The stratigraphic and geographic distribution of giant craters and remobilised sediment mounds on the mid Norway margin, and their relation to long term fluid flow

Stratigraphic development of the south Vøring margin (Mid-Norway) since early Cenozoic time and its influence on subsurface fluid flow

“…Evacuation structures are most likely to form if there is large overpressure developed through time which cannot be dissipated by diffused fluid flow. Evacuation structures are reported also from the Møre Basin, south of the study area, which are attributed to overpressure-related expulsion (Lawrence and Cartwright, 2010). The HHA extends further south and it may not be surprising that the headwall of the earliest slide in the Storegga region, (the Y slide; Lawrence and Cartwright, 2009) started close to the inflexion point of the HHA.…”

How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!

“…This interpretation can probably be considered highly likely when stepping down occurs over a closed area in map view. A published example of such a behavior, in which fluid flow is considered as a likely mechanism by the authors, is the set of giant craters observed by Riis et al (2005) and Lawrence and Cartwright (2010) in the Møre Basin, midNorway margin. By contrast, ramp-and-flat geometries such as those shown by Bull et al (2009) appear to trend downslope, without a clear relationship to a potential hydrocarbon trap deeper down.…”

“…Sediment evacuation is usually observed through the collapse/foundering of a package of sediment below its initial locus of deposition, thereby occupying the space of series that are displaced or removed during the process. In the case documented by Riis et al (2005) and Lawrence and Cartwright (2010), biostratigraphic data from boreholes provided evidence of the stratigraphic inversion between the evacuated mass and the deposits through which evacuation had occurred. When no direct calibration (e.g., borehole) is available, diagnosis of evacuation requires evidence that the present-day position of the package interpreted as "foundered" is incompatible with normal sedimentary processes, such as erosion followed by infill, or en masse resedimentation (e.g., head scarp of a slump).…”

“…Kilometer-scale sediment evacuation under cover is a process that has been described in several contexts-for instance, chambers of mud volcanoes (e.g., Planke et al 2003;Stewart and Davies 2006;Deville 2009;Deville et al 2010), silica ooze "diapirism" (e.g., Riis et al 2005;Lawrence and Cartwright 2010), or hydrate pockmarks and collapsed pockmarks, their fossil counterpart (e.g., Sultan et al 2010;Imbert and Ho 2012). Sediment evacuation is usually observed through the collapse/foundering of a package of sediment below its initial locus of deposition, thereby occupying the space of series that are displaced or removed during the process.…”

Seafloor features and fluid migration in the Capel and Faust basins, offshore eastern Australia

“…Mega-pockmarks have been identified in various places around the world (e.g., in the North SeaeJudd and Hovland, 2007;Cole et al, 2000; on the West African marginePilcher and Argent, 2007; on the Norwegian margineLawrence and Cartwright, 2010; in the Gulf of CádizeLeón et al, 2010) and are generally related to fluid escape processes at the seafloor. These mega-pockmarks, when associated with strings of pockmarks, pockmark gullies and collapses, are interpreted to have formed through the interaction of slope failure and fluid escape processes.…”