Correlating and dating non-marine sequences by Magnetostratigraphy

Magnetostratigraphy uses records of changes in polarity of the geomagnetic field preserved in sedimentary sequences to correlate between wells and to date the sediment. Individual normal and reverse polarity intervals ("Chrons") typically range from ~10 thousand to 10 million years in duration. Example

Since geomagnetic polarity reversals are synchronous globally, their records represent 'absolute' time planes in sedimentary sequences which can provide a robust stratigraphic correlation framework. This is especially useful in biostratigraphically barren sequences. Furthermore, sets of reversals often carry distinctive 'fingerprints', which can be matched with appropriate parts of the standard geomagnetic polarity time scale, to constrain the age of the sediment.

Configuration of the axial dipole geomagnetic field during (A) a normal polarity interval and (B) a reverse polarity interval.