New Record of Magnetic Properties of Late Quaternary Sediments from the Eastern Arabian Sea (off Goa): Inferences on Palaeoclimate

Abstract

The mineral magnetic parameters such as low field magnetic susceptibility (χlf), anhisteritic remanent magnetization (χARM), saturation isothermal remanent magnetization (SIRM) and the ratio parameter (χARM/SIRM) were measured on 96 samples of a 4.7 m long gravity core SK-17, collected from the central part of the western Indian margin (off Goa) at 840 m water depth (lat. 15° 15′N and long. 72° 58′E). Records of magnetic properties indicate major variations during three time slices: between 30–14 ka, 13.5–10.5 ka and 9–5.5 ka. Low values of χlf, SIRM and χARM/SIRM between 30 and 14 ka indicate the low concentration of magnetic minerals, which appears to be primarily related to the dilution and/or dissolution effects due to high content of CaCO₃ during 17–15 ka and 24–23 ka and OC content during 22–18 ka. Maximum values of the studied magnetic parameters during 13.5–10.5 ka are suggestive of the deposition of higher concentration of ferrimagnetic minerals. The fine grained nature of these magnetic minerals further points towards their eolian origin, probably linked to the arid condition during this period which is broadly equivalent to the northern Hemisphere cold Younger Dryas event. The magnetic mineral concentration since the last 10 kyr (the Holocene) does not vary much except a moderate increase during 9.5–8 ka. However, high values of SIRM and χARM/χlf in the early Holocene (9–5.5 ka) that appear to be not significantly affected by either dilution or dissolution, indicate high fluvial discharge due intensification of the southwest monsoon. Low values of magnetic parameters since 5 kyr (late Holocene) and corresponding high OC content suggest diagenetic control of latter over the record of former.