I learned quite a bit about nucleosynthesis, but haven't revisited it in decades.
There are three main processes for synthesizing heavy elements. In the s-process (slow), neutrons are absorbed by heavy nuclei slowly enough that the nucleus has time to beta decay, if it is too neutron rich to be stable. The s-process happens in red giant stars, and the products can be released by stellar winds and planetary nebula formation.
In the r-process (rapid), neutrons are added very quickly to heavy nuclei, which absorb as many neutrons as they can and then, once the neutron bombardment ceases, beta decay back to stability. I don't recall whether we knew where the r-process happened when I was studying this, but this result would be r-process.
In the p-process (proton), nuclei grow by having protons added one at a time. This is presumed to happen in supernovae, and p-process nuclei are rare.
Isotopes coming from the s process will have abundances inversely proportional to their neutron cross section, because that cross section determines how quickly they move on. Also, while many isotopes can be produced by several of these processes, some can only be produced by one. My understanding is that these methods indicate that the s process is the predominant source of heavy elements. However this table (pointed out by other /. posters) contradicts my understanding, so possibly my knowledge has become outdated.
Can someone with more recent knowledge comment on how these new results can be reconciled with isotope abundances?