TERTIARY PERIOD

Table 4: Geologic time scale. To see more information about a period, select one from the chart. interval of geologic time lasting from 66.4 to 1.6 million years ago (see Table). It constitutes the first of two periods of the Cenozoic Era, the second being the Quaternary. The Tertiary has five subdivisions, which from oldest to youngest are the Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. Some authorities prefer not to use the term Tertiary and instead divide the time interval encompassed by it into two periods, the Paleogene Period (66.4 to 23.7 million years ago) and the Neogene Period (23.7 to 1.6 million years ago). interval of geologic time lasting from 66.4 to 1.6 million years ago. It constitutes the first of two periods of the Cenozoic Era, the second being the Quaternary. The Tertiary has five subdivisions, which from oldest to youngest are the Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. Some authorities prefer not to use the term Tertiary and instead divide the time interval encompassed by it into two periods, the Paleogene Period (66.4 to 23.7 million years ago) and the Neogene Period (23.7 to 1.6 million years ago). During most of the Tertiary Period the spatial distribution of the major continents was to a large extent similar to that of today. Emergence and submergence of land bridges between continents, particularly between North and South America, Eurasia and Africa, and Asia and North America, critically affected the migration of both continental and marine faunas and floras. The most important Tertiary geologic events, however, were those that influenced the topography of the continents. Virtually all the major existing mountain belts and ranges, notably the Andes, the Rockies, the Alps, the Himalayas, and the Atlas Mountains, were formed either partly or wholly during episodes of mountain building during the Tertiary. In the early Tertiary, climatic conditions were generally considerably warmer than today. Evidence from deep-sea cores shows that these conditions were terminated by a sharp, global episode of cooling at the end of the Eocene. During the Oligocene and particularly the Miocene, glacier ice built up in the Antarctic, eventually forming a massive ice sheet that greatly affected oceanic and atmospheric circulation patterns. The Miocene and Pliocene were characterized by relatively weak oscillations between warmer and cooler global conditions that gradually became more pronounced until an episode of major cooling about 1.6 million years ago marked the effective beginning of the Quaternary Period and its glacial-interglacial cycles. The beginning of the Tertiary marked the onset of the Cenozoic Era, the era of recent life. A major worldwide faunal change took place at the end of the Cretaceous Period that preceded the Tertiary. On land the dinosaurs and pterosaurs became extinct, as did the giant marine reptiles, such as the ichthyosaurs, mosasaurs, and plesiosaurs, of the oceans and inland seas. Ammonites and several other groups of marine invertebrates also died out at this time. The belemnites barely survived into the Paleocene. Deep-ocean sediments reveal that a series of planktonic organisms quite suddenly became extinct close to the Cretaceous-Tertiary boundary. Whether or not these multiple extinctions can be related to some common cause or event is still a matter of considerable and unresolved controversy, though there is growing evidence that the impact of an asteroid (or meteorite) in the Caribbean region triggered the extinctions. The Tertiary faunas that replaced those of the Cretaceous possessed a much more modern aspect, and, indeed, the British geologist Sir Charles Lyell, who originally defined the Eocene, Miocene, and Pliocene stages, did so on the basis of the percentage of species recorded from each of these stages that could still be found living in modern seas and oceans. On land the disappearance of the dinosaurs was followed by a considerable evolutionary diversification of mammalian faunas. Compared with their smaller Cretaceous ancestors, many groups of mammals demonstrated a definite trend toward larger size. Tertiary land vegetation was certainly richer and more varied than that of the Cretaceous. Angiosperms, predominantly woody trees and shrubs, had already become the principal constituents of the vegetation over large areas by the Late Cretaceous, and during the mid-Tertiary many low-growing herbaceous taxa, including grasses, evolved. This led directly to the development of grazing in several different lineages of mammals and to an expansion of other herbivorous groups, such as the land mollusks. At the same time, a very important diversification of insects, particularly such orders as Lepidoptera (butterflies and moths), Coleoptera (beetles), and Hymenoptera (ants, bees, and wasps), was taking place in which coevolution with particular species or genera of angiosperms clearly occurred. The Tertiary was also the period of expansion and diversification of the Primates, which evolved from the Insectivora. The earliest generally accepted hominid fossils, those of Australopithecus, come from rocks of Pliocene age (5.3 to 1.6 million years old) in Eastern Africa. An australopithecine species is thought to be ancestral to modern human beings. Among marine organisms, gastropod mollusks and bony fishes evolved rapidly and are often associated with increasing specialization of ecological niches and feeding habits. Planktonic Foraminifera, because of their rapid evolution and wide dispersal, are of particular importance in the understanding of Tertiary marine stratigraphy and climate. Paleontologic, paleomagnetic, and isotopic studies of deep-sea sediment cores containing foraminiferans provide a reasonably accurate correlation and dating of Tertiary marine sediments both at the continental margins and in the deep oceans. Additional reading Sources on the Tertiary Period include Stephen Jay Gould, Time's Arrow, Time's Cycle: Myth and Metaphor in the Discovery of Geological Time (1987); M.J. Hambrey and W.B. Harland (eds.), Earth's Pre-Pleistocene Glacial Record (1981); and William J. Frazier and David R. Schwimmer, Regional Stratigraphy of North America (1987). Studies of the environment of this interval of Earth history include John M. Armentrout, Mark R. Cole, and Harry Terbest, Jr., Cenozoic Paleogeography of the Western United States (1979); and Kotora Hatai, Tertiary Correlations and Climatic Changes in the Pacific (1967). Flora and fauna of the period are studied in Charles B. Beck (ed.), Origin and Early Evolution of Angiosperms (1976); W.B. Harland et al. (eds.), The Fossil Record (1967); Donald E. Savage and Donald E. Russell, Mammalian Paleofaunas of the World (1983); and R.J.G. Savage, Mammal Evolution: An Illustrated Guide (1986). William A. Berggren Tertiary environment Paleogeography Figure 1: Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins The present-day continentocean configuration is the result of a complex sequence of events involving the dynamic evolution and geometric rearrangement of the major landmasses and oceans that began almost 200 million years ago. By the beginning of the Cenozoic the continentocean geometry had assumed an essentially modern, or recent, aspect with several notable exceptions. The fragmentation and dispersal of the Southern Hemispheric supercontinent Gondwana continued in the Cenozoic. Australia separated from Antarctica in the late Paleocene (Figure 1), and the initial subsidence of the South Tasman Rise (at the eastern end of the AustraliaAntarctica marginal contact) in the late Eocene resulted in a shallow but inexorably widening connection between the Indian and Pacific oceans (see Table). The injection of relatively warm eastward-flowing currents and associated evaporation at relatively high latitudes set the stage for the initiation of glaciation on Antarctica by early Oligocene time about 34 million years ago. Progressive separation of the two continents led to the initiation of the circum-Antarctic Current, which sweeps around Antarctica and thermally isolates it from the effects of warmer waters and climates to the north. The junction of India and Asia occurred during the middle Eocene approximately 45 million years ago and resulted in an effective, though not total, blockage of the westward-flowing Tethys. This was achieved about 18 million years ago with the junction of Africa and Asia near present-day Iran. Although the eastern and western Tethyan seaway was now severed, brief intermittent marine connections were reestablished 14 to 13 million years ago. The present-day Mediterranean Sea is the geologically recent descendant of the Tethys. Between six and five million years ago the western remnant of the formerly extensive Tethyan seaway was subject to a brief (approximately one-million year) paroxysm that saw the entire basin virtually isolated from the world ocean; it experienced severe desiccation and the precipitation of a vast suite of evaporite deposits which reach up to several kilometres in thickness. The basin was subsequently refilled by the Atlantic and underwent significant geologic evolution during the past five million years. About one million years ago this part of the ancient Tethys was transformed into the Mediterranean Sea by the elevation of the Gibraltar sill and the consequent isolation of the basin from deep oceanic bottom waters and development of the present-day circulation pattern (see Table). In