Silica diagenesis in <scp>C</scp>enozoic mudstones of the <scp>N</scp>orth <scp>V</scp>iking <scp>G</scp>raben: physical properties and basin modelling

Wrona, Thilo; Jackson, Christopher; Huuse, Mads; Taylor, Kevin G.

doi:10.1111/bre.12168

Cited by 17 publications

(26 citation statements)

References 71 publications

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“…The co-existence of silica diagenesis and polygonal fault systems in other basins (Davies FIGURE 2 | (a) Simplified structural map of the North Viking Graben, North Sea, highlighting major faults; the Horda, East Shetland Platform and Utsira High (after Holgate et al, 2013) al., 2006) has led some authors to suggest a genetic link between polygonal faulting and diagenesis (Shin et al, 2008;Davies et al, 2009;Cartwright, 2011;Davies and Ireland, 2011). It is thus worth noting that the transformation from opal-A to opal-CT probably migrated upward through the lower Hordaland Group, initiating in the Middle or Late Eocene and continuing, potentially, to the present (Wrona et al, 2017a). Apart from the opal-A/CT transformation, the Hordaland Group shows no other significant compositional and diagenetic changes affecting physical rock properties (Wrona et al, 2017b).…”

Section: Geological Settingmentioning

confidence: 99%

“…This study uses well data from exploration well 35/10-1 and 35/11-5, which constrain the age, composition, and diagenetic state of the Hordaland Group mudstones in the North Viking Graben (Wrona et al, 2017a). Moreover, we use checkshot data from exploration well 31/2-8 to convert a sub-volume of the 3-D seismic volume from time-to depth domain ( Figure S1).…”

Section: Data Well Datamentioning

confidence: 99%

“…We also map a high-amplitude seismic reflection produced by the opal-A/CT transformation (Wrona et al, 2017a), calculating the coherency attribute (sensu Bahorich and Farmer (1995), along this horizon to highlight the geometry and extent of the polygonal fault system (Figure 2b). Because the polygonal fault system contains >1,500 faults in the study area (Figure 2b), we select a representative sub-volume (7.5 × 6.2 × 1.8 km) in which to conduct a quantitative geometric and displacement analysis (Figure 3).…”

Section: Seismic Interpretationmentioning

confidence: 99%

“…Muraoka and Kamata, 1983), whereas 64% (88 out of 137) display asymmetric, b-type profiles, with the bulk of displacement occurring below their mid-point (Figures 8D-F). Faults with b-type profiles show the highest displacements (up to 200 m) in the lower Hordaland Group, i.e., strata that were likely undergoing the opal-A/CT transformation (Wrona et al, 2017a; Figure 8F). Whereas fault heaves are relatively high (up to 200 m) (Figure 8E), throws are only slightly higher (up to 50 m) in these strata than observed at shallow depths ( Figure 8D).…”

Section: Fault Displacementmentioning

confidence: 99%

“…where g is the gravitational acceleration (9.81 m s −2 ), ρ s is the average (bulk) density of the lower Hordaland Group (∼2,000 kg m −3 ; Wrona et al, 2017a) and z is the depth (0-1 km). The pore fluid pressure can be expressed as the sum of the hydrostatic (p h ) and excess pore fluid pressure (p e ):…”

Section: Fault Mechanicsmentioning

confidence: 99%

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Kinematics of Polygonal Fault Systems: Observations from the Northern North Sea

Wrona¹,

Magee²,

Jackson³

et al. 2017

Preprint

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Layer-bound, low-displacement normal faults, arranged into a broadly polygonal pattern, are common in many sedimentary basins. Despite having constrained their gross geometry, we have a relatively poor understanding of the processes controlling the nucleation and growth (i.e., the kinematics) of polygonal fault systems. In this study we use high-resolution 3-D seismic reflection and borehole data from the northern North Sea to undertake a detailed kinematic analysis of faults forming part of a seismically well-imaged polygonal fault system hosted within the up to 1,000 m thick, Early Palaeocene-to-Middle Miocene mudstones of the Hordaland Group. Growth strata and displacement-depth profiles indicate faulting commenced during the Eocene to early Oligocene, with reactivation possibly occurring in the late Oligocene to middle Miocene. Mapping the position of displacement maxima on 137 polygonal faults suggests that the majority (64%) nucleated in the lower 500 m of the Hordaland Group. The uniform distribution of polygonal fault strikes in the area indicates that nucleation and growth were not driven by gravity or far-field tectonic extension as has previously been suggested. Instead, fault growth was likely facilitated by low coefficients of residual friction on existing slip surfaces, and probably involved significant layer-parallel contraction (strains of 0.01-0.19) of the host strata. To summarize, our kinematic analysis provides new insights into the spatial and temporal evolution of polygonal fault systems.

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Section: Geological Settingmentioning

confidence: 99%

Section: Data Well Datamentioning

confidence: 99%

Section: Seismic Interpretationmentioning

confidence: 99%

Section: Fault Displacementmentioning

confidence: 99%

Section: Fault Mechanicsmentioning

confidence: 99%

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Kinematics of Polygonal Fault Systems: Observations from the Northern North Sea

Wrona¹,

Magee²,

Jackson³

et al. 2017

Preprint

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Impact of silica diagenesis on the porosity of fine‐grained strata: An analysis of Cenozoic mudstones from the North Sea

Wrona

Taylor

Jackson

et al. 2017

Geochem Geophys Geosyst

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Silica diagenesis has the potential to drastically change the physical and fluid flow properties of its host strata and therefore plays a key role in the development of sedimentary basins. The specific processes involved in silica diagenesis are, however, still poorly explained by existing models. This knowledge gap is addressed by investigating the effect of silica diagenesis on the porosity of Cenozoic mudstones of the North Viking Graben, northern North Sea through a multiple linear regression analysis. First, we identify and quantify the mineralogy of these rocks by scanning electron microscopy and X‐ray diffraction, respectively. Mineral contents and host rock porosity data inferred from wireline data of two exploration wells are then analyzed by multiple linear regressions. This robust statistical analysis reveals that biogenic opal‐A is a significant control and authigenic opal‐CT is a minor influence on the porosity of these rocks. These results suggest that the initial porosity of siliceous mudstones increases with biogenic opal‐A production during deposition and that the porosity reduction during opal‐A/CT transformation results from opal‐A dissolution. These findings advance our understanding of compaction, dewatering, and lithification of siliceous sediments and rocks. Moreover, this study provides a recipe for the derivation of the key controls (e.g., composition) on a rock property (e.g., porosity) that can be applied to a variety of problems in rock physics.

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