Question

Which of the following types of fossils are formed when the animals or plants are buried between the layers of mud or sand, its body is crushed and leaves its impression on the sediments?

• A. Mould and cast
• B. Petrified fossils
• C. Actual remains
• D. All of the above

Answer 1

The correct option is A Mould and cast

Cast and mold are a type of fossilization where the physical characteristics of organisms are impressed onto rocks. Organisms buried in sediment may decay or dissolve away leaving a cavity or mold. If this space is subsequently filled with sediment, an external cast can be made. Usually the hard parts of an organism such as shells of mollusks, skeletal structures of coelenterates, bones and teeth of vertebrate, chitinous exoskeleton of arthropods, trunks of trees leave the best impression, as they are usually composed of calcium carbonate, calcium phosphate, silica or chitin which provide a rigid structure and does not decay as easily. Thus the correct answer is option A.