ORIGIN OF SEDIMENT ACCUMULATION IN THE OR INOCO DELTA AND THE GULF OFPARIA - AMAZON RIVER SEDIMENT INPUT

The suspended matter transported by the Orinoco to the Orinoco delta o riginates mainly in the Colombian Andes. The four clayey minerals (kao linite, chlorite, illite and smectite) are always present in the delta ic suspensions, the delta deposits and the gulf of Paria. Illite conte nts are always dominant except in those regions of the gulf of Paria s ituated far from the mouths of the Orinoco tributaries characterized b y smectites. In the delta, illite contents which are minimal during th e dry season increase noticeably during the wet season which is marked by a high Liquid and particulate matter discharge. In the delta, the clay mineralogy of the substrate is comparable to that of dry season s uspensions (February), thus showing a sedimentation composed of partic ulate matter carried by the Orinoco and Amazon rivers. In the wet seas on, the high liquid and particulate discharges circulate through the d elta, then enter and disperse in the Caribbean Sea and the near Atlant ic. The clay mineralogy described in the gulf of Paria show that this allochthonous participation of the Amazon in the deltaic sedimentation of the Orinoco is much more pronounced there. In this region, the spa tial variations in illite content show this mineral to be a good marke r for circulation.