The biostratigraphy of the Lower Jurassic of the Stowell Park Borehole

The ammonite biostratigraphy of the Lower Jurassic of the Stowell Park Borehole was originally compiled by L.F. Spath (1956) and summarised in Green and Melville (1956). For the present report it was considered impracticable to reidentify the nearly 5000 specimens used in these papers and also in Melville (1956) ~ Spath's ammonite nomenclature has been reinterpreted to update the biozonation which is now based principally on Dean, Donovan & Howarth (1961), Cope and others (1980), Ivimey-Cook & Donovan (1983), Phelps (1985) and Howarth (1992). This updating has included the use of the generic synonomy lists compiled by Donovan, Callomon and Howarth (1981), and by revision of selected specimens. The results of this review are given in Figures la and lb which also shows, against a metricated graphic log of the borehole, Spath's original zonation and this reinterpretation with the ranges of many of the recorded generic taxa. This revision supercedes the approximate zonal reinterpretation in Ivimey-Cook (1971, Fig. 5). The ammonite biostratigraphy of the British Sinemurian was also considered by Page (1992) who proposed a number of ammonite correlated 'Horizons'.