Major Jurassic subdivisions. 1 geological time terms 2 chronostratigraphical (time-rock) terms † Harland et al. (1990) * Gradstein and Ogg (1996) (95% confidence level).

(a)–(c), (e) Palaeogeographical reconstructions for the British area during the late Mid and Late Jurassic (based on Cope and Rawson in Bradshaw et al., 1992; Cope, 1995b). In many cases, the extent of land areas is uncertain. (d) Main structural elements affecting sedimentation in the British area in the Mid–Late Jurassic (terminology as used in this volume). The ‘London Platform’ is a structural high, the limits of which remained generally constant. The emergent part of the Platform, the position and limits of which varied, is referred to as the ‘London Landmass’. (Compiled from various sources.)

Simplified sketch map showing occurrences of Oxfordian–Kimmeridgian rocks in Britain (onshore area only).

Chronostratigraphical subdivisions and ammonite biohorizons recognized in the Oxfordian and Kimmeridgian stages in Britain (for sources, see text). AmC = Ampthill Clay Formation; KC = Kimmeridge Clay Formation; WWF = West Walton Formation. In Dorset, where the Kimmeridgian succession is more complete, additional ‘beds’ (KC50–63) up to the base of the overlying Portland Group (Portlandian) have been detailed by Gallois (2000). (See the Tyneham Gap–Hounstout GCR site report, this volume.)