I think, if I am going to use this as my main argument, I would broaden it to microfossils generally. The debate would center around whether a flood model can explain the patterns of microfossils across space and time.
The pitch would be as follows:
Just as the fossil fuel industry relies upon radiometric dating to construct basin models in areas where there has been volcanic activity or igneous deposition, it relies heavily on microfossils to construct its models in areas where there is, or was once, a marine environment.
In such soils, it is common to find the fossilized remains of micro organisms that made hard shells, such as ostracods, forminera and others. What’s more, the morphology of those shells shows variation over time, or in some cases by environment, and often have analogs to similar creatures that exist today.
Paleontologists working for oil companies regularly examine soils brought up from the tips of oil wells to find the microscopic fossils, and there is a catalogue against which thier morphologies are compared that is used to determine the age of the rocks for the purposes of finding oil. This allows drillers to make sure they are in the right part of a geologic formation as they dig different wells, or drill directionally.
Similarly, when conducting exploration, keeping track of what kind of microfossils are in the soil can allow you to determine whether you are drilling in to an ancient river bed, or a lakeside, or an ancient wetland, depending on what the fossils look like. This is a clear and consistent pattern, and that pattern is useful because it helps us find oil.
The challenge, in essence, to the creationist is to provide a mechanism that explains why the morphology of these microorganisms changes over space and time in a way that matches the information provided by radiometric dating, and that corresponds with hypotheses about what the palaeoecology of the formation would have been, to a degree that it is economically prudent to rely on that information, given the YEC contention that the relationship is spurious.
In particular it should be noted that the differences between many of these microfossils species are so slight that they are often in the same genus and in some cases are likely the descendants of each other. They often have the same intelligences, mobility and habitat as each other and yet the morphology varies according to the depth of the sedimentary layers. As such, the usual explanations given for why birds and dinosaurs are above fish and clams well not help in this case. The organisms are too similar.
Is this a better angle than the “give me your calculations” thing I started off with?