Triggering of the largest Deccan eruptions by the Chicxulub impact

TL;DR

The paper hypothesizes that the Chicxulub impact triggered the largest Deccan flood basalt pulse, the Wai Subgroup (Poladpur, Ambenali, Mahabaleshwar), which may account for >70% of Deccan main-stage eruptions and occurred within ~100,000 yr of the Cretaceous-Paleogene boundary. It argues that impact-generated seismic energy densities of ~0.1–1.0 J/m³ in the upper mantle could have transiently increased permeability in the Deccan plume head, but the hypothesis remains to be tested by high-precision dating.

Key findings

• Deccan volcanism was already underway millions of years before Chicxulub, so the impact could not have initiated it; instead, the paper proposes triggering of the enormous Wai Subgroup pulse, which includes flows with single-eruption volumes approaching ~10,000 km³ and lengths >1000 km.
• Seismic modeling suggests Chicxulub could have generated energy densities of order 0.1–1.0 J/m³ throughout the upper ~200 km of Earth’s mantle, exceeding the ~10⁻¹–10⁰ J/m³ threshold inferred for triggering magmatic volcanoes from historical earthquakes.
• Independent evidence is interpreted as consistent with rapid mantle mobilization: Wai Subgroup dikes lack consistent orientation, Nd isotopes show stronger mantle signatures and less crustal contamination than underlying formations, and REE inversion indicates the lithospheric lid remained at ~60 km before, during, and after the Ambenali eruption.
• The paper estimates that the Wai Subgroup may have erupted over ~100,000 yr, with permeability-response modeling giving magma transport time scales of ~10³–10⁸ yr and a likely midrange of 10⁴–10⁶ yr.

Methods

• Synthesis of Deccan stratigraphy, volume estimates, published ⁴⁰Ar/³⁹Ar ages, paleomagnetic polarity data, biostratigraphy, dike orientations, and Nd/Sr/Pb and rare earth element geochemistry, plus new field and Google Earth observations of the Poladpur-Bushe contact.
• Seismic scaling from Chicxulub impact energy (~3 × 10²³ J), assumed seismic conversion efficiencies of 10⁻²–10⁻⁵, and estimated moment magnitudes of Mw ~9–11, compared with historical earthquake-triggered eruption thresholds.
• A generalized diffusive melt-migration model using hydraulic diffusivity D = κ/(µβ_eff), permeability κ ~10⁻¹⁵–10⁻¹⁰ m², and length scale L = 300–500 km to estimate response times of the deep Deccan magmatic system.

Limitations

• The paper states that existing radioisotopic age constraints on Deccan volcanism are not very precise, that the physical mechanisms by which earthquakes trigger volcanic eruptions are unknown, and that high-precision dating is needed to confirm or reject the hypothesis.
• The paper also states that the new field observations of the Poladpur-Bushe contact are preliminary, that no global study of possible Chicxulub-triggered eruptions was carried out, and that biostratigraphic interpretations depend on whether foraminifera are reworked or in place.
• Evident from the text: the causal claim is a plausibility argument based on timing coincidence and modeling, not a demonstrated mechanism; the authors acknowledge an alternative sudden plume-flow pulse, and volume estimates depend on assumed formation footprints and extents.