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 Thus unpublished descriptions in industry reports of unconformities in the Upper Cretaceous of West Greenland have become of special interest since the initiation of a project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.
Highlights
Since Ehman et (I/.·S (1976) repon is unpublished. and in order to put our observations and conc1usions in contcxL a summary of the evidence for unconformities at Atåta kGa and Kugssinerujuk presented by EhOlan el al. is provided
We have examined this surfaee at close quarters at two places, and have confirmed that it is a listric fault
AIthough we have found no evidenee of pronouneed primary relief in the surfaee at the base of unit II, and ean show that where the eontaet between the Atane Formation and unit II is steep, it is a fauIt, we agree with Ehman et al (1976) that there is a marked break at the base of unit II
Summary
Since Ehman et (I/.·S (1976) repon is unpublished. and in order to put our observations and conc1usions in contcxL a summary of the evidence for unconformities at Atåta kGa and Kugssinerujuk presented by EhOlan el al. is provided. In order to put our observations and conc1usions in contcxL a summary of the evidence for unconformities at Atåta kGa and Kugssinerujuk presented by EhOlan el al. "The strongest support for the occurreoce of a loeal hiatus during Late Cenomanian-Turonian time is the section at Kugssincrujuk (D-3) Oll northern Disko Island. The 880 toot [268 ml sample loeated below the unconformity zone yielded a good Middle Ccnomanian assemblage. That al 959 reet [292 ml, above the unconformity, is described as good Senonian." The section measured by Ehman el a(. 240 m a.s.l.) there is a well dcvcloped conglomcratc which marks the base of a mudstone-dominated sequence 147 m thick (unit II of the present report); samples from this At 185 m in their section (c. 240 m a.s.l.) there is a well dcvcloped conglomcratc which marks the base of a mudstone-dominated sequence 147 m thick (unit II of the present report); samples from this
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