Figure 3: Oxygen and carbon-isotope data from the Bearreraig section in Scotland.
Lithology, stratigraphy and transgressive/regressive (T/R) phases are from refs 25, 54, 76. Intervals lacking well-preserved ammonite fossils are indicated by grey shading and so denote limited age uncertainty. Shading in the graphic log denotes darker lithology. Transgressive/regressive phases denoted T/R. Shading behind the oxygen-isotope data highlight warm (red) and cool (blue) palaeotemperatures. The oxygen-isotope values increase abruptly in the murchisonae zone and at that time the unconformity was at maximum extent35,36. Note that this increase in the oxygen-isotope values occurs with a clear facies change from deeper to shallower water. There is a hint of other small palaeotemperature changes in conjunction with T/R cycles, but the magnitude of the T/R cycles and the palaeotemperature changes is small in comparison to the change across the Early/Middle Jurassic transition with perhaps the exception of the humprhresianum zone.
