Seismic geomorphology of submarine landslides in the Chalk Group of the Danish Central Graben: implications for reservoir potential

Abstract

This study documents a variety of deposits created by submarine landslides within the Upper Cretaceous to lowermost Palaeocene Chalk Group in the Danish Central Graben and investigates the impact of remobilization on porosity. Improved visualization of the landslides in 3D seismic data compared to previous studies was facilitated by better seismic data quality for the Chalk Group, the availability of a large stack of stratigraphy-consistent horizons, and the use of spectral decomposition data. The illustrated examples are chosen to reflect the spectrum of deformation styles seen in the chalk and are all having a well penetrating the affected succession. They include a large collapse (375 km2) of an inversion ridge within the Kraka and Gorm formations, a field of large slide blocks (100–1000 m, 10–26 m) of likely lowermost Danian age embedded in the uppermost Ekofisk Formation, a debris flow system within the uppermost Tor Formation likely originating from the Ringkøbing-Fyn High, and fine-grained bottom current sediment waves within the lowermost Danian Ekofisk Formation. In general, porosities are higher (10-25 porosity units) in the remobilized chalk compared to time-equivalent pelagic chalk in nearby reference wells. In earlier studies this has been linked to lack of bioturbation (resulting in limited grain repacking) in the remobilized chalks due to high sedimentation rates, resulting in a relative open fabric during initial burial. In contrast, surrounding and covering pelagic deposits could be much more effectively bioturbated leading to tighter grain packing during burial. The insights of this study help in seismic characterization of mud-grade carbonate oozes and find important applications reservoir modelling of mud-grade carbonate reservoirs (also in the light of carbon capture and storage), and in palaeo-reconstructions of pelagic seafloors since submarine landslides provide kinematic indicators.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5830839

The Hidden Giant: How a rift pulse triggered a cascade of sector collapses and voluminous secondary mass‐transport events in the early evolution of Santorini

“…Horizons h4, h5 and h6 (green, orange, and blue lines) are the basal reflectors of the corresponding units (U4‐U6) as established in Preine et al (2022). Seismic facies based on concepts of Mitchum et al (1977) and interpretation based on Bull et al (2009) and Smit and Stemmerik (2022)…”

“…This lateral variation is typical for MTDs and reflects the transition from proximal slumps of granular material into more disintegrated, water‐saturated, cohesive debris flows and turbidity currents in the distal domain (e.g. Bull et al, 2009; Smit & Stemmerik, 2022; Watt et al, 2012, 2019, 2021). This is observed both at the west (Figure 3a) and to the east (Figures 4–6) of Santorini.…”

Regional assessment of gravity‐driven deformation offshore Namibia (West Africa)—Styles, distribution and controlling factors

“…A wealth of literature provides analysis of slope failure events based on field (e.g., Alsop et al, 2017, 2020; Alves & Lourenco, 2010; Butler & McCaffrey, 2010; Farrell & Eaton, 1987; Martinsen, 1989; Ogata et al, 2012; Poprawski et al, 2021; Strachan, 2002; Woodcock, 1979) and geophysical data (e.g., Alves, 2015; Bull et al, 2009; Frey‐Martínez et al, 2005; Gee et al, 2006; Jackson, 2011; Moscardelli et al, 2006; Nugraha et al, 2020; Sawyer et al, 2009; Smit & Stemmerik, 2022; Wu et al, 2021). Comparably, little research has been carried out at a regional scale to understand how lateral variability of margin characteristics can affect gravity‐driven processes (e.g., Moscardelli & Wood, 2016; Naranjo‐Vesga et al, 2020; Völker et al, 2012).…”