In 1879, Charles Darwin characterized the sudden and unexplained rise of angiosperms during the Cretaceous as an "abominable mystery." The diversification of this clade marked the beginning of a rapid transition among Mesozoic ecosystems and floras formerly dominated by ferns, conifers, and cycads. Although the role of environmental factors has been suggested [Coiffard C, Gómez B (2012) Geol Acta 10(2):181-188], Cretaceous global climate change has barely been considered as a contributor to angiosperm radiation, and focus was put on biotic factors to explain this transition. Here we use a fully coupled climate model driven by Mesozoic paleogeographic maps to quantify and discuss the impact of continental drift on angiosperm expansion and diversification. We show that the decrease of desertic belts between the Triassic and the Cretaceous and the subsequent onset of long-lasting humid conditions during the Late Cretaceous were driven by the breakup of Pangea and were contemporaneous with the first rise of angiosperm diversification. Positioning angiosperm-bearing fossil sites on our paleobioclimatic maps shows a strong match between the location of fossilrich outcrops and temperate humid zones, indicating that climate change from arid to temperate dominance may have set the stage for the ecological expansion of flowering plants.climate modeling | paleogeography A ngiosperms have gradually dominated terrestrial environments after their appearance during the Early Cretaceous (1, 2). Their radiation was characterized by high and rapid diversification (3, 4), high rates of speciation throughout the Cretaceous (5), and unprecedented ecological dominance. Most hypotheses to explain angiosperm radiation invoke biotic (instrinsic) factors, such as pollinating insects (6), coevolution with herbivorous insects (7), morphological novelties (8), or ecophysiological innovations (9-11) as well as macroevolutionary patterns (1). However, recent studies have shown that extrinsic influences combined with biotic factors may drive species diversity at the multimillion-year time scale (6, 12), reviving the potential role of global climate change (13, 14) on angiosperm radiation. Such a combination is supported by fossil data, as illustrated by the latest studies based on the European megafossil plant record that provided a scenario in which angiosperm radiation was concomitant, in space and time, with the evolution of the physical environment (15).Although the Cretaceous climate is described as warm and equable, onset of such climatic conditions is gradual (16) and results from long-term processes that occurred throughout the Mesozoic. Climate simulations were conducted using a fully coupled ocean-atmosphere general circulation model (FOAM) for five continental configurations, from the Middle Triassic [225 million years ago (Ma)] to the Late Cretaceous (70 Ma). The coupling of the Lund-Potsdam-Jena dynamic global vegetation model (LPJ) within FOAM experiments helped to account for vegetation feedbacks on the climate system and to bui...
International audienceThe geodynamic processes that control the opening of the central segment of the South Atlantic Ocean (between the Walvis Ridge and the Ascension FZ) are debated. In this paper, we discuss the timing of the sedimentary and tectonic evolution of the Early Cretaceous rift by drawing eight paleogeographic and geodynamic maps from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollen) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains, with a two phases evolution of the pre-drift ("rifting") times: a rift phase characterized by tilted blocks and growth strata, followed by a sag basin. The southern domain includes the Namibe, Santos and Campos Basins. The northern domain extends from the Espirito Santo and North Kwanza Basins, in the south, to the Sergipe-Alagoas and North Gabon Basins to the north. Extension started in the northern domain during the Late Berriasian (Congo-Camamu Basin to the Sergipe- Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain (emplacement of the Parana-Etendeka Trapp). Extension started in this southern domain during the Early Barremian. The rift phase is shorter in the south (5-6 Ma, Barremian to base Aptian) than in the north (19 to 20 Myr, Upper Berriasian to base Aptian). The sag phase is of Middle to Late Aptian age. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age. From the Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower organic-rich one with no more highs. The lake migrates southward in two steps, until the Valanginian at the border between the northern and southern domains, until the Early Barremian, north of Walvis Ridge
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