Subduction history reveals Cretaceous slab superflux as a possible cause for the mid-Cretaceous plume pulse and superswell events

Abstract

Subduction is a fundamental mechanism of material exchange between the planetary interior and the surface. Despite its significance, our current understanding of fluctuating subducting plate area and slab volume flux has been limited to a range of proxy estimates. Here we present a new detailed quantification of subduction zone parameters from the Late Triassic to present day (230 – 0 Ma). We use a community plate motion model with evolving plate topologies to extract trench-normal convergence rates through time to compute subducting plate areas, and we use seafloor paleo-age grids to estimate the thickness of subducting lithosphere to derive the slab flux through time. Our results imply that slab flux doubled to values greater than 500 km3/yr from 180 Ma in the Jurassic to 130 Ma in the mid-Cretaceous, subsequently halving again towards the Cretaceous-Paleogene boundary, largely driven by subduction zones rimming the Pacific ocean basin. The 130 Ma spike can be attributed to a two-fold increase in mid-ocean ridge lengths following the break-up of Pangea, and a coincident increase in convergence rates, with average speeds exceeding 10 cm/yr. With one third of the total 230 - 0 Ma subducted volume entering the mantle during this short ~ 50 Myr period, we suggest this slab superflux drove a surge in slab penetration into the lower mantle and an associated increase in the vigour of mantle return flow. This mid-Cretaceous event may have triggered, or at least contributed to, the formation of the Darwin Rise mantle superswell, dynamic elevation of the South African Plateau and the plume pulse that produced the Ontong-Java-Hikurangi-Manihiki and Kerguelen plateaus, among others. The models presented here contribute to an improved understanding of the time-evolving flux of material consumed by subduction, and suggest that slab superflux may be a general feature of continental dispersal following supercontinent breakup. These insights may be useful for better understanding how supercontinent cycles are related to transient episodes of large igneous province and superswell formation, and the associated deep cycling of minerals and volatiles, as well as leading to a better understanding of tectonic drivers of long-term climate and icehouse-to-greenhouse transitions.

Ice, Fire, or Fizzle: The Climate Footprint of Earth's Supercontinental Cycles

“…To limit the model parameter space and not introduce additional degrees of freedom in the absence of similarly rigorous observational constraints for both epochs, we again take arc and MOR lengths to remain unchanged through the Pangean and Rodinian cycles. We neglect, for example, new plate motion modeling constraints suggesting that an increase in MOR length contributed to a factor of 2 increase in the flux of material subducted at continental arcs from 180 to 130 Ma (East et al, ). We also ignore contributions of crustal carbonate to magmatism and to topography production and weathering since Pangea breakup (Lee et al, , ).…”

“…Figure 5 and Lenardic et al, 2011;Robin et al, 2007;Thayalan et al, 2006). Plate reconstructions and geological data suggest that subduction zones probably encircled Rodinia and to a lesser extent Pangea by the time these supercontinents were each formed (e.g., East et al, 2019;Evans, 2009;Lee et al, 2013;Le Pichon et al, 2019;Li et al, 2013;Müller et al, 2016). Depending on the continuity, geometry, and age of subducting slabs, such a planform can have varied consequences for the character and extent of mantle thermal mixing.…”

“…Although numerical simulations and laboratory experiments Lenardic et al, 2011;Robin et al, 2007;Thayalan et al, 2006) show that the changing planform of mantle stirring during isolation and in an isolation-to-remixing regime can cause this volcanism to cluster in time after breakup, consistent with the Pangea proxy data in Figure 4, this behavior is inevitably sensitive to the geometric setup of any model and to the detailed planform of subducting slabs. Indeed, this sensitivity of the timing of LIP volcanism to the planform of subduction and MOR spreading is inferred from new plate motion models of Pangea breakup (East et al, 2019). A practical consequence is that it is not possible to reliably parameterize changes in this class of volcanism in terms of globally averaged values for V s or T m,o .…”

Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures

“…Yet, many hypotheses have been proposed to explain the extinction of dinosaurs 39 , and little is known about the drivers of a putative decline 3 , 10 , 11 , 28 , 31 , 40 . Identifying causal mechanisms for the demise of dinosaurs can be challenging because there are so many possibilities in the Cretaceous, including the continued breakup of the supercontinents Laurasia and Gondwana 41 , 42 , intense and prolonged volcanism 43 , climate change, fluctuations in sea levels 44 , 45 , and novel ecological interactions with rapidly expanding clades like flowering plants 46 – 49 and mammals 50 – 52 . Testing and teasing apart the effect of all these drivers on dinosaur diversification remain difficult, and, for instance, previous studies have found mixed support for the hypothesis that global dinosaur diversity is tied to sea-level fluctuations 18 , 40 , 53 , 54 .…”

Spatiotemporal Variations in Surface Heat Loss Imply a Heterogeneous Mantle Cooling History

“…Note the strong time-dependence, and that present-day heat loss from Earth's mantle represents an absolute minima for the 400-0 Ma time period, having been up to ∼15 TW higher in the past (Figure 1b). These variations are driven by changes to the age-area distribution of the seafloor (Figure 1c), which are caused by fluctuations in the rates of seafloor spreading and subduction during the supercontinent cycle (e.g., East et al, 2020;Karlsen et al, 2019a). This emphasizes the need for a long time-series (ideally spanning one complete supercontinent cycle) of heat flow to robustly infer long-term average values.…”