Jochen Manfred Knies

Phone: 73904116

Collaborative work in Germany

Figure 1: Map of the study area in Vestnesa Ridge and locations of the drilling cores (MeBo) and griavity cores (GC).
Within the Norcrust project, we are studying the paleo-records of methane emission from different seep environments.

By Pierre-Antoine Dessandier and Giuliana Panieri

On Vestnesa Ridge (NW Svalbard), we sampled sediment cores using the MeBo drill system and gravity cores during the cruise MSM57 (summer 2016) in two active pockmarks called Lunde and Lomvi (Fig. 1).

The X-Ray Fluorescence (XRF) Core Scanner allows us to measure most of the natural elements in sediment cores, in order to reconstruct the past environmental or climatic changes. XRF analyses were processed at MARUM (Bremen University), every cm on MeBo 125, 126 and 127 and on gravity cores 2 and 3, representing 4951 cm measured (Fig. 2).

Figure 2: A) XRF core scanner and B) section of MeBo core prepared for the scanning.

The objective of these XRF analyses is to determine, based on the elements concentration, some particular periods characterized by elements peaks. These peaks are due to environmental or climatic changes at a regional scale and allow us to link chronological tie points between the different cores. We particularly focused on the elements Ca, Al, K, Zr, Ti, Fe, S and Sr. These elements could indicate changes in terrestrial sediment supply from various sources (e.g. Zr, Ti, K), periods of anoxia (e.g. Fe, S) or periods of strong biological production. (e.g. Ca) We are particularly interested in Sr/Ca peaks that indicate aragonite precipitation (fig. 3). The precipitation of aragonite in the sediments  could be an indicator of the presence of methane derived authigenic carbonate, directly linked with strong emissions of methane in the past.

Figure 3: XRF scans of the MeBo 125, yellow layers indicate Sr/Ca maxima expected to be linked with authigenic carbonate precipitation. The red layer is indicative of Fe and Mn increase, which could be related to low oxygen conditions.

The other objective is to define the most interesting periods in terms of environmental changes and methane emissions to target these periods for future geochemical and micropaleontological studies (Fig. 4).

In these targeted samples, the assemblages of benthic foraminifera will be investigated to highlight climatic changes and methane emissions. The isotopic signal on their tests will be measured to provide crucial information on the frequency and strength of the methane emissions. We will particularly focus on the negative excursions of the d13C, indicative of methane emissions recorded by benthic foraminifera.

We thank to Gerhard Borhmann and all his team for this exciting collaboration. We also thank Ursula Röhl and Vera Lukies for their help at MARUM.

Figure 4: Sampling of the MeBo and gravity cores for future analyses of micropaleontology and magnetic susceptibility.