Terrestrial climate and biogeochemistry

Wetlands are widely distributed in temperate climates. Currently around 6% of Earth’s land surface is covered by peat and it is likely that this percentage was higher in the geological past, especially during periods when the hydrological cycle was more intense (e.g. Eocene). Peat bogs contain high amounts of organic matter (> 40 wt.% TOC), making them very suitable for organic geochemists. Currently a main part of my research focuses on the development and application of organic geochemical proxies based on the distribution of GDGTs (glycerol dialkyl glycerol tetra ethers, for an introduction about GDGTs click here) and hopanes in peats. For this purpose I have developed a global peat database that contains peat samples from virtually every peat forming environment.

fig_2-location-peats-for-calibration_revised
Location of peats that are part of the global database (Naafs et al., 2017. GCA)

Using modern peat from across the world, I am determining what the dominant environmental control (e.g., vegetation, temperature, pH, water content) on the GDGT distributions is. Although GDGT-based proxies are mainly applied to marine and lake sediments, GDGTs are extremely abundant in peats and recent work showed the potential for the application to peats (Weijers et al., 2011), potentially opening up a completely new set of (high-resolution) palaeo-archives. However, the controls on GDGT distributions in peats are poorly understood and constrained. In addition, hopanes are abundant in modern peat. Hopanes are produced by bacteria and their distribution as well as stable carbon isotopic composition can provide information about wetland biogeochemistry in the geological past.We aim to use the database of modern peat to develop novel paleoclimate proxies, especially a paleothermometer and proxy to reconstruct the past dynamic of the methane cycle in peat.

The next step of this research is the application of the novel organic geochemical proxies to ancient peats and lignites (lithified lignites). Especially immature lignites from past greenhouse periods such as the Paleogene are of interest to develop a better understanding of terrestrial climate and biogeochemistry in a high pCO2 world. This research is done in collaboration with Gordon Inglis and Rich Pancost and is funded by the European Research Council (ERC) through the advanced ERC grant “The Greenhouse Earth System“.