In the North Indian Ocean, fluctuations of the Neogene to Pleistocene detrital clay sedimentation have been investigated by 1 300 X-ray diffraction analyses of samples collected from two basins: the Arabian Sea (Site 721 ODP Leg 117) and the Central Indian Basin (SHIVA Cores 1990). The Arabian Sea Basin displays a pelagic and continuous sedimentation, without any Indus turbiditic supply. Palygorskite-rich levels from aeolian and detrital Somalian and Arabian supplies alternate with illite-rich levels from Himalayan-Tibet Complex erosion. Spectral analyses of mineralogical parameters measured on XR diffractograms allow to observe frequencies that are close to those of the Milankovitch cycles of the earth's orbital parameters. The periodic influences change with time from a precession dominated signal to a signal dominated by tilting. This shift appears at 2,3 My and reflects the transition from a dominant regional effect (monsoon) to a global and more complex effect (extension of the Northern ice sheets). These results show that the clay fraction could be an accurate marker of short-term paleoclimate variations and confirm previous observations obtained from magnetic susceptibility measurements. They allow to propose a sedimentological model controlled by climate. The Central Indian Basin receives Bengal Fan supplies on its northern distal part and pelagic supplies from equatorial divergence to the south. Mineralogical, spectral, geochemical (major and trace elements) and isotopic (Sr-Nd) clay fraction studies of five cores, distributed along a North-South transect 80 degrees E from 1 degrees to 10 degrees S, allow to explain Late Miocene to Pleistocene smectites/illites fluctuating assemblages and to propose a sedimentary model. Latitudinal evolutions attest a north source-area for primary minerals (Himalayan Complex) and a northern and southern origin for kaolinites (Indo-Gangetic Plain. South Indian Peninsula, Sri Lanka, Australia, Indonesian Arc). As smectites are detrital, from the same source-area as illites i.e Himalayan-Tibet Complex, clay fluctuations reflect variable paleoenvironmental conditions. Late Miocene to Early Pliocene orbital control, by eccentricity, affects illite to smectite weathering conditions in the Indo-Gangetic Plain. From Early Pliocene to Pleistocene, control is aperiodic and tectonic, then tectonic and climatic during Late Pleistocene. Lithological alternances (black/green facies) reflect NW lateral supply with organic material (South Indian Peninsula, Sri Lanka) or carbonates (Chagos-Laccadive Ridge). Diagenetic events suggested by geochemical and isotopic results are associated with biogenic levels and consist of two simultaneous phenomena: neoformation in the bulk sediment and adsorption from seawater on clay particles.