Morocco. We analyze the abundance and distribution of elements (Si, Al, Ca, Fe, Ti, and K) and element ratios, and plant-wax derived n-alkane parameters to trace sediment provenance and transport processes. The results indicate a high concentration of terrigenous elements (Si, Fe, K, Ti, and Al) and low concentrations of calcium (Ca) in the continental samples, while the marine sediments show the opposite. This difference is mainly due to the marine biogenic origin of Ca. Element ratios involving Ca (e.g., Fe/Ca and Ti/Ca) are sensitive to dilution effects like enhanced marine biological productivity and carbonate dissolution. Sediment composition reflects weathering and transport dynamics, with Fe/K ratios indicating erosion controlled mainly by physical processes. Aeolian input dominates offshore the Draa basin, while fluvial supply is stronger off the Souss-Massa and Tensift basins. Higher Zr/Al ratios in river sediments (Draa, Souss-Massa) suggest zircon enrichment, whereas lower marine values reflect hydrodynamic sorting. Ti/Zr ratios point to fluvial dominance in the Tensift and Souss-Massa basins but greater aeolian influence in the Draa, while Ti/Al ratios further highlight riverbed sorting before ocean delivery. Additionally, Plant-wax n-alkane concentrations ranged widely, from 40–76,000 ng/g in river sediments to 24–170 ng/g in marine sediments. This strong contrast, together with CPI values of 1.6–57 on land versus 0.5–3.6 offshore, and ACL values of 29.4–30.4 versus 29.0–29.7, reflects both degradation and dilution processes during transport from land to ocean. The study area, encompassing the Tensift, Souss-Massa, and Draa river basins, is a semiarid to arid region influenced by both Saharan dust and episodic river discharge, providing a key region to investigate source-to-sink processes. By integrating inorganic and organic proxies, we show that aeolian signals dominate offshore the Draa basin, whereas fluvial inputs prevail offshore the Souss-Massa and Tensift basins.