Multiple geochemical and paleobiological parameters define a “climatic whiplash” during CAMP volcanism

Eruptions of the Central Atlantic Magmatic Province (CAMP) at 201.6 Ma are linked to the end-Triassic extinction (ETE) on land via competing radiative forcings, which caused extreme alternations in warming and cooling and humidity and aridity (climatic whiplash) [c.f., (1)]. Although ETE effects on land-plant diversity are often described as minor, tropical flora exhibit significant changes in plant physiognomy, paralleling pCO₂ and hydrological variations recorded from the same strata.

Most dramatic is the extirpation of the vesicate pollen group exemplified by Patinasporites and Enzonalosporites, known to have low latitudinal preferences. In the Late Triassic Pangean tropics, this likely voltzialian conifer group remained a major component of the palynoflora up to the ETE and the time of the earliest known CAMP lavas, whereas it is progressively rarer or absent in older, more northerly Late Triassic strata, and virtually absent in the paleoarctic. This trend is consistent with the northward drift of central Pangea, but the diachronous last appearances have resulted in some biostratigraphic mischief, if other markers are ignored. Also dramatic is the tropical expansion of the dipteridaceous fern Clathropteris meniscoides. This tough-leaved fern is abundant at mid- to high-latitudes in Late Triassic and Early Jurassic continental units of Pangea but absent from tropical Late Triassic-Early Jurassic assemblages except during the earliest to peak CAMP eruptive interval, where it becomes common or even dominant. In fact, its spores (Granulatisporites and Converrucosisporites) comprise the "fern spike" in the Newark Basin at the ETE (2, 3).

Both of these floral phenomena are inconsistent with warming as an extinction driver during the CAMP episode and instead are consistent with CAMP-driven mega-volcanic winters. A similar pattern is seen among continental tetrapods, where insulated forms (e.g., pterosaurs, dinosaurs, mammals) preferentially survive while all large non-insulated pseudosuchians perish (4).

Cheirolepidaceous conifer leaf and stomatal morphology from deposits show trends related to CAMP events (5). These include short, scale-like leaves with thickened cuticle and sunken stomata that are traditionally interpreted as adaptations to heat and evaporative stress, but are also seen in cold-adapted conifers, suggesting these traits are "poly-tolerance" (6) adaptations. In fact, tropical conifer assemblages directly associated with the ETE have the thickest and shortest leaves of all tropical forms, suggesting adaptations to freezing.

Further, hydrological conditions based on hydrogen isotope data captured in n-alkanes suggest amplified precession and obliquity pacing (7). This observation is consistent with both amplification of the hydrological system during times of CAMP-driven high pCO₂ seen in pedogenic carbonates, molecular proxies from chlorophyll degradation products, and volcanic winters reflected in the floral disruption patterns. From these collective observations, we suggest that "climatic whiplash" at seasonal- and Milankovitch-timescales was a critical driver of the continental ETE and associated floral responses, and that such processes may have panned out elsewhere in Earth history.

References:

1, Swain+ 2025 Nature Rev Earth Env 6:35-50. 2, Olsen+ 2002 Science 296:1305. 3, Fowell+ 1994 GSA Spec Pap 288:197. 4, Olsen+ 2022 Sci Adv 8:eabo6342.  5, Cornet 1977 PhD thesis, PA State. 6, McCulloh+ 2022Tree Phys  43:1-15. 7, Landwehrs+ 2022 PNAS 119:e2203818119.