Much Wenlock Limestone Formation

Much Wenlock Limestone Formation

Age: 426-423 million years (Silurian, Wenlock)

Overview

Silurian rocks in Herefordshire and Worcestershire are used as markers for this period of earth history throughout the world. They mark a time when the world’s great oceans were in the process of closing, leading to the formation of marine sandstones, mudstones and limestones. The rocks are also famous for their diversity and richness of fossils, and this has led to accurate sub-divisions of the period being devised: the Llandovery (443-428Ma), Wenlock (428-423Ma), Ludlow (423-419Ma) and the Pridoli (419-416Ma). All four of these time frames are represented in the two counties.

In Worcestershire the outcrop of Silurian rocks generally follows a north-south linear trend, beginning just north of the Malvern Hills and continuing along the central and eastern half of the Teme Valley, before splitting into two outcrops around Abberley. The Much Wenlock Limestone outcrop is extensive and forms a strong linear ridge running from the Malvern Hills in the south, to the Abberley Hills in the north, with a break in the outcrop between the Teme Valley and Martley due to faulting. In Herefordshire, the Much Wenlock Limestone forms ridges in the Woolhope Dome (central Herefordshire), May Hill (southern Herefordshire) areas and around the Ludlow Anticline (northern Herefordshire).

The Much Wenlock Limestone Formation falls within the Mid-Silurian Wenlock series.

Lithology

Perhaps the most famous rock formation in England, the Much Wenlock Limestone is known for its abundance of fossils, many of which were first recorded in the two counties, and are found no-where else in the world. Consisting of bedded limestones, both nodular and massive in nature, interbedded with mudstones and occasional bentonites, the unit was deposited in a vast shallow, tropical sea shelf. The Formation has been extensively quarried for both aggregate and lime. As a result, numerous quarries and exposures have been recorded along the entirety of its outcrop, all of which have yielded a number of fossils. The Formation has been the centre of much ground breaking research, studying a period of geological history with a rich biodiversity.

Sites

Abberley Hall (East), Champions Site, Worcestershire

Linton Quarry, Champions Site, Herefordshire