Comment on cp-2021-122

line 25–27: Authors should specific about trends vs peak values (cooling versus cold). The 1.5 million year offset means that it is crucial that the authors place the timing of deposition of the Waipawa organofacies and the SST trends relative to the carbon isotope maximum and the oxygen isotope maximum. To me, “cooling” refers to a decreasing trend in temperature, rather than a temperature minimum. Does the deposition of the Waipawa organofacies now coincide best with the benthic foram d13C trends, the d18O maximum or with the SST minimum? Some careful rewording might be

I understand the introduction gives the potential importance of understanding Waipawa organofacies deposition in the context of past climate change, with CO2 drawdown as mechanism and that would fit well with the scope of the journal. However, given the primary focus of the study, to characterize the black shale OM content, and understand the enigmatic enrichment in 13carbon, I would suggest the authors focus the introduction a bit more on existing investigations in other black shales. As it is now, the reader expects a "CO2 drawdown paper" but gets quite detailed analyses of OM composition and geochemistry instead. Meanwhile, the quantification of CO2 drawdown and a convincing argumentation for why the found signals can only be caused by CO2 drawdown, is largely missing. Assessing the way the aims of the paper are introduced may be a bit outside my tasks as a reviewer, but I feel the way it is now has the introduction somewhat disconnected to the bulk of the paper.
The aim of the study is to find the cause of the 13C-enriched OM. The authors argue for CO2 drawdown as a cause, and indeed that could be one of the reasons (although there are some others as well). However, the authors add cooling as supporting argument for that (it is cooling, so there must have been a CO2 decline), and I think this drives down a dangerous road towards circular reasoning. First of all, they drive away from all the possible other reasons other than CO2 drawdown of why this region cools. Evidence of Paleocene cold conditions mostly comes from southwest Pacific SST data, which represent at best local signals. The authors mention another reason for regional cooling themselves: increased upwelling of deep water. Benthic foram records might be biased by an unknown amount of ephemeral ice volume, and cannot be taken as paleotemperature proxy as such. Secondly, if the cooling is indeed global, the relation to radiative forcing has the issue that long-term trends in benthic foram d13C (representing carbon cycle) and d18O (representing temperature/ice volume) are out of phase by 1.5 Myrs. Westerhold et al., 2011 provides dissolution as a potential but uncertain reason for this, but as long as this is unresolved, the community has to entertain the idea that this represents a genuine signal, with understanding of the 1.5myr delay unexplained. Then, If the abstract and the rest of the paper reads as if it was shown that CO2 drawdown caused the d13C enrichment, people will use the paper as evidence for CO2 decline in the Paleocene, while actually that conclusion was drawn with the use of (local) SST decline as argument. Then CO2 reconstructions and temperature reconstructions have lost their independence, which is a tricky road.
Other factors may explain why d13C of higher plants might be shifting carbon isotope values over these time scales: lapse rates, for instance (Körner et al., 1988;doi: 10.1007/BF00380063). Could the authors find evidence to exclude the possibility that a change in altitude of the catchment caused some of the d13C excursion in the terrestrial components? I feel that the authors should more carefully exclude other arguments to explain the changes in d13C before the conclusion is drawn that CO2 drawdown caused it. This means acknowleding other potential factors.
Another (in my mind) obvious omission in the paper is the implications of the reconstructed intense river runoff signal in the records for local paleogeography and paleoenvironments. Many records of the Waipawa organofacies come from the east coast of NZ, which today, owing to a high mountain range and prevailing westerly winds, is in an intense rain shadow. The observation of intense river runoff in the Paleocene on the eastcoast of NZ could mean 2 things: (1) prevailing easterly winds in the Paleocene, which is unlikely, but could be verified in model simulations (2) absence of a rain shadow, which means absence of a strong mountain divide. I believe this must be discussed in the paper, and because the evidence for intense runoff is way clearer than the link to atmospheric CO2 drawdown, I would suggest the authors focus their paper towards the implications for local paleogeography, hydrology and paleoenvironment.

Comments in chronological order
Abstract line 25-27: Authors should specific about trends vs peak values (cooling versus cold). The 1.5 million year offset means that it is crucial that the authors place the timing of deposition of the Waipawa organofacies and the SST trends relative to the carbon isotope maximum and the oxygen isotope maximum. To me, "cooling" refers to a decreasing trend in temperature, rather than a temperature minimum. Does the deposition of the Waipawa organofacies now coincide best with the benthic foram d13C trends, the d18O maximum or with the SST minimum? Some careful rewording might be needed here to make it really clear.
Line 109: the SST data of ODP Site 1172 are indeed published by Hollis et al., 2014, but note that these were updated in Bijl et al., 2021 with higher resolution, and beyond TEX86. Moreover, the primary source for the organic d13C data is Röhl et al., (2004; Geophysical monograph series 151). This should be acknowledged.
What I would suggest, is that the authors add a small plate presenting wide brightfield microscope images of the palynofacies, highlighting the main palyno groups. It might sound obvious for people working with palynofacies, but given the importance of this dataset for the story, I feel some visual support is warranted. The inshore-to-offshore trends in Fig. 14 are all but compelling. There is also a good reason why: global average sea level was really low, which means accommodation space was reduced. If the transect does not include sites off the slope (and Mead Stream is top slope, if I am correct), you will not find much of a transect when terrestrial input is so intense.
In section 6.4, I am loosing the connection to the new results. I propose the authors revisit this section to see how it can be more closely connected to their results and implications.