Seasonal calibration of the end-cretaceous Chicxulub impact event

Abstract

The end-Cretaceous Chicxulub impact triggered Earth’s last mass-extinction, extinguishing ~ 75% of species diversity and facilitating a global ecological shift to mammal-dominated biomes. Temporal details of the impact event on a fine scale (hour-to-day), important to understanding the early trajectory of mass-extinction, have largely eluded previous studies. This study employs histological and histo-isotopic analyses of fossil fish that were coeval with a unique impact-triggered mass-death assemblage from the Cretaceous-Paleogene (KPg) boundary in North Dakota (USA). Patterns of growth history, including periodicity of ẟ18O and ẟ13C and growth band morphology, plus corroborating data from fish ontogeny and seasonal insect behavior, reveal that the impact occurred during boreal Spring/Summer, shortly after the spawning season for fish and most continental taxa. The severity and taxonomic symmetry of response to global natural hazards are influenced by the season during which they occur, suggesting that post-impact perturbations could have exerted a selective force that was exacerbated by seasonal timing. Data from this study can also provide vital hindsight into patterns of extant biotic response to global-scale hazards that are relevant to both current and future biomes.

Late Cretaceous sturgeons (Acipenseridae) from North America, with two new species from the Tanis site in the Hell Creek Formation of North Dakota

“…The Tanis site of North Dakota has been of much interest recently because it is thought to contain the horizon from ca. 66 Ma in which the Chicxulub asteroid had recently struck off the Yucatan coast causing one of this planet's great extinction events (DePalma et al, 2019(DePalma et al, , 2021. The impact of the asteroid marked the end of the Cretaceous and the beginning of the Paleocene, and it is thought by some paleontologists to have led to the extinction of 70% of the Earth's species (Jablonski, 1994).…”

Calibrations without raw data - a response to "Seasonal calibration of the end-cretaceous Chicxulub impact event"

“…The End-Cretaceous mass extinction, which included the demise of the non-avian dinosaurs, is easily the most famous of the big five mass extinctions, and is unique in that it is a geologically instantaneous event triggered by a meteorite impact 1,2,3,4 . The recently published papers by DePalma et al 5 and During et al 6 both attempt to uncover the time of the year this impact occurred to try to get closer to understanding the selectivity and severity of the extinction, and both conclude that the meteorite impacted in spring 5,6 or early summer 5 . The work of the During et al team was known to DePalma and colleagues, and their manuscript was under review with Nature after a preprint 7 had been posted.…”

“…The work of the During et al team was known to DePalma and colleagues, and their manuscript was under review with Nature after a preprint 7 had been posted. The DePalma et al paper (which was not shared with During and colleagues before publication) was submitted two months later but was published first 5,6 .…”

“…This last signal is relevant because most extant sturgeons are anadromous whereas extant paddlefishes exclusively inhabit freshwater habitats. 18,19 The oxygen isotopic graphs of the sturgeons in DePalma et al 5 display large annual variations, presumably reflecting the anadromous nature of these fishes, whereas the corresponding graphs for paddlefishes show little variation 5 . Despite these trophic environmental differences, the carbon isotopic graphs for the sturgeons and paddlefishes are essentially identical 5 ; the sturgeon carbon isotopic records do not reflect the expected difference in food availability, and thereby 13 C uptake, between the marine and freshwater realm [9][10][11][12][13][14][15] .…”

“…18,19 The oxygen isotopic graphs of the sturgeons in DePalma et al 5 display large annual variations, presumably reflecting the anadromous nature of these fishes, whereas the corresponding graphs for paddlefishes show little variation 5 . Despite these trophic environmental differences, the carbon isotopic graphs for the sturgeons and paddlefishes are essentially identical 5 ; the sturgeon carbon isotopic records do not reflect the expected difference in food availability, and thereby 13 C uptake, between the marine and freshwater realm [9][10][11][12][13][14][15] . It appears that even though the paddlefishes were purely freshwater fish while the sturgeons were anadromous, both taxa recorded the same trophic 13 C signature, as though the sturgeons were maintaining a freshwater diet even in the marine realm.…”