Anomalous K-Pg-aged seafloor attributed to impact-induced mid-ocean ridge magmatism

Abstract

Eruptive phenomena at all scales, from hydrothermal geysers to flood basalts, can potentially be initiated or modulated by external mechanical perturbations. We present evidence for the triggering of magmatism on a global scale by the Chicxulub meteorite impact at the Cretaceous-Paleogene (K-Pg) boundary, recorded by transiently increased crustal production at mid-ocean ridges. Concentrated positive free-air gravity and coincident seafloor topographic anomalies, associated with seafloor created at fast-spreading rates, suggest volumes of excess magmatism in the range of ~10⁵ to 10⁶ km³. Widespread mobilization of existing mantle melt by post-impact seismic radiation can explain the volume and distribution of the anomalous crust. This massive but short-lived pulse of marine magmatism should be considered alongside the Chicxulub impact and Deccan Traps as a contributor to geochemical anomalies and environmental changes at K-Pg time.

Fig. 1. The distribution of high-passed gravity and topographic anomalies by the age of the seafloor and their relationship to the timing of the Chicxulub impact.

(A) PDFs for high-passed gravity anomalies by the age of the seafloor. White box highlights K-Pg–aged seafloor. (B) The blue line shows probabilities for gravity anomalies between 5 and 20 mgal (in percent). The black line shows the same data after subtracting the median in a 10-My wide moving window. (C and D) Same as (A) and (B), but for high-passed global seafloor topography.

Fig. 2. Locations of anomalous seafloor at different points in time.

(A) Present-day locations of seafloor created within 1 My after K-Pg. Seafloor created at half-spreading rates above and below 35 mm/year are in colors and black, respectively. (B) Reconstruction with GPlates (49) of fast-spreading seafloor to locations at K-Pg time. Colors show the maximum gravity anomaly within 2° of the location before reconstruction.

Fig. 3. Morphology and context for the seafloor anomalies.

(A) Distributions of anomalies near K-Pg–aged crust derived from global seafloor gravity and topography data from 60 to 70 Ma. Dashed and solid black lines (left axis) show the lognormal mean area and variance of contiguous regions exhibiting gravity anomalies greater than 5 mgal against the mean age in 1-My bins. Red line (right axis) shows the corresponding total volume of these anomalies above the mean elevation of surrounding seafloor. (B) Comparison of detrended gravity anomalies from Fig. 1B with the mean half-spreading rate for crust created at half-spreading rates above 35 mm/year.

Fig. 4. Comparison between oceanic gravity anomalies and other metrics of geologic change over the last 100 Ma.

The vertical dashed line in all panels marks K-Pg. (A) The probabilities of gravity anomalies between 5 and 20 mgal for all fast-spreading seafloor and for fast-spreading seafloor in the Pacific and Indian oceans are shown by the black, blue, and orange lines, respectively. The median in a 10-My wide moving window has been subtracted from each curve. (B) Average half-spreading rates for seafloor created at half-spreading rates above 35 mm/year for the globe, Pacific Ocean, and Indian Ocean are shown by the black, blue, and orange lines, respectively. (C) Global sea level over the past 100 My (39) resampled to 1-My intervals. Values are relative to the present day.