based on whole rocks and subsequent studies have revealed that metamorphism has most likely compromised their paleointensity record (see discussion in Usui et al., 2009). Below we highlight the salient observations about the field that are robust for the interval equal to and older than the Proterozoic-Archean boundary (Figure 3).

As noted earlier, there is a general consensus that the field was predominately dipolar at $\sim$2.5 Ga [@Smirnov2004; @Biggin2008; @Smirnov2011]. The dynamo appears to be reversing, although the sparse rock record allows different interpretations of the reversal rate. @Dunlop2004 and @Coe2006 first argued that reversal rates might have been low. No long sedimentary sequences with paleomagnetic data are available to justify this interpretation for times before the Archean-Proterozoic boundary, and the thermal alteration of sediments of this age questions whether such data will ever be available. The interpretation is instead based on the sampling of lavas that are associated with large igneous provinces exposed in the Superior Craton of Canada and in the Pilbara Craton of Western Australia [the $\sim$2.7-2.8 Ga Fortesque Group; @Strik2003]. However, magmatic activity associated with these large igneous province could have occurred in pulses (as it has during the Phanerozoic). If so, much less time is 