Magnetostratigraphy of the Upper Triassic Chinle Group of New Mexico: Implications for regional and global correlations among Upper Triassic sequences

Zeigler, Kate E.; Geissman, J. W.

doi:10.1130/ges00628.1

Cited by 27 publications

(7 citation statements)

References 78 publications

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“…This earliest equatorial occurrence of salientians demonstrates that this group had a Pangean distribution during the early stages of their evolution in the Triassic. This equatorial record from the Chinle Formation (deposited between palaeolatitudes 58S and 158N; [33]) records a shifting palaeoclimate between a warm and humid megamonsoonal climate and an arid post-monsoonal climate [34] further affected by orbital eccentricities in the Early Jurassic [35]. That salientians are known from the overlying Kayenta Formation (Prosalirus; [14]) suggests they survived the aridification of this region in the early Mesozoic.…”

Section: (C) Descriptionmentioning

confidence: 88%

The earliest equatorial record of frogs from the Late Triassic of Arizona

et al. 2019

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Crown-group frogs (Anura) originated over 200 Ma according to molecular phylogenetic analyses, though only a few fossils from high latitudes chronicle the first approximately 60 Myr of frog evolution and distribution. We report fossils that represent both the first Late Triassic and the earliest equatorial record of Salientia, the group that includes stem and crown-frogs. These small fossils consist of complete and partial ilia with anteriorly directed, elongate and distally hollow iliac blades. These features of these ilia, including the lack of a prominent dorsal protuberance and a shaft that is much longer than the acetabular region, suggest a closer affinity to crown-group Anura than to Early Triassic stem anurans Triadobatrachus from Madagascar and Czatkobatrachus from Poland, both high-latitude records. The new fossils demonstrate that crown anurans may have been present in the Late Triassic equatorial region of Pangea. Furthermore, the presence of Early Jurassic anurans in the same stratigraphic sequence ( Prosalirus bitis from the Kayenta Formation) suggests that anurans survived the climatic aridification of this region in the early Mesozoic. These fossils highlight the importance of the targeted collection of microfossils and provide further evidence for the presence of crown-group representatives of terrestrial vertebrates prior to the end-Triassic extinction.

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Section: (C) Descriptionmentioning

confidence: 88%

The earliest equatorial record of frogs from the Late Triassic of Arizona

et al. 2019

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“…The main cause of the transition to drier and warmer climate was believed to be the northward movement of the North America continent from the equator into the drier midlatitudes (Dubiel et al, 1991;Kent and Tauxe, 2005;Kent and Irving, 2010). However, recent magnetostratigraphy of the Chinle Formation at the Petrified Forest National Park is suggestive of a restricted northward movement during the middle to late Norian and Rhaetian (Zeigler and Geissman, 2011). Alternatively, the uplift of the Cordilleran arc could have caused an increasing rain shadow over the Chinle sedimentary basin, blocking the influx of moist tropical air (Litwin, 1986;Atchley et al, 2013;Nordt et al, 2015).…”

Section: Climate Change During the Norianmentioning

confidence: 99%

Norian vegetation history and related environmental changes: New data from the Chinle Formation, Petrified Forest National Park (Arizona, SW USA)

et al. 2017

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Fossil plant assemblages including spores and pollen grains provide useful information on past ecosystems and the response of terrestrial biotas to various environmental perturbations. New quantitative palynological data from the Chinle Formation of the American Southwest suggest that a floral turnover occurred in the middle Norian (between 217 and 213 Ma). Analysis of plant communities reveals that this turnover was followed by a complete reorganization of the riparian vegetation, driven by changes in fluvial styles and the tectonic regime of the basin, as well as a gradual transition toward a more arid climate. Marked increases in Klausipollenites gouldii, Patina sporites spp., and Froelichsporites traversei are probable indicators of environmental stress, such as increased aridity, perturbations of atmospheric pCO 2 , acid rain, and atmospheric aerosol accumulation due to volcanism in connection with the Pangean rifting and uplift of the Cordilleran arc. Comparison of the vegetation turnover with younger assemblages from the Chinle Formation in New Mexico revealed similar floral turnover patterns, suggesting two distinct drier periods as a result of multiple climatic oscillations. The climate-induced floral turnover may have contributed to the vertebrate faunal turnover as the loss of wetland habitat space and an increase in xerophytic plants may have dwindled the supply of palatable vegetation for herbivores. The onset of the floral turnover in Arizona roughly corresponds to the Manicouagan impact event, but a direct causal link is still speculative.

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“…The Upper Triassic Chinle Formation of Arizona and northern New Mexico has been the primary source for examining early dinosaur diversity in western North America (e.g., Hunt et al 1998;Nesbitt et al 2007). New age constraints suggest that all or nearly all of the Chinle Formation is Norian in age , although some of the uppermost units might be Rhaetian (Zeigler 2008;Zeigler & Geissman 2008). The best-known assemblage from near the base of the Chinle Formation is the Placerias Quarry in northern Arizona (Camp & Welles 1956;Long & Murry 1995;Fiorillo et al 2000).…”

Section: 6+'-'4)mentioning

confidence: 99%

Evaluating hypotheses for the early diversification of dinosaurs

Irmis

2010

Earth and Environmental Science Transactions of the Royal Socie

138

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Many hypotheses have been proposed for the rise of dinosaurs, but their early diversification remains poorly understood. This paper examines the occurrences, species diversity and abundance of early dinosaurs at both regional and global scales to determine patterns of their early evolutionary history. Four main patterns are clear: (1) sauropodomorph dinosaurs became abundant during the late Norian–Rhaetian of Gondwana and Europe; (2) Triassic dinosaurs of North America have low species diversity and abundance until the beginning of the Jurassic; (3) sauropodomorphs and ornithischians are absent in the Triassic of North America; and (4) ornithischian dinosaurs maintain low species diversity, relative abundance and small body size until the Early Jurassic. No one hypothesis fully explains these data. There is no evidence for a Carnian–Norian extinction event, but sauropodomorphs did become abundant during the Norian in some assemblages. No clear connection exists between palaeoenvironment and early dinosaur diversity, but environmental stress at the Triassic–Jurassic boundary is consistent with changes in North American dinosaur assemblages. Elevated growth rates in dinosaurs are consistent with the gradual phyletic increase in body size. This study demonstrates that early dinosaur diversification was a complex process that was geographically diachronous and probably had several causes.

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Magnetostratigraphy of the Upper Triassic Chinle Group of New Mexico: Implications for regional and global correlations among Upper Triassic sequences

Cited by 27 publications

References 78 publications

The earliest equatorial record of frogs from the Late Triassic of Arizona

The earliest equatorial record of frogs from the Late Triassic of Arizona

Norian vegetation history and related environmental changes: New data from the Chinle Formation, Petrified Forest National Park (Arizona, SW USA)

Evaluating hypotheses for the early diversification of dinosaurs

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