Australia: The Land Where Time Began

A biography of the Australian continent 

Triassic climates — State of the art and perspectives

According to Preto et al. a non-zonal pattern which was dictated by a strong global monsoonal system, the effects of which were most evident in the Tethys realm, characterised the climate of the Triassic Period. The aggregation of the supercontinent Pangaea was complete by the Triassic, and the formation of this supercontinent is related to this strong monsoonal regime, and oscillations of climate existed within this framework. Preto et al. suggest that the harsh hot-house conditions were characteristic of the Late Permian, and they also suggest that it is possible the climatic conditions precipitated the mass extinction event at the close of the Permian. They also suggest these difficult conditions were probably maintained during the Early Triassic and may account for the impoverishment of the distinctive faunal and floral associations of the Lower Triassic. Carbonate production remained high, at least in the western Tethys realm, though metazoan reef builders were probably the most affected by the climatic conditions at this time. Locally, episodes of humidity characterised the Middle Triassic, though their geographic distribution has not yet been clarified. An episode of increased rainfall has been documented worldwide, the Carnian Pluvial Event, was the most distinctive climate change that occurred within the Triassic. A number of hypotheses have been proposed for its causes: circulation changes in the ocean or atmosphere that were driven by plate tectonics; the maximum continental aggregation leading to a peak of the global monsoon; or triggering by the eruption of a large igneous province. The subsequent Carnian and Norian seem to have been climatically stable, though recently minor climate changes have been described from these periods of time. Climatic changes, warming and increased rainfall in particular, are also associated with the mass extinction event at the close of the Triassic, though most of the evidence for this has been found in the northern parts of the  Central Atlantic Magmatic Province, and the global climate change pattern at the Triassic/Jurassic boundary is not yet resolved. Preto et al. say there are many facets of the Triassic climate that are intriguing and need further research. So far palaeoclimate studies of the Triassic have been carried only locally by the use of different proxies. In order to correctly depict the temporal and geographic patterns of the Triassic climate the proxies require inter-calibration.


It is not simple to reconstruct the climate of the Triassic as there were many oscillations to and from humid conditions, at least in the region of the Tethys, and it is difficult to assess the geographical distribution of the climatic zones, to a large extent as a result of the global monsoonal system that is believed to have been stronger than that of the present (Wang, 2009).  According to Preto et al. an understanding of the temporal and spatial pattern of this climatic variability is still some way from being achieved, with possible exception of the system boundary intervals, probably a result of the diverse proxies that have been used to date to reconstruct palaeoclimates of the Triassic. This review has highlighted the way in which different parts of the Triassic were studied by using evidence from either palaeontology or sedimentology, not more than a few works attempting a more inclusive approach, with palaeontological, isotopic or modelling studies (e.g., Kutzbach & Gallimore, 1989; Korte et al., 2005; Hochuli & Vigran, this issue; Kiessling, 2010-this issue). Preto et al. say the record of Triassic palaeoclimate, that is rather dispersed, needs to be brought together, possibly by switching to more objective proxies and inter-calibrating the geochemical, palaeontological and sedimentological datasets. Multidisciplinary works in key localities that are representative of different climatic zones still remain unavailable. Also, there is insufficient information on the timing of climatic events, as well as their geographical distribution.

Some degree of variability of climate can be observed throughout the Triassic, even in time intervals that have traditionally been considered to be stable, though the strongest climate changes appear to have occurred during the Early Triassic and the middle of the Carnian.

Included in this volume are important reviews of carbonate systems from the Triassic (Kiessling, 2010-this issue; Stefani et al., 2010-this issue), which highlight the large amount of information that is available on carbonate platforms from the Triassic. The story of the production of carbonate during the Triassic needs to be revised in light of the reassessment of the time scale of the Triassic, especially with reference to the Lower Triassic. It has been considered that the Lower Triassic was a time of reduced carbonate production (Payne et al., 2004), characterised by a gap in the reef building organisms and many Lazarus taxa, such as calcareous algae and echinoderms, that reappear at a later time in the Lower Triassic (e.g., Broglio Loriga et al., 1983; Wignall et al., 1998) or in the Middle Triassic (e.g., Gaetani et al., 1981; Senowbari-Daryan et al., 1993). Net rates of carbonate accumulation are also to be recalculated as the duration of the Induan stage has been shortened as a result of recent geochronological studies, with the result that some localities, such as the central Dolomites, in 80-90 m/Myr, a figure that is close to or higher than that of recent carbonates. Therefore, after the end-Permian extinction event, there is not a crisis of carbonate production, though there is a crisis of reef-building biota, which is in agreement with the general observations of Kiessling et al. (2003).

Several recent studies have focused on the Carnian Pluvial Event (see, in this issue, Kozur &Bachmann; Roghi et al.). Preto et al. say this event is clearly a milestone in the climatic and sedimentary evolution of the Triassic. An hypothesis that the Carnian Pluvial Event might have been a climate and oceanographic perturbation that was similar in both its causes and its effects on the carbon cycle, and physico-chemical modifications of waters in the deep ocean, to Oceanic Anoxic Events (OAEs) in the Jurassic and Cretaceous, or to Palaeocene-Eocene Thermal Maximum (PETM), triggered by a large igneous province eruption (Furin et al., 2006; Rigo et al., 2007). The Carnian Pluvial Event may become an important analogue for climate change in the future, if this is true, and specifically it corresponded to an atmospheric CO2 maximum, as it is the case for several similar events in the Mesozoic and Cainozoic. Though in contrast to the PETM and all OAEs from the Jurassic and Cretaceous, the Carnian Pluvial Event occurred in an “aragonite seas” phase (Stanley & Hardie, 1998; Stanley, 2008), i.e., with a seawater chemistry that was similar to that of the present. Consequently, the Carnian Pluvial Event could be a better analogue than, e.g., the PETM for the understanding of ocean acidification driven by climate and it consequences on carbonate producers in shallow water.

The recent reassessments of the time scale of the Triassic require also that the climate history of the Late Triassic be re-examined, as well as a different interpretation of the carbonates from the Early Triassic. Specifically, the Norian stage is characterised by a stable climate (but see Berra et al., 2010-this issue), now corresponds to a duration of about 20 Myr. The stability of the Norian is therefore a long-standing one, though Preto et al. suggest it is probably only apparent, as a result of the lack of palaeoclimatic data.

Sources & Further reading

  1. Preto, N., E. Kustatscher and P. B. Wignall (2010). "Triassic climates — State of the art and perspectives." Palaeogeography, Palaeoclimatology, Palaeoecology 290(1–4): 1-10.


Author: M. H. Monroe
Last Updated 05/01/2016
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