Local Geological Site 102: Geoconservation at Ufton Fields

Introduction

The Ufton Fields Local Geological Site 102 (GR: SP380617) is located within the Warwickshire Wildlife Trust (WWT) Nature Reserve (car park at GR: SP378615 PC CV33 9PU). The Reserve sits on the top of the escarpment where Lias rocks of the Lower Jurassic overlie rocks of Triassic age. In the 1950s what is now the Reserve was the site of a commercial quarry producing limestone for the cement industry, although limestone from along the escarpment has traditionally been used for house and wall building. Abandoned in the 1960s, the quarry has been recolonised by vegetation. The 78 acre site was gifted to Warwickshire County Council in 1972 and has been declared as a Site of Special Scientific Interest (SSSI) mainly for its invertebrates. It is now managed by the Wildlife Trust. The focus of the geological interest is an outcrop of unquarried White Lias Limestone (Langport Member) which warrants conservation and designation as a LGS because there are now very few such exposures, accessible or otherwise, in Warwickshire.

The Geological Context

cross section

As you drive from the Fosse Way (B4455) towards Ufton (on the A425) you are crossing a relatively flat area (66 – 70m) underlain by reddish/brown Mercia Mudstone [Photo 1]. This rock dates from the Triassic Period, about 225 – 220 million years ago, when the area was land and had a desert climate. At this time Britain was about 20-25 degrees north of the Equator. The mudstone is thought to have its origin as blown sand being deposited in temporary desert lakes (playa lakes). As you climb the steeper slope below the village you cross some beds of Triassic Arden Sandstone, laid down as deposits of sand washed down river channels during flash floods. There is an excellent view back across the Mercia Mudstone lowland from the top of the scarp in the White Hart car park in Ufton.

However at the top of the scarp, [Photo 2] on which Ufton village stands, you cross onto rocks which are of marine origin, dating either side of the Triassic/Jurassic boundary. A shallow tropical/sub-tropical sea, less than 100m deep, encroached over Britain covering the older rocks. Britain had now drifted to about 35 degrees north of the equator and the conditions were similar to those of Caribbean today. The rocks exposed in the Ufton Fields Nature Reserve are limestone and shale. The Portland Cement Company was attracted to one of these marine rocks – the limestone of the Langport Member, but known to the quarrymen and more widely as the White Lias.

[If you want to read more about how the change from the deposition of the terrestrial Mercia Mudstone to the marine limestone and shale came about, click the link below and look at Box 1.]

Quarrying at Ufton

The White Lias limestone is available near the surface of the dip slope of the Ufton escarpment. The quarry, which was restored and became the Nature Reserve, lies to the north of the road named ‘Ufton Fields’. It was worked in the 1950s and early 1960s. Previously quarrying had been carried out further to the South East of the Reserve in an area which has now been landfilled between Ufton Hill Farm and Monkey Barn Farm (GR SP 394613). [Photo 3] The limestone was used predominantly in the cement industry, as was the case in other areas of Warwickshire where the limestone is found, accounting for the largely abandoned quarries at Rugby, Long Itchington, Bishops Itchington and Stockton.

Although the limestone is relatively near the surface it is overlain by about 5m of Saltford Shale, above which is a veneer of glacial till about a metre thick. (The till can easily be recognised by the ‘Bunter’ pebbles entrained within it but which are readily weathered out onto the surface of the fields). [Photos 4a and 4b]

Fortunately both the shale and the till are unconsolidated so their removal, to expose the limestone, was relatively easy. [Photo 5] The quarrying method used was to work from the south-east to the north-west across the outcrop stripping the overburden off and dumping it in ridges successively as quarrying the limestone progressed. Occasionally bits of abandoned equipment can be found. [Photo 6] When quarrying ceased many of the hollows between the spoil ridges flooded or are waterlogged. The larger hollows make attractive small lakes. [Photo 7] Scrub and woodland colonised the tipped overburden.

