Down in the Basement:
The Oldest Rocks of the Yorkshire Dales
The rocks of the basement were laid down in the periods we call the Ordovician (named after the Celtic Ordovices tribe who inhabited landscapes composed of these rocks in Scotland) and the Silurian (named after the Silures tribe of Wales) between 480 and about 415 million years ago!! 'England' was then part of the continent of Avalonia, beneath the equator - while Scotland, Ireland and North America lay in the continent of Laurentia, across the Iapetus Ocean. Imagine the Iapetus as being an Atlantic - but separating two vastly different continents in a different location on the globe ...
The Ingletonian are also famously exposed in the old Pecca Slate Quarry on the waterfalls walk.
Note the vertical bedding here - and think of the forces that must have been involved. Incredible!
As we move east from Ingleton the beds are slightly younger. These are dipping beds of Upper Ordovician rocks of the 'Norber Formation' - containing some fossils and limestones and being much 'muddier' in composition - with less evidence of any 'cooking' by pressure and heat. Here again, at Nappa Scar - you can clearly see a 'sliced off' anticline - the stump of an ancient mountain - with the limestone bedded on top. During the Devonian period (416 - 360 million years ago) the entire mountain ranges were lifted out of the sea by further tectonic activity and exposed to erosion, before the early Carboniferous seas drowned the mountain stumps allowing limestones to bed down on top! You can see this clearly here.
Here at Studrigg Scar in Crummackdale we see a still younger formation, known as the 'Austwick Formation' from the later Silurian Period, with their beds rising steeply to the former anticline - and the Great Scar Limestone bedded down on top. This is a classic 'unconformity' with a massive time distance between the two rocks.
And younger still - we have the very smooth Silurian rocks of the Horton Formation - or Horton Flags - exploited here at Dry Rigg Quarry. Each rock represents the grading of sediment on a sea bed in turbid conditions ....