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ABSTRACT
Climate during the Early Cretaceous in tropical South America has often been reconstructed as arid. However, some areas seem to have been humid. We reconstructed the floristic composition of two tropical stratigraphic successions in Peru using quantitative palynology (rarefied species richness and abundance), and used the abundance of aridity vs. humidity indicator species to infer the predominant climate conditions of this region. The Berriasian to Hauterivian La Merced succession was dominated by fern spores and was predominantly humid. The Albian Aguas Frias succession yielded rich palynofloras, with 127 species, and also indicates predominantly humid conditions. These results support the hypothesis that the west margin of South America was humid during the Early Cretaceous, thus improving the tropical climate reconstructions during the Cretaceous severe global warming episodes.
Acknowledgements
Financial support for this project came from the Smithsonian Tropical Research Institute, the Anders Foundation, 1923 Fund and Gregory D. and Jennifer Walston Johnson, and a Geological Society of America (GSA) research grant. Thanks to Pierre-Olivier Antoine and his team in Montpellier for field support. The authors thank Dr Mohamed Zobaa and two anonymous reviewers for comments and suggestions. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the US government.
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No potential conflict of interest was reported by the authors.
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Notes on contributors
Paula J. Mejia-Velasquez
PAULA J. MEJIA-VELASQUEZ is an adjunct professor at the University of Hawaii – Leeward Community College. She received her MS and PhD from the University of Florida, and her BS in biology from the Universidad de Antioquia (Colombia). As part of her doctoral research she reconstructed the palynofloras of different tropical successions of Lower Cretaceous age from South America and determined the climatic implications derived from the floristic composition. Her research interests are tropical biostratigraphy, early evolution of flowering plants in the tropics and climatic reconstruction using palynofloras.
Steven R. Manchester
STEVEN MANCHESTER is Curator of Paleobotany at the Florida Museum of Natural History, University of Florida. His research examines the systematics, biogeography and palaeobotanical record of various extant angiosperm families employing data from fossil flowers, fruits, seeds, leaves, woods and pollen.
Carlos A. Jaramillo
CARLOS A. JARAMILLO is a staff scientist with the Smithsonian Tropical Research Institute in Panama. His research investigates the causes, patterns and processes of tropical biodiversity at diverse scales in time and space. He is also interested in Mesozoic and Cenozoic biostratigraphy of low latitudes, developing methods for high-resolution biostratigraphy and the palaeobiogeography of the Tethys.
Luis Quiroz
LUIZ QUIROZ is a PhD candidate at the University of Saskatchewan, Canada. His research deals with the field of ichnology and sedimentology, and their relations with stratigraphy, palaeoecology and palaeoclimate. He primarily focuses on understanding the dynamics of shallow- to marginal-marine systems in both modern and ancient environments, but with particular emphasis in tropical America.
Lucas Fortini
LUCAS FORTINI is a quantitative ecologist with expertise in population and community ecology. His research interests are currently focused on determining the impacts of climate change on Pacific Island ecosystems, but he also has significant research experience in tropical forest ecology and management.