Santa B a r b a r a , California 93106, U.S.A. E xperim ental shock studies of highland an d m are soils in the range of a few to 50 k b ar (5 x 109 Pa) have given the following results: (1) Shock, if less th a n 20 kbar, does not change the m agnetic characteristics of the soil substantially an d only w eak an d unstable shock rem anence is generated in a field of 0.5 O e. (2) Shock of betw een 20 an d 50 k b ar lithifies the soil and gives rise to stable shock rem anence. A cquisition is

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... xim ately linear in field for a given shock level. At 30 kbar the acquisition p aram eter for the highland soil was 10-5 G cm3 g _1 O e-1. In this range of 20-50 k b ar the products o f shock are petrologically and m agnetically sim ilar to certain regolith breccias. (3) Shock dem agnetization preferentially dem agnetizes the softer p a rt of therm o rem anent m agnetization (t.r.m .) and hence makes it relatively harder. T h e significance of these results is th a t shock rem anence is likely to be the cause of the n a tu ra l rem an en t m agnetization (n.r.m .) of certain regolith breccias and shock m ay modify the p rim ary rem anence of other samples.