Naslov
Vegetation dynamics of riparian plant communities in the Norian on the western margin of Pangea (Chinle Formation, Petrified Forest National Park, Arizona, SW USA).

Autori
Viktoria Baranyi, Wolfram M. Kürschner, Paul Olsen, William G. Parker

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

Izvornik
Abstract Book / - , 2016, 204-204

Skup
XIV International Palynological Congress

Mjesto i datum
Salvador, Brazil, 23.10.2016. - 28.10.2016

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Chinle, Norian, palynology, vegetation, climate

Sažetak
The Chinle Formation hosts a remarkable Norian terrestrial ecosystem with rich floral remains and vertebrate fossils. A floral turnover and reorganisation of riparian plant communities occurred in the Norian Chinle Formation of the American SW indicating ongoing climate change towards more arid climate and severe environmental perturbation. New palynological data suggest that approximately simultaneously with a vertebrate turnover event, a floral turnover occurred in the middle part of the Sonsela Member. The analysis of the plant communities revealed that this turnover was followed by a complete reorganization of the riparian vegetation driven by the tectonic regime of the hinterland, fluvial styles and gradual transition towards more arid climate. The newly formed riparian community hosted Cupressaceae-Araucariaceae related plants suggested by the presence of Araucariacites australis, Inaperturopollenites sp. and Perinopollenites elatoides in the pollen record in this interval. The presence of trees with similar stature to modern day Araucariaceae and Cupressaceae was allowed by the more stable overbank settings proposed for the upper part of Sonsela Member based on the sedimentological observations. The frequent flooding events and crevassing in the lower Sonsela Member according to the sedimentology didn’t support the presence of these trees in the proximity of the stream ; they colonized probably more stable environments further from the stream. The migration of these plants closer to the stream might be connected to the increase in aridity and drop of groundwater table after the turnover which eliminated the presence of plants with shallow penetrating roots in the floodplain. Besides the re-organization of riparian communities the rapid loss in the sporomorph diversity and significant increase in the ratio of Klausipollenites gouldii, aberrant Klauispollenites gouldii morphotypes, the increase in Patinasporites spp. and Froelichsporites traversei are also indicators of environmental stress, possibly more arid climate and the perturbation of the global carbon cycle and increased pCO2. Comparison of the vegetation turnover with definitely younger assemblages from the Chinle Formation in New Mexico showed the same turnover patterns suggesting two distinct drier periods implying climatic oscillations in the upper Norian of the American SW. The climate induced floral turnover contributed to the extinctions and turnover in the vertebrate fauna because the contraction of the previously inhabited wetland areas and different food sources provided by new plants. The floral and faunal turnover are all temporally close to the Manicugan impact event suggesting that around 215.5 Ma severe environmental perturbations took place and affected the Chinle ecosystem.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA