Abstract
The Tertiary, sedimentary sequence on the south coast of the Nûgssuaq peninsula, North Greenland (The Upper Atanikerdluk Formation) is described. The type area on the south-eastern part of the peninsula (the Atanikerdluk area) shows the Upper Atanikerdluk formation divided into 5 members: Plateau basalts 5. Point 976 member 4. Aussivik member 3. Umiussat member 2. Naujât member 1. Quikavsak member Cretaecous (Atane formation) The Plateau basalts rest upon the Upper Atanikerdluk formation which again rests unconformably upon the Atane formation (Cretaceous). The first occurrence of subaeric lavas is found in Aussivik member. West of the type area (Pautut and more westerly) the basalt volcanism began earlier, and here the number of sedimentary members of the type area substituted by products of the volcanism (basalt breccia and Plateau basalts) is increasing the more westerly one comes. The basal Quikavsak member is only visible locally owing to its origin as an infilling of a river-valley in connection with the Paleocene transgression. This fossil river-valley can be traced from Atanikerdluk (purely fluviatile) by Pautut to Nûk kitdleq, where a marine intercalation has yielded a minor fossil fauna making the Paleocene age probable by its accordance with an occurrence of marine, fixed Lower Paleocene fauna in a delta deposit at Angmârtussut (the Agatdalen valley), whose stratigraphic equivalence to Quikavsak member is proved. With 1) this fixed point in the Agatdalen valley, 2) the faunal agreement between this occurrence and Nûk kitdleq, 3) the agreement between the fossil flora of the fixed occurrence at Angmârtussut and Quikavsak member at Atanikerdluk and the other occurrences of this member at the south coast of the Nûgssuaq peninsula as well as 4) the same position in the geological course of events, all these occurrences of Quikavsak member and the litho-stratigraphically equivalent occurrences at Angmârtussut are linked together as Lower Paleocene deposits. This dating thus applies to the known fossil floras "Upper Atanikerdluk A" and "Upper Atanikerdluk B" of O. Heer. A short survey of the fossil floras from the localities described is given. Finally, Macclintockia Kanei (Hr.) Sew. & Conw. is stated zone fossil of the Lower Paleocene of West Greenland.
Highlights
Marine fossils in the western occurrences of Quikavsak mombor and its equivalents of the Agatdalen valley show that it is the Paleocene transgression that set in. It is this transgression which ean most obviously be registered in tho delta deposits in the areas of the Agatdalen valley and determined as Lower Paleocene (ROSENKRANTZ 1951)
In this area the same succession is observed as on the south coast of the Nugssuaq peninsula, the profile being much like that at Atå: Tho coarse clastic delta deposits succeeded by bituminous shale, the fossils of which showing the Paleocene age, and overlain by basalt breccia
By the investigation described it was pointed out that the Tertiary sequence of the south coast of the Nugssuaq peninsula can be divided into 5 members of which the lowermost (Quikavsak member) and the basal bed of the folIowing (Naujåt member) prove to belong to the Lower Paleocene
Summary
On an overall view of the profiles described here (pI. 4) it may be ascertained that the Tertiary sequence everywhere rests unconformably on the older substratum. Umiussat member: As Naujåt member this eontinues from Naujåt to Kingigtoq-Ugpatdluk (Gieseekes Monument) and as mentioned it may be assumed to oeeur in a landslide below the basalt breccia, but above Naujåt member at Ipeqarfiunge It is not known more westerly, nor in the .Agatdalen area. The marine invasion has taken place immediately before the final infilling of the river-bed with sediments, seeing that the fossils of Pautlit were found in the uppermost 5m of the member and as at Nlik kitdleq just below the overlying basalt breccia. Whether this represents the maximum of the transgression is uncertain; but it seems natural that Nauj at member is aresult of the continued transgression. The ash may offer a further support to the assumption that the eruptions have started in an area north to west in relation to the southeastern part of the Nligssuaq peninsula, though a closer investigation of the whole sedimentary area is neeessary for a final and closer statement on this basis
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