Discover North Yorkshire and Explore the Fossils and Geodiversity of Aysgarth Falls
- Wayne Munday
- 2 hours ago
- 4 min read
Sip back and discover North Yorkshire and explore the fossils and geodiversity of Aysgarth Falls a natural landmark of the Yorkshire Dales National Park. Situated along the scenic River Ure in Wensleydale the Aysgarth Falls are a designated Site of Special Scientific Interest (SSSI) offering the visitor a remarkable series of cascading Upper, Middle and Lower Aysgarth waterfalls carved through fossiliferous Carboniferous limestone and layered sedimentary rocks of the Yoredale Series. This is a landscape shaped over 300 million years ago beneath tropical seas and sculpted by the last Ice Age. The Yoredale Series limestones around Aysgarth Falls contains a diverse range of Carboniferous marine fossils including crinoids, brachiopods, corals, bryozoans, bivalves and gastropods.
At the heart of Aysgarth Falls geodiversity is its Carboniferous limestone bedrock part of the Yoredale Series a sequence of sedimentary rocks composed of alternating layers of hard limestone, shale, and sandstone. These rocks were laid down during the Carboniferous Period around 340 million years ago when the area was situated near the Equator beneath a warm and shallow tropical sea.
The limestone formed from the accumulated remains of marine organisms such as corals and shellfish whose calcium-rich skeletons compressed over time to create the white-grey limestone. The Shales were formed from muds and silts deposited in deeper, quieter waters and sandstones from sediment carried by river deltas.
The nearly horizontal alignment of the Yoredale Series has given the surrounding hills a terraced appearance with resistant limestone and sandstone layers forming prominent scars while softer shale layers have been more heavily weathered and eroded. This bedrock provides the foundation for the dramatic stepped waterfalls at Aysgarth. The River Ure has carved through these alternating layers wearing away the softer shales faster than the harder limestone. This uneven erosion has undercut the limestone causing sections to collapse and forming the distinctive stepped profile of the falls.
During the Devensian glaciation the most recent glacial period in Britain and Ireland that reached its peak around 27,000 years ago as part of the broader Last Glacial Maximum. Glaciers sculpted the Wensleydale valley and Bishopdale area deepening it and depositing large volumes of till, clay, boulders, and meltwater sediments.
A key factor in the creation of the falls was how glacial erosion was more aggressive in the Bishopdale area and carved a valley deeper than in Wensleydale. When the ice retreated the Wensleydale valley floor was higher than Bishopdale forming a rock step where the rivers met and an ideal setting for the formation of a waterfall. As post-glacial meltwater surged through this landscape it cut into the Yoredale Series forming the gorge and cascading waterfalls seen today.
The landscape surrounding Aysgarth Falls also bears the hallmarks of glacial deposition and erosion. Glaciofluvial features such as drumlins, eskers, kames and kettles are scattered across the valley.
Lady Hill west of Aysgarth is a classic drumlin an elongated and oval-shaped hill composed of unsorted glacial till commonly found in groups in former glaciated areas. Drumlins have a distinctive shape with a steeper slope facing the direction of glacier movement and a gentler slope downstream. Ranging in size up to several kilometres long and over 50 meters high drumlins are believed to form beneath glaciers through either deformation, deposition or reshaping of existing sediments by flowing ice.
Freeholders Wood is not only a centuries-old woodland on the southern riverbank but also has kames or irregular hills of sand, gravel and glacial till formed by meltwater deposits at the edges of the local glacier. Left behind as the glacier retreated they commonly appear in clusters.
These glacial features contribute to this part of North Yorkshire's rich geodiversity alongside other karst scenery phenomena such as limestone pavements, dry valleys, sinkholes and caves all formed from the natural dissolution of limestone over millennia.
The marine fossil rich limestone beds within the Yoredale Series include the Gayle Limestone dating back to between 330.9 - 330.3 million years ago to the Brigantian - the uppermost substage of the Visean Age of the Carboniferous Period.
The Gayle Limestone tells a story of fluctuating sea levels and dynamic marine environments during the Carboniferous Period. It has an abundance of crinoids often preserved as star-centred ossicles and a variety of extinct rugose corals including the Dibonophyllum recognisable by its trumpet-shaped calyx the bulbous central body that houses the main organs of the animal.
Also, Syringopora, characterised by clusters of interconnected corallites of skeletal cups or tubes secreted by individual coral polyps making up the colony. Brachiopods are also common alongside other marine fossils like Gastropods. Microscopic fossils called Conodonts or tooth-like fossils include Gnathodus girtyi, G. homopunctatus, and Lochriea commutata reveal a depth stratification where some species look to prefer shallower more turbulent waters while others thrived in deeper and calmer waters according to the setting of the limestone.
Aysgarth Falls in North Yorkshire offers visitors a remarkable glimpse into deep time. The fossil-rich Gayle Limestone formed over 330 million years ago in tropical seas underlies the stepped waterfalls sculpted by post-glacial meltwater cutting through alternating layers of limestone, shale and sandstone. This landscape’s story of environmental change is further enriched by glacial landforms, karst features and ancient woodlands. Together, these natural elements make Aysgarth Falls an essential destination for anyone exploring the north of England.
