The contact between shallow-dipping Layered Series and the mineralogically equivalent Marginal Border Series was one of the most striking features of the Skaergaard intrusion. As the geologic map more or less shows, the extensive, petrographic divisions in the thick Layered Series thins but continues up the pluton walls and around onto its roof. While details of these different regions vary, the petrology is essentially the same; each was deposited during the same time interval by roughly the same magma that was crystallizing the same assemblage. The Marginal Border Series-Layered Series contact is amazingly sharp where we saw it on Ivnarmiut Island, on the easternmost side of Mellemø¸ Island, and on the western side of the pluton on Kraemer Island (no good photos of the contact from there).
Example of steeply dipping layering in the MBS on Mellemø Island. This is essentially a vertical section through the colliform layering of the MBS. In this vertical section the colliform layer bump-and-cusp pattern, seen on horizontal sections (below), do not show. This indicates that the colliforms are, in three dimensions, shaped like partial cylinders, perhaps like parallel celery stalks laid with the convex sides nested against concave sides. Center of the pluton is to the right.
Example of layering in the shallowly-dipping Layered Series, eastern Kraemer Island. This is the upper part of LZc right below the MZ which is visible on the hear horizon. Water in the distance is Uttental Sund, above which is the toe of Forbindelses Glacier. Small autoliths are visible, and some truncated layers. I show this to remind the viewer what it looks like.
A view of the Layered Series (UZa)-Marginal Border Series (UZa) contact. The UZa rocks of the Marginal Border Series are on the right and dip at ~70° to the left. The UZa rocks are on the left and dip at ~20° to the left. The contact is in the middle of the photo and is very sharp: layers ramp from one to the other over only a couple of meters.
Another perspective of the same region as the photo two above. View is looking up the gently dipping Layered Series beds (under the photographer and the man with the shovel) to the ramp up to the Marginal Border Series that is on the steepest part of the wall.
Another cut through the contact between the Layered Series (left, dipping ~20° to the left) and the Marginal Border Series (right, dipping at ~70° to the left). Here the ramp is less prominent.
Looking east at the east end of Mellemø Island. Rocks at the image bottom and extending into the water, are of the Marginal Border Series LZc*, with nearly vertical layering. The dark rocks farthest out into the water are from the MZ, with layering lapping up against the MBG.
