Balder Formation

updated to follow: Stratigraphic Guide to the Rogaland Group, Norwegian North Sea. Harald Brunstad, Felix M. Gradstein, Jan Erik Lie, Øyvind Hammer, Dirk Munsterman,  Gabi Ogg, and Michelle Hollerbach. Newsletter on Stratigraphy, vol 46/2 pp137-286, 2013.

Rogaland Group

Members of the Formation

Odin Member | Radøy Member |


Unit definition

The Balder Formation is the uppermost formation of the Rogaland Group (Fig. 125) .

Fig. 125. Lithostratigraphic summary chart of the Balder Formation (color) with members.


The Balder Formation name was given by Deegan and Scull (1977) to the tuffaceous shales above the Sele Formation in the North Sea.

Derivatio nominis

The formation was named after the Balder Field in Norwegian blocks 25/10 and 25/11. Balder was a son of Odin, and one of the most famous gods in Norse mythology.

Type well

Norwegian well  25/11-1 (Fig. 126) from 1780 to 1705 m (Deegan and Scull 1977), coordinates N 59°10'57.39", E 02°24'28.18". Cores.

Fig. 126. Well 25/11-1 Composite log Rogaland Group. Stratigraphic position of the Balder Formation is outlined in stratigraphic column to the right.

Reference wells

Norwegian well 30/2-1 (Fig. 127) . Depth 1993 to 1917 mRKB. Coordinates N 60°52'05.42", E 02°38'49.16". Cores: Core 1 and 2.

Norwegian well 15/9-17 (Fig. 128) . Depth 2253 to 2204 m. Coordinates N 58°26'44.19", E 01°56'53.58". No cores.

Fig. 127. Well 30/2-1 Composite log Rogaland Group. Stratigraphic position of the Balder Formation is outlined in stratigraphic column to the right.

Fig. 128. Well 15/9-17 Composite log Rogaland Group. Stratigraphic position of the Balder Formation is outlined in stratigraphic column to the right.


The Balder Formation is composed of laminated light to dark grey, fissile shales with interbedded grey, green and buff, volcanic tuffs (Fig. 129) . The formation has occasional stringers of limestone, dolomite and siderite and is often pyritic. Tuffs are sometimes sandy. In the lower part of the formation, the mudstone is well laminated with light to medium grey indurated silicious mudstone alternating with medium to dark grey soft, fissile mudstone. In the upper part of the formation, the mudstone is soft and poorly laminated. The tuffs mostly occur as thin strata, up to a few centimeters in thickness, with sharp bases, commonly normal graded, and are interpreted as undisturbed ash fall. In cores from Viking Graben wells, structureless units, tens of centimeters thick, displaying dewatering structures are observed. These beds are interpreted as resulting from gravity flow re-sedimentation of primary air-fall tuff (Knox & Holloway, 1992; Malm et al., 1984).

Sandstones units named the Odin Member and the Radøy Member are locally present in the Balder Formation (Fig. 1 and Fig. 132) .

Fig 1: Location map of the Members of the Balder Formation.

A core description log example is shown in Fig. 130.

Fig. 129. Core photo from Balder Formation well 25/7-5. Drilled by Norsk Hydro. Photo from NPD Fact Pages at

Fig. 130. Core description log from well 25/7-5. Section covers upper parts of the Lista Formation with upper parts of the Heimdal Member, the Sele Formation with sandstones belonging to Hermod Member, and most of the Balder Formation.

Wire line log characterization

The shales of the Balder Formation are generally characterized by low gamma readings and high sonic reading. Spikes with high acoustic velocities are frequently seen, and can be related to thin beds or nodules of carbonate or cemented tuffs.

Upper Boundary

The top of the Balder Formation is taken at the top of a prominent bell shape, often expressed as base of a high gamma peak and a low acoustic trough. The lower tuff rich parts of the lower Balder Formation can often be distinguished as a zone or a "belly" of higher acoustic velocities.

Lower boundary

From wire line logs the Balder Formation is characterised by a bell shaped log response. At the base a shift from high gamma readings and low acoustic velocities in the Sele Formation to lower gamma readings and higher acoustic velocities in the Balder Formation is seen. Lithologically an abrupt increase in tuffaceous interbeds from Sele upwards into the Balder Formation can be seen.


The Balder Formation is 75 m thick in the type well. Generally its thickness varies from less than 20 m to more than 100 m. Normally it is between 40 and 60 m. Sandstone units belonging to Balder of over 200 m occur in the central and northern parts of the Viking Graben; maximum thickness is 285 m, including the Odin Member.

