Effects of hydrodynamics and sea-level changes on sediment export from an isolated carbonate platform (Glorieuses archipelago, SW Indian Ocean)

The Glorieuses Archipelago, a carbonate platform in the southwestern Indian Ocean, provides a unique setting to explore how hydrodynamic, eustatic, and topographic controls influence the export of carbonate sediments to deep‐sea basin. We combine high‐resolution bathymetry, seismic stratigraphy, sedimentological analyses, and geochemical proxies on deep-sediment core from the northeastern semi-exposed leeward deep seafloor sub-basin and two deep-sediment cores from the sheltered western leeward sub-basin to characterize slope deposits through Late Quaternary glacial–interglacial cycles. Bathymetric and seismic data reveal a major bathymetric depression on the semi-exposed leeward flank filled by mass‐transport deposits from platform‐edge collapses, while the gently inclined sheltered leeward margin hosts cyclic‐step sediment waves and lobate extensions. Mineralogy, elemental compositions, and granulometry reveal alternating layers of calciturbidites marked by high magnetic susceptibility, interspersed with background muds of low Sr/Ca ratios. A robust age model, constructed from stable‐isotope (δ18O) measurements on benthic foraminifera (Cibicides wuellerstorfi), documents at least three glacial–interglacial transitions. Turbidite frequency and thickness indicate enhanced carbonate remobilization during glacial lowstands, contrary to the classical highstand shedding paradigm, driven by wave and storm reworking of terrace‐stored sediments at depths of 35–80 m. This phenomenon has been introduced as the wash-off of the platform during glacial periods. Geochemical proxies confirm extensive aragonite dissolution below the lysocline/aragonite compensation depth, yielding consistently low Sr/Ca ratios (mean 0.53) that mirror distal leeward records. The absence of terrigenous signals (Ca/Fe) suggests minimal Madagascar‐derived input or efficient bypass through the adjacent deep channel flowing eastward of the archipelago. Integrating these findings with published western Glorieuses datasets reveals a coherent archipelago‐scale sedimentation model: leeward remobilization during glacial lowstands and shedding during interglacial highstands.