Final answer:
Carbonate sediments composed of biotic fragments like shells are known as bioclastic sedimentary rocks, which include formations such as chalk limestone and can contain visible fossils.
Step-by-step explanation:
The term that describes carbonate sediments composed of shells or other carbonate fragments from once-living plants or animals is bioclastic sedimentary rocks. These sediments often include material like coccolithophores and diatoms, which produce calcium carbonate structures, as well as fossils of marine animals like foraminifera. Over geologic time scales, these sediments accumulate on the ocean floor and can lithify into rocks like limestone, which serves as a significant carbon reservoir on Earth. Carbonate sediments can also encompass findings such as bivalve shells, coral chips, and imprints of ancient life forms like trilobites.
Examples of sedimentary rocks containing organic matter include chalk limestone, which is derived from microscopic marine animals and algae, and marl, which is a combination of carbonate and clay materials. In some instances, the sedimentary rock may contain visible fossils, such as the belemnite fossils found in certain limestone formations or the diverse fossilized marine organisms in the Capitan Formation.