S12. Limestone - Peloidal-rich biomicrite / wakestone
Click the microscope button to view a thin section for this sample.
Click the microscope button to view a thin section for this sample.

Fact sheet

S12. Limestone - Peloidal-rich biomicrite / wakestone

This sample can be classified using the Dunham/Folk Classification. Dark grey fine grained limestone with ostracod fragments. Dark muddy lst with >10 % grains mud supported.  % content: grains 20% (mostly ostracod / brachs <0.5 mm), sparite cement 10% (mainly within bivalved shells), micrite 70 % (entire micrite matrix incl peloids), no non-carbonate components. Non-skeletal grains: 95% peloids, 5% ooids, 5% grapestones, also calcispheres. Skeletal grains: 100% ostracod (most likely as small thin shells) vs. brach shells. Classification: Peloidal-rich biomicrite / wackestone. Diagenesis: Some evidence of compaction and sutured contacts. Flattened peloids. Cement crystals are non-syntaxial calcite crystals that fill previous pore space. Perhaps larger spar crystals formed after micrite mud - calcitisation. 

About this collection

A group of iCRAG members (UCC, TCD, NUIG and UCD) in partnership with The Open University have created a new collection of Irish rocks and associated learning materials for the Virtual Microscope of Earth Sciences.

The project which is entitled 'The Geoscience e-Laboratory (Geo-LAB): Developing Digital Teaching and Learning Resources for the Virtual Microscope' seeks to develop open access teaching resources in the form of interactive exercises and assessment rubrics for the Virtual Microscope.

The Collection was created using funding from the Faculty of Engineering, Mathematics and Science at Trinity College, Dublin, and the National Forum Teaching and Learning Enhancement Fund. One sample (Merensky Reef) showcasing x-ray element maps in addition to the usual PPL/XPL/REF images was funded by Prof. Balz Kamber's MetalIntelligence EU training network grant.

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: