Magnetic and calcareous-nannofossil stratigraphy of the lower Palaeogene formations of the Hampshire and London basins

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Abstract
A magnetostratigraphic study of the lower Palaeogene formations exposed in the Hampshire and London basins, southern UK, has led to the identification of eight stratigraphically distinct normal polarity magnetozones within an otherwise reverse polarity sedimentary sequence which spans the Late Palaeocene to Middle Eocene. A complementary study of the calcareous nannofossil biostratigraphy of these sections, and related sections elsewhere in NW Europe, allows a correlation of this succession of normal polarity magnetozones with the biostratigraphically-calibrated geomagnetic polarity timescale, based on marine magnetic anomalies. It is concluded that the normal polarity chrons corresponding to anomalies 20, 21 and 23 are recorded within the Huntingbridge, Earnley and Wittering Divisions of the Bracklesham Group respectively, that anomalies 24A and 24B are represented within Divisions D to B2 of the London Clay, and anomaly 26 is represented in the lower part of the Thanet beds. An additional normal polarity magnetozone within the Oldhaven beds is believed to represent a short normal polarity event between anomalies 24B and 25. Anomalies 22 and 25 appear not to be represented in the UK lower Palaeogene succession because of major unconformities at the Early/Middle Eocene boundary (within the Wittering Division of the Bracklesham Group) and within the Late Palaeocene respectively. The former appears to correlate with a widespread erosional event in the oceans identified from seismic records ( Vail et al. 1979 ) and interpreted as reflecting a major eustatic sea level fall.

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