Category:Magnetostratigraphy of the Chalk Group
Magnetostratigraphy is of very limited use in the Upper Cretaceous because the Cenomanian to Santonian interval falls within a single normal polarity zone, designated 34N (Gale, 2000). Above this, the base of the reversed polarity magnetochron 33R has been recognised in the Chalk Group at Culver Cliff and Scratchell's Bay (Isle of Wight) and Seaford Head (Sussex), where it is in the middle of the U. socialis Zone, within the upper Santonian (Gale et al., 1995). The start of the next normal polarity magnetochron, 33N, is in the B. mucronata Zone at Culver Cliff (Gale et al., 1995). Montgomery et al. (1998) showed that minor polarity inversions occurred within the above magnetochrons as recognised in southern England, which had not previously been detected in magnetostratigraphical studies elsewhere. The latter was partly explained by the apparently high sedimentation rate in the Chalk of southern England (c. 53 m per million years), allowing short-lived magnetostratigraphical events to be preserved in the rock record.
GALE, A S, MONTGOMERY, P, KENNEDY, W J, HANCOCK, J M, BURNETT, J A, McARTHUR, J M. 1995. Definition and global correlation of the Santonian-Campanian boundary. Terra Nova, 7, 607-610.
GALE, A S. 2000. Late Cretaceous to Early Tertiary pelagic deposits: deposition on greenhouse Earth. In WOODCOCK, N & STRACHAN, R (eds), Geological History of Britain & Ireland (Blackwells).
MONTGOMERY, P, HAILWOOD, E A, GALE, A S & BURNETT, J A. 1998. The magnetostratigraphy of Coniacian - Late Campanian chalk sequences in southern England. Earth and Planetary Science Letters, 156, 209-224.
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