In the Latrobe Valley of Australia such unusually thick coal beds exist. Does anyone have any hypothesis on the origin of these brown coal beds hundreds of meters thick?
Dear Paul, just a short idea,
Although I do not know the geological basement in the mentioned site in Australia, I think you should focus on that. In Germany we have several examples of coals that show a huge thickness of hundred metres or more. The Eocene Geiseltal is one of these and not only famous for its fossil vertebrates. The underground is made of carbonates, gypsum and salt deposits, and their leaching and related subsidence over huge periods of time enabled both a continuous growth and long lasting persistence of the swamp and resulted in the preservation of the accumulated organic material.
Best wishes Ronny
Bob Gastaldo and others described the formation of domed peats that rise high above their surroundings in Kalimantan. If such peats were buried, they would result in unusually thick coal beds, though tectonism or sea level change would have to be invoked to lend enough accommodation space for the accumulation of hundreds of meters of brown coal.
Dear Paul,
I agree with Ronny. It is most probable that continuous tectonic subsidence, which is in equilibrium with the vegetation addition through growth, have one of the most important impacts on formation of thick coal beds. Such case we have in Slovenia (Velenje). Lignite bed reaches max. thickness of up to about 160 m. Besides, you have to take into consideration whether syn- or post-depositional tectonic processes (e.g. compression/folding, thrusting...) could have additionally contributed to the thickness increase. This should, of course, be seen in deformational patterns, if any.
I thank all of you for responding to this question. I have seen the German brown coals, but I am more familiar with the Victorian brown coals of the Latrobe Valley of southern Australia. The general situation there is that very thick (100-200 m) low-ash brown coal beds are separated by interbeds of lacustrine clay with abundant lump resin. Because of the heat the brown coal has to be constantly kept wet to control fires in the open pits. Assuming a peat accumulation rate of 5 cm/yr, each brown coal bed took about 20,000 yr to accumulate.The low ash can be explained by a domed-peat model and a gradually sinking basement (subsidence) equal amount of peat accumulation, and lack of clastic inflex into the peats.. It is remarkable the absence of partiings in the brown coals themselves.
Thank you Ronny , Tennille, Andrew, and , Mirka for your insightful discussion.
Best wishes, Paul Lyons.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Energy