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Geological Society, London, Special Publications; 1964; v. 1; p. 203-205;
DOI: 10.1144/GSL.SP.1964.001.01.18
© 1964 Geological Society of London

Part 4: Stratigraphical Review

The Jurassic period

Michael Kingsley Howarth, B.SC., PH.D., F.G.S.

Department of Palaeontology, British Museum (Natural History), Cromwell Road, London, S.W.7

Seven critical biotite ages and five minimum glauconite ages for the Jurassic are discussed in relation to the time-scales of Holmes (1959) and Kulp (1961). It is proposed that the date for the base of the system should be amended to 190-5 m.y., the date for the end of the period remaining at 135 m.y.; the estimate for the length of the Jurassic is thus increased by 10 or 15 m.y. to 55–60 m.y.