U–Pb geochronology of bentonites from the Upper Cretaceous Kanguk Formation, Sverdrup Basin, Arctic Canada: constraints on sedimentation rates, biostratigraphic correlations and the late magmatic history of the High Arctic Large Igneous Province

Abstract

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.

Influence of the High Arctic Igneous Province on the Cenomanian/Turonian boundary interval, Sverdrup Basin, High Canadian Arctic

“…The emplacement/eruption duration of the late phase is considered to be < 1 myr (Kingsbury et al, 2018). These late Cenomanian ages correlate well with age estimates derived from foraminiferal biostratigraphy and carbon isotope stratigraphy (Schröder-Adams et al, 2014;Herrle et al, 2015) and a bentonite age of <98.3 ± 1.8 Ma (Davis et al, 2016) of the Bastion Ridge Formation at Glacier Fiord. Formation, which represents the widespread Albian/Cenomanian disconformity (Embry and Dixon, 1990;Schröder-Adams et al, 2014).…”

“…In addition, several CA-ID-TIMS weighted 206 Pb/ 238 U zircon dates of bentonites ( Fig. 4) including one from the Bastion Ridge Formation and five from the Turonian part of the Kanguk Formation above OAE2 6 have been determined (Davis et al, 2016). The bentonite in the middle of the Bastion Ridge Formation yielded a weighted 206 Pb/ 238 U zircon age of 98.3 ± 1.8 Ma, suggesting a maximum age for the sampled horizon.…”

“…The stratigraphically oldest bentonite of the Turonian bentonite swarm within the Kanguk Formation yielded a weighted 206 Pb/ 238 U zircon age of 93.03 ± 0.21 Ma. Coupling this age with the top of the positive carbon isotope excursion closely placed to the Cenomanian/Turonian boundary at 93.9 Ma a sedimentation rate of 19 m Ma -1 is calculated for the lower Turonian (Davis, et al, 2016).…”

Cretaceous basalts of the High Arctic large igneous province at Axel Heiberg Island (Canada): Volcanic stratigraphy, geodynamic setting, and origin

“…This absence is in stark contrast to the pervasive mafic dyke and sill intrusives observed in most pre‐SFF strata in the same areas. The only evidence of magmatism hosted within the Kanguk Formation is the presence of bentonites (Davis, Schröder‐Adams, Galloway, Herrle, & Pugh, ), but these are geochemically unrelated to the SFF and do not necessarily represent intrabasinal volcanism. Other younger magmatic events in the region include the Wooton Intrusion on NW Ellesmere Island, which is similar in age to the Kanguk bentonites (92–93 Ma; Estrada, Piepjohn, Henjes‐Kunst, & von Gosen, ; Trettin & Parrish, ; Figure ), and linked to the next youngest magmatism, the bimodal, Campanian‐Maastrichtian Hansen Point volcanics (Embry & Osadetz, ; Figure ).…”

“…There are two published whole‐rock Ar‐Ar ages from the Strand Fiord basalts, which fall into this range: Tarduno et al () reported an age of 95.3 ± 2 Ma and Villeneuve and Williamson () obtained an age of 96.1 ± 1.9 Ma (Figure ). In addition, Davis et al () obtained U/Pb dates from zircons in bentonites 60 m above the base of the Kanguk Formation (93.03 ± 0.21 Ma, in the Early Turonian) and from a bentonite about 48 m from the base of the Bastion Ridge Formation at Glacier Fiord (98.3 ± 1.8 Ma, in the Early Cenomanian in GTS2012 time scale; Gradstein et al, ). Thus, we believe from multiple lines of evidence that the eruption age of the SFF basalts is within the Cenomanian and the crystallization age of 96 Ma was used for isotopic age correction purposes in later analysis.…”