The Upper Kaena sedimentary geomagnetic reversal record from southern Sicily

Abstract

A detailed paleomagnetic and rock magnetic record of the upper Kaena polarity reversal was determined from late Pliocene marine marls in southern Sicily. Two separate characteristic magnetization components were distinguished: a low‐temperature (LT) component between 200° and 50°C and a high‐temperature (HT) component between 500° and 580°–610°C. The two components record the reversal in a slightly different way, but both were acquired in an early stage following deposition, most probably by authigenic (biogenic) formation of magnetic minerals. The actual (R‐N) reversal, via E and horizontal inclinations, seems to take 3.3 kyr and is followed by a stable normal interval (3.3 kyr) and subsequently by a significant excursion (50°–60°) in declination (3.6 kyr). Relative intensities were lower during a time‐span of 5.6 kyr and show a minimum of 10% of the nontransitional values, but during the excursion, no intensity changes are apparent. The VGPs of the HT component are confined to a longitude between India and Australia; those of the LT component oscillate between this same longitude and one passing over North and South America. We conclude that most if riot all observed features are largely determined by the remanence acquisition process which is complicated by authigenic formation of magnetic minerals and cyclically fluctuating paleoredox conditions. This has not only resulted in considerable smoothing but also in delayed NRM acquisition in specific sedimentary intervals. We believe that the observed “excursion” is a sedimentary artifact and not related to geomagnetic field behavior during transitions. We emphasize that many reported “geomagnetic” features may in fact be due to the sedimentary remanence acquisition process.