Palaeogeography, Palaeoclimatology, Palaeoecology 515 (2019) 1–5 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Preface Mesozoic and Cenozoic palaeogeography, palaeoclimate and palaeoecology in the eastern Tethys T 1. Introduction of Tethys-fringing landmasses and the biotas that occupied these areas. Reconstructing the evolutionary history of the region has become a It is now more than 100 years since Suess advanced the concept of complex challenge that must overcome multiple phases of deformation, the Tethys Ocean in 1893. Since the 1960s when the theory of plate subduction, and stratal erosion. The harsh climate and extreme eleva- tectonics became established, the Tethys region has attracted the at- tion in the plateau region have further hindered fieldwork to resolve the tention of many geologists because it has experienced a complex evo- history of the eastern Tethys. lution involving numerous continental fragments drifting in several The papers contained in this special issue include the latest research discrete stages from the Gondwanan margin in the Southern results in magmatic petrology, geochemistry, palaeontology and sedi- Hemisphere northward to amalgamate with Eurasia in the Northern mentology from the eastern Tethys (Fig. 2). A multitude of issues re- Hemisphere (Chang and Cheng, 1973; Şengör, 1979; Tapponnier et al., lating to the evolution of the Tethys are covered, such as the timing of 1981; Audley-Charles, 1983; Allègre et al., 1984; Chang et al., 1986; initiation of the Neo-Tethys, the properties of the Bangong-Nujiang Chatterjee et al., 2013). The subsequent orogenies associated with Tethys, the rifting process of the Indian plate, palaeoenvironmental consecutive microplate collisions caused great changes to the regional events during Tethyan evolution, the impact on terrestrial ecosystems topography and environments, which researchers now realize had of closure of the Tethys, and the effects of uplift of the Qinghai-Xizang global impacts on climate, biotic evolution, and biogeography (e.g., Plateau. These advances provide insights into and will stimulate further Molnar and Tapponnier, 1975; Audley-Charles, 1987; Raymo and research on the evolution of the eastern Tethys. Ruddiman, 1992; Molnar et al., 1993; Ramstein et al., 1997; An et al., 2001). 2. Contents of this SI: topics and progress The vast literature on the evolution of the Tethys Ocean highlights several critical scientific issues that require further investigation. These 2.1. Breakup of Pangea include especially: (1) what was the extent of the Tethys and its sur- rounding landmasses at the time that Pangea began to break up?; (2) When did Pangaea split into Laurasia and Gondwana or, equiva- when and how did the Cimmeride terranes rift from Gondwana and lently, when was the Hispanic Corridor established? Various studies collide with proto-Eurasia?; (3) what was the motion history of the have inferred ages ranging from the middle Late Triassic (Norian) to the Indian plate during its northward journey, and when and where did it late Early Jurassic (Pliensbachian). On the basis of the temporal and collide with Eurasia?; (4) when did the Neo-Tethys come into being and spatial distribution of some pan-tropical cosmopolitan Jurassic epi-by- subsequently close up?; (5) what was the driving force behind con- ssate pectinid and epi-cemented ostreid bivalves, Sha (this volume) tinental fragmentation that gave rise to the Neo-Tethys?; (6) what concludes that the Hispanic Corridor was formed, or the northern processes were involved in the uplift of the Qinghai-Xizang Plateau, and Atlantic opened, in the earliest Jurassic (Hettangian) or even as early as what was the chronology of uplift events?; (7) what were the impacts of the latest Triassic (end of the Rhaetian). these events on Earth's climate and biotas? (Fig. 1). The answers to each question are complex and involve a multitude of geological phenomena. 2.2. Rifting of India from Gondwana In particular, a detailed understanding of the palaeogeography and palaeoenvironmental characteristics of the Tethyan region at each stage When and how the Indian Plate rifted from Gondwana and drifted of its geological history is crucial for understanding the evolution of its northward is key to reconstructing the evolutionary history of the Neo- biota and biogeography. Tethys. The separation of the Indian Plate from Australia–Antarctica The eastern part of the Tethys, which encompasses a wide area now and its drift northward occurred concurrently with the subduction of ranging from China and central Asia in the north, through Indochina in the Neo-Tethys before the Indian-Eurasian collision. Although previous the east, to Australia, New Zealand and Antarctica in the south, wit- studies have indicated the initiation of this separation in the Late nessed the step-wise breakup of Gondwana during the Mesozoic and Jurassic or Early Cretaceous (Li and Powell, 2001; Veevers, 2004; early Cenozoic (Fig. 2; Şengör, 1979; Tapponnier