ASBOG Practice Exam

Detachment faults typically juxtapose what types of rocks?

1. Mildly to highly metamorphosed against unmetamorphosed

2. Igneous against sedimentary

3. Metamorphosed against volcanic

4. Unmetamorphosed against volcanic

The correct answer is: Mildly to highly metamorphosed against unmetamorphosed

Detachment faults are characterized by a significant vertical displacement often found in areas of crustal extension. The correct answer indicates that they typically juxtapose mildly to highly metamorphosed rocks against unmetamorphosed rocks. This juxtaposition occurs because as tectonic forces stretch and thin the crust, one block may undergo significant metamorphism due to increased temperature and pressure at depth, whereas the adjacent block remains relatively unaffected by these conditions and retains its original, unmetamorphosed state. This type of faulting frequently occurs in regions such as metamorphic core complexes, where sections of the crust have been exhumed, revealing the metamorphosed rocks beneath. Understanding the characteristics of these juxtaposed rock types is crucial for geologists when studying the structural evolution of earth materials and predicting the behavior of similar geological settings. Other choices involve inappropriate relationships of rock types that do not align with typical detachment faulting scenarios. For instance, igneous rocks against sedimentary or volcanic rocks do not reflect the metamorphic processes and conditions that are prevalent in detachment fault systems.