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Paleo-peatlands as organic carbon pools in geological history

paleo-peatlands,carbon pool,Milankovitch cycle,carbon accumulation rate,net primary productivity (NPP)

Theme 3: Earth-Life Co-evolution Through Time > Session 3c: Life-Mineral Interactions during the Plant Terrestrialization

Peatlands, as one of the important ecosystems, have the ability of long-term carbon sequestration, and are an extremely important carbon pool, which play a vital role in the global carbon cycle. Paleo-peatlands are the main storage for terrestrial carbon, and they are also important records of paleoclimate. Net primary productivity (NPP) of the paleo-peatland refers to the fixed carbon of peatland in the primary production process, and studying the NPP in paleo-peatlands is of great significance for understanding the generation, development, and evolution of paleo-peatlands.

Geologists read the stratigraphic cycles using paleoclimate proxy records and link the recognized sedimentary oscillations to the Milankovitch cycles. Information recorded by the geophysical logs can be an ideal paleoclimate proxy which has been commonly used in the study of cyclostratigraphy. The logging response of gamma-ray, density, and resistivity can reflect the variation in ash yield and the V/I (vitrinite to inertinite) ratio in a coal seam. Spectral analyses of geophysical data from thick coal seams can help identify the significant signals of Milankovitch period parameters, and then the period of coal deposition can be calculated. Further considering the carbon loss during coalification, the long-term average carbon accumulation rate and net primary productivity (NPP) of paleo-peatlands in coal seam can be estimated.

The source of carbon in vegetation including paleo-peatlands is atmospheric CO₂, fixed through photosynthesis. Therefore, the different atmospheric CO₂ levels in different geological ages should result in different NPP values of paleo-peatlands. Several case studies for the Late Permian, Middle Jurassic, Early Cretaceous and Holocene showed that the NPPs of paleo-peatlands are mainly controlled by the atmospheric CO₂ contents. The higher NPP values are associated with the higher atmospheric CO₂ contents. Therefore, it can be suggested that NPP values could be a possible proxy of global atmospheric CO₂ during geological periods.