Stratigraphy and age of the Eocene Igtertivâ Formation basalts, alkaline pebbles and sediments of the Kap Dalton Group in the graben at Kap Dalton, East Greenland

Apatite fission-track analysis (AFTA) data in two Upper Jurassic core samples from the 231 m deep Blokelv-1 borehole, Jameson Land, East Greenland, combined with vitrinite reflectance data and regional AFTA data, define three palaeo-thermal episodes. We interpret localised early Eocene (55– 50 Ma) palaeotemperatures as representing localised early Eocene heating related to intrusive activity whereas we interpret late Eocene (40–35 Ma) and late Miocene (c. 10 Ma) palaeotemperatures as representing deeper burial followed by successive episodes of exhumation. For a palaeogeothermal gradient of 30°C/km and likely palaeo-surface temperatures, the late Eocene palaeotemperatures require that the Upper Jurassic marine section in the borehole was buried below a 2750 m thick cover of Upper Jurassic – Eocene rocks prior to the onset of late Eocene exhumation. As these sediments are now near outcrop at c. 200 m above sea level, they have been uplifted by at least 3 km since maximum burial during post-rift thermal subsidence. The results are consistent with estimates of rock uplift on Milne Land since the late Eocene and with interpretation of Ocean Drilling Program (ODP) data off South-East Greenland suggesting that mid-Cenozoic uplift of the margin triggered the marked influx of coarse clastic turbidites during the late Oligocene above a middle Eocene to upper Oligocene hiatus.

Section: Timing Of Burial and Exhumationmentioning

confidence: 97%

Burial and exhumation history of the Jameson Land Basin, East Greenland, estimated from thermochronological data from the Blokelv-1 core

Green¹,

Japsen²

2018

“…The first volcanics were partly erupted in a marine environment in Paleocene time. Furthermore, there are marine sediments within the youngest flood basalts, the lower Eocene Igtertivâ Formation, and within the lower Eocene to lower Oligocene Kap Dalton Group (Soper & Costa 1976;Nielsen et al 1981;Larsen et al 1989Larsen et al , 2002Larsen et al , 2013. The presence of marine deposits above and below the Main Basalts, which were extruded on a largely horizontal plain, implies that the landscape was low-lying during the volcanic eruptions.…”

Section: Cenozoic Cover and Unconformitiesmentioning

confidence: 99%

“…Fig.27Post-basalt heating of lower Eocene sediments at Blosseville Kyst(Larsen et al 2013;Japsen et al 2014). End-Eocene C6 palaeotemperatures in three samples (yellow circles) correspond to burial below a c. 2.5 km thick Eocene succession assuming a palaeothermal gradient of 25°C/km and a surface temperature of 20°C.…”

mentioning

confidence: 99%

Episodic burial and exhumation in North-East Greenland before and after opening of the North-East Atlantic

Japsen

Green²,

Bonow

et al. 2021

The geology of North-East Greenland (70–78°N) exposes unique evidence of the basin development between the Devonian collapse of the Caledonian Orogen and the extrusion of volcanics at the Paleocene–Eocene transition during break-up of the North-East Atlantic. Here we pay special attention to unconformities in the stratigraphic record – do they represent periods of stability and non-deposition or periods of subsidence and accumulation of rocks followed by episodes of uplift and erosion? To answer that and other questions, we used apatite fission-track analysis and vitrinite reflectance data together with stratigraphic landscape analysis and observations from the stratigraphic record to study the thermo-tectonic history of North-East Greenland. Our analysis reveals eight regional stages of post-Caledonian development: (1) Late Carboniferous uplift and erosion led to formation of a sub-Permian peneplain covered by coarse siliciclastic deposits. (2) Middle Triassic exhumation led to removal of a thick cover including a considerable thickness of upper Carboniferous – Middle Triassic rocks and produced thick siliciclastic deposits in the rift system. (3) Denudation at the transition between the Early and Middle Jurassic affected most of the study area outside the Jameson Land Basin and produced a weathered surface above which Middle–Upper Jurassic sediments accumulated. (4) Earliest Cretaceous uplift and erosion along the rifted margin and further inland accompanied the Mesozoic rift climax and produced coarse-grained sedimentary infill of the rift basins. (5) Mid-Cretaceous uplift and erosion initiated removal of Cretaceous post-rift sediments that had accumulated above the Mesozoic rifts and their hinterland, leading to cooling of Mesozoic sediments from maximum palaeotemperatures. (6) End-Eocene uplift was accompanied by faulting and intrusion of magmatic bodies and resulted in extensive mass wasting on the East Greenland shelf. This event initiated the removal of a thick post-rift succession that had accumulated after break-up and produced a peneplain near sea level, the Upper Planation Surface. (7) Late Miocene uplift and erosion, evidenced by massive progradation on the shelf, resulted in the formation of the Lower Planation Surface by incision below the uplifted Upper Planation Surface. (8) Early Pliocene uplift raised the Upper and the Lower Planation Surfaces to their present elevations of about 2 and 1 km above sea level, respectively, and initiated the formation of the present-day landscape through fluvial and glacial erosion. Additional cooling episodes of more local extent, related to igneous activity in the early Eocene and in the early Miocene, primarily affected parts of northern Jameson Land. The three earliest episodes had a profound impact beyond Greenland and accompanied the fragmentation of Pangaea. Younger episodes were controlled by plate-tectonic processes, possibly including dynamic support from the Iceland Plume. Our results emphasise that gaps in the stratigraphic record often reflect episodes of kilometre-scale vertical movements that may result from both lithospheric and sub-lithospheric processes.

“…The intrusions are older than the Igtertivâ Formation at Kap Dalton on the Blosseville Kyst which comprises two parts dated at 49.1 ± 0.5 Ma and 43.8 ± 1.1 Ma (Larsen et al 2013). Larsen et al (2013) found significant geochemical differences between the Igtertivâ Formation basalts and the underlying 55 Ma lavas of the Skraenterne Formation, in particular in the rare-earth element (REE) ratios. As seen in Fig.…”

Section: Discussionmentioning

confidence: 94%

“…The older magmas were probably generated under similar conditions beneath relatively thick lithosphere. Hald & Tegner (2000), Larsen et al (2013), Larsen et al (2014) and unpublished GEUS data (2008-2010. A few crustally contaminated samples are not plotted.…”

Section: Lml3mentioning

confidence: 95%

Igneous intrusions in the cored Upper Jurassic succession of the Blokelv-1 borehole, Jameson Land Basin, East Greenland

Larsen

2018

The fully cored Upper Jurassic succession in the Blokelv-1 borehole in the Jameson Land Basin, East Greenland, is intersected by igneous intrusions at four levels; the intrusions comprise a c. 15 cm thick dyke and three sills with thicknesses of 0.7, 1.2 and 1.9 m. The sills consist of fine-grained, sparsely plagioclase-olivine-phyric basalt with chilled contacts to the sediments. Analyses of two sills gave very similar results. The sills are tholeiitic basalts with compositions similar to the main group of dykes and sills in the Jameson Land Basin, and the Blokelv-1 sills are thus considered to belong to this group which has been dated at c. 53 Ma. The intrusions form part of a 55–51 Ma suite of tholeiitic basalt intrusions that was emplaced over an area extending for over 500 km north-to-south within the sedimentary basins of East and North-East Greenland.