Abstract

Silurian palaeomagnetic data from all continents are compiled in an attempt to define the polarity history of the Earth’s magnetic field during the period. Data sets from Llandovery, Ludlow, and Pridoli strata often display evidence of field reversals (i.e. the presence of both normal and reverse polarity magnetization directions) despite the fact that the palaeomagnetic sample collections may cover only a limited stratigraphic range in each case. Palaeomagnetic data from rocks of Wenlock age are exclusively of normal magnetic polarity. A comparison of the available Silurian data with published Ordovician palaeomagnetic results suggests that the frequency of magnetic field reversals increased from Ordovician to Silurian times. Palaeomagnetic data sets are not yet available from a continuous Silurian stratigraphic sequence of any great duration, so the Silurian magnetostratigraphy is still at a much more preliminary stage than that for the Ordovician. Apart from the Wenlock, all Silurian series have some intervals with frequent (<2 Ma) polarity reversals. Constant polarity (for durations in excess of 2 Ma) in the Ordovician and Silurian are only apparent during the Arenig (reverse), the early Caradoc (normal), the late Caradoc (reverse), the Ashgill (normal) and the Wenlock (normal). Data are still particularly sparse in Tremadoc and Llandovery rocks.

First Page Preview

First page PDF preview
You do not currently have access to this article.