The mysterious Mid-Carnian “Wet Intermezzo” global event

Abstract

Approximately 230 million years ago in the middle of the Carnian stage of the Upper Triassic, the sedimentary records in different regional basins display dramatic changes. Tropical carbonate platforms abruptly ended, and engorged river systems left widespread sand-rich layers across inland basins and coastal regions. This pulse lasted less than a million years in some basins, but constituted a permanent shift in others. Following this event, the Late Carnian has the earliest record of significant dinosaurs on land and the emergence of the calcareous nannoplankton in the oceans that now govern Earth's carbon cycle. This "most distinctive climate change within the Triassic" has been interpreted by some geoscientists as a global disruption of the Earth's land-ocean-biological system. The eruption of the Wrangellia large igneous province may have been the trigger for a sudden carbon-dioxide-induced warming and associated increased rainfall in some of these regions. Indeed, some workers have proposed that this "wet intermezzo" warming event is a useful analog to aid in predicting the effects of our future greenhouse on land ecosystems and ocean chemistry. However, the understanding of the onset, duration, global impacts and relatively rapid termination of this postulated warming pulse has been hindered by lack of a global dataset with inter-calibrated terrestrial and marine biostratigraphy, precise radio-isotopic ages, stable isotope records of temperature and the carbon system, and cycle-calibrated rates of regional and global change.

Sedimentology, clay mineralogy and palaeosols of the Mid-Carnian Pluvial Episode in eastern Spain: insights into humidity and sea-level variations

“…A few years later, however, a world-wide effect of this humid phase was reported by . Since then, this episode has been described in many basins (Berra & Jadoul 2002;Hornung & Brandner 2005;Rigo et al 2007;Retallack (2009); Roghi et al 2010;Kozur & Bachmann 2010;Lukeneder et al 2012; Arche and López-Gómez 2014;Ogg 2015;Mader et al 2017, among others).…”

Geochemical study of the vertebrate assemblage zones of the Santa Maria Supersequence (Middle to Late Triassic), Paraná Basin, Brazil

“…), could be related to the global event named "Wet Intermezzo" or Carnian Pluvial Episode (CPE), whose stipulated age is between 230 and 232 Ma. (Furin et al 2006, Ogg 2015. In the Riograndia's AZ Table 6.…”

“…This suggests that the megamonsoon would have happened in a relatively short, though expressive, time, at least in that region. Although these evidences point to a rapid great humidity event in the Carnian, Ogg (2015) suggests that biostratigraphic calibrations (in both marine and continental environments) and radioisotopic dating should be made to delimitate the real duration of this episode.…”

Bounded by crises: An overview of the evolution of marine ostracods during the Triassic

“…Recognized from deltaic to shallow marine successions of the Dolomites (e.g., Krystyn, 1978;Breda et al, 2009) to deep-water settings of the Himalayas and Lagonegro Basin (Hornung et al, 2007a;Rigo et al, 2007), it has been attributed to an increase in rainfall and is associated with extinction and biotic turnover (e.g., Ruffell, 1989, 1990;Roghi et al, 2010). This event has been given several names: "Carnian Wet Intermezzo" in the Germanic Basin, "Carnian Pluvial Event" in northern Europe, "Reingraben turnover" in the Northern Calcareous Alps, "Raibl Event" in the Italian Dolomites (e.g., Schlager and Schöllnberger, 1974;Simms & Ruffell, 1989Hornung and Brandner 2005;Hornung et al, 2007a, b;Kozur and Bachmann, 2010;Dal Corso et al, 2012;Ogg, 2015).…”