The Te and Hg Record of Deccan Traps and NAIP Volcanism in Late Maastrichtian – Early Eocene Sediments

Abstract

The Cretaceous-Paleogene (K-Pg; ~66 Ma) extinction and the Paleocene Eocene Thermal Maximum (PETM; ~56 Ma) were two major environmental and biotic crises in Earth’s history. While both coincide with the emplacement of Large Igneous Provinces (LIPs), uncertainties persist about the role of the Deccan Traps and the North Atlantic Igneous Province (NAIP) respectively in these events. In both cases, the reconstruction of cause and effect of environmental perturbations is hampered by the difficulty in determining the timing of volcanism relative to environmental change and extinction. The main phase of the Deccan volcanism initiated at ~66.5 Ma in C24n and lasted for about 1 Myr, overlapping with the Chicxulub impact at ~66.03 Ma and the Cretaceous-Paleogene boundary (KPB) extinction. In case of the NAIP, linking the eruptive history to the light carbon excursion (CIE) and rapid warming at the P-E boundary (~56.01 Ma) remains difficult, thus raising questions about the trigger for the CIE. Some studies found volcanic degassing to be sufficient to account for the CIE, in which case the main period of volcanic activity was short, and initiated at the Paleocene-Eocene boundary. Alternatively, the light carbon originates from magmatic tapping of carbon-rich sediments or destabilization of methane clathrates. In order to tie Large Igneous Province (LIP) volcanism to consequent environmental perturbations, we present tellurium (Te), mercury (Hg) and other trace element proxies from a complete sedimentary profile at Wadi Nukhul, Egypt spanning about 12 Myr from the late Maastrichtian to the early Eocene. A peak in Te in the latest Maastrichtian corresponds to the Late Maastrichtian Warming Event, and may be coincident with early Deccan volcanism on the Malwa Plateau. Te concentrations rise again up to 467 ppb immediately before the KPB, possibly reflecting eruptions of the massive Wai Formation at the Deccan Traps. Te concentrations are close to crustal average values (~10 ppb) throughout most of the Paleocene, and another spike of 465 ppb can be recognized at Paleocene – Eocene (PE) boundary. In contrast, the Hg record for this period is less clearly influenced by volcanism. Hg/TOC ratios peak in the Late Maastrichtian and earliest Eocene, but similarly high values occur throughout the section. Using a vast set of trace elements, we rule out changes in lithology, accessory mineral content, or changing redox and productivity conditions as controlling factors on Te concentrations. We use nannofossil zone ages to calculate sedimentation rates and elemental fluxes. We show that an increase in Te during the late Cretaceous coincides with the late Maastrichtian warming event and that the eruption of the Wai group initiated before the Chicxulub impact. Deccan volcanism likely contributed to climate instability and may have amplified the effects of bolide impact on the biotic crisis. Furthermore, an abrupt increase in Te concentrations coinciding with the opening of the North Atlantic at the P-E boundary, suggest highest volcanic degassing concurrent with the CIE. We, therefore, conclude that atmospheric injection of volcanic CO2 may have been the major driver of the negative CIE.