Network of Offshore Records of Geology and Stratigraphy

NORLEX

Tumler Member [new]

Introduction

The Tumler Member is a new member developed in the upper part of the Kvitnos Formation in the Vøring Basin. It is characterised by sandstones and thin interbeds of mudstones of Late Cretaceous, Santonian age and can be distinguished from the Campanian, sandstone-rich, Spekkhogger Member developed in the overlying section of the type well 6707/10-1 by a thick (>100m) interval of mudstones.

The Tumler Member has a similar, but geographically more restricted distribution than the overlying Spekkhogger Member within the Vøring Basin, and is interpreted as being deposited under similar depositional processes i.e. mainly by episodic high density turbidity currents within a large scale submarine fan complex that developed in response to the initial phase of rifting between the north Atlantic region and the Norwegian Sea.

Name

English/ Norwegian and any previous names: The Tumler Member was originally assigned to the ‘Lysing Formation’ by the operatorP Norway in the type well 6707/10-1 in spite of it being recognised as being a younger age. The sand unit is recorded on the NPD fact pages as the lower part of the informal Delfin Formation.

Derivatio nominis: The name Tumler is derived from the Norwegian name for the bottle-nosed dolphin species Tursiops truncates. The species is a member of the sea going dolphin family (Delphinidae) and together with the killer whale Orca and is the most numerous dolphin species on a world basis. The species has a cosmopolitan distribution from tropical to cold temperate waters and its Norwegian distribution in the North Sea and southern parts of the Norwegian Sea form its most northerly extent.

Lithology

The Tumler Member mainly consists of sandstones with thin interbeds of mudstones and occasional limestone and dolomite stringers.

The sandstones are white - very light grey or medium light grey - dark grey, very fine to coarse, predominantly fine to medium, locally very coarse, clear to translucent quartz grains, friable, locally hard, predominantly loose, angular to sub-rounded, predominantly sub-angular to sub-rounded, moderately to well sorted, siliceous cement, locally weak to moderately calcareous or kaolinitic cement, rare dolomite cement, silty, locally with argillaceous matrix, common glauconite in parts, micaceous, locally with common plant fragments, pyritic, with poor to moderate visible porosity.

The mudstones are medium grey to brownish grey, rarely dark grey to olive black, soft to firm, moderately hard, amorphous to sub-blocky, silty, commonly grading to siltstone or as thin laminae with sandstones, carbonaceous, slightly micro-micaceous, traces of very fine disseminated pyrite, trace glauconite, non to slightly calcareous, commonly grading to siltstones.

The occasional dolomite stringers are light brown to dark yellow brown, olive grey in part, moderately hard to brittle, argillaceous, occasionally sandy, cryptocrystalline grading to limestone.

The minor limestones are very light grey, white, soft to firm, blocky, argillaceous or sandy.

Sample depository

Palynological preparations (organic matter depository)

Type well 6707/10-1: 4 slides from core samples covering the interval 4119.5m -– 4138.2m and 1 ditch cuttings sample at 4147m deposited at the NPD (OD preparations).

Reference well 6706/11-1: 9 slides from core samples (cores#3 and #4) covering the upper part of the Tumler Member over the interval 3108m – 3136m and 11 slides from ditch cuttings samples between 3146m – 3461m deposited at the NPD (RRI preparations).

Core photographs

Type well 6707/10-1: Core#10 covering the interval 4118mMD -4138.20mMD.

The deepest core (core#10) cut in the extensive coring programme of the Nyk High well 6707/10-1 recovered sandstones and minor mudstones of the (new) Tumler Member. These together with those of the overlying Spekkhogger Member (new herein) were collectively described by Kittilsen et al. (1999) as part of their ‘Lysing Formation’.

Reference well 6706/11-1: Cores#3 and #4 between 3107.5mMD - 3136.65mMDRKB.

6707/10-1, 4118-4123 m	6707/10-1, 4123-4128 m	6707/10-1, 4128-4133 m
6707/10-1, 4133-4138 m	6707/10-1, 4138-4138 m
6706/11-1, 3107-3212 m	6706/11-1, 3112-3117 m	6706/11-1, 3117-3122 m
6706/11-1, 3122-3127 m	6706/11-1, 3127-3132 m

Thickness

The Tumler Member has only been penetrated in a few wells located in the Vøring Basin to- date. The member varies in thickness from 302m e.g. 6707/10-1 (type section) to 368m e.g. 6706/11-1 based on released well data.

Geographical distribution

[Map] Sandstones of the Santonian Tumler Member lie below those of the Campanian Spekkhogger Member and have a similarly, but geographically more restricted distribution in the Vøring Basin based on the available well data. In wells 6607/5-1 and 6607/5-2 on the Utgard High and 6605/8-1 on the Fles North structure, time equivalent mudstones of the Kvitnos Formation are developed and provide an easterly and southern limit on the members distribution based on the available released well data. This distribution of the Tumler Member is more restricted than the overlying Spekkhogger Member where sandstones are present in well 6607/5-2, on the westerly flank of the Utgard High. The westerly limit of the member is undefined since the time equivalent section is below the well TD in well 6704/12-1, drilled on the Gjallar Ridge.

