Magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion. We show here that the magnetic susceptibility signature, found in two forms, resides mainly in paramagnetic and other detrital constituents in most marine rocks. The first form is a short-term, low-magnitude, high-frequency cyclic climate signature that is often useful for regional correlation. The second form is a longer term, higher magnitude, low-frequency signature resulting from transgressive and regressive events that can be used for global correlation. Fluctuations in detrital input, due to eustatic-based erosion, are the primary cause of events. These fluctuations are driven by large-scale processes such as global orogenic cycles. However, variations in carbonate productivity cannot be ruled out when explaining the low-magnitude climate-driven cyclicity also observed in magnetic susceptibility data sets.