What kinds of features distinguish one geologic system from another?

A geologic system is a set of rocks and rock formations that were formed during a specific period of Earth's history. This includes all the rocks formed in a specific way or within a specific time frame. A geologic system can be classified based on different factors such as the type of rocks, the process of formation, and the age of the rocks.

Some of the factors that can distinguish one geologic system from another are: 1. Rock Types: The type of rocks found in a geologic system, such as sedimentary, igneous, or metamorphic rocks, can differ from one system to another. 2. Formation Process: Geologic systems form under different environmental conditions and processes, such as volcanic activity, sedimentation, or tectonic movements. 3. Age: The age of the rock formations in a geologic system can help differentiate one system from another. Different geologic systems were formed during different time periods, which can be identified using radiometric dating techniques and the study of fossils. 4. Fossil Content: Some geologic systems contain unique or specific fossil assemblages; the presence or absence of certain fossils can help in differentiating one geologic system from another. 5. Lithology: The physical characteristics of the rocks, such as grain size, composition, and texture, can also be a distinguishing factor between different geologic systems. 6. Structural Features: Geologic systems may also be differentiated based on the presence of certain structural features like folds, faults, or intrusions within the rock formations.

By examining the factors listed in Step 2, geologists can differentiate between different geologic systems in the real world. For example, the Cretaceous System can be distinguished from the Jurassic System based on their age, fossil content, and rock types. The Cretaceous System is younger than the Jurassic System, it contains specific fossils like the ammonite Acanthoplites, and has characteristic rock types such as chalk and sandstones. Similarly, the Paleozoic System can be distinguished from the Mesozoic System based on the rock types, age, and the presence of trilobite fossils, which are specific to the Paleozoic era.