Mineral Magnetic Signature of the Early Holocene Intense Monsoon Conditions Recorded in Sediments from the Southwestern Indian Continental Margin

We studied three sediment cores from the southwestern continental margin of India for their mineral magnetic properties like magnetic susceptibility (χ_If), susceptibility of anhysteretic remanent magnetisation (χ_ARM), isothermal remanent magnetisation (IRM), saturation isothermal remanent magnetisation (SIRM) and inter-parametric ratios (χ_ARM/χ_If and χARM/SIRM), besides particle size characteristics. We demonstrate here that magnetic susceptibility and other mineral magnetic parameters can be used to demarcate the Early Holocene intense monsoon conditions. High values of χ_If, χ_ARM IRM_20mT,SIRM and χ_ARM/χIf and χ_ARM/SIRM in the core-bottom indicate the peak wet period -11 to 9 ka B P. The values decrease rapidly at 8 38 ka B P, in concert with a reduction in rainfall. Our interpretation is strengthened by particle size data on a limited number of samples. Silt and sand contents are higher in the pre-8.38 ka B P, high-susceptibility samples than in the post-8.38 ka B P, low-susceptibility samples. The high values of concentration-dependent parameters and χ_ARM/χ_If in the core-tops are probably due to an increase in rainfall during the past 100-400 years. We also used the mineral magnetic parameters to correlate the sedimenct cores.