Skade Member

Hordaland Group, Lark Formation


Named after the female giant in Norse mythology, the wife of the god Njord.

Well type section

Norwegian well 24/12-1 from 1007 to 851 m, coordinates N 59°02'29.80", E 01°52'57.93" (Figure xx). No cores.

Well reference section

Norwegian well 15/9-13 from 1224 to 1143 m, coordinates N 58°22'25.96", E 01°56'02.86" (Figure xx). No cores.


Up to 300 m in the southern Viking Graben (e.g. in well 16/1-4 ). The thickness is 156 m in the type well and 81 m in the reference well. The formation shows a general eastward thinning.


The Skade Member consists of alternating sandstones and thinner claystones. The sandstones are clear to light grey, usually fine to medium-grained and occasionally coarse-grained. The sand grains are subrounded to rounded, and moderately to well sorted. Marine fossil fragments, including shell debris, and mica and abundant glauconite are present. In some wells the claystones are silty. Towards the southern pinchout of the Skade sands (Figure xx) the formation comprises a stacked succession of coarsening- upward units, each up to 50m thick.

While in the Viking Graben the typical Skade sands are present, toward Tampen the lithology becomes more muddy, and grades laterally in the xxxxx formation.

Basal stratotype

The lower boundary is marked by a general coarsening upwards trend together with a general decrease in gamma-ray response. The underlying upper Oligocene strata comprise a predominantly mudrock succession, with intercalated thin sands present in the northern Viking Graben. In the north there is a marked coarsening upwards trend from mudstones to siltstones and silty-sandstones, while in the south this trend is less pronounced. The basal sands and siltstones may be rich in glauconite.

Characteristics of the upper boundary

The upper boundary of the member corresponds approximately to the top levels assigned an Early Miocene age (according to the biostratigraphy and Sr-isotope stratigraphy of Rundberg & Eidvin, 2005). The Skade sands are overlain by mudstones which onlap the middle Miocene erosive surface to the east. In the southern Viking Graben these authors identified the upper boundary of the Skade Member, synonymous with the Hordaland/Nordland transition, as coinciding with a very distinctive high radioactive marker, a high-amplitude seismic reflector, and a high gamma-ray log marker. (Figure xx). This unconformable surface is interpreted as a base middle Miocene sequence boundary.

Logs from well 15/3-3 (pdf)
Logs from well 15/9-13 (pdf)
Logs from well 16/1-1 (pdf)
Logs from well 24/12-1 (pdf)


See figure xx - Lateral extent of the sands of the Skade Member


A characteristic assemblage of mostly pyritised diatoms, together with sponge spicules, radiolaria, agglutinated benthic and planktonic foraminifera (index taxa to be named) here is typical of the lowermost horizons of this formation. The Skade sands differ from the overlying middle Miocene mudstone unit by lacking the presence of a Bolboforma badenensis and Bolboforma reticulata assemblage (Rundberg & Eidvin, in prep.).


Early Miocene (Rundberg & Eidvin, in prep.), and previously assigned to Oligocene by Isaksen & Tonstad (1989). It has been noted by several workers that the Oligocene/Miocene boundary is often difficult to determine in well sections, using either biostratigraphy or seismic. This is particularly pertinent in the north Viking Graben. Based on both biostratigraphy and Sr-isotope stratigraphy, the top of the Skade sands corresponds closely to the top of the Lower Miocene. See note on age of Utsira Member.

Depositional environment

Isaksen & Tonstad (1989) interpret the depositional environment to be an open marine setting with deposition occurring in response to a global sea-level regression.

home previous page