LATE PALEOZOIC REMAGNETIZATION IN LIMESTONES OF THE CRAVEN BASIN (NORTHERN ENGLAND) AND THE ROCK MAGNETIC FINGERPRINT OF REMAGNETIZED SEDIMENTARY CARBONATES

Samples of Lower Carboniferous chatburn and Pendleside limestones collected from 27 sites in the Craven Basin (northern England) carry a syn-Hercynian remagnetization residing in magnetite. The paleomagnetic directions are all of reversed polarity consistent with a Kiaman Superchron remagnetization. The partially (62%) tilt corrected mean direction has the minimum correlation statistic implying a synfolding magnetization. The resulting pole appears to be Late Carboniferous in age, and there is no indication of any magnetization component that predates the remagnetization event. The magnetization appears to be of the same type as the synfolding remagnetizations documented in several Appalachian carbonate units. Jackson (1990) reported that remagnetized Appalachian carbonates have distinctive hysteresis properties, and we have obtained similar hysteresis loops from remagnetized Paleozoic carbonates from the Craven Basin (England), the Great Basin (Nevada), Alaska, and New York State. The hysteresis loops are all ''wasp-waisted'' and yield highly anomalous hysteresis ratios, compared to data from synthetic or ''typical'' magnetite-bearing samples. In contrast, unremagnetized limestones from Italy show hysteresis behavior which is more typical for magnetite-bearing rocks (Channell and McCabe, this issue). These results suggest that remagnetization in magnetite-bearing carbonates can be readily detected on the basis of hysteresis properties, prior to a full-scale paleomagnetic investigation.