Precambrian, Ordovician and Silurian Periods (over 545 to 417 million years ago) – Ancient Roots
Over 500 million years old, the ancient roots of the Dales, the greywacke sandstones and slates of the Precambrian Ingleton Group, are seen in the quarries and waterfalls of the Rivers Twiss and Doe in Chapel le Dale, upstream from Ingleton, and further east near Horton in Ribblesdale.
The succeeding strata are missing, as this basement sequence was folded and eroded before it was overlain by the late Ordovician and Silurian rocks of the Windermere Supergroup. These grey slates and greywacke sandstones began life as muddy and sandy submarine flows (turbidity currents) (1 and 2) in a deep ocean basin, and were deposited over a time interval that spanned 446-417 million years ago.
Figure: Pre-Carboniferous rocks of the Craven Inliers (Source: Aitkenhead et.al., 2002) © BGS (NERC)
Photo: Thornton Force, Ingleton – Precambrian Ingleton Group rocks, unconformably overlain by the limestones of the Carboniferous, Great Scar Limestone Group