Deep-Sea Research. Vol. 38. No. 2. pp 1~g-[~44 It,lqt. fllC~g...4)i49tql $31~) 4- 0.till Pnnted m Great Britain. ~ lg~t Pergamon Press pie Lithogenic fluxes to the deep Arabian Sea measured by sediment traps V. RAMASWAMY,* R. R. NAIR,* S. MANGANINI,# B. HAAKE~. and V. IrrEKKOT+ (Received 13 March 1990; in revisedform 26 June 1990; accepted 9 August 1990) Abstract--Particle fluxes measured continuously for one year at three locations in the Arabian Sea using time-series sediment traps show that lithogenic sedimentation processes are strongly coupled to biological processes. The vertical flux of lithogenic matter is controlled by episodic production and fluxes of biogenic matter. lllite and quartz are the dominant clay minerals in the traps at all three locations. Smeetites generally range between 2 and 8%. but show higher fluxes up to 25% in the central and eastern Arabian Sea during the southwest monsoon period. Most of the river discharge is retained on the continental shelf, and less than 5% of the annual input of lithogenic material to the Arabian Sea is deposited in the deeper part as hemipelagie sediments. INTRODUCTION THE Arabian Sea has received substantial amounts of tcrrigenous material from the Indus River since Eocene times (KoLLA and COUMES, 1984). Other sources, such as the rivers draining the west coast of India, as well as eolian input from the arid regions of North Africa, Arabia, Pakistan and India, also have contributed variable amounts of lithogcnic material (WEaER, 1974). This accumulation of terrigcnous material has resulted in the formation of an extensive dccp-sca tim covering an area of 1.1 x 10~' km 2 (CouMES and KOLLA, 1984; KOLLA and COUMES, 1984). Scdiment traps have bcen used for over a decadc in different parts of the world oceans for collection of sinking particles (HoNJO, 1985, DEUSER, 1986). Time-series sediment traps allow us to study the seasonal variations in the flux of these materials to the sea floor (HoNJO and DOHERTY, 1988). Data are presented on lithogenic fluxes and mineralogy of sediment trap material collected during continuous sediment trap experiments at three locations in the eastern, central and western Arabian Sea (Fig. 1). THE STUDY AREA The Arabian Sea is strongly influenced by the southwest (June to September) and moderately by the northeast (December to February) monsoons and the associated reversal of surface currents (WvRTKt, 1973). Summer upwelling along the coasts of *National Institute of Oceanography, Dona Paula, Goa 403(X)4, India. i'Woods Hole Oceanographic Institution. Woods Hole, MA 02543, U.S.A :[:Institute of Biogcochcmistry and Marine Chemistry. Hamburg University. Bundcsstrassc 55, D-2000 Hamburg 13, Germany. 169