Scientist from MTU  were involved in several research areas and sub-projects within MARUM during the funding periods until 2017, namely GB3 and SD2 in the period of


Project GB3: Contribution of cold seeps to geological processes, carbon fluxes, and ecosystem


A. Boetius, G. Bohrmann, H. Sahling, F. Wenzhöfer; D. de Beer, N. Dubilier, M. Elvert, T. Feseker,

T. Goldhammer, K.-U. Hinrichs, S. Kasten, J. Notholt, T. Pape, V. Spieß, G. Wegener

Spatial and temporal variations in geophysical, geological, biogeochemical and biological processes

associated with hydrate formation and hydrocarbon gas emission from the seafloor will be

identified and quantified.

Cold seeps are sources of gases and reduced fluids to the hydrosphere, and with respect to gases,

potentially to the atmosphere (Jørgensen and Boetius 2007). The main objective of GB3 is to

gain a holistic, quantitative understanding of spatial and temporal variations of the geological, geochemical

and microbial processes controlling fluid flow and hydrocarbon emission at cold seeps

(Fig. GB4), and to improve the knowledge of the distribution and activity of cold seeps on continental

margins, in order to assess their contribution to global hydrocarbon budgets.

Recent investigations suggest that the number of active submarine mud volcanoes, gas chimneys,

pockmarks and shallow-hydrate reservoirs is much higher than anticipated, and that hydrocarbons

emitted from deep-sea seeps can reach the upper ocean (Sahling et al. 2008). However,

the spatial and temporal dynamics of gas emission from active submarine seeps remain poorly

quantified. Hydrocarbons and their products of anaerobic degradation are rich in chemical energy,

which is utilized efficiently by assemblages of microorganisms and chemosynthetic symbioses

(Boetius et al. 2000, Dubilier et al. 2008). However, in some systems considerable quantities

of hydrocarbons can escape the biological filter (Niemann et al. 2006). Quantifications of fluidflow

patterns linked to consumption of methane, sulfide, oxygen and other reactants are needed

for assessing the role of cold seeps in regional and global element budgets (Felden et al. 2010).

By using satellite imaging, geospatial statistics and long-term observations we will be able to esMARUM

2012-2017 54 Geosphere-Biosphere Interactions

timate the distribution of hydrocarbon flux to the ocean surface (Solomon et al. 2009) and the

temporal dynamics. This knowledge is key to evaluating the effects of both natural and anthropogenic

oil and gas leakages on deep-sea communities. We will focus on seeps of polar and temperate

margins as natural laboratories to study the timescales and ecosystem impact of petroleum

degradation, especially in the light of seafloor warming in response to climate change (Westbrook

et al. 2009). Geomicrobiological laboratory experiments and high-resolution molecular

studies will contribute to assessing the impact of hydrocarbon transformation on deep-sea ecosystems

(Schubotz et al. 2011a, b, Holler et al. 2011). Past variability of fluid flow will also be assessed,

e.g. by the analysis of authigenic minerals that typically precipitate in relation to AOM

(Nöthen and Kasten in press.). This project closely interacts with GB2 to assess the production

and migration of hydrocarbons, and with GB4 to compare the role of vents and seeps in carbon,

sulfur, nitrogen, and energy cycling.

Key hypotheses:

● Sedimentary, oceanic and tectonic conditions have a major impact on gas hydrates, free

gas formation and migration.

● The distribution of shallow gas hydrates and strength of hydrocarbon leakage determines

the distribution and composition of chemosynthetic communities and mineral precipitates.

● Local, regional and global methane emission rates from the ocean have been underestimated

due to incomplete knowledge of their lateral extent, their control mechanisms and

transport pathways to the ocean surface.

Project SD2: Climatic control on large-scale sedimentary structures

T. Schwenk, T. Hanebuth, T. Mörz, D. Hebbeln, R. Henrich; A. Bartholomä, M. Elvert,

A. Freiwald, S. Kasten, H. Keil, H. Lantzsch, H. Müller, M. Strasser, V. Spieß, T. v. Dobeneck

Depositional structures on continental shelves and slopes will be investigated in the field and assessed

by numerical modeling to quantify the climatic control (sea level, material availability,

ocean circulation) on shelf and slope sediment dynamics on centennial-to-millennial timescales.

