Focused fluid flow in passive continental margins

Abstract

Passive continental margins such as the Atlantic seaboard of Europe are important for society as they contain large energy resources, and they sustain ecosystems that are the basis for the commercial fish stock. The margin sediments are very dynamic environments. Fluids are expelled from compacting sediments, bottom water temperature changes cause gas hydrate systems to change their locations and occasionally large magmatic intrusions boil the pore water within the sedimentary basins, which is then expelled to the surface. The fluids that seep through the seabed at the tops of focused fluid flow systems have a crucial role for seabed ecology, and study of such fluid flow systems can also help in predicting the distribution of hydrocarbons in the subsurface and deciphering the climate record. Therefore, the study of focused fluid flow will become one of the most important fields in marine geology in the future.

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps

“…Studies on passive margins offshore Europe and Asia have also advanced this explanation for focused fluid flow in areas of high sedimentation rates under excess pore pressure (Berndt, 2005). This interpretation is consistent with the non-aquifer model of Dugan and Flemings (2002), where rapid sediment loading during the Pleistocene sea-level lowstand created overpressure gradients, forcing fluids to migrate upward and outward toward the seafloor.…”

“…A variety of driving mechanisms has been proposed to explain methane venting at cold seeps, including hydrological and tidal pumping, warming of bottom water (Suess, 2014), excess pore pressure in areas of high sedimentation along the passive margins of Europe and Africa (Berndt, 2005), seismic activity (e.g., Fischer et al, 2013), and links to sea-level lowstands (e.g., Teichert et al, 2003;Feng et al, 2010;Liebetrau et al, 2014). In many of these cases, a major mechanism for methane release is a change in hydrostatic pressure and/or temperature, and subsequent hydrate dissociation, as in the case of the South China Sea (Han et al, 2014) and Svalbard (Westbrook et al, 2009;Berndt et al, 2014).…”

“…The isotopic composition of shells from chemosynthetic bivalves living close to fluid vents represents an important archive of the nature and variability of the venting. While previous studies have investigated authigenic carbonate formation and cold seeps in other settings (Han et al, 2014;Suess, 2014;Bayon et al, 2015) and fluid flow in passive margins (Berndt, 2005), this is the first study to examine the origin of the authigenic carbonates, the source fluids, and the timing of methane emissions on the northern USAM. This paper explores the geochemistry, mineralogy, and petrology of authigenic carbonates and bivalve shells recovered by ROVs from both the Norfolk and the Baltimore Canyon seep fields with the aim of tracing the origin and flow pathways of gas and fluids at both sites.…”

Deep-seated faults and hydrocarbon leakage in the Snøhvit Gas Field, Hammerfest Basin, Southwestern Barents Sea

“…Gas chimneys are acoustic maskings which create dimmed and distorted amplitudes and does not show any clear stacking unlike seismic pipes which show vertical stacking of high or low amplitude anomalies (Andresen, 2012;Berndt, 2005;Løseth et al, 2011Løseth et al, , 2001Moss and Cartwright, 2010). They are described in different ways in the literature as columnar disturbances, wipeout zones, dimmed and distorted amplitudes in seismic data (Andresen and Huuse, 2011;Berndt, 2005;Heggland, 1998;Heggland et al, 1999;Hustoft et al, 2010;Løseth et al, 2009).…”

“…They are described in different ways in the literature as columnar disturbances, wipeout zones, dimmed and distorted amplitudes in seismic data (Andresen and Huuse, 2011;Berndt, 2005;Heggland, 1998;Heggland et al, 1999;Hustoft et al, 2010;Løseth et al, 2009). The gas chimneys in this study are associated with high-amplitude anomalies (HAAs) at their roof zones (Figure 1.2a).…”