The metasedimentary Dalradian Supergroup of Scotland formed a stratigraphy more than 20km thick over the period 800-500 Ma. It consists of numerous limestones and black shales, many of which are sulphidic. These have been analysed for carbon and sulphur isotopes and geochemical trends, which give an insight into the changing climate and ocean chemistry. During this period of earth history, the climate was very unstable, moving between greenhouse and icehouse conditions, the oxygen content of the atmosphere jumped from around 1% to close to present day levels, and this has a knock-on effect on sulphate content of the oceans. The trends observed in Scotland can be linked to global isotopic stratigraphies of the Neoproterozoic, providing constraints for the age of the middle Dalradian, and a different viewpoint on the current controversies concerning this.