Clastic Limestone:
* Description: A type of limestone composed of broken fragments (clasts) of pre-existing carbonate materials like shells, coral, or other limestone fragments. These clasts are cemented together by calcium carbonate.
* Formation: Clastic limestones form in environments where:
* Erosion of existing carbonate rocks occurs.
* The fragments are transported and then deposited in a new location.
* The fragments are cemented together over time by calcite.
* Characteristics:
* Often contains a variety of clast sizes.
* Can be angular or rounded, depending on transport distance.
* Texture might be granular or brecciated.
Fossiliferous Deposition:
* Description: Refers to the process of deposition where fossils are embedded within sediment.
* Formation: Fossiliferous deposition occurs in any environment where:
* Organisms with hard parts (shells, bones, etc.) die and their remains are buried by sediment.
* The sediment preserves the remains, preventing decomposition.
* Characteristics:
* Can occur in various types of sediment, including limestone, sandstone, shale, etc.
* The abundance and type of fossils depend on the environment and the organisms present.
Relationship:
* Clastic limestones are often fossiliferous: Since they are composed of broken carbonate fragments, many of these fragments are likely to be fossil shells or other skeletal remains.
* Fossiliferous deposition can occur in other rock types: Fossiliferous sediments are not exclusive to limestone; they can form in any sedimentary environment where organisms with hard parts are present.
In summary:
* Clastic limestone describes a type of rock formed from carbonate fragments.
* Fossiliferous deposition describes a process of sediment accumulation with fossils.
Therefore, a clastic limestone can be considered a fossiliferous deposit, but not all fossiliferous deposits are clastic limestones.
