The stratigraphy of the island can be sub-divided into three components:
- Cretaceous basement complex
- Post-cretaceous trough sediments, volcanics and intrusives
- Overlying Cenozoic (tertiary) limestones
The Cretaceous basement complex consists of volcanics, volcaniclastics and associated intrusives and coarse clastics, except in the Hanover Block, which is predominantly marine shales. At the end of the cretaceous period, the island was uplifted resulting in an unconformity marking the Cretaceous/Tertiary boundary.
Post Cretaceous deformation and the east north east rift faulting predominates this period resulting in the formation of the Wagwater and Montpelier-Newmarket troughs. In the Wagwater, arenaceous sediments derived from surrounding highlands were supplemented by volcanic extrusions through trough margin lines of weakness. All Wagwater equivalent sedimentary or volcanic trough sediments that may have existed in the Montpelier-Newmarket Trough were completely covered by Tertiary limestones and are not exposed at the surface.
The Cenozoic White and Yellow Limestones unconformably overlie the Cretaceous basement complex of the crustal blocks forming the highlands, and conformably overlie the post Cretaceous trough sediments. This unit covers approximately 70% of the island. Intrusive activity was confined largely to the late Mesozoic and early Cenozoic, with major deformation occurring during the Paleocene and post Miocene.