An allochem is a discrete carbonate fragment, such as an ooid, peloid, or fossil shell, that formed elsewhere and was moved by water currents before settling into its final resting place. In carbonate petrology, these grains act much like the sand grains in a sandstone. Identifying the types and sorting of allochems helps geologists reconstruct the ancient marine environments where the limestone formed.
Heard on the job
The core sample is packed with skeletal allochems, indicating a high-energy reef environment.