Description

2011 has been a good year for the classic section through the Upper Ludlow of the Silurian. Located along the Bread Walk, a delightful riverside path on the opposite bank of the River Teme from Ludlow town, the calcareous siltstone succession of the Ludlow Series has drawn international attention for nearly two centuries. These rocks represent shallow water continental shelf conditions at the margins of the Iapetus Ocean as it was closing some 420 million years ago. The shelly fauna show rapid evolution as the species came under environmental stress (as did the graptolites, preserved much more commonly in the deeper water facies to the west). Direct evidence of that stress is present too, in the form of volcanic ash bands and seismites (convoluted bedding caused by liquefaction as earthquakes rocked the ground).
The Ludlow Series of the Upper Silurian are subdivided into four formations, all of which are defined at this location and thus protected by SSSI, GCR and LGS (formerly RIGS) status. From young to old these are: Upper Whitcliffe Formation, Lower Whitcliffe Formation, Upper Leintwardine Formation, Lower Leintwardine Formation. The base of the Upper Whitcliffe Formation is exposed in the disused quarry above the rock steps along the Bread Walk, cleared of vegetation that obscured it some three years ago by the Friends of Whitcliffe Common. Earlier this year an information board was placed within the quarry to indicate the geological importance of the site and illustrate its fossils.
However, the equally important exposure by the small waterfall where the bases of both the Lower Whitcliffe and the Upper Leintwardine Formations are defined has been inaccessible for many years. These sites, almost on the hinge of the Ludlow Anticline, were visited in July 2011 by the International Subcommission on Silurian Stratigraphy. This provided the impetus for the Friends of Whitcliffe Common to once again undertake a significant amount of vegetation clearance, with assistance from the Shropshire Wildlife Trust team of volunteers. As a result, the classic exposure is once again visible. The photographs show both the general setting and the full thickness of the Upper Leintwardine Formation, recognisable by its honeycomb style of weathering due to karstic solution of calcareous nodules. The contacts with the overlying Lower Whitcliffe and underlying Lower Leintwardine are marked by small arrows ringed in red (top left and bottom right respectively).
This winter would therefore be a good time to revisit these classic exposures and, if the weather is inclement, take shelter in the nearby Charlton Arms close to the Ludlow Bone Bed and examine the poster display indicating why this bed too is of international importance. The Shropshire Geological Society has also supported excursions in this area, listed on the Trail Guides page of the SGS web site (e.g. Etheridge et al., 2007). The scientific description and further references are presented by David Siveter within GCR volume 19, pages 345-350 (available online at: http://www.thegcr.org.uk/Sites/GCR_v19_C05_Site2596.htm).