times, when Marsupiocrinus and Gissocrinus werecommon reef animals.

TRILOBITES are probably the most famous fossilfound on Wren’s Nest. Calymene (e) was so commonlyfound by the quarrymen in the 19th century that itbecame known as the “Dudley Locust” or the ‘DudleyBug’ and was incorporated into the town’s coat-of-arms as a symbol of the limestone mining industry.Another common trilobite is Dalmanites (f). Trilobiteswere arthropods, related to modern crabs and lobsters,but they lacked the claws and special mouthparts oftheir carnivorous relatives and probably grazed onplants for food. Whole fossil trilobites are rarely found.The animals had to moult in order to grow, sheddingtheir outer skin or exoskeleton in pieces. Most trilobitefossils are therefore of moulted exoskeletons and not ofdead animals.Some of the easiest fossils to find on Wren’s Nest areBRACHIOPODS, such as Atrypa (g), Strophonella (h)and Leptaena (i). These are often confused withBIVALVES, like Goniophora (j) and Pteronitella (k),which were much rarer. The most obvious differencebetween the two types of fossil is that bivalves havevalves or shells which are identical whereasbrachiopods’ valves are of different sizes. Todaybivalves are far more common than brachiopods.Other animals that lived on the reef includedGASTROPODS (sea snails) like Poleumita (l) andAcroculia (m). Gastropods were probably vegetarian,but there were predatory animals on the reef as well.ORTHOCERAS (n) were relatives of modern daysquids and cuttlefish. They had cone-shaped shellswhich could be several metres long and they wereprobably carnivores, using the long tentaclessurrounding the head to catch smaller animals.Another predatory creature on the reef was theEURYPTERID or sea-scorpion (o). Eurypterids werearthropods, like trilobites, but they were much larger,growing up to 2 metres long and had claws for catchingprey.

Quarrying at Wren’s Nest

The limestone rocks at Wren’s Nest have beenexploited by man for hundreds of years. Originally therock was used as a local building stone and it can beseen in the walls of Dudley Castle and Dudley Priory.Later it was discovered that burnt limestone, or lime,was a good fertiliser and the demand for the rockincreased. Lime was produced by placing alternatelayers of limestone and coal in a kiln and burning it for

GEOLOGY

Wren’s Nest was declared a National Nature Reserve in1956, the first to be designated for its outstandinggeology and we celebrate its 50th anniversary in 2006.Wren’s Nest is of international importance both for thequality and quantity of its fossils, but also for its valueas an educational resource. Wren’s Nest Hill and MonsHill are made of Wenlock limestone composed of theremains of ancient sea creatures that lived more than400 million years ago. This period of geological time isknown as the Silurian. These ancient fossils are sobeautifully preserved that they are displayed inmuseums throughout the world and geologists comefrom far and near to study and collect them.

Many of the best fossils were found in the 18th and19th centuries. During this time the limestone rock wasbeing excavated and burnt to produce lime, animportant material for agriculture and industry. Thismining activity left great scars on the flanks of the hilland many large and spectacular caverns.

The Silurian World

The Dudley area would have looked very differentduring Silurian times. Shallow seas covered theMidlands and the nearest land lay many miles to theeast of Wren’s Nest. Plants were just beginning tocolonise the land, but the seas were full of life, some ofwhich would seem familiar to us today. At Wren’s Nest

small coral reefs grew upproviding a home forthousands of animals andplants, many of whichhave been preserved asfossils within thelimestone. Some of themost common fossilanimals to be found hereare illustrated (right).

There were many types of CORALS in the reef,Favosites (a) and Halysites (b) were compound typeswhere many tiny coral animals (polyps) lived together;solitary corals like Dokophyllum (c) were less common.

CRINOIDS grew in sheltered areas behind the mainreef, in patches of sand or soft sediment. They are oftencalled “Sea Lilies” because they look so much likeplants, with roots, a stem and a flower-like ‘cup’ on top,but they were actually animals and are related tostarfish and sea-urchins. Crinoids (d) still live in theseas today but are rarer than they were in Silurian

The Geology of the

Dudley Metropolitan Borough Council wishes toacknowledge the financial support of English Nature

Background: Reef Limestone

several days. The lime powder was then raked out fromthe bottom of the kiln. Several of these kilns can still beseen on the west side of the Nature Reserve. In theearly 18th century a method was found to smelt ironusing coal, so limestone, which was used as a flux inthis process, became a valuable commodity.

At first only surface outcrops of limestone werequarried, but soon the quarrymen began to digunderground to get to the purest and most valuabledeposits. By the start of the 19th century, the minesand caverns extended so deep that it was too difficultto haul the rock to the surface; thus a system ofunderground canals was built so that the limestonecould be carried away by barge to furnaces elsewherein the Black Country.