Seismic characterization

Top Balder reflector

The top of the Balder Formation (Top B2) is often defined at a positive acoustic impedence contrast that varies in strength. It is often weak and difficult to pick.

Base Balder/Top Sele reflector

The base of the Balder Formation (Near Top S2/Base B1) is often characterised by a marked negative acoustic impedence.

Top Tuff zone - The Tuff Marker (Top B1)

The top of the Balder tuff rich zone (Top of zone B1) is a pronounced seismic surface that can be regionally identified. It is characterised by a positive amplitude event and the velocities increase downwards in Zone B1 relative to B2 related to a downward increase in silica cementation (Knox & Holloway, 1992). This seismic event is often more distinct and easier to pick than the Top Balder Formation, and is sometimes mistaken for the true top Balder Formation.


Lower Eocene (Early Ypresian).


The upper boundary of the Balder Formation is slightly below the top of dinocyst Deflandrea oebisfeldensis at the upper level of frequent D. oebisfeldensis. In terms of palynology the base of the Balder Formation is at the top of the Acme of Cenodinium wardenense. Characteristic shelly microfossils are pyritized pillbox-shaped diatoms belonging in Fenestrella antiqua, ranging throughout the Balder unit, and not occurring stratigraphically higher. The Balder Formation is assigned to Zone NSR3 - Fenestrella antiqua, of Gradstein & Bдckstrцm (1996), and to dinocysts zones D5b - D7a in Luterbacher et al. (2004), of Early Ypresian, earliest Eocene age.

Some diagnostic microfossils of the Balder formation are shown in Fig. 131.

Fig. 131. Some diagnostic microfossils of the Balder Formation. Left: Deflandrea oebisfeldensis Alberti 1959b. Dorsal view. Holotype dimensions: pericyst length = 150 µm, pericyst width = 88 µm., Right: Cerodinium wardenense (Williams and Downie 1966c) Lentin and Williams 1987. Dorsal view. Holotype dimensions: pericyst length = 57 µm, pericyst width = 46 µm, endocyst length = 36 µm, endocyst width = 43 µm. From the ODP Drilling Program at

Correlation and subdivision

The Balder Formation can be subdivided into a lower (B1) and an upper (B2) unit (Knox & Holloway, 1992). The base of the B1 zone is taken at the common Ceratopsis wardenense. B1 is the lower and older zone, and is generally more tuffaceous than the B2 zone. Due to sparse biostratigraphic diagnostic criterias internally, the sub division into the two zones is based on wire line log pattern recognition. The B1 zone has higher velocity and lower gamma readings than the upper parts of B2, and often there is a pronounced transition into lower values gamma and sonic log values going into the B2 zone. The top of the B2 zone is picked near the top of the bell shape defining the Balder Formation from wire line logs, coinciding with the common Deflandrea oebisfeldensis and common Hystrichospheridium tubiferum events. Internally in the Balder Formation two sandstones are found, the Odin Member sandstones with a distribution in western areas of the Norwegian North Sea and the Radøy Member with a distribution in the north-eastern areas of the North Sea.

Geographic distribution

The Balder Formation is present in most of the areas where Paleocene sediments are also present. Only along the eastern flanks where Paleocene sediments are partly truncated, the Balder Formation is partly or completely eroded. The distribution of the Balder Formation with its respective members, is shown in Fig. 132.

Fig. 132. Distribution of the Balder Formation and its sandstone members.

Depositional environment, volcanic activity and deposition of tuffs

The North Sea basin restriction that started with the deposition of the Sele Formation continued through the deposition of the Balder Formation. The Balder Formation was deposited in a generally deep marine, anoxic environment, mainly as hemipelagic sediments with frequent income of tuffaceous rain caused by ash falls from volcanic activity.

There was probably more than one volcanic source for the extensive tuffaceous components of the sediment, but in general they seem to have been connected to volcanic eruptions associated with the onset of break up of the Greenland and European continents. The igneous activity in the North Atlantic shows a wide age-range, but peaks between 55 and 50 Ma (Torsvik et al, 2002), spanning syn rift and a continental break-up phase. Large amounts of tuffaceous ash material were probably introduced into the atmosphere and distributed over vast areas of North Europe during the rift late rift phase.

The delicate lamination in the lower, tuff-rich mudstones is probably related to varying proportions of diatoms, reflecting seasonal variations in productivity (Knox & Holloway, 1992). The upward change from tuff-rich to tuff-poor mudstone at the B1/B2 boundary is believed to reflect a rise in sea-level combined with a decrease in pyroclastic activity. The trend of upwards-increasing gamma values in the B2 mudstones is interpreted as reflecting continued deepening (Knox & Holloway, 1992), and gradually decreased tuffaceous input.

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