Paul:

Your question is not very clear. The primary production of vegetal matter needed for coalification (Peat- Lignite - Bituminous - Anthracite grades) was very different in different epochs. Pennsylvanian coals are generated in large stretches of warm-humid swamps by Glossopterid vegetation. Cretaceous-Miocene coals occur sporadically in areas where different vegetal matter was deposited with annual rainfall exceeding evaporation. What is wrong with Climatic and Tectonic models?

Paul, to make coal one needs productivity (in plant form) and a subsidence rate sufficient to remove the organic matter from oxidation.  "Tectonic models", depending on what you're using,  may not have a high enough resolution to "see" that type of subsidence.  Doesn't mean they're wrong, just not the correct tool for the task.  The high productivity does not need to be year-round.  You need sufficient light & precipitation during the growing season.  At the equator, that could be year round, but at high latitudes that only needs to be during the summer.  In high latitudes, removing the vegetation from oxidation risk can be accomplished by freezing the subsurface.  Climate models can give you the correct parameters for light, temperature, and precipitation, and possibly permafrost, but tell you nothing about subsidence. 

The wrinkle comes in when you are comparing different geologic periods.  The Pennsylvanian is the least like today in terms of floral types & climate.  At that time, you only have gymnosperms and they do not completely cover the landmasses.  By the Cretaceous, angiosperms have been introduced.  These cover more areas across the globe than gymnosperms.  In the Miocene, grasses became an important floral component and virtually all landmasses are covered by some vegetation (except very arid deserts and ice-covered areas). 

The reason floral types & geographic distribution of flora are important is due to a climate feedback mechanism called precipitation recycling.  Essentially what happens is that plants, through evapotranspiration & soil creation, increase the water vapor in the air around where the plants are living.  By increasing the atmospheric water vapor the ability to rain increases (if there is no water vapor it cannot condense as rain).  Which means, for much of geologic time (Devonian through Oligocene) the overall degree of precipitation has increased and the areal coverage of that increased precipitation has increased.  It has been estimated that 30% the annual avg precipitation in the Amazon is due to precipitation recycling.  Forested landscapes have the greatest amount of precipitation recycling. When grasses evolve in the Miocene this trend is disrupted.  Grasses actually dry out an area.  This mean that there is less precipitation in an area covered by grass than an area covered by forest.

Modern climate models contain this feedback mechanism in their vegetation module.  Climate models without a vegetation component may show the correct direction of climate change, but not the correct magnitude.  This was identified by several researchers in the late 1990's.  Martin Claussen has several papers on the greening of the Sahara in the mid-Holocene that discuss this mechanism and it's impact.  The ramification of this is that all climate models prior to the very late 1990's or early 2000's will be wrong for periods from Modern - Carboniferous, but correct, or nearly so for older time periods (ignoring other breakthroughs in climate research). 

Coal is the geological history of the forest buried into the ground, after which the complex geological formation. Carboniferous - Permian geological history of the most important coal-forming period, indicating that the much warmer and humid climate than right now, suitable for growing trees, dense forests.

So, I am sure the climatic models, nowadays,  are misleading by mediums, “Al Gore politician modeler" & climate specialists, not by the true weather information.

Hi Paul:

I think for Miocene coal forming environments we do see close analogs in the modern world.

The match of German Miocene (and North American Eocene) lignites with Taxodium swamps in SE USA for the Eocene to Miocene Metasequoia and other taxodioid Cupressaceae is pretty good, and for the Australian Miocene lignites (Latrobe Valley, state of Victoria), the peat forming swamps of Borneo are a good match for the mix of tree taxa.

For the Cretaceous, it depends al lot whether you mean early, mid or late, and I think where in the world too; Araucarian dominated vs. other gymnosperm dominated. By the Late Cretaceous angiosperms are approaching Cenozoic abundances and tree stature, and so the chemistry of the leaves and the hydrological interactions within the landscape are pretty similar. But Early Cretaceous the angiosperms are minor or absent, and extinct gymnosperms are prominent with different leaf chemistries (N:P ratios likely different due to varying lignin levels for pteridosperms vs.angiosperms); this will affect decomposition rates and so peat accumulation rates.

For Pennsylvanian coals, this is accentuated.

The other factor (as commented on by Judy Parrish more than a decade ago) is climate; warmer wetter past geological epochs have no real analog climates in the Holocene, especially at high latitudes / polar regions which have thick coal sequences. It is well established that decomposition varies with both moisture and temperature ... as well as N content of leaves and soll water. The Miocene has a much closer global climate to the Holocene than any of the others, although still with Polar forests (mostly Pinaceae + dicots, vs. taxodioid Cupressaceae in the Eocene and Late Cretaceous) in the Arctic.

Cheers

David

hi David,

Thanks for your thoughtful answer to my question, which I will give you an up vote on.  However, one has to take into  consideration tectonic framework as well as the flora and climate.

Hi Paul

Thanks. yes, tectonic controls matter. The coal basins (Eocene) in British Columbia are mostly grabens and half grabens, from crustal relaxation (extensional tectonics), leading to some very thick seams (Allenby Fm., Princeton Basin and Tullameen Basin; also Hat Creek), and similarly so in the Latrobe Valley Late Eocene to Miocene sequence (extension between the Australian mainland and Tasmania). Individual seam thickness in both of these can exceed 150 m, with the whole sedimentary sequence exceeding 1 km containing multiple thick minable seams.

D.