[1] A range of ages have been proposed for the timing of India-Asia collision; the range to some extent reflects different definitions of collision and methods used to date it. In this paper we discuss three approaches that have been used to constrain the time of collision: the time of cessation of marine facies, the time of the first arrival of Asian detritus on the Indian plate, and the determination of the relative positions of India and Asia through time. In the Qumiba sedimentary section located south of the Yarlung Tsangpo suture in Tibet, a previous work has dated marine facies at middle to late Eocene, by far the youngest marine sediments recorded in the region. By contrast, our biostratigraphic data indicate the youngest marine facies preserved at this locality are 50.6-52.8 Ma, in broad agreement with the timing of cessation of marine facies elsewhere throughout the region. Double dating of detrital zircons from this formation, by U-Pb and fission track methods, indicates an Asian contribution to the rocks thus documenting the time of arrival of Asian material onto the Indian plate at this time and hence constraining the time of India-Asia collision. Our reconstruction of the positions of India and Asia by using a compilation of published palaeomagnetic data indicates initial contact between the continents in the early Eocene. We conclude the paper with a discussion on the viability of a recent assertion that collision between India and Asia could not have occurred prior to ∼35 Ma.

on his work in my discussions of the biology of the larger foraminifera as presented in Chapter 1.I would like to refer readers to Prof Lukas Hottinger's outstanding web pages "Illustrated glossary of terms used in foraminiferal research" which can be found at http://paleopolis.rediris.es/cg/CG2006_M02/4_droite.htm. Some of these illustrations are reproduced in this book, courtesy of Prof Hottinger.I would like to thank Prof McMillan for access to his South African collection of larger foraminifera, Dr Michelle Ferrandini, Université de Corse, for access to her Corsican collections and Prof K. Matsumaru for access to some of his original material.I would also like to thank the Natural History Museum, London for giving me access to their excellent collection, which includes type species of many early workers. I would like to thank all scientists who contributed to this collection and thus to my book. My gratitude is also expressed to the Senckenberg-Forschungsinstitut und Naturmuseum, Germany for their Permian collection and UCL Geological Sciences, Micropalaeontology unit collections. I am particularly grateful for the assistance of Mr Jim Davy, UCL, and in Mr Clive Jones, NHM. Mr Jones was very helpful in locating specimens and his methods of filing and storing the NHM collection were so very useful.Finally, I am especially grateful for the careful editing and reviewing carried out by Prof Alan Lord (of the Senckenberg-Forschungsinstitut und Naturmuseum, Germany) and Prof David Price (UCL). Prof Price' s advice throughout the book, and our useful discussions on the causes of extinctions gave me many ideas on the relationship between sensitive, small, living organisms, such as the larger foraminifera, and large scale geological processes. I also thank him for helping me to look into the wider processes involved in evolution and for his encouragement.

No abstract

Mass extinctions are recognized through the study of fossil groups across event horizons, and from analyses of long-term trends in taxonomic richness and diversity. Both approaches have inherent flaws, and data that once seemed reliable can be readily superseded by the discovery of new fossils and/or the application of new analytical techniques. Herein the current state of the Cretaceous-Tertiary (K-T) biostratigraphical record is reviewed for most major fossil clades, including: calcareous nannoplankton, dinoflagellates, diatoms, radiolaria, foraminifera, ostracodes, scleractinian corals, bryozoans, brachio-pods, molluscs, echinoderms, fish, amphibians, reptiles and terrestrial plants (macrofossils and palynomorphs). These reviews take account of possible biasing factors in the fossil record in order to extract the most comprehensive picture of the K-T biotic crisis available. Results suggest that many faunal and floral groups (ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs) were in decline throughout the latest Maastrichtian while others (diatoms, radiolaria, benthic foraminifera, brachiopods, gastropods, fish, amphibians, lepidosaurs, terrestrial plants) passed through the K-T event horizon with only minor taxonomic richness and/or diversity changes. A few microfossil groups (calcareous nannoplankton, dinoflagellates, planktonic foraminifera) did experience a turnover of varying magnitudes in the latest Maastrichtian-earliest Danian. However, many of these turnovers, along with changes in ecological dominance patterns among benthic foraminifera, began in the latest Maastrichtian. Improved taxonomic estimates of the overall pattern and magnitude of the K-T extinction event must await the development of more reliable systematic and phylogenetic data for all Upper Cretaceous clades.

Our new stratigraphic, sedimentological, and micropaleontological analysis, integrated with basalt geochemistry, sandstone petrography, and detrital-zircon U-Pb and Hf isotope data, suggests the revision of current models for the geological evolution of the Asian active margin during the Cretaceous. The Xigaze forearc basin began to form in the late Early Cretaceous, south of the Gangdese arc, during the initial subduction of the Neotethyan oceanic lithosphere under the Lhasa terrane. Well-preserved stratigraphic successions document the classical upwardshallowing pattern of the forearc-basin strata and elucidate the origin of the associated oceanic magmatic rocks. The normal midocean-ridge basalt (N-MORB) geochemical signature and stratigraphic contact with the overlying abyssal cherts (Chongdui Formation) indicate that the Xigaze Ophiolite formed by forearc spreading and represents the basement of the forearc sedimentary sequence. Volcaniclastic sedimentation began with thick turbiditic sandstones and interbedded shales in the late Albian-Santonian (Ngamring Formation) followed by shelfal, deltaic, and fl uvial strata (Padana Formation), with fi nal fi lling of the basin by the Campanian age. Forearc sandstones do not show the classical trend from feldspatholithic volcaniclastic to quartzo-feldspathic plutoniclastic compositions, indicating limited unroofi ng of the Gangdese arc prior to collision. U-Pb age spectra of detrital zircons are unimodal with a 107 Ma peak in the lower Ngamring Formation (104-99 Ma), bimodal with a subordinate additional peak at 157 Ma in the middle Ngamring Formation (99-88 Ma), and multimodal with more abundant pre-Mesozoic ages in the upper Ngamring and Padana Formations (88-76 Ma). These three petrofacies with distinct provenances document the progressive erosional evolution of the Gangdese arc, with uplift of the central Lhasa terrane and expanding river catchments to include the central Lhasa terrane during the Late Cretaceous.