Complex sentence: The reduction of sulfate to sulfide favors the lighter sulfur isotopes (32 S) and becomes depleted in the heavier isotopes (34 S), meaning that this lighter sulfide bonds with Fe 2 + to form FeS 2 which is then partially preserved in the sediments.
Split into simpler sentences: The reduction of sulfate to sulfide favors the lighter sulphur isotopes (32 S) and becomes depleted in the heavier isotopes (34 S). This lighter sulfide then bonds with Fe 2 + to form FeS 2 which is then partially preserved in the sediments.