RV SONNE Fahrtbericht / Cruise Report SO277 OMAX: Offshore Malta Aquifer Exploration, Emden (Germany) – Emden (Germany), 14.08. – 03.10.2020

Berndt, Christian; Urlaub, Morelia; Jegen, Marion; Faghih, Zahra; Reeck, Konstantin; Franz, Gesa; Barnscheidt, Kim Carolin; Wollatz-Vogt, Martin; Liebsch, Jonas; Schramm, Bettina; Elger, Judith; Kühn, Michel; Müller, Thomas J.; Schmidt, Mark; Spiegel, Timo; Timm, Henrike; Hinz, Anina-Kaja; Sager, Thore F.; Hilbert, Helene-Sophie; Rohde, Lea; Korbjuhn, Torge; Reissmann, Silvia; Diller, Nikolaj

doi:10.3289/geomar_rep_ns_57_20

Cited by 7 publications

(10 citation statements)

References 37 publications

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“…The observed resistivities are 2–5 times larger than the background seawater‐saturated UCL resistivities along lines 5 and 6. Both R1 and R3 extend to the seafloor, yet no freshened groundwater discharge was registered by the CTD (conductivity, temperature, depth) sensor (mounted on the CSEM system) and pore water sampling from gravity cores (Berndt et al., 2021). These observations, together with a lack of a confining unit above the resistivity anomalies, suggest that the latter are unlikely to be associated with OFG.…”

Section: Discussionmentioning

confidence: 99%

Electrical Resistivity Anomalies Offshore a Carbonate Coastline: Evidence for Freshened Groundwater?

Haroon

Micallef

Jegen

et al. 2021

Geophysical Research Letters

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Carbonate lithologies host considerable quantities of the Earth's freshwater resources and partially supply a quarter of the global population with drinkable water. Carbonates constitute substantial amounts of the global coastlines, yet it is not known if and how they can sustain freshened groundwater offshore. Here, we use controlled source electromagnetic, seismic reflection, and core sample data to derive a lithological model for the eastern margin of the Maltese Islands and identify four distinct resistivity anomalies within the Upper Coralline Limestone, Globigerina Limestone, and Blue Clay formations. The anomalies hosted in the former are likely associated to low porosities, whereas the anomaly within the latter is indicative of pore fluid freshening. Hydrogeological modeling suggests that freshened pore fluids, emplaced during sea-level lowstands and preserved in low permeability units, are potentially still found within carbonate shelves. However, resource potential is low due to its relict nature and low permeability host environment.

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Section: Discussionmentioning

confidence: 99%

Electrical Resistivity Anomalies Offshore a Carbonate Coastline: Evidence for Freshened Groundwater?

Haroon

Micallef

Jegen

et al. 2021

Geophysical Research Letters

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“…Closer to the seafloor, the lack of subhorizontal HRS (Figure 4c) suggests that gas migration is mostly subvertical even though seafloor seepage does occur (Berndt, 2013). A highly reflective patch of the seafloor west of the active seep site contains massive carbonates based on video observations (Berndt, 2013), but no gas flares have been found in hydroacoustic data. The fluid flow system underneath these carbonates might be intermittent because gas hydrate may periodically clog the vertical flow pathways feeding the seafloor vent.…”

Section: Discussionmentioning

confidence: 99%

“…At a large scale, BSRs cover an area of more than 15,000 km 2 both in the accretionary wedge and in the SCS (Chi et al, 1998; Liu et al, 2006). In addition, Lin et al (2009) investigated geological controls on gas hydrate occurrences in the area SW of Taiwan, while hydroacoustic data and geochemical data sets derived from sediment cores and bottom‐water samples (Berndt, 2013; Chen et al, 2017; Chiu et al, 2006; Chuang et al, 2010; Liu et al, 2006; Oung et al, 2006) identified hydrate related fluid venting in the region. Also, seafloor photographs by deep‐tow camera systems and sediment samplers show carbonates, carbonate mounds, chimney structures, and chemosynthetic communities associated with bacterial mats (Berndt, 2013).…”