Background: Halysites

Reef Limestone

Seven Sisters cavern circa 2000

WREN’S NESTNational Nature Reserve

Fossilised exoskeletonof a Dalmanites trilobite

Poleumita, a fossil sea-snail or gastropod

Halysites, a compound coral

Sagenocrinusa commonSiluriancrinoid

Marsupiocrinuswith roots still

attached to thestem

Calymene blumenbachii,the ‘Dudley bug’

Strophonella strophonellaa common brachiopod

Typical Silurian brachiopods

Leptaena depressa

Atrypa reticularis

n

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gf

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WREN’S NESTNational

Nature Reserve

WARDEN’SOFFICE

A457 SEDGLEY ROAD

A4123 BIRMINGHAM NEW ROAD

A4168 PRIORY RD

WREN’S HILL ROAD

PARKES HALL

ROAD

LINWOOD RD

To WOLVERHAMPTON

To DUDLEY CARPARK

BluebellPark

MAYFIELD

RDBLUEBELL ROAD

ToBIRMINGHAM

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(Metres)

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Seven

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Blueb

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Blueb

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Lime P

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FieldField

Field

Fo

ssil Co

llecting C

od

e

1.For your ow

n safety please

DO

NO

Tclim

b on the rock

exposures. R

ock faces can be

unstable and

dangerous.

2.The use of ham

mers or other

tools on the reserve is ST

RIC

TLY

P

RO

HIB

ITE

D.

Never collect

fossils directly from

rock faces.

3.Fossils m

ay be collected

from the

loose material at the b

ase of slop

es. Please only take aw

ay a few

small rep

resentative samp

les.

4.For help

with id

entification please

contact the Ward

en Service on

01384 812785 or Dud

ley Museum

on 01384 815575. R

emem

ber to

keep a note of the exact location

your fossil was found

.

5.If you no longer w

ish to keep your

fossils, remem

ber never throw

them

away! D

onate them to the

Museum

or the Ward

en Service

for others to enjoy.

THA

NK

YO

U

1

2

3

4

5

6

7

7

11

8

9

10

KE

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eological trail markers

- see separate field

guide

View

point

Footpaths

Step

s

Security Fence

Reserve B

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The Geology of theWREN’S NESTNational Nature Reserve

As the quarrymen worked they found many wonderfulfossils. These were purchased by dealers, to be soldthrough local fossil shops. No doubt the vastmajority must have been lost forever in the furnaces ofthe ironworks.By the early 20th century there was much less demandfor Wren’s Nest limestone and by 1924 it was no longerprofitable to mine and the quarries were closed. Todayall the former underground workings are closed to thepublic. It is however, still possible for groups to view theoriginal ‘Seven Sisters’ by prior arrangement with thewarden service. Please phone for details. The SevenSisters are massive rock pillars that once supported theroof of a vast cavern complex descending 100 metresbelow the ground. Only five pillars of the original sevennow remain.In 1973 the Dudley Canal Trust opened up part of theunderground canal network beneath nearby Castle Hilland narrowboat trips are now run from the BlackCountry Museum into the famous Singing Cavern.Here an exciting audio-visual show re-creates life in alimestone mine.

Safety InformationRock exposures can be unstable and visitors arerequested to exercise care and caution when visitingthe reserve. Due to essential engineering works it hasbeen necessary to extend the safety fencing and re-route certain paths. We apologise for anyinconvenience this may cause. Please remain ondesignated paths and observe any path closures ordiversions. It is strictly prohibited to enter the areasinside the safety fences.Visitors to the Reserve do so entirely at their own risk.Neither Dudley Metropolitan Borough Council orEnglish Nature can accept liability or responsibility forloss, damage or injury to property or, in absence ofnegligence, to persons.

Other publications availableThe Wildlife of Wren’s Nest National Nature ReserveWren’s Nest National Nature Reserve GeologicalHandbook and Field Guide

Wren’s Nest Warden ServiceThe nature reserve has a team of three full timewardens who maintain and care for the site’s geologicalfeatures and wildlife. We always welcome help fromvolunteers. For more information on volunteering or tobook a school visit, guided walk or illustrated talkplease contact 01384 812785.

Dudley Museum & Art GalleryTo complement your trip to Wren’s Nest pay a visit tothe Museum & Art Gallery. Here there is an extensivegeological collection and fine displays of fossils fromWren’s Nest and the local coal measures. Staff areavailable on weekdays to offer general advice ongeology. Books, fossil replicas, posters, postcards etc.are available in the Museum shop. ADMISSION FREE.Dudley Museum & Art Gallery, St. James’s Road,Dudley, West Midlands DYl 1 HUContact - The Keeper of Geology Tel. (01384) 815575.

Geological SocietiesThe Black Country Geological Society is made up ofboth professional and amateur geologists. Meetings areheld at the Ward Arms and Dudley Museum in Dudley.The society arranges talks and field trips. For moreinformation contact the society at www.bcgs.info

Background: Flower meadow at Wren’s Nest National NatureReserve.

View of the Quarry

The Ripple Beds

www.dudley.gov.uk

WREN’S NEST

WREN’S NEST

National Nature Rese

rveN

ational Nature Reserv

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