A new tectonic model, postulating the growth of giant subduction-accretion complexes along a single magmatic arc now found contorted between Siberia and Baltica, shows that Asia grew by 5.3 million square kilometres during the Palaeozoic era. Half of this growth may have occurred by the addition of juvenile crust newly extracted from the mantle, supporting models of considerable continental growth continuing throughout the Phanerozoic eon.

Evolution of the Altaid tectonic collage and Palaeozoic crustal growth in Eurasia

The Central Asian Orogenic Belt ( c . 1000–250 Ma) formed by accretion of island arcs, ophiolites, oceanic islands, seamounts, accretionary wedges, oceanic plateaux and microcontinents in a manner comparable with that of circum-Pacific Mesozoic–Cenozoic accretionary orogens. Palaeomagnetic and palaeofloral data indicate that early accretion (Vendian–Ordovician) took place when Baltica and Siberia were separated by a wide ocean. Island arcs and Precambrian microcontinents accreted to the active margins of the two continents or amalgamated in an oceanic setting (as in Kazakhstan) by roll-back and collision, forming a huge accretionary collage. The Palaeo-Asian Ocean closed in the Permian with formation of the Solonker suture. We evaluate contrasting tectonic models for the evolution of the orogenic belt. Current information provides little support for the main tenets of the one- or three-arc Kipchak model; current data suggest that an archipelago-type (Indonesian) model is more viable. Some diagnostic features of ridge–trench interaction are present in the Central Asian orogen (e.g. granites, adakites, boninites, near-trench magmatism, Alaskan-type mafic–ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, rhyolitic ash-fall tuffs). They offer a promising perspective for future investigations.

/pdf/tectonic-models-for-accretion-of-the-central-asian-orogenic-4rjcoan76s.pdf

Tectonic models for accretion of the Central Asian Orogenic Belt

Gondwana dispersion and Asian accretion: Tectonic and palaeogeographic evolution of eastern Tethys

The origin and early evolution of land plants in the mid-Palaeozoic era, between about 480 and 360 million years ago, was an important event in the history of life, with far-reaching consequences for the evolution of terrestrial organisms and global environments. A recent surge of interest, catalysed by palaeobotanical discoveries and advances in the systematics of living plants, provides a revised perspective on the evolution of early land plants and suggests new directions for future research.

/pdf/the-origin-and-early-evolution-of-plants-on-land-25o6hryi4f.pdf

The origin and early evolution of plants on land

Configuration of Columbia, a Mesoproterozoic Supercontinent

We review the highlights of the 1988 symposium on Palaeozoic Biogeography and Palaeogeography, and present a revised set of 20 Palaeozoic base maps that incorporate much of the new data presented at the symposium. The maps include 5 major innovations: (1) A preliminary attempt has been made to describe the motion of the Cathaysian terranes during the Palaeozoic; (2) a more detailed description of the events surrounding the Iapetus Ocean is presented; (3) an alternative apparent polar wandering path for Gondwana has been constructed using the changing distributions of palaeoclimatically restricted lithofacies; (4) new palaeomagnetic data have been incorporated that places Laurentia and Baltica at more southerly latitudes, and adjacent to Gondwana, during the Early Devonian; Siberia is also placed further south in the light of biogeographic data presented at the symposium; (5) Kazakhstan is treated as a westward extension of Siberia, rather than as a separate palaeocontinent. The relationships between climatic changes, sea level changes, evolutionary radiations and intercontinental migrations are discussed

https://mem.lyellcollection.org/content/memoirs/12/1/1.full.pdf

Revised World maps and introduction

Palaeozoic Palaeogeography and Biogeography

Climatically-related sedimentary facies and faunal distributions have been combined with palaeomagnetic data to make provisional reconstructions of the early Cambrian world. Laurentia, Baltica and Siberia appear to have formed a continental group which rifted apart from each other prior to 600 Ma. The consolidation of much of Gondwana probably occurred (in the Pan-African orogeny) well before the Cambrian, though the assembly of several east Asian terranes is still speculative. The archaeocyathan reefs of Siberia, southern Europe and Morocco, with their bigotinid trilobite fauna, suggest that these areas were adjacent to each other and at low latitudes. Avalonia had close faunal links with western Gondwana, but lacked bigotinids and archaeocyathans and may have been situated off west Africa and Florida. During the early Cambrian, there was a northward migration of Laurentia towards the Equator as its separation from Baltica and Siberia increased, and a southward movement of Gondwana.

Early Cambrian continental reconstructions

The recognition of many small terranes bordering the Early Paleozoic Iapetus Ocean has entailed the revision of previous models, that only discussed the relations between the major continents. In this paper we illustrate the development of Iapetus through 1OO Ma by means of six maps drawn by computer graphics. In addition to paleomagnetic data, we have used biogeographic affinities, sedimentary facies, tectonic events and the distribution of igneous rocks to develop our assessment of continental and terrane distributions, and the positions of arcs and trenches. The tectonic model presented here is thus much more complex than the model first postulated by Wilson (1966) invoking the presence of a "Wide ocean in the Caledonides and Northern Appalachians, or the original plate tectonic model proposed by Dewey (1969). Subsequent models for the development of Iapetus have been proposed which we have taken into account in this review.

W. S. McKerrow

Papers

Revised World maps and introduction

Palaeozoic Palaeogeography and Biogeography

Early Cambrian continental reconstructions

Ordovician to Devonian Development of the Iapetus Ocean (Paleoceanographic Mapping Project Report No. 08-0185)