Geology of the Austwick Area

Austwick Geology

The village is located on the west side of the Pennines in the valley of Austwick Beck, which is a headwater tributary of the Wenning and Lune rivers. The valley of Austwick Beck has steep sides and is surrounded by extensive uplands.

The underlying rocks are of Paleozoic age.  The oldest rocks are sandstones, gritstones and slates of Ordovician and Silurian age.  These formations form the rock surface in the valley.  They are well exposed in Crummack Dale to the north of the village where they are strongly folded along east-west axes.  The rocks are relatively impervious and restrict the flow of groundwater.

Massive limestone rock formations of Lower Carboniferous age rest above the older Ordovician and Silurian formations.  The contact between them is unconformable whereby the Carboniferous limestone strata are more or less horizontal relative to the strongly folded older formations the surface of which had been eroded to form an ancient rolling landscape.  The limestone formations appear as scarp slopes along the valley sides and karstic pavements in the uplands.  They are well drained via joints and bedding planes, which enlarge as infiltrating precipitation slowly dissolves the limestones ultimately resulting in the formation of the caves and potholes in the surrounding area.  The infiltrating precipitation collects as groundwater in the limestone formation and flows through the joints and bedding planes.  The discharge of this groundwater emerges as springs locally at the contact of the limestone with the underlying relatively impervious Ordovician and Silurian rocks.  One such spring at Norber was the source of water supply to the village until recently.

Limestones, sandstones, and shales of the Yoredale Series and then the Millstone Grit rest above the Lower Carboniferous “Great Scar Limestones.” These rock strata are exposed on the upper slopes and summit of Ingleborough to the north and Penyghent to the northeast.

Austwick Geology

Figure 1: The village of Austwick looking west across the valley of Austwick Beck from a well jointed limestone pavement near the summit of Oxenber. The Craven Faults extend from the upper right to the centre left separating the uplands in the foreground and midground from the lowlands in the distance.  The north Craven Fault diverges from the South Craven Fault in the vicinity of Austwick and extends to the right along the valley below the limestone pavement.

 

Austwick Geology

Figure 2: Norber looking north.  The Silurian-Carboniferous contact is at the foot of the limestone scarp.  Springs, which emerge from this contact, are the source of the stream and were the source of the Austwick water supply.  The boulders, which appear along the summit of Norber, are erratic boulders of Silurian rocks deposited on the younger Carboniferous limestones by ice during the last Pleistocene glaciations.

The Craven Fault system passes through the Austwick area marking the west side of the uplands. The downthrow is to the west where downfaulted rocks are of Upper Carboniferous age. Two parallel North and South Craven Faults pass through the Ingleton area to the southeast. Near Austwick the two faults diverge. From this location the North Craven Fault continues up the valley of Austwick Beck, across Ribblesdale towards Grassington. The south Craven fault continues south eastward to beyond Settle. Giggleswick scar to the southeast of Austwick is a result of the faulting.

Austwick Geology

Figure 3: View looking east across the valley of Austwick Beck and into Ribblesdale from Norber The glacial erratic boulders of Silurian age are in the foreground.

Austwick Geology

Figure 4: The unconformable Silurian-Carboniferous contact below Norber; the path is on the Silurian rocks. The base of the Carboniferous rocks is formed of incompetent limestone rubble into which a notch has been eroded.