Review Summary:

The authors develop a cosmogenic depth profile model for complexly aggraded deposits (specifically braided river deposits). Their model can consider rapid accretion events with intermittent phases of either stability or steady-state surface erosion (or aggradation) and is modular such that any number of accretion events can be employed based on stratigraphic information. They apply this model to a fairly high-res 10Be depth profile (with a handful of 26Al datapoints) and employ various depositional scenarios for a mid-Pleistocene gravel deposit in Belgium. The authors demonstrate that a scenario with a multi-stage accumulation history is necessary to meaningfully fit the profile data and to produce reasonable age estimates for the deposition intervals. This work is significant methodological contribution to the cosmogenic nuclide community and serves as an important demonstration for the need to include sedimentological information into cosmogenic depth profile models. I think this work is suitable for Geochronology and recommend publication after the authors address the following minor comments.

Comments:

General 1) it is assumed that inheritance is constant over the multiple deposition phases for the specific application of this model. That seems reasonable in this case, but is there a mechanism for the model to incorporate different inheritances for the different deposition cycles? Will the model code also be made available to others?

General 2) Uncertainties are reported throughout without indication of whether they are 1- or 2-sigma. Please indicate what they are, either with a global statement like “all reported uncertainties are 1-sigme), or with local statements if they are not all consistent.

Lines 129-130: The 10Be half-live value shown here is the combined value of both Chmeleff et al. 2010 and Korschinek et al. 2010. Please cite both references. Also, I believe the 705 ka half-life for 26Al is from Nishiizumi 2004.

Figure 3: I find the shaded region on panel (a) difficult to view. I also think this figure would benefit from a simple, regional scale map for context.

Line 204: What is the geosite? Is it a cutbank? A mine? A little more context would be useful here along with a field photo if available.

Line 210: Was there any reason, aside from cost, to not analyze 26Al for all 14 with the 10Be?

Figure 5: This is a great explanatory figure.

Line 320-321: This statement of uncertainty is a bit awkward. I think it means most concentrations have an uncertainty between 5-7%?

Line 339-344: So, and I am assuming these are 1-sigma errors, 7.41 +/- 0.92 is statistically 6.75. I get why the authors want to describe the context of a potentially higher depositional ratio, but phrasing the end of this section with “we cannot discard the hypotheses” that they all had a ratio similar to 6.75 seems to imply that an alternative hypothesis is somehow preferable. I think the authors can more simply state that their measured ratio is consistent with that of near surface production for a range of moderate to high erosion rates.

Table 2: Is the mass of the 9Be carrier mass the mass of the carrier itself or the 9Be? If it’s the carrier, please indicate the concentration of the carrier in ug 9Be/g. Also, it is somewhat awkward to report ratios for the lab blanks in e-14 and e-15 and the samples in e-12. Also, why were there no blanks for the 26Al reported here? There appears to have been a correction made for a blank according to line 240—does this mean a batch blank is not used, just a general background value? Please explain.