Are there Late Cretaceous unconformities in the onshore outcrops of the West Greenland basin?

Abstract

Unconformities seen in onshore sections often provide a clue as to the age of sequence boundaries seen in offshore seismic sections. Thus unpublished descriptions in industry reports of unconformities in the Upper Cretaceous of West Greenland have become of special interest since the initiation of a project involving a reinterpretation of all industry data acquired offshore West Greenland in the 1970s. A reinvestigation of two of the most prominent of these unconformities, between Cenomanian and ?Campanian-Maastrichtian and between Cenomanian and ?'Senonian' respectively, confirmed that the unconformities exist, but cast doubt on the reliability of the palynological dating of the sediments above the unconformities. At both localities the sediments above the unconformities contain frequent layers of conglomerate with clasts of reworked sediments, in particular of dark mudstones like those seen in the Upper Cretaceous non-marine Atane Formation which underlies the unconformities. In these circumstances reworked pollen are likely to be encountered in the upper sections, making dating of these sections difficult. Elsewhere in the area Lower Paleocene sections are known to contain an almost exclusively Late Cretaceous palynomorph assemblage. Provisionally, therefore, the sections above the unconformities examined are placed in the Lower Paleocene, and the unconformities at their base are interpreted as being due to the end-Cretaceous movements known to have taken place in this part of West Greenland.