A preliminary test of the press-pulse extinction hypothesis: Palynological indicators of vegetation change preceding the Cretaceous-Paleogene boundary, McCone County, Montana, USA

Abstract

Many workers consider the Cretaceous-Paleogene extinction the archetypal catastrophic pulse event caused solely by the Chicxulub bolide impact. However, based on a global scale analysis of marine animals, the Cretaceous-Paleogene boundary is a candidate for an extinction enhanced by the coincidence of press and pulse disturbances. We make a preliminary test of key predictions of the press-pulse hypothesis using palynological data. We document a local palynological extinction of 21% at the Cretaceous-Paleogene boundary, which is consistent with extinction rates of 15% to 30% at other localities in the Hell Creek type area and throughout North America. We also fi nd a decline in the number of dicot angiosperm pollen taxa between −3.5 m and −2.5 m below the boundary. We document a low-palynospecies-richness interval between −1.4 m and −1.0 m that includes extirpation, but not extinction, of some palynospecies. These changes in species richness are not correlated with changes in depositional style or pollen preservation, indicating that they may represent a biological rather than entirely taphonomic signal. Review and reanalysis of previously published data from other localities in the western interior of North America suggest similar declines in species richness within approximately the same stratigraphic interval. However, many of the species absent during the low-species-richness interval reappeared before the Cretaceous-Paleogene boundary, suggesting changes in community structure and composition before the terminal Cretaceous event-a key prediction of the press-pulse hypothesis-rather than gradual extinction in the latest Cretaceous.

End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change

“…It is therefore impossible at this point to separate the influences of the meteorite and the additional volcanism in driving the second phase of extinction or in causing the second warming pulse. Nevertheless, the full magnitude of the end-Cretaceous extinction at this site can be attributed to the combined influence of Deccan Traps volcanism and the meteorite impact event, previously described as a press-pulse extinction mechanism 48 49 . Importantly, the pre-KPB warming, which itself correlated with significant extinction, may have increased ecosystem stress, making the ecosystem more vulnerable to collapse when the meteorite hit.…”

Early mammalian recovery after the end-Cretaceous mass extinction: A high-resolution view from McGuire Creek area, Montana, USA

“…The color change between gray and yellow sediments occurs below the MCZ coal and is roughly coincident with a ~10-cm-thick carbonaceous shale layer. This carbonaceous shale layer is also coincident with a negative carbon isotope excursion (measured near the Z-Line locality at McGuire Creek), which Arens et al (2014) claystone nor the Nirvana bentonite layer, which was derived from a tephra unique to the IrZ coal found in Garfield County (Ickert et al (2015), is readily apparent. It is therefore possible that the carbonaceous shale layer may be roughly correlative to the IrZ coal.…”

“…It grades laterally into coal, and ~4 cm from the top of the layer is a 1-2-cm-thick fine-grained pink (Munsell color 5 R 6/2) siltstone. This carbonaceous shale layer can be visually traced to the carbonaceous shale measured by Arens et al (2014) where the negative carbon isotope excursion was identified. A 1-2-cm-thick, lightgray to pink claystone forms the lower bound to the carbonaceous shale.…”

Variation in the shape and mechanical performance of the lower jaws in ceratopsid dinosaurs (Ornithischia, Ceratopsia)

“…Similarly, Arens et al. () provided evidence on the relative abundance of angiosperms rather than gymnosperms at the Cretaceous–Paleogene boundary in the Hell Creek Formation, even if angiosperms were characterized by a species decline during the Late Maastrichtian. Recent works (Lupia et al.…”