If you want to read more about the change in depositions from the limestone to the shale which overlies it, click the link below to look at Box 2

Ufton Village

White Lias limestone is thinly bedded, easy to work and splits naturally into brick-shaped blocks. [Photo 8] Long before the creamy-white limestone was quarried commercially the local community used it for buildings and walling within the village and surrounding area. Many domestic cottages, particularly along the road named ‘Ufton Fields’ are examples of this. The parish church, standing prominently on top of the escarpment, is built mainly of White Lias limestone, [Photo 9] as is The White Hart pub, close by the church [Photo 10].

But if you look closely at the church you can see other stones have been used [Photo 11]. The large greyish, coarse-grained corner stones of the tower are Arden Sandstone, possibly quarried from immediately downhill from the White Hart. [Photo 12] There are also randomly placed red sandstone blocks (probably Kenilworth or Coventry Sandstone) in the walls and sandstone has been carved for the window surrounds. [Photo 13]

The Local Geological Site 102 – Ufton Fields

The limestone horizon which was quarried is well bedded and jointed, about 70 cm thick and the conserved face is about 8 m long and 1 m deep. [Photo 14] It is fine grained and slightly muddy, typical of the White Lias (Langport Member) which is a creamy-white limestone deposited in a warm, shallow, clear and carbonate-rich sea. The limestone here does not appear to be very fossiliferous, although one fossil was found in the lower part of the bed [Photo 15] .

There is evidence of the joints having been opened, in some cases by tree roots and in others by unloading, probably by the removal of the overburden during quarrying. [Photo 16] The bed dips at about 5o degrees to the South East and extends, unquarried and unconserved but rather overgrown, in a west- east direction for a least 50m. The cessation of quarrying has left behind a substantial and rare Warwickshire outcrop of the White Lias (Langport Member) on a site now protected by Warwickshire Wildlife Trust. It is for this reason that it has been designated as a Local Geological Site. Nearby LGS 52 – Ufton Hill Farm – is the site of earlier quarrying, now landfilled [Photo 3].

Above the outcrop of the limestone is a steep bank [Photo 17] composed of a blue/dark grey sticky, stoneless shale with the consistency of plasticine. It is stratigraphically above the limestone and is identified by the British Geological Survey as Saltford Shale. As yet it has not been possible to expose the contact between the two beds, largely because the shale is very prone to slumping. [Photo 18]

In places, at the top of the slope, there is a gravelly bed of glacial till up to 1m thick, consisting of a clay matrix with rounded pebbles. The till has not been formally dated but it must be at least 200 000 years old, as the last British ice advance, which occurred within the last 100 000 years and ended about 11 000 years ago, did not reach Warwickshire.

If you want to read more about the dating of the rocks in the LGS, click the link below and look at Box 3

There are other WGCG Local Geological Sites which have geology related to this site: 21, 31, 32, 45, 52, 60, 83 and 95. Not all sites have public access. Details can be found on the LGS section of the website which will give you additional information about their geology.

Warwickshire Wildlife Trust Nature Reserve

Map of reserve

Thanks to a £12,000 of grant from the Tesco’s Bags of Help scheme, new interpretive signage has been installed across the site, with the aim of improving visitor experience. Developments include a new welcome sign at the reserve car park and entrance (GR SP 378615) and a guided trail exploring the geological and quarrying history, as well as introducing visitors to some of the wildlife living on this former industrial site. Plants thrive on the lime-rich soil, bird life is diverse and invertebrates prosper. Grassland areas are maintained through a mix of cutting and grazing. Periodic clearing of trees and dense vegetation in the scrub and woodland areas lets in more light, encouraging diversity of age and height structure of the woodlands, thus benefiting a whole host of wildlife.

This Ufton Fields site, once farmland (as shown on the 1951 Ordnance Survey map) then industrial quarry, shows how land can recover and be recolonised by plants and animals in a relatively short time if left undisturbed, although this may be different from its pre-industrial use. The active management by WWT since 1972 ensures maximum benefit for a wide range of wildlife, and the designation of SSSI continues, enabling you and future generations to enjoy the Reserve.

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