| Computer Code: |
HEIS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Paleocene Epoch (GP)
— Paleocene Epoch (GP) |
| Lithological Description: |
The Heimdal Sandstone Member consists of thick sandstone units associated with more thinly bedded alternations of sandstone and mudstone. The sandstones are friable to lightly cemented, moderately sorted and of very fine to coarse sand grade. They include minor and variable amounts of glauconite and are locally associated with thin beds of reworked chalk. The interbedded mudstones are light to medium grey grading to olive-grey and green-grey; they are poorly bedded, variably silty, and generally non-calcareous. |
| Definition of Lower Boundary: |
The base of the Heimdal Sandstone Member is marked by a downward change from sandstone to green-grey mudstone, associated with an increase in gamma-ray values and a decrease in velocity. The distinction between sandstones of the Heimdal Sandstone Member and those of the underlying Maureen Formation is not always straightforward because the intervening Lista mudstone is often thin, and thus difficult to recognize in cuttings alone. In specific sections, the interpretations presented here differ from those of previous authors. Thus, sandstones in Quadrants 2 and 3, questionably assigned by Mudge & Copestake (1992) to the Maureen Formation, are here assigned to the Heimdal Sandstone Member on the basis of limited biostratigraphic evidence. Conversely, sandstones in the Beryl Embayment, assigned by Morton et al. (1993, fig.6) to the Heimdal Sandstone Member, are here included in the Maureen Formation; this interpretation is based on the consistent occurrence above these sandstones of a high-gamma marker (e.g. 9/13-4 & 9/19-7Z) that in well 9/18a-4 is associated with the C. lenticularis biomarker (Mudge & Copestake 1992, fig.5). |
| Definition of Upper Boundary: |
The top of the Heimdal Sandstone Member is generally well defined by a downward change from green-grey or grey-green mudstone to sandstone, associated with a decrease in gamma-ray values and an increase in velocity. In some sections, a narrow interval of thinly interbedded sandstone and mudstone overlies the main sandstone development (e.g. 3/12-1, 9/18a-4). In parts of Quadrant 16, the overlying Lista mudstone is thin or possibly absent. Where a sandstone unit occurs between Sele and Lista mudstones, as in parts of the South Viking Graben, positive assignment to one or the other formation is dependent on core data. |
| Thickness: |
Reaches over 400 m in the Viking Graben. |
| Geographical Limits: |
The Heimdal Sandstone Member occurs over much of the Viking Graben. In the Norwegian sector, the unit is given formation status. |
| Parent Unit: |
Lista Formation (LIST)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Norwegian Sector North Sea well N25/4-1 (Deegan and Scull, 1977, p.32, fig.39): 2067-2423 m (6781-7949 ft) below KB. |
| Reference Section |
North Sea well 3/12- 1: 1788.5-1981.5 m (5867-6501 ft) (Knox and Holloway, 1992). |
| Reference Section |
North Sea well 9/18a- 4: 2327.5-2568 m (7636-8425 ft) (Knox and Holloway, 1992). |
| Reference(s): |
| Morton, A C, Hallsworth, C R and Wilkinson, G C. 1993. Stratigraphic evolution of sand provenance during Paleaocene deposition in the Northern North Sea area. In: Parker, J R (ed). Petroleum geology of Northwest Europe:Proceedings of the 4th Conference.Geological Society,London 73-84. |
| Mudge, D C and Copestake, P. 1992. Lower Palaeogene stratigraphy of the northern North Sea.Marine and Petroleum Geology,9,287-301. |
| Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. |
| Knox, R W O'B and Holloway, S. 1992. 1. Paleogene of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
