The majority of Orkney's Sedimentary Rocks are Middle Devonian in age - Eifelian and Givetian. Upper part of Hoy and Upper Eday Sands edge into the Upper Devonian Frasnian.

The Tertiary climate was much warmer but less varied than that of the Quaternary. Maximum warmth was probably achieved during the Eocene.

As no sediments of this age are known on land in Scotland, the main events can only be inferred by reference to offshore sediments.

Our understanding is poor of the timing of the major events that have shaped the terrain of Orkney. This uncertainty reflects the fact that Orkney has been an area of net erosion for much of the last 60 million years.

The period since the last interglacial has seen many rapid and marked shifts in the climate of Scotland. Although the terrestrial stratigraphic record is still poorly understood, there is growing evidence for the existence of major ice masses during several intervals during the Late Pleistocene.

The orbital eccentricity, the obliquity and the precession of the equinoxes all affect the earth climate in regular predictable cycles which can often be detected in the geological record stratigraphically or chemically utilising mathematical analysis.