Nebbhval Member [new]

updated to follow: Stratigraphic Guide to the Cromer Knoll, Shetland and Chalk Groups of the North Sea and Norwegian Sea. Felix M. Gradstein & Colin C. Waters (editors), Mike Charnock, Dirk Munsterman,  Michelle Hollerbach, Harald Brunstad, Øyvind Hammer & Luis Vergara (contributors). Newsletter on Stratigraphy, vol 49/1 pp71-280, 2016

Shetland Group, Nise Formation

Introduction

The Nebbhval Member is a local member of the Nise Formation characterised by sandstones and interbedded mudstones developed in the south-western part of the Vestfjorden Basin.

Timing suggests that the Nebbhval Member is related to the same tectonic episode that introduced the thick Spekkhogger Member sandstones into the deeper Vøring Basin. This has been attributed to the initial phase of Campanian-Paleocene rifting that led to the continental separation between the North Atlantic and the Norwegian Sea.

Whereas the sandstones of the Spekkhogger Member are considered to have been derived from the north or northeast, the sandstones of the Nebbhval Member are probably derived from the Norwegian mainland. The Nebbhval sands have been assigned to Zone NCF16, dated as Late Cretaceous, earliest Campanian age

Name

English/ Norwegian and any previous names: In the type well 6610/3-1, the Nebbhval Member was noted informally as an 'intra Nise sandstone' by the operator Statoil and is currently indicated as a unit without a formal name on the NPD fact pages.

Derivatio nominis: Nebbhval is the Norwegian name for the northern bottlenose whale species Hyperooden ampullatus. This is a toothed whale up to 10m size that can be found in increasing numbers in the deeper water areas of the Norwegian Sea around Iceland and Jan Mayen in addition to west of Svalbard and in the North Atlantic.

Lithology

The Nebbhval Member consists of interbedded sandstones and mudstones.

The sandstones are light olive grey to olive grey, clear to transparent or translucent quartz grains, fine to medium, occasionally medium or coarse to very coarse in places, moderately sorted, angular to sub-rounded, white to light grey matrix, moderate calcareous cement, friable to moderately hard, occasionally micaceous with common glauconite.

The mudstones are medium dark grey to olive grey, predominantly firm, moderately hard, sub-fissile to blocky, micro-micaceous, micro-pyritic, slightly or moderately calcareous and sandy or silty in parts.

Thickness

The Nebbhval Member varies in thickness from 24 m, e.g. 6610/3-1 (type section), to 40 m.

Geographical distribution

The Campanian Nebbhval Member is restricted to the Nordland III area located in the south-westerly part of the Vestfjord Basin in Quadrant 6610 where it varies from 24m to 40m based on released well data.

Sample depository

Palynological preparations (organic matter depository)

Type well 6610/3-1: 7 slides from 6 core samples and 1 swc sample covering the interval 2293.4m - 2318m available at the NPD (Statoil preparations).

Core photographs

Type well 6610/3-1: cores #3 to #5 covering the interval 2292m - 2313.9m.

6610/3-1, 2292-2296 m
6610/3-1, 2296-2300 m
6610/3-1, 2300-2301 m
6610/3-1, 2301-2305 m

6610/3-1, 2305-2306 m
6610/3-1, 2305-2309 m
6610/3-1, 2309-2313 m
6610/3-1, 2313-2313 m

 

Type well

Well name: 6610/3-1
WGS84 coordinates: N 66°55'29.70, E 10°54'06.28
UTM coordinates: 7424470.29 N 583170.4 E
UTM zone: 32
Drilling operator name: Den norske stats oljeselskap a.s.
Completion date: 17.02.1993
Status: Suspended, re-entered later.
Interval of type section (m) & thickness in type well (m): 2306 m (2309.43 m uncorrected core depth) - 2282 m, and 24 m thickness.

Click for large version (PDF)

Reference well

None designated.

Upper and lower boundaries

Upper Boundary

In the type well 6610/3-1 the top of the Nebbhval Member is taken at a downward change from mudstones of the Nise Formation to sandstones with interbedded mudstones. It is marked on wireline logs by a sharp downward decrease in gamma-ray values and increase in sonic velocity and resistivity values.

Lower Boundary

The base of the Nebbhval Member is defined by a downward increase in gamma-ray values and an associated decrease in average resistivity values reflecting the change from sandstones to mudstones. In the type well, 6610/3-1, there is only a slight increase in average sonic velocities at 2306 m MD, and the downward increase in average density values is a few metres lower at 2313 m MD.

Well log characteristics

In the type well 6610/3-1 the log character is irregular to serrate reflecting the heterolithic, interbedded nature of the Nebbhval Member.

Biostratigraphy

The Nebbhval Member is located between the dinocyst markers LCO Trithyrodinium suspectum and LO Spongodinium 'cristatum' and is earliest Campanian age.

Deeper in the section is the LO Valensiella reticulata. Within this member is an influx of Chatangiella bondarenkoi that may be useful for local correlation.

Age

Late Cretaceous, earliest Campanian. The base of the Nebbhval Member lies close to the Santonian /Campanian boundary.

Correlation

The sandstones and interbedded mudstones of the Nebbhval Member pass laterally into mudstones of the Nise Formation.

The Nebbhval Member is a time equivalent of the oldest part of the Spekkhogger Member developed in the Vøring Basin and part of the K85-K90 sequence of Vergara et al. (2001) and K70 sequence of Færseth and Lien (2002) and Lien (2005). These sandstones were probably generated during the same Campanian rifting event associated with the Spekkhogger Member although they have a different source direction towards the Norwegian mainland.

Depositional environment

There is limited published data available on the depositional setting of the Nebbhval Member. The sandstones are interpreted as part of a sand prone slope fan, presumably with a source from the Norwegian mainland (see palaeogeography of Vergara et al., 2001, figure 11).

The microfaunas, recovered from cores in the type section 6610/3-1 within this member, are dominated by abundant, simple, tubular, agglutinated foraminifera e.g. Rhabdammina spp. This suggests a deep water, bathyal palaeoenvironment and bottom conditions with lower oxygen.

References

Færseth, R. and Lien, T. 2002 Cretaceous evolution in the Norwegian Sea - a period characterized by tectonic quiescence. Marine and Petroleum Geology, 19, 1005 -1027.

Lien, T. 2005. From Rifting to drifting: effects on the development of deep-water hydrocarbon reservoirs in a passive margin setting, Norwegian Sea. Norwegian Journal of Geology, 85, 319-332.

Vergara, L., Wreglesworth, I., Trayfoot, M., Richardsen, G. 2001. The distribution of Cretaceous and Paleocene deep-water reservoirs in the Norwegian Sea basins. Petroleum Geoscience, 7, 395-408.

home previous page