Which clastic fragment is the fourth item listed alongside oolites, intraclasts, and fossils in limestone?

• A. Pellets
• B. Chert
• C. Calcite
• D. Cement

Answer: (A)

Pellets are the small, rounded grains formed from fecal material produced by marine organisms. In limestone, these pellets are counted as clastic fragments alongside oolites, intraclasts, and fossils. Oolites are tiny spherical grains with concentric calcite layers, intraclasts are broken pieces of existing carbonate rock, and fossils are the preserved remains of organisms. Pellets stand out because they are discrete grain fragments derived from biological processes, not minerals or diagenetic cement. The other options don’t fit this role: chert is a silica-rich rock not typically a clastic fragment in limestone, calcite is the mineral composing most limestone, and cement is the binding material that cements grains together rather than a grain itself. Therefore, pellets best complete the list.