Dynamics of the erosion in the Irrawaddy River basin during the last two climatic cycles (280-0 ka).

Core MD77-169, located in the Andaman Sea, is characterized by epsilon (Nd) (0) ranging between -9.5 and -11, implying that the Irrawaddy River is the main contributor of detrital material. The pedogenic clays (smectite and ka olinite) to primary mineral (feldspar, quartz, illite and chlorite) ratios show strong precessional cycles, suggesting that they are controlled by pas t changes in the monsoon intensity. Wet periods of summer monsoon reinforce ment are characterized by the increase of chemical weathering and/or physic al erosion of the Irrawaddy plain soils. (C) 2001 Academie des sciences / E ditions scientifiques et medicales Elsevier SAS.