Cephalopod Bed, Oolitic Limestone
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Fact sheet

Cephalopod Bed, Oolitic Limestone

This sample of fossil-rich rock comes from the limestone escarpment at Wotton Hill, Gloucestershire, which contains exposures of rocks of the lower and middle Jurassic Periods. The lowest part of the Wotton Hill exposures consists of the Bridport Sand Formation, which is overlain by the 'Cephalopod bed' from which this sample comes. The 'Cephalopod bed' is rich in carbonate fossil molluscs, including ammonites and belemnites. It can be classified as a limestone, although it is relatively rich in quartz grains and is overlain by the 'Scissum Beds' (part of the Leckhampton Limestone) of the Middle Jurassic.

The rock thin section illustrates both silt-rich and carbonate-rich areas. The framework of grains includes small quartz grains and fossil fragments, including bivalves, ammonites and belemnites with a micritic cement. Cavities in fossil bivalves are filled by a sparry calcite cement. A large part of the centre of the section is rich in angular quartz grains (50–100 microns) and might be classified as a siltstone. This feature is probably the result of infilling a cavity on the sea floor that was composed mainly of shell fragments, some broken but some remaining almost whole.

Additional images
  • Fossiliferous limestone - width 8.5 cm
  • Fossiliferous limestone - width 4.6 cm
  • Fossiliferous limestone - width 9 cm
  • Fossiliferous limestone - width 2.2 cm
  • Fossiliferous limestone - width 4.8 cm
  • Fossiliferous limestone - width 2.8 cm
51.646501, -2.357653
Wooton on Edge, Gloucestershire
About this collection

The United Kingdom Virtual Microscope (UKVM) collection consists of igneous, sedimentary and metamorphic rocks from around the UK.

It is intended as a teaching resource, helping to tell the story of the common rock types and how they form, and reflecting the history of the UK at the margins of the continent of Europe. The collection is a series of teaching sets, for example igneous rocks from the North Atlantic Igneous Province and SW England; high-temperature metamorphic rocks from Scotland and low-temperature metamorphic rocks from Wales; and sedimentary rocks, including English limestones and sandstones.

Sample details

Rock-forming mineral
Category guide  
Category Guide
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Selecting one or more period, for example 'Jurassic'.
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: