Chen Xu

This publication combines the interpretations of two major sets of data. One is the geophysical data that is used to interpret the position of the tectonic plates through geologic time. The other is based on a long time search of the geological literature to find, record and evaluate the lithologic descriptions of countless reports around the globe; paying careful attention to those lithologies that have climatic implications. The introduction to this volume includes a detailed discussion of the lithologies, mineralogies and biogeographies that are considered to be the most reliable in identifying the climatic conditions existing during their formation and how they are used or not used in this compilation. These include coal, cyclothems, laterite, bauxite, lateritic manganese, oolitic ironstone, kaolin, glendonite, tilites, dropstones, calcretes, evaporites, clay minerals, palms, mangroves, and crocodilians. Additionally, several others are discussed but not used for specified reasons. These include eolian sandstone, silcrete and some specific paleobotanical methodologies. Global paleoclimatic zones based on the climatically interpreted data points are identified during twenty-eight time periods from Cambrian to Miocene using paleotectonic reconstructed maps. The paleoclimate of each time period is summarized and includes a discussion of the specific referenced data points that have been interpreted to be the most reliable available for that time period and location.

11 páginas, 2 figuras.The extensive work carried out during more than a decade by the International Subcommission on Ordovician Stratigraphy has resulted in a new global classification of the Ordovician System into three series and seven stages. Formal Global Boundary Stratotype Section and Points (GSSPs) for all stages have been selected and these and the new stage names have been ratified by the International Commission on Stratigraphy. Based on a variety of biostratigraphic data, these new units are correlated with chronostratigraphic series and stages in the standard regional classifications used in the UK, North America, Baltoscandia, Australia, China, Siberia and the Mediterranean-North Gondwana region. Furthermore, based mainly on graptolite and conodont zones, the Ordovician is subdivided into 20 stage slices (SS) that have potential for precise correlations in both carbonate and shale facies. The new chronostratigraphic scheme is also tied to a new composite δ13C curve through the entire Ordovician.Support from the National Science Foundation of China research grant no. 40532009.Peer reviewe

Xu Chen , Jiayu Rong, Junxuan Fan, Renbin Zhan , Charles E. Mitchell, David A.T. Harper, Michael J. Melchin, Ping'an Peng, Stan C. Finney, and Xiaofeng Wang. Episodes 2006;29:183-96. https://doi.org/10.18814/epiiugs/2006/v29i3/004

Based on the global graptolite genera and higher rank taxa, we propose three radiation stages through the Ordovician. The isograptid type of development is present within anisograptids predominating in the Tremadocian. Thus, the evolutionary radiation of the Anisograptid fauna from Tremadocian is proposed as the beginning of the Ordovician graptolite radiation. The second graptolite radiation event is the radiation of the Dichograptid fauna, which began from the T. fruticosus Biozone. The third radiation event, the radiation of Diplograptid fauna began immediately after that of the dichograptids. This radiation includes the peak in total diversity of all the Ordovician graptoloids in the Nemagraptus gracilis Biozone. The radiation extended through the Sandbian and Katian and then was interrupted by a major extinction during the early Hirnantian. Thus, the Ordovician graptolite radiation events coincide with those of the three graptolite faunas proposed by Bulman. The distribution and expansion of the Ordovician graptolites in South China may exemplify the graptolite origination pattern, which begins from the slope belt and expanded into both the shelf and oceanic zones. Copyright © 2006 John Wiley & Sons, Ltd.

We have studied the pattern of graptolite species turnover during the latest Ordovician mass extinction based on four continuous Ashgillian to earliest Llandovery sections together with data from more than 30 other published sections. The studied sections represent relatively shallow-water and deeper-water belts in the Yangtze Platform region. Using temporally scaled range data, species diversities and extinction and origination probabilities have been calculated using several analytical methods, including a capture-mark-recapture method. We test the statistical significance of these results and the apparent taxonomic selectivity of extinction and origination via Monte Carlo simulations and contingency analysis. Graptolite species diversity within the Yangtze Platform rose steadily during the late Ashgill, until in the mid-late Paraorthograptus pacificus Chron, when rising extinction risk overtook origination. Diversity dropped to very low levels during the early Hirnantian when extinction probab...