Section: Geologic Settingmentioning

confidence: 99%

A Shallow Seabed Dynamic Gas Hydrate System off SW Taiwan: Results From 3‐D Seismic, Thermal, and Fluid Migration Analyses

et al. 2020

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Large amounts of methane, a potent greenhouse gas, are stored in hydrates beneath the seafloor. Sea level changes can trigger massive methane release into the ocean. It is not clear, however, whether surficial seafloor processes can cause comparable discharge. Previously, fluid migration was difficult to study due to a lack of spatially dense seismic and thermal observations. Here we examine a gas hydrate site at Four-Way-Closure Ridge off SW Taiwan using a high-resolution 3-D seismic cube, together with bottom-simulating reflections (BSRs) mapped in the cube, a thermal probe data set, and 3-D thermal modeling results. We document, on a scale of tens of meters, the interaction between surficial sedimentary processes, fluid flow, and a dynamic gas hydrate system. Fluid migrates upward through dipping permeable strata in the limb, the slope basin, and along thrust faults and ridge-top normal faults. The seismic data also reveal several double BSRs that underlie seabed sedimentary sliding and depositional features. Abrupt changes in subsurface pressure and temperature due to the rapid seabed sedimentary processes can cause a rapid shift of the base of the gas hydrate stability zone. This shift may be either downward or upward and would result in the accumulation or dissociation of hydrate in sediments sandwiched by the double BSRs, respectively. We propose that dynamic surficial processes on the seafloor together with shallow focused fluid flow affect hydrate distribution and saturation at depth and may even result in methane expulsion into the ocean if such localized features are common along convergent plate boundaries. Plain Language Summary Gas hydrates are ice-like compounds in marine sediments. Shallow surface dynamic processes may affect the hydrate saturation beneath the seabed. We combine 3-D seismic and thermal probe data, with numerical geothermal modeling to investigate the geological processes controlling the distribution and formation of gas hydrates beneath thrust ridge anticlines. We also study fluid flow patterns under the seabed and found that localized fluid flow and rapid surficial erosional processes have significantly altered the temperature and pressure conditions of hydrate bearing sediment strata at depth, ultimately influencing gas hydrate formation and dissociation. We propose to conduct hydrate exploration close to thrust anticlines, where such active processes might enrich the saturation of gas hydrates or even influence fluid emission into the ocean if similar processes are widespread along continental margins.

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“…One multichannel seismic reflection profile (P2000_2115_2857), obtained by RV Sonne expedition SO277 (Berndt et al, 2021), was taken into consideration. The profile crosses the shelf across the study area (Figure 2A, right transect).…”

Section: Seismic Reflection Profilementioning

confidence: 99%

Controls on mesophotic carbonate facies and sediment distribution across the Maltese shelf, central Mediterranean Sea

Bialik,

Coletti,

Berndt

et al. 2024

Preprint

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Although ~20% of global carbonate occurs on extra-tropical shelves, our understanding of these depositional environments still lags far behind that of tropical carbonate platforms. The Maltese shelf in the central Mediterranean offers an opportunity to study in situ facies distribution in a light-dominated extra-tropical carbonate platform and the factors controlling them. The Maltese shelf visually exhibits three main facies: seagrass meadows; sand flats/bedforms and maerl. While visually distinctive, the allochem composition of the sediment does not offer a clear differentiation of all three but rather a gradient. This gradient is marked by increasing grain size with depth, a transition from green to red calcareous algae and an increase in the fraction of low Mg calcite. While some of these features could be explained by changes in light availability, other factors are also in play. Internal waves, currents and baffling by seafloor vegetation appear to play important roles in governing the sedimentary texture and composition across the Maltese shelf. The role of vegetated substrate is of greater importance in Mediterranean C-type carbonate factories and could be an important marker to identify them in the geological record.

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RV SONNE Fahrtbericht / Cruise Report SO277 OMAX: Offshore Malta Aquifer Exploration, Emden (Germany) – Emden (Germany), 14.08. – 03.10.2020

Cited by 7 publications

References 37 publications

Electrical Resistivity Anomalies Offshore a Carbonate Coastline: Evidence for Freshened Groundwater?

Electrical Resistivity Anomalies Offshore a Carbonate Coastline: Evidence for Freshened Groundwater?

A Shallow Seabed Dynamic Gas Hydrate System off SW Taiwan: Results From 3‐D Seismic, Thermal, and Fluid Migration Analyses

Controls on mesophotic carbonate facies and sediment distribution across the Maltese shelf, central Mediterranean Sea

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