The sedimentary systems of continental shelves and slopes host various large-scale depositional

and erosional features whose formation processes are controlled by sediment flux, hydrodynamic

conditions, sea level, and local topography (Nittrouer et al. 2007). All of these parameters commonly

interact with each other in a complex way and react strongly to climatic conditions. The

effect of climatic forcing on locally confined depocenters (shelf mud belts, shelf sand fields,

lowstand deltas, slope contourites), elongated depressions (paleo-valleys, slope canyons), and

characteristic erosional features (furrows, scars) will be studied by interdisciplinary approaches.

Major advances supporting such studies are provided through the MeBo system, which has already

been successfully applied for SD studies at the Uruguay margin, and by the newly developed

GOST system providing in-situ geotechnical data.

Key hypotheses:

 Major transgressions cause significant reorganization of the entire shelf system that is best

recorded in shelf-crossing paleo-valleys.

Our understanding of paleo- and modern sediment dynamics related to transgressive scenarios

is limited due to the often discontinuous nature of open-shelf sedimentary records. Paleo-valleys

formed during sea-level lowstands offer a great preservation potential for early transgressional

sedimentary sequences (Green, 2009). Using seismic, sedimentological, geotechnical and numerical

modeling approaches, transgressional sedimentary sequences will be investigated following

in the wake of the last deglacial sea-level rise (Vink et al. 2007). Understanding the development

of shelf (re-)organization during transgressions is also of societal relevance. Regions of interest

are the Elbe/Weser paleo-valley and its tributaries in the central North Sea, and the continental

shelf off Uruguay.

 Deciphering the formation history of shelf depositional and erosional elements is essential to

properly interpreting their sensitive records of environmental variability.

Locally confined sediment depocenters and erosional features in shelf systems reflect the variability

of hydrodynamic and climatic conditions (Hanebuth et al. 2011). Evolution of these elements

will be assessed by high-resolution seismo-acoustic mapping and ground-truthing (sedimentology,

geochemistry) combined with numerical sediment-transport modeling. Dislocation of such

depocenters (by sediment supply, current-topography interaction, relocation of transport pathways,

sea level) leads to a reorganization of the entire shelf system including sedimentary links

MARUM 2012-2017 70 Sediment Dynamics

from shelf to slope. We will calculate volumes and masses of sediment depocenter successions

and integrate them into a shelf-wide, LGM-to-present numerical sediment-distribution model to

unravel the dominant environmental forces and to extract responses within the shelf-slope system

in a prognostic way. Regions of interest are the shelves off SE South America, NW Spain

and the SE North Sea.

 Climate change controls the complex build-up of contouritic depositional systems by the interaction

of different forces (e.g. sea level, ocean circulation, sediment input from land, etc.).

Contouritic depositional systems are generated by long-lasting contour-parallel currents whose

strengths and boundaries are forced by variations in climate and sea level. Their architecture is

also controlled by the interaction of ocean currents with local factors such as sediment supply

and bottom topography, and by events such as abyssal storms (Rebesco and Camerlenghi,

2008). The relative impacts of these forces on depositional geometries will be assessed. Additionally,

processes triggering the sediment instability frequently observed within contouritic deposits

will be investigated. Focusing on the current-dominated slope off Argentina/Uruguay,

seismo-acoustic, sedimentological, geochemical, geotechnical and transport/depositional modeling

approaches will be used to decipher the relevant long- and short-term processes.

 Sediment dynamics within submarine canyons are governed by climate-controlled down-slope

transport processes and the interaction of along-slope transport and seafloor morphology.

Canyon systems operate either as primary conduits for sediments from the continental margin to

the deep sea or as major sediment sinks. Sea-level changes control the sediment delivery by

changing the shelf configuration and by influencing the dynamics of bottom currents, and therefore

their interaction with the canyon topography (Henrich et al. 2009). The type and volume of

material available and the sediment transport mode are linked to the climatic regime. In particular,

variations in the frequency and volume of turbidite successions will be explored in the context of

regional paleoceanographic (contour-currents) and paleoclimatic changes. We will apply geophysical,

geotechnical, sedimentological (MeBo drilling) and geochemical methods to the study of

canyon systems off SE South America and NW Africa.

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