Evidence for aridity-driven dust flux to the northwest Arabian Sea and for decoupling of the dust and upwelling systems

Abstract: Late Quaternary records of dust grain size, dust flux (mass accumulation rate; MAR) and dust mineralogy from ODP Site 722 on the Owen Ridge, northwest Arabian Sea, have been used to: (1) infer environmental conditions in the continental source areas: (2) determine the spectral response (frequency and phase relationships) ofdust MAR and mineralogy to environmental changes associated with global ice volume variations and orbital insolation patterns a d (3) evaluate potential associations between the continental (dust) and marine (upwelling) systems over the past 800 ky. The terrigenous dust component is composed of smectite, illite, palygorskite, kaolinite, chlorite, quartz, plagioclase feldspar and dolomite. This is consistent with the composition of source areas currently supplying sediment to the Arabian Sea. An R-mode factor analysis identifies four mineral assemblages: three reflect arid continental source conditions and one reflects more humid conditions. Total dust MAR, two of the three 'arid ' factor assemblages, and six of the seven minerals associated with the 'arid ' factors are coherent with the marine isotopic record of global ice volume over at least one primary orbital frequency, with input maxima during glacial (arid) hcmicycles. In contrast, wind strength and upwelling intensit