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Original Article |
1 1Palaeontological Institute, University of Zürich, Karl Schmid-Strasse 4, 8006 Zürich, Switzerland (e-mail: peter.hochuli@erdw.ethz.ch)
2 2Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK
3 3Geological Institute, ETH Zürich, Sonneggstr. 5, 8092 Zürich, Switzerland
New stratigraphically controlled pollen data from the late Early Cretaceous of Portugal allow a recalibration of the classical continental succession of the Potomac Group (USA), which has long been used to demonstrate the gradual morphological changes of angiosperm leaves and pollen. The Portuguese record represents the best dated succession of angiosperm pollen assemblages of the interval between the late Barremian and the mid-Albian. Comparison of the angiosperm pollen record of the Potomac Group with the pollen assemblages from Portugal and with other independently dated records indicates that the distinct differences in the angiosperm pollen assemblages between the three formations of this group (the Patuxent Formation, Arundel Clay Formation and Patapsco Formation) are related to discontinuities. Our revised age model for the Potomac Group implies a major discontinuity between the Arundel Clay (of early Albian age), and the Patapsco Formation (of mid-Albian–early Cenomanian age). The Portuguese record reveals a so far undocumented radiation phase of angiosperms within the early Aptian to mid-Albian in which monocolpate angiosperm pollen of monocot and/or magnoliid affinity appear as a highly diversified group. These new findings imply that the onset of the radiation of monocots–magnoliids preceded the radiation of eudicots by at least 10 Ma.