et al., 1981; Audley- Metcalfe, 2013), little direct evidence has been forthcoming from the Charles, 1983; Allègre et al., 1984; Chang et al., 1986; Li and Powell, Qinghai-Xizang Plateau to indicate concomitant subduction. Zeng et al. 2001; Veevers, 2004; Chatterjee et al., 2013; Metcalfe, 2013). The se- (this volume) report newly discovered rift-related dolerites from paration of Australia from Antarctica, and New Zealand from Australia southern Tibet that provide magmatic clues to the breakup of India represented the final stages of Gondwanan breakup at the eastern end from eastern Gondwana. These magmatic rocks of earliest Cretaceous of the Tethys. The collision of India with southern Eurasia caused the age (~142 Ma) denote relatively high melting temperatures indicative Himalayan orogeny, which has severely distorted the geological record of partial melts of a rising asthenospheric mantle that was triggered by https://doi.org/10.1016/j.palaeo.2018.11.014 Available online 22 November 2018 0031-0182/ © 2018 Published by Elsevier B.V. Preface Palaeogeography, Palaeoclimatology, Palaeoecology 515 (2019) 1–5 Major tectonic events Biotic and palaeo- Time/time interval Ma environmental changes represented in this SI Period Q Ng Wang et al Barrier for mammals 20 Steinthorsdottir et al.; Ai et al E/O cooling 40 Pg lateau PETM 60 K/Pg extinction Jiang et al 80 Li et al Zhang et al Qinghai-Xizang P OAE 2 & 100 Closure of Bangong-Nujiang Tethys CTB extinction Ran et al K McLoughlin and Pott Uplift of 120 Neo-Tethys of Contraction Lin and Li OAE 1 India-Eurasia India-Eurasia collision 140 Zeng et al 160 J 180 Sha et al Drift of India/ Subduction of Neo-Tethys of India/ Subduction Drift 200 Birth of Neo-Tethys TJB extinction 220 Yu et al T 240 fromRift of India Australia-Antarctica Rift GondwanaRift of Recovery after PTME Luo et al Fig. 1. A summary of key events in the evolution of Tethys as studied by previous researchers and authors in this issue. Selected changes in biotas and pa- laeoenvironments during the period are also illustrated (data according to Ogg et al., 2016). The time (green star) or time interval (green bar) represented by each contribution to this SI is plotted. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) rifting. This magmatic evidence may mark the earliest phase of the palaeontology and volcanic petrology support the hypothesis that the breakup between India and Australia-Antarctica in the northeastern Neo-Tethys began to subduct during the Cenomanian. sector of the rift zone. However, this process was probably slow, as a palynofloristic analysis (Li et al., this volume) shows that these two regions were not sufficiently separated at that time to hinder exchanges 2.4. Impacts of tectonic events on palaeoenvironments and biotas of land floras. Palynofloras from southern Xizang are strongly similar to those of Australia and Antarctica until the Albian. By the Albian, India Tectonic events, such as continental drift and collision, resulted in was completely separated from Australia—at which time distinct pa- palaeogeographic changes in the Tethyan region that influenced ocean lynofloristic differences become apparent between the two continents. circulation as well as regional palaeoenvironments and biotas. Investigations of these biological and environmental changes through time can provide insights into relationships between lithospheric tec- 2.3. Initiation of Neo-Tethys subduction tonic evolution and the biotas occupying separate terranes, and, thus, provide a historical basis for assessing the impact of today's global Li et al. (this volume) propose a reconstruction of the drift history of change. the Indian plate during the Cretaceous by employing comparative Previous studies have revealed some major events in the analyses of the palynofloras between southern Xizang, Australia and Mesozoic–Cenozoic biological and environmental evolution of the Africa. Their conclusion suggests that the northward drift of the Indian Qinghai-Xizang Plateau. For example, Wan et al. (2003) recorded a plate, or subduction of the Neo-Tethys, began in the Cenomanian. It is major extinction of foraminifera and calcareous nannoplankton near notable that this conclusion is supported by petrogeochemical data of the end of the Cenomanian in southern Xizang (Tibet). Zhang et al. (this Ran et al. (this volume), who discovered subduction-related volcanic volume) examine this event from the perspective of the oceanic ni- rocks with an age of 97.1–90.1 Ma from the southern margin of the trogen cycle. They found that the marine faunal turnover coincided Lhasa Block, providing direct evidence for the northward subduction of with the perturbation of the N cycle, suggesting that the expansion of the Neo-Tethys along the southern margin of the Lhasa Terrane in the anoxic watermasses may have played an important role in the extinc- early Late Cretaceous. Therefore, the new, independent results from tion of marine organisms in the eastern Tethys.