A virtually complete succession of shallow-marine, epicontinental Lower Jurassic strata crops out in excellent exposures along the North Yorkshire coast (U.K.). Borehole control of the inland continuation of these deposits, together with the availability of a detailed ammonite biostratigraphy, allows for the construction of a cross-section correlating the relatively thick succession of the Cleveland Basin (exposed in the coastal sections) with the more condensed succession on the adjacent Market Weighton High (encountered in boreholes). This study is concerned with only the Hettangian to Pliensbachian part of the Liassic succession, corresponding to the informal 'lower Lias' and 'middle Lias' divisions...