I propose very few details and a low probability (and as I add more details from ‘someone burned a lot of carbon’ I give even less), and the scenario outlines above total carbon release could be split between an artificial release and later positive feedbacks (seafloor clatherate and the like). As for no trace, finding bedding planes within the PETM itself is a celebrated event in many places and trying to hit a bedding plane within a short period is hard, and I would need to look into the work of a scientist I really like about erosion rates across continental crust to see what the odds of a carbon deposit near the surface now being near the surface millions of years ago would be...
Well Australia is right beside Antarctica at that time. Its coal deposits are Permian/Jurassic and the continent has hardly changed geologically. Would seem like an obvious place to mine. A civilization mining and burning coal on large enough scale to impact climate is also going to have to manage quick a bit of other tech (esp metallurgy) as well, with the evidence also conveniently hidden. So from Baysian perspective we have quite a number of competing hypotheses for PETM founded on evidence but hard to constrain as to relative effect. The “ancient civilization” hypothesis has no evidence supporting it that I can see. I would of course shift my beliefs rapidly if evidence of past civilization appeared. Calculating sedimentary flux (proxy for erosion rate) through time is routine input into basin modelling. I would guess data exists for practically all sedimentary basins with any potential for hydrocarbons. (And paleogene flux from Australia is really low). Can you be more specific about what carbon deposit you are talking about. (Erosion rates are also estimated from fission-track dating and similar techniques but this is really only relevent to high erosion rate features ie mountain chains). I should say that I am deep in accumulating this kind of data for whole of NZ as it is input into models for surface heat flow that I am helping out with.
I propose very few details and a low probability (and as I add more details from ‘someone burned a lot of carbon’ I give even less), and the scenario outlines above total carbon release could be split between an artificial release and later positive feedbacks (seafloor clatherate and the like). As for no trace, finding bedding planes within the PETM itself is a celebrated event in many places and trying to hit a bedding plane within a short period is hard, and I would need to look into the work of a scientist I really like about erosion rates across continental crust to see what the odds of a carbon deposit near the surface now being near the surface millions of years ago would be...
Well Australia is right beside Antarctica at that time. Its coal deposits are Permian/Jurassic and the continent has hardly changed geologically. Would seem like an obvious place to mine. A civilization mining and burning coal on large enough scale to impact climate is also going to have to manage quick a bit of other tech (esp metallurgy) as well, with the evidence also conveniently hidden. So from Baysian perspective we have quite a number of competing hypotheses for PETM founded on evidence but hard to constrain as to relative effect. The “ancient civilization” hypothesis has no evidence supporting it that I can see. I would of course shift my beliefs rapidly if evidence of past civilization appeared. Calculating sedimentary flux (proxy for erosion rate) through time is routine input into basin modelling. I would guess data exists for practically all sedimentary basins with any potential for hydrocarbons. (And paleogene flux from Australia is really low). Can you be more specific about what carbon deposit you are talking about. (Erosion rates are also estimated from fission-track dating and similar techniques but this is really only relevent to high erosion rate features ie mountain chains). I should say that I am deep in accumulating this kind of data for whole of NZ as it is input into models for surface heat flow that I am helping out with.
Should add that constraints on d13C of source for PETM are getting better. eg https://www.pnas.org/content/117/39/24088 - favouring volcanic (-6) rather than coal (-25) or gas (-60).