Mey Member

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, Lista Formation

Unit definition

The Mey Member is attributed to the intra Lista Formation sandstones in subarea SW in Figs. 1 and 72.

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

 

Name

In the Central Graben of the North Sea this unit was formerly called the Andrew Formation. The Mey Member was introduced by Knox and Holloway (1992), and attributed to all major sandstone units and associated tuffaceous deposits within the Lista Formation of the Outer Moray Firth and the Central Graben. The Mey Member includes the Andrew Member (Lower Mey) and the Balmoral Member (Middle and Upper Mey) of Neal (1996) on the UK side of the North Sea (see also Kilhams et al. 2012).

 

Derivatio nominis

The Mey Member is named after the Castle Mey, Caithness, Scotland.

Type well

UK well 21/2-1: Depth 2002.5 - 2356.5m RKB. Coordinates N57°55'14.490", E 00°15'46930". Defined by Knox & Holloway (1992).

Reference wells

Norwegian well 7/11-2 (Fig. 73): Depth 3027-3107m RKB. Coordinates 57°4'15.20" N 2°24'26.50" E. Cores 3030.6-3046.2m RKB.

Norwegian well 7/11-1 (New, this study, Fig. 74). Depth 2975-3070 m RKB. Coordinates N 57°04'15.60", E 02°26'24.40". No cores.

Norwegian well 1/5-2 (New, Fig. 75). Depth 3137 - 3190m RKB. Coordinates N 56°34'41.59", E 02°38'30.53". No cores.

Fig. 73. Well 7/11-2 composite log Rogaland Group. Stratigraphic position of the Mey Member is outlined in stratigraphic column to the right.

Fig. 74. Well 7/11-1 composite log Rogaland Group. Stratigraphic position of the Mey Member is outlined in stratigraphic column to the right.

Fig. 75. Well 1/5-2 composite log Rogaland Group. Stratigraphic position of the Mey Member is outlined in stratigraphic column to the right.

Composition

The Mey Member typically consists of stacked units of fine- to medium-grained, or occasionally coarse-grained, sandstones with common mudstone and chalk clasts (Figs. 76-78).

The non-tuffaceous sandstones of the Mey Member mostly range from fine to medium, occasionally coarse, sand grade, and commonly include angular clasts of mudstone or limestone. Rounded and glauconite stained pebbles of chalk and flint are encountered in some beds. The sandstones consist of a succession of superimposed sandstone units, often with sharp, erosional base, interbedded with typical variegated, bioturbated Lista mudstones. Primary structures are scarce, with most sandstones being structureless or displaying water escape structures (Knox & Holloway 1992). The sandstones include sporadic zones of calcite cementation, with pervasive cementation in the lowermost sandstone unit (Mey L1 Sub-member, see below), reflected as consistently higher sonic velocities. Sandstone intrusions are frequently found associated with the upper boundary of sandstones bodies often with an abundance of angular and tabular mudstone clasts.

Fig. 76. Core Photograph Mey Member well UK30/14-1. Well sorted sandstones with mud flakes. The well is drilled at the Flyndre Discovery at the Norwegian/UK Boundary. Photography by H.Brunstad.

Fig. 77. Core Photograph Mey Member well 7/7-1. The photograph is taken from the cores described above.

Fig. 78. Well 7/7-1 Core description log.

Wireline log characterization

Upper boundary

The Lista Formation shales may envelope or overlie the Mey Member, and the boundary is characterised by higher gamma-ray readings and lower velocity upwards into the Lista Formation. Where the Forties Member directly overlies the Mey Member, the boundary may be more difficult to define, but the Forties Member generally has a lower velocity than the Mey Member. This boundary can be difficult to determine in the Norwegian sector of the North Sea.

Lower boundary

The Mey Member usually overlies shales of the Lista and in places the Våle Formation. The boundary is characterised by lower gamma readings and increased velocity upwards from the Lista or Våle Formation below.

 

Thickness

The Mey Member reaches thicknesses of more than 500 m in the Moray Firth area, but crossing the Norwegian boundary in the Central Graben, the Mey Member thickness usually does not exceed more than some tens of meters.

Seismic characterization

Seismic expression is highly variable due to the variable composition of the Mey sandstones. In some areas the top and base of the sandstones can be picked confidently (Fig. 79) whereas in other cases the sandstones are mapped out based on seismic isopach thickenings between mappable events as MFS or sequence boundaries.

By applying the technique of S/G cross plotting explained in chapter 3, the minimum threshold thickness for the presence of Mey sandstones can be assessed.

Fig. 79. Seismic section through a lobe shaped thickness anomaly of the Mey Member. Example is from the blocks 1/5 - 1/6 area, between Flyndre and Albuskjell discoveries.

Age

Late Middle to Late Paleocene (Late Selandian to Early Thanetian)

Biostratigraphy

The biostratigraphic subdivision of the Mey Member is directly comparable to that of the Lista Formation, with the A. gippingensis acme biomarker and the P. pyrophorum biomarker allowing further subdivision (Knox & Holloway, 1992).

Correlation and subdivision

The Mey Member is more or less time-equivalent with the Heimdal Member of the northern North Sea. To some extent the two fan systems seem to intermix across the Fladen Ground Spur (Figs. 1), but they are separated here by a line of supposed minimum sandstone thickness (Knox & Holloway, 1992).

The Mey Member is divided into units Mey L1, L2 and L3 Submembers. Mey L1 Sub-member corresponds to the Andrew Member, Mey L2 Submember to Balmoral, and Mey L3 Submember to Glamis Member of Mudge & Copestake (1992a).

Geographic distribution

The Mey Member is distributed in the Outer Moray Firth area and extends into the Central Graben, lapping onto the eastern margins of the basin in the Central Graben (Fig. 72).

Depositional environment

In general, the Mey sandstones were laid down in outer shelf, slope and basin environments, with the shelf sands being redistributed to form a slope apron made up of superimposed, laterally coalescing fans (Parker 1975; Stewart 1987). Shelfal areas were in general located west of the Central Graben, whereas in the Central Graben the sandstones were deposited by gravity flows in submarine slope to distal basin floor settings.

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