Naslov
Correlation and provincialism among Late Triassic (Norian) low and high latitude plant assemblages: an example from the Chinle Formation (Petrified Forest National Park, Arizona, USA)

Autori
Baranyi, Viktória ; Reichgelt, Tammo ; Olsen, Paul E. ; Parker, William G. ; Kürschner, Wolfram M.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstract volume / - , 2017, 12-13

Skup
32nd Winter Meeting of the Norwegian Geological Society

Mjesto i datum
Oslo, Norveška, 09.01.2017. - 11.01.2017

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Domaća recenzija

Ključne riječi
Norian, Chinle, palynology

Sažetak
Correlation of the palynological assemblages from the low latitude Chinle Formation in North America and the high latitude or Tethyan assemblages in Europe is difficult, because of vegetation provincialism as a result of climatic heterogeneity. This significant offset between the European and American palynofloras is the result of the generally hot and semi-arid climate in the eastern part of Pangea and the western Tethyan realm and a more humid tropical belt in lower latitudes. The Norian is characterized by dolomite formation in the Alpine realm and playa lake deposits in the northwest European realm. However, in lower latitudes in western Pangea, fluvial environments supported rich riparian vegetation due to the seasonally wet climate until the middle Norian. The differences in climate resulted in a significant offset between the stratigraphic ranges of some European Carnian/Norian index taxa. In some cases the parent plants of some typically Carnian taxa from Europe thrived longer in the American southwest. Due to this offset, the Chinle Formation in North America was thought to encompass the Carnian and Norian stages based on palynostratigraphy, but palaeomagnetic correlations and recent radiometric dating suggested middle to late Norian age. We documented the first time the occurrence of the pollen Perinopollenites elatoides from the middle part of the Chinle Formation (Sonsela Member) that represents the only evidence so far from the pollen record that indicates the Norian age of the Chinle Formation and is in agreement with magnetostratigraphy and radiometric dating. This species also provides the first correlation possibility to European coeval palynofloras. Moreover, new palynological data suggest that approximately simultaneously with a vertebrate turnover event, a floral turnover occurred in the middle segment of the Chinle Formation around 215 Ma. As a consequence of the new age assignment, the floral and faunal turnover could be constrained to a horizon that may coincide with the Manicougan impact event dated as 215 Ma. This biotic event may also correlate with a significant climate shift towards more arid climate due to the northward shift of the North American continent, and probable pCO2 perturbations from volcanism related to Pangean rifting and the uplift of the Cordilleran Arc. Besides the vegetation change and the rapid diversity loss, the floral turnover around 215 Ma was associated with an increase in opportunistic plant types (e.g., Majonicaceae, Voltziaceae) and an increase in mutant aberrant pollen morphotypes. A similar event without the aberrant pollen types could be distinguished in a younger horizon of the Chinle dated as 211 Ma old. The separation of these two events was only possible based on the precise radiometric dating. In contrast to representing one event, the two events point out the possibility of multiple biotic turnovers that are most likely controlled by cyclic environmental perturbation such as climatic oscillations. However, the aberrant pollen morphotypes are confined to the event around 215 Ma and they might represent the effect of the environmental stress associated with the Manicougan impact event.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA