To construct a geomagnetic time scale, the two correct pieces of information needed are:
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The magnetic direction of rocks along the surface of Earth - This helps in understanding the historical geomagnetic field orientations and variations over time.
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The age of rocks along the surface of Earth - This provides a timeframe for when specific magnetic orientations occurred, allowing for the construction of a chronological scale of geomagnetic reversals and patterns.
So the correct answers are:
- the magnetic direction of rocks along the surface of Earth
- the age of rocks along the surface of Earth