sign in sign up
<<
Home , Boulder clay

Ichthyosaur

Boulder Chalky Clay is a (a glacial deposit) forming the vertebrae of Ichthyosaur (left) gently rolling and Plesiosaur (right) landscape These are the central parts of the across Suffolk, vertebrae (back bones) of ending roughly formidable reptilian predators of along the line of the A12 road. © R Markham Claydon Jurassic seas. Ichthyosaurs were superficially fish or It forms the high quality farmland of Suffolk, and dolphin like, had very there is a fine section, up to 9 metres thick, in the large eyes, with their sea-cliff at Kessingland and Pakefield. limbs being short steering paddles; this Numerous chalk , and much-scratched rocks fossil was found in the containing Jurassic may be found in gardens and boulder clay at ploughed fields on the boulder clay. These are glacial Debenham. Plesiosaurs were often of erratics ('wandering stones'). considerable size, to a length of more than 12 metres, and had well developed paddles for swimming. This The ice-sheet eroded Jurassic clay from vertebra is from Creeting St Mary. Their skeletons were the area of Fenland and then the broken up by the ice-sheet. Chalk escarpment between Newmarket and Swaffham before fanning out towards the east and Geological Maps south-east to deposit its load of boulder clay on Suffolk. The British Geological Survey, Keyworth, Nottingham, publishes 1:50,000 geological maps of Suffolk, 176 Lowestoft, 189 Bury St Edmunds, 190 Eye, 191 Saxmundham, 206 Sudbury, 207 Ipswich and 208,225 Woodbridge and Felixstowe, also 1:250,000, 52N00 East Anglia (Quaternary). They are also available from UKGE Limited, 10 Elliot Avenue, Reydon, Southwold, Suffolk, IP18 6QX; telephone 0870 922 0091, www.ukge.co.uk

Boulder Clay This leaflet is published by the Suffolk RIGS Group (GeoSuffolk), 2005, who wish to acknowledge the financial support of English Nature and UKGE Ltd. RIGS are Regionally Important Geological and Geomorphological Sites. We aim to promote understanding and appreciation of the geo-resources of Suffolk. (RM 2005)

Please follow the 'Countryside Code'

To join us or find out more, contact Ipswich Museum DIRECTION OF ICE-SHEET 01473-433 550, or 440,000 YEARS AGO English Nature Suffolk Team Designed by Ark Design Co. Printed by Riverside Print. Photographs Riverside of Printed by Ark Design Co. Designed by specimens © Ipswich Borough Council Museums and Galleries on 01284-762 218. Striated boulder Ice Age erratics in Suffolk From Hadleigh Road, Ipswich The scratches were produced when the Discover rocks and fossils many millions of years old brought to Suffolk by an ice-sheet about was trapped in the moving ice sheet and ground against bedrock at 440,000 years ago during the Ice Age. Here are some erratics you may find in boulder clay country the base of the ice or against other rocks within the ice.

Septarian Nodule Plesiosaur From Whitton, Ipswich Granite A Jurassic mudstone nodule with Granite is a coarse-grained light- internal cracks filled with calcite coloured igneous (once-molten) rock. Fossil Oyster, Gryphaea arcuata crystals forming veins which It occurs in northern , weather out. Scotland and Scandinavia, exposed at A bivalve shell of Early Jurassic age (about 190 million the surface after millions of years of years old). It has a very thick, convex under valve and a . This specimen was found in lid-like small valve, and is the boulder clay of Great Blakenham. popularly know as the Kimmeridge Shale Devil's Toe-nail Oyster. They A thinly-layered rock made of and originate in Jurassic clays in clay-size particles, often containing the Midlands and Yorkshire. fossil shells. This specimen was found This specimen was found in the Dolerite at Great Blakenham, over forty miles boulder clay at Stowupland. Dolerite is a medium-grained dark- from the parent rock in the Fenland. coloured igneous rock, occurring in geological features such as the Great Whin Sill of northern England. This Belemnite specimen was found in the boulder clay This is the internal shell from an extinct mollusc of Creeting St Mary, and shows which flourished in Jurassic and Cretaceous are soft carbonate rocks which characteristic sphaeroidal (spalling off of seas. It is related to the cuttlefish and can travel for great distances in an concentric shells from the rock). In such rocks a hand lens squid which swim in modern seas. This icesheet without undergoing chemical and often a microscope are necessary to see the crystals. Jurassic specimen is from the decomposition. This specimen is boulder clay of Great Blakenham. Jurassic Oolitic limestone, composed of small spherical carbonate particles, Fossil Sea-urchin (Echinoid) and was found at Claydon. This high-domed roughly oval sea-urchin is Echinocorys. It is preserved in flint. The Ammonite original shell of this sea-urchin Some fossil ammonites still show has been dissolved by acidic the pearly lustre of their original Spilsby groundwater, leaving a outer shell. Worn specimens Black phosphate nodules, fossil cavity and preserving infilled with rock often show zig- shells and small rounded grains external and internal zag lines on the surface, which mark of quartz are cemented by features. This specimen the complex folds of partitions between shiny crystalline calcite. This originated in Chalk of Late internal chambers. Ammonites are extinct but have specimen was found at Great Cretaceous age, is about a living relative, the Pearly Nautilus of the Indian Ocean Blakenham, having been brought 80 million years old, and western Pacific. This Jurassic specimen (about 155 from Lincolnshire or The Wash area by and was found at Hintlesham. million years old) is from the boulder clay of Corton. the icesheet.