New constraints on the thermal history of North-East Greenland from apatite fission-track analysis

Apatite fission-track analyses from the area north of Jameson Land, East Gr eenland, indicate that the region has undergone at least three phases of co oling during the Mesozoic and Cenozoic, Two major periods of cooling during the Tertiary have been identified: a middle Tertiary episode, in which coo ling began between 40 and 30 Ma, and a late Tertiary episode, in which cool ing began between 10 and 5 Ma, The middle Tertiary event is synchronous wit h emplacement of major intrusive bodies associated with continental rifting hydrothermal effects. The late Tertiary event appears to be related to ero sion associated with uplift resulting from changes in the North Atlantic sp reading direction and associated events. No paleothermal effects have been identified related to the onset of rifting in the early Tertiary. Results f rom samples farthest from the continental margin reveal an earlier event in which fooling began between 225 and 165 Ma. The origin of this event is no t clear, but it may reflect uplift and erosion associated with recognized u nconformities within the Jurassic section.