High-precision 40Ar/39Ar dating of pleistocene tuffs and temporal anchoring of the Matuyama-Brunhes boundary

‘Radical interpretations’ preclude the use of climatic wiggle matching for resolution of event timings at the highest levels of attainable precision

“…O isotope stratigraphies (as highlighted by Mark et al, 2017;Valet et al, 2016), the data we present are exceptionally robust and our conclusions are supported by other datasets (Bronk Ramsey et al, 2012;Lisiecki and Raymo, 2009, Mark et al, 2014, 2013, Sagnotti et al, 2016Skinner and Shackleton, 2005;Valet et al, 2014). Much of these data have been ignored by Channell & Hodell (2017) in their critique of our work, but are essential for accurate interpretation of our results.…”

“…Our data are further supported by the fact that Valet et al (2014) place the Australasian Tektites at 790 ± 5 ka, which is indistinguishable from the age we propose for the same tektite horizon in ODP 758 (786 ± 2 ka, Mark et al, 2017), and the age of Termination IX at 788-789 (± 5 ka) (Valet et al, 2014) is also indistinguishable from our reported Termination IX age (785.6 ± 0.8 ka, Mark et al, 2017). The temporal alignment of three data points between two local records with different sedimentation rates, albeit one record at considerably higher precision, as well as data from Italy (Sagnotti et al, 2016(Sagnotti et al, , 2014 and North America (Mark et al, 2017), is compelling and should not be disregarded.…”

“…Ar dated lava flows that are associated with the geomagnetic reversal (Mark et al, 2017). Channell & Hodell (2017) do not discuss these records.…”

“…Much of these data have been ignored by Channell & Hodell (2017) in their critique of our work, but are essential for accurate interpretation of our results. Clearly the age of the last full reversal of the Earth's magnetic field (the Matuyama-Brunhes geomagnetic reversal, MBB) is important and as such, data suggesting inaccuracies in previous ages (and indeed other approaches that have attempted to constrain the event in time) (e.g., Mark et al, 2017) require scrutiny and when required, clarification. We provide such clarification here.…”

“…The age model for this core is an order of magnitude lower precision than our age model (± 5 ka versus ± 0.6 ka, respectively) and shows that the relative palaeo-intensity (RPI) drop associated with the MBB occurred at 784 ± 5 ka, which is indistinguishable from the global average age for the MBB that we calculate, 783.4 ± 0.6 ka. The key issue to highlight here is that in a slow sedimentation record the MBB transition displays as essentially instantaneous in time, represented by a spike in the RPI or a rapid transition in palaeo-magnetic direction (Figure 2, Mark et al, 2017). When comparing such records to a high sedimentation record (Valet et al, 2014), which show a more complex and protracted history (Figure 2, Valet et al, 2014), the instantaneous event is equivalent to the onset of the MBB transition in the high sedimentation core and not the mid-point of the transition.…”