Arctic OAE1a Triggered By the Barents Sea Large Igneous Province?

Abstract:

Chemostratigraphic and biostratigraphic analysis of newly sampled tuff and organic rich mudstone material from the Lower Cretaceous succession on Spitsbergen shows clear anomalies that can be linked to OAE1a and LIP activity. Geochemical analyses from core samples demonstrate a sapropel-rich, anoxic interval in strata containing an early Aptian palynomorph assemblage. A negative d¹³C excursion followed by a positive excursion is recorded in the same interval, and is considered an associated effect of the Anoxic Event. New age constraints on the Lower Cretaceous strata on Svalbard have been produced from basaltic sills and dykes in Cretaceous and older rocks (U/Pb and Ar/Ar), as well as a bentonite layer within the lower Cretaceous succession. The bentonite age yielded an early Aptian age within a stratigraphic interval containing mid-Barremian palynomorphs, which may imply an incorrectly placed Barremian-Aptian boundary according to the International Commission on Stratigraphy. LIP activity in and around the Barents Sea area was pronounced in the Early Cretaceous, and significant volumes of sediment were subjected to emplacement of volcanic material within the strata, causing large-scale sediment degassing. A causal link between LIP activity and the Oceanic Anoxic Event 1a (OAE1a) is suggested. The data provide an oceanographic and geochemical context for the Lower Cretaceous strata in the Boreal Basin, and provide reference for similar approaches to contemporaneous strata in the neighbouring areas, such as the Sverdrup and Alaska basins.