“…Full details of the geochemical fingerprinting of these tephra layers are presented in a previous study 13 . These chemical signatures closely match the ignimbrites and lavas of the Kap Washington Group in North Greenland 14 , indicating that this series is the most likely source (Fig. 4).…”
Section: Discussionsupporting
confidence: 59%
“…The close proximity of the tephra layer to the basal unconformity (7.1–11.7 m) corroborates the hypothesis that the cessation of Kap Washington volcanism was broadly contemporaneous with the formation of the Central Basin 16 .Figure 4A summary of chondrite-normalised 56 REE data, showing the mean values of the basal Todalen bentonite (dashed line) and later Firkanten and Basilika tephras (solid line) 13 . For comparison, the range of values from the Palaeocene exposures of the NAIP from East and West Greenland 19, 20 are shown in yellow, the range in values from the Kap Washington Group in North Greenland 14 in pink, and the range of volcaniclastic deposits in Ellesmere Island attributed to the Nares Strait 17 in blue. All Central Basin samples show relative REE enrichment with respect to the entire range of measured NAIP rocks.
…”
Radioisotopic dating of volcanic minerals is a powerful method for establishing absolute time constraints in sedimentary basins, which improves our understanding of the chronostratigraphy and evolution of basin processes. The relative plate motions of Greenland, North America, and Eurasia changed several times during the Palaeogene. However, the timing of a key part of this sequence, namely the initiation of compression between Greenland and Svalbard, is currently poorly constrained. The formation of the Central Basin in Spitsbergen is inherently linked to changes in regional plate motions, so an improved chronostratigraphy of the sedimentary sequence is warranted. Here we present U-Pb zircon dates from tephra layers close to the basal unconformity, which yield a weighted-mean 206Pb/238U age of 61.596 ± 0.028 Ma (2σ). We calculate that sustained sedimentation began at ~61.8 Ma in the eastern Central Basin based on a sediment accumulation rate of 71.6 ± 7.6 m/Myr. The timing of basin formation is broadly coeval with depositional changes at the Danian-Selandian boundary around the other margins of Greenland, including the North Sea, implying a common tectonic driving force. Furthermore, these stratigraphic tie points place age constraints on regional plate reorganization events, such as the onset of seafloor spreading in the Labrador Sea.
“…Full details of the geochemical fingerprinting of these tephra layers are presented in a previous study 13 . These chemical signatures closely match the ignimbrites and lavas of the Kap Washington Group in North Greenland 14 , indicating that this series is the most likely source (Fig. 4).…”
Section: Discussionsupporting
confidence: 59%
“…The close proximity of the tephra layer to the basal unconformity (7.1–11.7 m) corroborates the hypothesis that the cessation of Kap Washington volcanism was broadly contemporaneous with the formation of the Central Basin 16 .Figure 4A summary of chondrite-normalised 56 REE data, showing the mean values of the basal Todalen bentonite (dashed line) and later Firkanten and Basilika tephras (solid line) 13 . For comparison, the range of values from the Palaeocene exposures of the NAIP from East and West Greenland 19, 20 are shown in yellow, the range in values from the Kap Washington Group in North Greenland 14 in pink, and the range of volcaniclastic deposits in Ellesmere Island attributed to the Nares Strait 17 in blue. All Central Basin samples show relative REE enrichment with respect to the entire range of measured NAIP rocks.
…”
Radioisotopic dating of volcanic minerals is a powerful method for establishing absolute time constraints in sedimentary basins, which improves our understanding of the chronostratigraphy and evolution of basin processes. The relative plate motions of Greenland, North America, and Eurasia changed several times during the Palaeogene. However, the timing of a key part of this sequence, namely the initiation of compression between Greenland and Svalbard, is currently poorly constrained. The formation of the Central Basin in Spitsbergen is inherently linked to changes in regional plate motions, so an improved chronostratigraphy of the sedimentary sequence is warranted. Here we present U-Pb zircon dates from tephra layers close to the basal unconformity, which yield a weighted-mean 206Pb/238U age of 61.596 ± 0.028 Ma (2σ). We calculate that sustained sedimentation began at ~61.8 Ma in the eastern Central Basin based on a sediment accumulation rate of 71.6 ± 7.6 m/Myr. The timing of basin formation is broadly coeval with depositional changes at the Danian-Selandian boundary around the other margins of Greenland, including the North Sea, implying a common tectonic driving force. Furthermore, these stratigraphic tie points place age constraints on regional plate reorganization events, such as the onset of seafloor spreading in the Labrador Sea.
