Kvitskjæving 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, Kvitnos Formation

Introduction

The Kvitskjæving Member is introduced for a unit of interbedded sandstones and mudstones of Santonian age within the Kvitnos Formation developed in the south-west Vestfjorden Basin in block 6610/3 (Nordland III area) of the Norwegian Sea. Limited published data are available on the depositional setting of these sandstones. These sediments are considered to have been deposited mainly as turbidites within a submarine fan system in a deeper marine, outer shelf to upper bathyal paleoenvironment.

Name

English/ Norwegian and any previous names In the type well 6610/3-1, the interval was informally designated ‘Lysing Sandstone I’ by the operator Statoil on the final completion log.

Derivatio nominis: Kvitskjæving is the Norwegian name for the Atlantic white-sided dolphin Lagenorhynchus albirostris and appropriately, a close relative of the Kvitnos (white-beaked dolphin). It is endemic to the North Atlantic area. In Norwegian waters, the species is seldom found north of Trondheimsfjorden and generally in water depths between 40-250m related to the continental shelf.

Lithology

The Kvitskjæving Member consists of interbedded sandstones and mudstones.

The sandstones are medium grey, clear to transparent quartz, fine to medium, occasionally coarse, poor to moderately sorted, sub-angular to sub-rounded and calcite cemented, moderately hard, sometimes argillaceous, micaceous and slightly glauconitic.

The mudstones are light olive grey to black, firm to moderately hard, blocky, partially silty to sandy, micro-micaceous to micaceous, micro-pyritic, carbonaceous, glauconitic and moderately calcareous, poor visible porosity.

Thickness

The Kvitskjæving Member varies in thickness from 9m to 39m based on released well data.

Geographical distribution

The Kvitskjæving Member is locally developed in the south-westerly part of the Træna Basin and Vestfjorden Basin (Quadrants 6609 and 6610). Based on released well data it has a maximum thickness of 39m in the type well 6610/3-1. On the Nordland Ridge and in wells 6610/7-1 and 6610/7-2 located in the Helgeland Basin on the Trøndelags Platform to the south, the equivalent section is represented by an unconformity. The northerly extent of the member away from wells 6609/5-1 and 6610/3-1 (original holes and sidetracks) is not determined due to a lack of well control in the Nordland VI area and the time-equivalent section in well 6710/10-1 being below the well TD depth.

Sample depository

Palynological preparations (organic matter depository)

Type well 6610/3-1: 4 slides from core samples deposited at the NPD covering the interval 2512.2m – 2530.4m (Statoil preparations). Additional micropalaeontological and palynological slides have been prepared by Robertson Research Int. Ltd. and PetroStrat in the course of non propriety multi-well studies.

Core photographs

In the type well 6610/3-1 core#6 interval 2514m-2531.47m represents the middle part of the member.


6610/3-1, 2514-2518 m
6610/3-1, 2518-2522 m
6610/3-1, 2522-2526 m

6610/3-1, 2526-2530 m
6610/3-1, 2530-2531 m 		 

 

Type well

Well name: 6610/3-1
WGS84 coordinates: N 66°55'29.70, E 10°54'06.28 (figure 2)
UTM coordinates: 7424470.29N 583170.04 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): 2543m - 2504m and 39m thickness.

 

Logs of the type well 6610/3-1 (click to enlarge)

 

Reference well

None designated. The member was also penetrated in the re-drilled well 6610/3-1 R but this well provides no additional information on the characteristics of the member compared to the original hole. In well 6609/5-1 the member is only 9m thick.

Upper and lower boundaries

Upper Boundary

The top of the Kvitskjæving Member is represented by a transition from predominantly argillaceous sediments of the overlying (and encompassing) Kvitnos Formation to a sequence of interbedded sandstones and mudstones. In the type well 6610/3-1 this boundary is represented by a gradual decease in gamma-ray, and increase in sonic velocity values. The upper boundary is better defined on resistivity logs in the type well where there is a downward increase in resistivity values.

Lower Boundary

In the type well 6610/3-1, the base of the Kvitskjæving Member is marked by a downward gradual change from interbedded sandstones and mudstones to more argillaceous sediments of the underlying Kvitnos Formation. It is characterised on logs by a downward increase in gamma-ray values (Figure 3.28), and a marked decrease in resistivity values but only a weak increase decrease in average sonic velocities.

Well log characteristics

The member is characterised by a serrate gamma-ray log profile reflecting the interbedded sandstone and mudstone content of the unit. The member shows funnel- and bell-shaped profiles in response to the transitional nature of both the lower and upper boundaries.

Type seismic section

Location of section

ST 9104-437 and SP. 335 (well 6610/3-1)

 

Biostratigraphy

The Kvitskjæving Member is developed below LO Whiteinella baltica and LO Stensioeina granulata polonica and between the LO and LCO Chatangiella ‘spinosa’ suggesting an early Santonian age.

The sporadic records of the Coniacian dino-cyst Florentina deanei above this member in the type well are considered reworked.

In the cored interval of the type well 6610/3-1 Hystrichosphaeridium difficile shows a marked increase in numbers within the middle part of the member that maybe useful for correlative purposes.

Age

The member is assigned to an early Santonian age, Late Cretaceous.

Correlation

The interbedded sandstones and mudstones of the Kvitskjæving Member pass laterally into the mudstones of the Kvitnos Formation.

The member is time equivalent to some minor and un-named lower Santonian sands penetrated in the deeper wells in the Vøring Basin e.g. Vema Dome well 6706/11-1 (3737m - 3750mMD RKB).

Depositional environment

Limited published data are available on the depositional setting of this member. The sandstones are considered to have been largely deposited as turbidites within a submarine fan system in a deep marine, outer shelf to upper bathyal paleoenvironmental setting. A simple agglutinated foraminiferal assemblage was observed in cores of the type well 6610/3-1 e.g. at 2528.65mMD, particularly with Rhabdammina, in agreement with above paleoenvironmental interpretation.  Needle fragments of the planktonic mollusc Inoceramus. Pyritised diatoms and nodosariid - calcareous benthic foraminiferal species are rare, e.g. smooth Lenticulina and Nodosaria spp.

Remarks

This member is stratigraphically younger than the Lysing Member, assigned a Coniacian age. It was referred to informally as the ‘Lysing Sandstone I’ by the operator on the final completion log of the type well 6610/3-1. On the NPD fact pages, the Kvitskjæving Member is the upper one of two units assigned informally to the Lysing Formation, separated by the Lange Formation. The latter is incorrect use of lithostratigraphy.

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.

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