Occurrences of formation tops in wells

Type well

Well name: 6707/10-1
WGS84 coordinates: N 67°04'07.85, E 07°00'36.51 (figure 2)
UTM coordinates: 7440629.70 N 413490.42 E
UTM zone: 32
Drilling operator name: BP Norway Ltd.
Completion date: 23.07.1997
Status: P & A
Interval of type section (m) & thickness in type well (m): 4241m-3939m and 302m thickness.

Reference well

Well name: 6706/11-1
WGS84 coordinates: N 67°04'24.77, E 06°27'47.70 (figure 2)
UTM coordinates: 7442018.41 N 389745.19 E
UTM zone: 32
Drilling operator name: Den norske stats oljeselskap a.s.
Completion date: 22.03.1998
Status: P & A
Interval of reference section (m) & thickness in reference well (m): 3469m - 3101m and 368m thickness.

Upper and lower boundaries

Upper Boundary

In the type well 6707/10-1, the top of the Tumler Member is taken at a downward change below a thick interval of mudstones within the lowermost part of the Nise Formation into an interbedded sequence of sandstones and mudstones. The change is transitional in the type well 6707/10-1 at 3939m MD RKB and the sandstone rich section is slightly deeper in the section at 3956mMD. The upper boundary is therefore marked by a decrease in gamma-ray and density log values and an increase in sonic velocities.

In the reference well 6706/11-1, the upper boundary is marked by an abrupt shift and marked decrease in gamma-ray values, presumably in response to rapid abandonment of the sand system.

Lower Boundary

The base of the Tumler Member is normally marked by a sharp downward change from sandstones to mudstones of the underlying Kvitnos Formation. In the type well 6707/10-1, it is defined on logs by a sharp downward increase in gamma-ray values, a decrease in sonic velocity and a sharp positive separation between neutron and density logs.

Well log characteristics

[Figure] In the type well 6707/10-1, the Tumler Member is characterised by at least three discrete sandstone units with blocky log profiles. The sandstone beds vary from approximately 5- 15m thickness. The mudstones generally form thin interbeds with the sandstones or more infrequently as discrete units with minor sandstone interbeds up to 15m thick. In the reference well 6706/11-1 the Tumler Member is mud-prone and characterised by a more finely serrate gamma-ray log profile although sandstone beds are more significant in the uppermost part.

Type seismic section

Biostratigraphy

The Tumler Member lies within a ranging middle-late Santonian age (Zone 25) being above the dinocyst markers LCO Heterosphaeridium difficile and LCO Chatangiella ‘spinosa’.

The upper boundary is developed below the LO Spongodinium cristatum. Planktonic foraminifera are generally absent in this member although the Santonian marker Whiteinella baltica is present in the overlying mudstones in association with the calcareous benthonic foraminifera Gavelinella-EEponides spp. and radiolarians. Probable reworking of early Santonian (or older) palynomorphs in association with positive recycled Cenomanian taxa was recorded in the reference well 6706/11-1.

Age

Late Cretaceous, middle – late Santonian (Zone 25). The Santonian Tumler Member can be distinguished from the overlying Campanian-aged Spekkhogger Member by a thick (approx. 100m) mudstone unit with radiolarians e.g. 6706/11-1.

Correlation

[Figure] The sandstones of the Tumler Member pass laterally into mudstones of the Kvitnos Formation. The Tumler Member is part of the K85 sequence of Vergara et al. (2001; as indicated by their chronostratigraphic ‘Wheeler-type’ well correlation, figure 6) and within the upper part of the K60 sequence of Færseth and Lien (2002) and Lien (2005).

Depositional environment

In the type well 6707/10-1, core #10 was taken within the Tumler Member as part of the extensive coring programme undertaken of the overlying Spekkhogger Member and the results are documented by Kittilsen et al. (1999). They described the whole sedimentary package collectively as being deposited under similar depositional processes and mainly by episodic high density turbidity currents or by linked debris flows which evolved from the tails of the turbidite flows within a large scale submarine fan complex. Although not specific to any particular cored interval, Kittilsen et al. (1999) observed that there was little evidence of erosion of the turbidite sandstones into the background mudstones suggesting the turbidite flows were largely unconstrained in this part of the submarine fan and predicted them to occur as laterally extensive sheet sands.

The subordinate, sand laminated mudstones and bioturbated background mudstones were considered to be of turbidity or hemipelagic origin. These mudstones in core yield a low diversity, deep-water agglutinated foraminiferal microfauna (DWAF) that are dominated by simple tubular forms and suggest a deep marine, bathyal palaeoenvironment with poorly oxygenated bottom conditions.

Remarks

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.

Gradstein, F., Kaminski, M.A. and Agterberg, F.P. 1999. Biostratigraphy and paleoceanography of the Cretaceous seaway between Norway and Greenland. Earth-Science Reviews, 46, 27-98.

Kittilsen, J. E., Olsen, R.R., Marten, R. F., Hansen, E.K. and Hollingworth, R.R. 1999. The first deepwater well in Norway and its implications for the Upper Cretaceous Play, Vøring Basin. In: Fleet, A.J. and Boldy, S.A.R. (eds) Petroleum Geology of Northwest Europe: Proceedings of the 5th Conference, Petroleum Geology 1986 Ltd. Geological Society, London, 1, 275- 280.

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.

Morton, A.C. and Grant, S. 1988. Cretaceous depositional systems in the Norwegian Sea; heavy mineral constraints. AAPG Bulletin, 82(2), 274-290.

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