Onset of main Phanerozoic marine radiation sparked by emerging Mid Ordovician icehouse

This is the final version. Available on open access from Springer Nature via the DOI in this recordThe Great Ordovician Biodiversification Event (GOBE) was the most rapid and sustained increase in marine Phanerozoic biodiversity. What generated this biotic response across Palaeozoic seascapes is a matter of debate; several intrinsic and extrinsic drivers have been suggested. One is Ordovician climate, which in recent years has undergone a paradigm shift from a text-book example of an extended greenhouse to an interval with transient cooling intervals - at least during the Late Ordovician. Here, we show the first unambiguous evidence for a sudden Mid Ordovician icehouse, comparable in magnitude to the Quaternary glaciations. We further demonstrate the initiation of this icehouse to coincide with the onset of the GOBE. This finding is based on both abiotic and biotic proxies obtained from the most comprehensive geochemical and palaeobiological dataset yet collected through this interval. We argue that the icehouse conditions increased latitudinal and bathymetrical temperature and oxygen gradients initiating an Early Palaeozoic Great Ocean Conveyor Belt. This fuelled the GOBE, as upwelling zones created new ecospace for the primary producers. A subsequent rise in δ(13)C ratios known as the Middle Darriwilian Isotopic Carbon Excursion (MDICE) may reflect a global response to increased bioproductivity encouraged by the onset of the GOBE.Our expeditions to Russia were mainly funded by the Carlsberg Foundation. C.M.Ø.R. and D.A.T.H. are particularly grateful to the Danish Council for Independent Research | Natural Sciences for their support of this specific project. C.M.Ø.R. further acknowledge support from the VILLUM Foundations Young Investigator Programme. A.L. was funded by the Royal Swedish Physiographic Society in Lund

Building mountain biodiversity: geological and evolutionary processes

Mountain regions are unusually biodiverse, with especially rich aggregations of small-30 ranged species that form centers of endemism. Mountains play an array of important roles for Earth's biodiversity, and impact neighboring lowlands through biotic interchange, changes in regional climate, and nutrient run-off. The high biodiversity of certain mountains reflects the interplay of multiple evolutionary mechanisms: enhanced speciation rates with unique opportunities for co-existence and persistence of lineages, shaped by long-term climatic changes 35 interacting with topographically dynamic landscapes. High diversity in most tropical mountains is tightly linked to bedrock geology, notably areas comprising mafic and ultramafic lithologies—rock types rich in magnesium and poor in phosphate that present special requirements for plant physiology. Mountain biodiversity bears the signature of deep-time evolutionary and ecological processes, a history worth preserving in the face of contemporary environmental changes

Asteroid breakup linked to the Great Ordovician Biodiversification Event

Author Posting. © Nature Publishing Group, 2007. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature Geoscience 1 (2008): 49-53, doi:10.1038/ngeo.2007.37.The rise and diversification of shelled invertebrate life in the early Phanerozoic took place in two major steps. During the Cambrian Explosion at ca. 540 Ma a large number of new phyla appeared over a short time interval. Biodiversity at the family, genus and species level, however, remained low until the Great Ordovician Biodiversification Event (GOBE) in the mid-Ordovician. This event represents the most intense phase of species radiation during the Paleozoic and the biological component of planet's seafloors was irreversibly changed. The causes of the GOBE remain elusive mainly because of a lack of detailed data relating faunal to environmental change. Here we show that the onset of the major phase of the GOBE coincides at ca. 470 Ma with the disruption in the asteroid belt of the L chondrite parent body, the largest documented asteroid breakup event during the last few billion years. The precise coincidence between an event in space and on Earth is established by bed-by-bed records of extraterrestrial chromite, osmium isotopes and invertebrate fossils in mid- Ordovician strata in Baltoscandia and China. We argue that frequent impacts on Earth of kilometer-sized asteroids accelerated the biodiversification. This is supported also by abundant mid-Ordovician fossil meteorites and impact craters.This study was supported by funds to B.S. from the National Geographic Society, Swedish Research Council (VR) and Crafoord Foundation and to D.A.T.H. from the Carlsberg Foundation