Tropical semi-arid shelves commonly sustain shallow-water carbonate factories that export bioclasts to adjacent coasts; however, their interactions with relict and modern siliciclastics remain under-constrained. We investigate a mixed siliciclastic-carbonate system along the Cear & aacute; coast (Brazil) by integrating sedimentology, XRF geochemistry, and remote-sensing mapping across 48 sediment samples spanning inner shelf to coastal environments (barriers, beaches, dunes, lake/lagoonal settings). Inner-shelf substrates are bioclastic-rich, sourced primarily from calcareous algae, benthic foraminifera, and molluscs, with mud-rich seagrass meadows acting as sediment traps. Siliciclastic grains tend to dominate most coastal settings; however, the medium-sand fractions in some beaches and barriers are bioclastic-rich, especially where the shelf slope decreases (< 10 m water depth) near the Itapag & eacute; Inflexion. A gentle slope, high shallow-water carbonate production, alongshore drift, cross-shore exchange, aeolian sediment transport, and low siliciclastic input from fluvial sources is interpreted to favor accumulation of mixed siliciclastic-carbonates in this semi-arid coastal study area. These results highlight the importance of understanding local controlling factors when developing models of mixed siliciclastic-carbonate sedimentation on semi-arid tropical coasts, rather than relying on a universal model. Future work should quantify bioclastic production and coastal storage, to constrain sediment interaction between highstand coastal zones and the inner shelf. Similar content being viewed by others