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Severest crisis overlooked-Worst disruption of terrestrial environments postdates the Permian-Triassic mass extinction.

Hochuli PA, Sanson-Barrera A, Schneebeli-Hermann E, Bucher H - Sci Rep (2016)

Bottom Line: This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian.Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years.Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis.

View Article: PubMed Central - PubMed

Affiliation: Institute and Museum of Palaeontology, University of Zurich, Karl Schmid-Str. 4, CH-8006 Zurich, Switzerland.

ABSTRACT
Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian-Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian-Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ(13)Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian-Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.

No MeSH data available.


Related in: MedlinePlus

Summary of Early Triassic floral events.Radiometric ages414267 together with a simplified bulk organic carbon isotope curve244850 are shown in relation to floral events documented in the Boreal Realm22242645 and on the North Indian margin232544.
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f2: Summary of Early Triassic floral events.Radiometric ages414267 together with a simplified bulk organic carbon isotope curve244850 are shown in relation to floral events documented in the Boreal Realm22242645 and on the North Indian margin232544.

Mentions: Generally climatic changes are the primary trigger for changes in vegetation patterns. Fast reactions of the plant communities-within time spans of 100 yrs-are reliably recorded in changes in pollen assemblages (e.g., Early Holocene afforestation in the Alps62). In order to understand terrestrial environmental changes in the Early Triassic indicated by pronounced negative δ13Corg shifts and the coeval floral turnovers we try to infer the corresponding climatic conditions. Proliferation of spores is generally associated with more humid conditions, based on the fact that pteridophytes need liquid water at least during part of their life cycle. Thus spore dominated assemblages are considered to reflect relatively humid conditions. Temperature values are much more delicate to infer from plant records. Recent data of δ18O measurements of pristine biogenic apatite of conodonts reveal considerable changes in temperatures near the PTME and during the Early Triassic15. These authors inferred relatively cool temperatures for the Griesbachian and a temperature increase for the Dienerian. The δ18O record of the Early Triassic follows the trends in the carbon cycle reflected in the δ13C curve. The marked shifts in these records, reflecting severe environmental disturbances, are accompanied by major changes in plant assemblages (Fig. 2). For the Salt Range sections the increased spore ratios near the GDB and in the middle Smithian can be directly linked to negative shifts of δ13Corg and to lower δ18O1523. These trends are interpreted to correspond to higher pCO2 and to higher temperatures that apparently induced at least seasonally increased humidity15. In contrast, the gymnosperms dominated assemblages of the late Smithian/early Spathian are associated with relatively positive δ13Corg values and δ18O values reflecting relatively cool temperatures15. Applying this relationship to the Induan succession of Kap Stosch, we suggest that the gymnosperm pollen dominated Griesbachian assemblages reflect relatively cool and dry conditions, which rapidly changed to hot and humid at the GDB.


Severest crisis overlooked-Worst disruption of terrestrial environments postdates the Permian-Triassic mass extinction.

Hochuli PA, Sanson-Barrera A, Schneebeli-Hermann E, Bucher H - Sci Rep (2016)

Summary of Early Triassic floral events.Radiometric ages414267 together with a simplified bulk organic carbon isotope curve244850 are shown in relation to floral events documented in the Boreal Realm22242645 and on the North Indian margin232544.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4920029&req=5

f2: Summary of Early Triassic floral events.Radiometric ages414267 together with a simplified bulk organic carbon isotope curve244850 are shown in relation to floral events documented in the Boreal Realm22242645 and on the North Indian margin232544.
Mentions: Generally climatic changes are the primary trigger for changes in vegetation patterns. Fast reactions of the plant communities-within time spans of 100 yrs-are reliably recorded in changes in pollen assemblages (e.g., Early Holocene afforestation in the Alps62). In order to understand terrestrial environmental changes in the Early Triassic indicated by pronounced negative δ13Corg shifts and the coeval floral turnovers we try to infer the corresponding climatic conditions. Proliferation of spores is generally associated with more humid conditions, based on the fact that pteridophytes need liquid water at least during part of their life cycle. Thus spore dominated assemblages are considered to reflect relatively humid conditions. Temperature values are much more delicate to infer from plant records. Recent data of δ18O measurements of pristine biogenic apatite of conodonts reveal considerable changes in temperatures near the PTME and during the Early Triassic15. These authors inferred relatively cool temperatures for the Griesbachian and a temperature increase for the Dienerian. The δ18O record of the Early Triassic follows the trends in the carbon cycle reflected in the δ13C curve. The marked shifts in these records, reflecting severe environmental disturbances, are accompanied by major changes in plant assemblages (Fig. 2). For the Salt Range sections the increased spore ratios near the GDB and in the middle Smithian can be directly linked to negative shifts of δ13Corg and to lower δ18O1523. These trends are interpreted to correspond to higher pCO2 and to higher temperatures that apparently induced at least seasonally increased humidity15. In contrast, the gymnosperms dominated assemblages of the late Smithian/early Spathian are associated with relatively positive δ13Corg values and δ18O values reflecting relatively cool temperatures15. Applying this relationship to the Induan succession of Kap Stosch, we suggest that the gymnosperm pollen dominated Griesbachian assemblages reflect relatively cool and dry conditions, which rapidly changed to hot and humid at the GDB.

Bottom Line: This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian.Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years.Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis.

View Article: PubMed Central - PubMed

Affiliation: Institute and Museum of Palaeontology, University of Zurich, Karl Schmid-Str. 4, CH-8006 Zurich, Switzerland.

ABSTRACT
Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian-Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian-Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ(13)Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian-Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.

No MeSH data available.


Related in: MedlinePlus