We appreciate the Comment by Herrmann et al. (2011) to our paper (Buggisch et al., 2010). When we compiled the data set for our publication, we were aware that we had not enough pre-Deicke conodont oxygen isotope data because Webers’ (1966) conodont collections from the Pecatonica Member did not yield enough specimens for isotope analysis. At that time, the recently published data of Herrmann et al. (2010) were not available for comparison. Therefore, we imported data of Herrmann et al. (2005), who reported δ18O values from 18.1‰ to 19.1‰ (VSMOW) for conodont samples from Minnesota and Missouri. According to Herrmann et al. (2005, p. 457), “The samples were all collected from limestone beds immediately below the widespread Deicke K-bentonite.”
Unfortunately, the position of the Deicke K-bentonite in our Figure 2 was drawn too low in the section. The senior author (W.B.) takes responsibility for this misplotting, which resulted in some subsequent misinterpretation. According to Webers (1966, p. 115), the Deicke K-bentonite is situated in a 0.25-ft-thick (∼7.5 cm) bed of bentonite and shale. There is no information that the conodont sample Pl16, which is taken from this bed, derives solely from the shale. Nevertheless, we have to admit that the onset of cooling seems to be older than the Deicke eruption.
The fact that the Deicke K-bentonite might have had no, or only a minor, effect at the end of the cooling phase does not exclude that intense volcanism triggered the first Late Ordovician icehouse (see Young et al., 2009). Although this intense volcanism started in the late Darriwilian, it reached a peak in the latest Sandbian with the Deicke and Millbrig megaeruptions. In summary, we agree with Herrmann et al. (2011) that further high-resolution conodont oxygen isotope records are needed to document the details of Middle to Late Ordovician climate history.