“…The preservation of thick bentonite beds in the Bastion Ridge and Kanguk formations indicates that explosive felsic magmatism occurred episodically over a period of up to 15 Ma, between ~98 Ma and 83 Ma, with particularly frequent deposition of bentonites between 93 and 83 Ma. Geochemical analyses of the bentonite layers within the Kanguk Formation have within-plate, alkaline signatures (Parsons, 1994), consistent with sources associated with younger magmatism in the HALIP (Thorarinsson, Holm, Duprat et al 2011, 2012; Estrada & Henjes-Kunst, 2013; Jowitt, Williamson & Ernst, 2014). The volcanic source area for the ash remains conjectural.…”
U–Pb ages of zircon from bentonites within the upper Cretaceous Bastion Ridge and Kanguk formations, Sverdrup Basin, provide constraints on sedimentation rates, biostratigraphic correlations, timing of Oceanic Anoxic Event 2 (OAE2) in the High Arctic, and the late magmatic history of the High Arctic Large Igneous Province (HALIP). A late Cenomanian to early Turonian age for the base of the Kanguk Formation is confirmed that supports correlations of the global OAE2 in the High Arctic. Sedimentation rates varied from 19 m Ma−1 between 93 and 91 Ma to 26 m Ma−1 between 91 and 83 Ma at Axel Heiberg Island. At Ellef Ringnes Island, the lower Kanguk Formation records high rates of ~70 m Ma−1 between 94 and 93 Ma, which decrease to rates comparable to those of the upper Axel Heiberg section. Differences in sedimentation rates may reflect differences in setting prior to the major transgression in the latest Cenomanian to early Turonian. The timing of Arctic occurrences of the Scaphites nigricollensis and Scaphites depressus ammonite zones is shown to be broadly comparable to that of lower-latitude occurrences within the Western Interior Seaway. An eruption frequency of 0.5–2.5 Ma characterizes the late alkaline phase of HALIP magmatism. Volcanic bed thicknesses of 10–50 cm suggest ash transport distances of less than 1000 km. Long-lived volcanic centres, in the area of the Alpha Ridge, northern Ellesmere Island or northern Greenland, were the likely source of volcanic ash over a period of 10–15 Ma.
“…From the late Cretaceous to the late Palaeogene, the Labrador Sea and Baffin Bay successively opened from south to north between Greenland and Canada (Chalmers & Pulvertaft, 2001). This caused SW-NE movement and counter clockwise rotation of Greenland (Srivastava, 1985;Okulitch & Trettin, 1991;Trettin, 1991a;Oakey & Chalmers, 2012;Hosseinpour et al, 2013) and extension with associated alkaline magmatism in the Lincoln Sea, North Greenland and Ellesmere Island (Trettin & Parrish, 1987;Estrada et al, 2010;Tegner et al, 2011;Thorarinsson et al, 2012Thorarinsson et al, ,2015. Seafloor spreading along the North Atlantic ridge caused Greenland to move northward, terminated rifting and volcanism in Labrador Sea (Thorarinsson et al, 2011;Døssing et al, 2013a) and resulted in the Eurekan Orogen on Ellesmere Island and North Greenland in the Eocene (Tessensohn & Piepjohn, 2000;Tegner et al, 2011;Oakey & Chalmers, 2012;Piepjohn et al, 2016).…”
We use new models of crustal structure and the depth of the lithosphere-asthenosphere boundary to calculate geopotential energy and its corresponding geopotential stress field for the High Arctic. Palaeo-stress indicators such as dykes and rifts of known age are used to compare the present-day and palaeo stress field. When both stress fields coincide, a minimum age for the configuration of the lithospheric stress field may be defined. We identify three regions in which this is observed. In North Greenland and the eastern Amerasia Basin the stress field is likely the same as during the late Cretaceous. In western Siberia, the stress field is similar to that of the Triassic. The stress directions on the eastern Russian Arctic shelf and the Amerasia Basin are similar to that of the Cretaceous. The persistent misfit of the present stress field and Early Cretaceous dyke swarms associated with the High Arctic Large Igneous Province indicates a short-lived transient change of the stress field at the time of dyke emplacement. Most rifts in the Amerasia Basin coincide with the stress field, suggesting that dyking and rifting were unrelated. We present new evidence for dykes and a graben structure of Early Cretaceous age on Bennett Island.
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