Lonar Lake: palaeomagnetic evidence of shock origin

Palaeomagnetic and rock magnetic investigations were carried out on oriented rock samples collected from the inner walls of Lonar Lake, which is believed to be a meteorite crater. These studies show systematic variation in some magnetic parameters (Qn, Jn, K and declination) whereas at surrounding localities these parameters show random variation. A soft secondary shock component, acquired in the present field, of D=9°, I=+47° (K=47.6, α95=6.4°) has been successfully isolated by vector difference analysis, whereas the stable primary vector is similar to that of Lower Tertiary period reverse magnetization. NRM and IRMs of the upper and lower flows respond differently to AF demagnetization as a function of their Hcr. It is shown that the NRM carried by the lower flows is similar to that of IRM probably reset by the meteorite impact because of their low Hcr carriers. It is suggested that such magnetic property variations are characteristic of shock origin and hence we propose an impact origin for Lonar Lake.