In the marine realm it saw the first appearance among the microplankton of coccoliths and dinoflagellates,[8][7][9] with the latter linked to the rapid diversification of scleractinian corals through the establishment of symbiotic zooxanthellae within them.
This climate change was probably linked to the eruption of extensive flood basalts as the Wrangellia Terrane was accreted onto the northwestern end of the North American Plate.
[10] Environmental disturbance and high extinction rates were observed for sediments of the Carnian stage long before a global climate perturbation was proposed.
Schlager & Schöllnberger (1974) drew attention to a dark siliciclastic layer which abruptly interrupted a long period of carbonate deposition in the Northern Limestone Alps.
[14][18] Several Carnian terrestrial formations (namely the Schilfsandstein of Germany and various members of the United Kingdom's Mercia Mudstone Group) are intervals of river sediments enriched with kaolinitic clay and plant debris, despite having been deposited between more arid strata.
[6] In 1989, a paper by Michael J. Simms and Alastair H. Ruffell combined these disparate observations into a new hypothesis, pointing to an episode of increased rainfall synchronous with significant ecological turnover in the mid-Carnian.
Their hypothesized climatic disturbance, which they named the Carnian pluvial episode, was tentatively considered to be a result of oceanic and/or volcanic instability related to the early rifting of Pangea, but at that time direct evidence of this was lacking.
[19] A strong critique by Visscher et al. (1994) argued that aridity-adapted pollen stayed abundant through the entire Carnian of Germany, suggesting that the Schilfsandstein was simply indicative of an invading river system rather than widespread climate change.
[16][24][19] Interest in the hypothesis was greatly enhanced by a 2008 meeting and workshop on Triassic climate at the Museum of Nature South Tyrol in Bolzano, Italy.
[31] Carbon and Osmium isotope records published over the coming years supported a strong link between the Carnian climate disturbances and the Wrangellia large igneous province, but many questions remain unanswered.
[33] The Carnian pluvial episode introduced markedly more humid conditions across the globe, interrupting the otherwise arid climate of the Late Triassic period.
[10] This volcanic activity was in turn probably related to the formation of the Wrangellia Large igneous province around the same time, which created vast quantities of igneous (volcanic) rocks that were accreted onto the northwest end of the North American Plate (now the Wrangell Mountains, Alaska, and an estimated 6km thick layer underlying most of Vancouver Island)[10] There is some evidence for seabed euxinia (no oxygen and high toxic sulfide concentrations) during the CPE.
[38][28][39][40] More precise stratigraphic evaluation of European outcrops has resolved this excursion into three or possibly four major pulses, spanning the late Julian and early Tuvalian.
Immediately after the CPE, hyperodapedontines were widespread and abundant in the late Carnian world, suggesting that they benefited from the climate fluctuations or floral turnover.
[50] Mammals, which evolved from eucynodont synapsids that survived the Smithian–Spathian boundary event, diversified but remained small and rare in the subsequent Norian with morganucodonts, haramiyids and symmetrodonts appearing in the United Kingdom, Germany, Greenland and Luxembourg.
The Carnian saw the reestablishment of large inland lakes and peat swamps, ending the Early-Middle Triassic "coal gap" caused by the Permian-Triassic mass extinction.
Through Julian 2, land-based sediments isolated and filled in marine basins, replacing carbonate-specialists such as bairdiids and healdiids with Bektasia, a platycopid tolerant of shallow siliciclastic seas.
Further shallowing across the Julian-Tuvalian boundary left only a few aberrant limnocytherids (Renngartenella, Simeonella) and cytherurids (Kerocythere) which could manage severe salinity fluctuations in the restricted coastal basins.
[57] The recent discovery of a prominent δ13C negative shift in higher plants' n-alkanes suggests a massive CO2 injection in the atmosphere-ocean system at the base of the CPE.
[58] According to an alternative hypothesis, the Carnian pluvial episode was a regional climatic perturbation mostly visible in the western Tethys and related to the uplift of a new mountain range, the Cimmerian orogen, which resulted from the closing of a Tethyan northern branch, east of the present European continent.
Summer monsoonal winds were thus intercepted by the Cimmerian mountain range and generated strong rain, thus explaining the switch to humid climate recognized in western Tethys sediments.