Age of Tertiary volcanic rocks on the West Greenland continental margin: volcanic evolution and event correlation to other parts of the North Atlantic Igneous Province

Abstract

Radiometric ages for undated parts of the volcanic succession and intrusions in West Greenland were obtained by the 40Ar–39Ar incremental heating method. Acceptable crystallization ages were obtained for 27 samples. Combined with published results the new data provide a volcanic stratigraphy correlatable throughout the Nuussuaq Basin. The thick onshore volcanic pile consists of four widespread formations: 62.5–61 Ma picrites (Vaigat Formation), 61–60 Ma depleted basalts (Maligât Formation and the Hellefisk-1 well), 60–58 Ma less-depleted basalts (Svartenhuk Formation) and 56–54 Ma enriched basalts (Naqerloq Formation). Two local successions comprise 53.5 Ma alkali basalts (Erqua Formation) and 38.7 Ma transitional basalts (Talerua Member). A central volcano developed on Ubekendt Ejland, leading to the Sarqâta qáqâ gabbro-granophyre intrusion at 57–55 Ma. Pre-break-up volcanism took place further south as early as 64–63 Ma. The offshore volcanic succession most probably comprises the known onshore succession plus some younger lavas. The change in spreading direction near the Paleocene–Eocene boundary took place west of the Nuussuaq Basin c. 56.2 Ma. Some tectonomagmatic events are correlatable across the entire North Atlantic Igneous Province. A quiescent 58–56 Ma period correlates with similar periods in East Greenland and the Faroes, and the Naqerloq Formation is coeval with the Eocene basalts in East Greenland. The Paleocene and Eocene tholeiitic basalts are distinguishable chemically; in early Eocene time, mantle typical of the Iceland plume seems to have extended beneath the whole West Greenland margin as well as the central East Greenland margin.

Regional distribution of volcanism within the North Atlantic Igneous Province

“…Stratigraphically, it is within the uppermost Beinisvørð Formation close to the break with the Malinstindur Formation of the FIBG Kiørboe 1999;Passey & Hitchen 2011). This break probably correlates to a volcanic hiatus observed throughout the NAIP from 58 to 56 Ma (Graham et al 1998;Storey et al 2007;Larsen et al 2015). Thus, the escarpment may indicate a period of subsidence and submergence prior to the main flood volcanism and final breakup at 56 Ma.…”

Origin of Bentonites and Detrital Zircons of the Paleocene Basilika Formation, Svalbard

“…Coevally with the termination of volcanism in the High Arctic, a Large Igneous Province formed in the North Atlantic region (NALIP). The NALIP is expressed in flood basalts on eastern Greenlandas well as flood basalts and alkaline tuffs in western central Greenland (Storey et al, , 2007Tegner et al, 1998;Larsen and Pedersen, 2009;Larsen et al, 2016). Moreover, Paleocene bentonites were observed on Svalbard as well as Ellesmere Island and are particularly widespread in the North Atlantic region (Figure 1; Major and Nagy, 1972;Dypvik and Nagy, 1978;Larsen et al, 2003a;Grist and Zentilli, 2004;Reinhardt et al, 2013).…”

A revised stratigraphy for the Palaeocene Agatdalen flora (Nuussuaq Peninsula, western Greenland): correlating fossiliferous outcrops, macrofossils, and palynological samples from phosphoritic nodules

“…The basin comprises sedimentary rocks of Late Cretaceous and Palaeocene age, now referred to the Nuussuaq Group (Dam et al 2009). These sediments are overlain by a thick succession of Palaeocene to Eocene volcanic rocks, interspersed by sediments, referred to the West Greenland Basalt Group (WGBG;Hald & Pedersen 1975, Pedersen 1985, Larsen et al 2015. The stratigraphy of the Agatdalen area was first outlined by Koch (1959) based on notes from A. Rosenkrantz.…”

“…5;Riisager & Abrahamsen 1999). The age of the volcanic Nauján-guit Member, of the Vaigat Fm, is 61.2±0.5 Ma (Larsen et al 2015). The geological map in Figure 3 shows the distribution of the sedimentary formations but not the subdivision of the volcanic rocks.…”

“…The location of the Agatdalen area on the Nuussuaq Peninsula is marked with a red box. Light and dark colours refer to the distribution of sedimentary and volcanic rocks on land and in the sea of the Palaeogene lavas above the sediments provide minimum ages for the plant-bearing sediments (Storey et al 1998, Schmidt et al 2005, Larsen et al 2015. In addition, interspersed pyroclastic layers in the Abraham Member of the Eqalulik Formation can be correlated to the absolute dated lavas by geochemical analyses .…”