Tectonism and volcanism at the southeast Greenland rifted margin: a record of plume impact and later continental rupture

Abstract

During Ocean Drilling Program Leg 152, Sites 914 through 919 were drilled on the southeast Greenland Margin along a transect from the middle shelf into the adjacent deep-water Irminger Basin 500 km south of the Iceland hot-spot track (Iceland-Greenland Ridge). Sites 915 through 918 penetrated the entire cover of postrift sediments, and three of these four sites sampled the volcanic basement of the seward-dipping reflector sequences (SDRS). The landwater feather edge of the SDRS was drilled at the most landward site, Site 917, where a 779.5-m-thick, south to southeastward dipping volcanic section was found to overlie steeply dipping, marine pre-rift sediments of unknown, possibly Cretaceous, age. The more seaward Site 915 (later deepened by Site 990) recovered two lava flows that are stratigraphically lcoated above Site 917 and located within the oldest part of the main SDRS wedge. The central part of the SDRS wedge was penetrated at Site 918 in the Irminger Basin where a 120-m-thick lava section was recovered below 1189 m of postrift sediments. A few sills and dikes were sampled. All other igneous units recovered were subaerially erupted and deposited lavas, some of which may have flowed over wet ground or into shallow water. Lava at Site 917 display compositions ranging from picrite over olivine basalt to basalt, dacite, and acid tuffs. The younger lavas at Site 915 and Site 918 have a quite uniform composition similar to depleted Icelandic tholeiites. Two major successions are defined: the older Continental Succession and the younger Oceanic Succession. The Continental Succession comprises the Lower and Middle Series laveas at Site 917, and the Oceanic Succession comprises the Uppers Series lavas at Site 817 and the main SDRS series lavas at Site 915 (and Site 990) and Site 918.(See original for remainder of abstract).