RECENT AND SUBRECENT CHANGES IN THE DISPERSAL OF AMAZON MUD

The dispersal of Amazon mud reaches from the mouth of the Amazon river to the Orinoco delta and to the eastern Caribbean, a distance of more than 1500 km. The present dispersal system has been in existence for at least 10(3) years, but the deposition of mud from this system has not been constant during that period. A change from net erosion to net deposition along the Suriname coast between 1947 and 1981 was found to coincide with a shift of the trade winds from a dominantly NE to a more ENE direction from 1959 onward, accompanied by an increase in mean wind velocity. The change to net-deposition can be explained by enhanced longshore transport of suspended matter with simultaneous reduction of erosion by reduction of the onshore wave energy component. The sequence of a recent mud deposit 100-200 years old off the Amazon river mouth separated by a period of non-deposition from an older mud deposit less than 1000 years old, agrees well with indications for a wetter period in the Amazon basin and in the Colombian Andes since about 200 years BP and a wetter period between 500 and 900 y BP. This implies that during wetter periods the suspended-sediment supply from the Amazon (and the Orinoco) was (is) higher.