Isotopic evidence of C4 grasses in southwestern Europe during the Early Oligocene-Middle Miocene

Michael A. Urban, David M. Nelson, Gonzalo Jiménez-Moreno, Jean Jacques Châteauneuf, Ann Pearson, Feng Sheng Hu

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

C4 plants are widely successful in the grass-dominated ecosystems of tropical, subtropical, and warm-temperate regions, largely as a result of their ability to limit photorespiration and improve water-use efficiency. A widely held paradigm is that low (<~400 ppm) atmospheric CO2 concentrations were an important factor selecting for the origin of C4 plants, although support in geological records is limited. We determined the carbon isotopic composition of 686 individual grass-pollen grains preserved in eight samples of lacustrine and shallow-marine sediments from three basins spanning the Early Oligocene to Middle Miocene in southwestern Europe. Grasses composed <15% of the total abundance of terrestrial pollen grains, and 26%-62% of the grass pollen was from C4 grasses. Thus C4 grasses occurred on the landscape as early as the earliest Oligocene, ~14 m.y. earlier than previous isotopic evidence of first C4 plants and before pCO2 fell during the Oligocene.

Original languageEnglish
Pages (from-to)1091-1094
Number of pages4
JournalGeology
Volume38
Issue number12
DOIs
StatePublished - Dec 2010

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