Final answer:
The primary iron-bearing mineral used in paleomagnetism is magnetite (Fe3O4), which can record Earth's magnetic field orientation in both igneous rocks and sedimentary deposits, enabling geologists to determine depositional age through magnetostratigraphy.
Step-by-step explanation:
The iron-bearing mineral integral to paleomagnetism is magnetite (Fe3O4). Magnetite, along with hematite (Fe2O3), is found in geologic formations such as banded iron formations (BIFs), which are layered sedimentary rocks that formed under specific early Earth conditions. These minerals record the Earth's magnetic field orientation at the time they were formed. When igneous rocks crystallize or sediments are deposited, magnetite crystals can align to the Earth's magnetic field. These recorded magnetic orientations can be studied through the analysis of sediment cores in a process known as magnetostratigraphy, which also helps determine the depositional age of the sediment. This is critical for understanding Earth's geologic history and changes in its magnetic field over time.