the Northern Hemisphere the fragmentation and separation of Eurasia was completed during the early Paleogene with the opening of the Norwegian-Greenland Sea about 56 to 55 million years ago. Breaching of the subsiding subaerial Greenland-Scotland Ridgeformed during the Hebridean-Greenland eruptive volcanic episode of the late Paleocene mentioned aboveallowed exchange of surface water between the Arctic and Atlantic oceans. Climatic conditions remained subtropical at high latitudes during the Paleogene as attested to by the remains of molluscan and shark faunas of tropical affinities in Spitsbergen. Furthermore, a fauna featuring such forms as the boid snake and durophagous alligator (a variety possessing teeth designed to crush food), as well as anguid and varanid lizards, emydid turtles, plagiomenids (flying lemurs), and paromomyids (primates), has been discovered on Ellesmere Island in the Canadian Arctic Archipelago, whose latitude has remained essentially stable77 Nduring the Cenozoic. Figure 2: Principal Cenozoic faunal migration routes and barriers. On the Eurasian continent the Ural Trough, a marine seaway linking the Tethys with the Arctic region that had constituted a barrier to the eastwest migration of terrestrial faunas, was terminated by regional uplift at the end of the Eocene (Figure 2). The resulting immigration of Eurasian faunas into western Europe and the consequent faunal changes that occurred in terrestrial vertebrate faunas is known as the Grande Coupure (Big Break) among vertebrate paleontologists. Relatively small changes in landsea geometry have played an important role in the migration of terrestrial faunas and ultimately in the evolution of life itself. For example, during the early Paleogene land mammal exchange between Europe and North America occurred freely via a northern route owing to the close proximity of Spitsbergen, eastern Canada, and the subaerial Greenland-Scotland Ridge. The separation of the former two and the partial subsidence of the latter about 50 to 49 million years ago (middle Eocene) led to the termination of this free interchange and the development of separate evolutionary patterns among terrestrial vertebrate faunas in Europe and North America. The only route for faunal exchange between Eurasia and North America was the Bering Land Bridge that united Siberia and Alaska. It seems to have been breached only in the past 2.5 million years, allowing the transit of cold water currents from the Pacific into the Atlantic. Evidence for this occurs in the form of North Pacific cryophylic molluscan faunas in the mid-Pliocene faunas of Iceland. To the south, the Atlantic and Pacific oceans had been linked since the Early Cretaceous by the Panamanic Seaway in the Central Americannorthwest Colombian region. This seaway prevented terrestrial faunal interchange between North and South America, with the possible exception of a brief interlude during the Paleocene. It was closed by the elevation of the Isthmus of Panama about three million years ago with two significant geologic results. First, the emergence of the Isthmus of Panama permitted a major migration in land mammal faunas between North and South Americathe so-called Great American Interchangewhich saw South American ground sloths in North America in areas as dispersed as California, the Great Plains, and Florida, and North American faunas as far south as Patagonia. Second, the emergence of the Isthmus of Panama deflected the westward-flowing North Equatorial Current northward where it enhanced the northward-flowing Gulf Stream. The latter then carried warm, salty waters into high northern latitudes, contributing to greater precipitation through evaporation over the region of eastern Canada and Greenland and eventually to the development of the polar ice cap, which began forming between 3 and 2.5 million years ago in the Northern Hemisphere. Significant geologic events The concept of dynamic paleogeography provides a unifying framework within which to understand the causal link between changes in oceanic circulation, climate, and evolutionwhich together constitute geologic events. These events may be divided into two categories: physical and biotic. The early Eocene opening of the Norwegian-Greenland Sea completed the fragmentation of the Northern Hemispheric supercontinent Laurasia and eventually united the Atlantic and Arctic oceans (see Table), although modern circulation patterns were not achieved until the subsidence of the GreenlandScotland Ridge about 15 million years ago. In the Southern Hemisphere the separation of Australia and Antarctica reached a critical point about 34 million years ago, at which time the continent of Antarctica was covered by a major ice sheet. The junction of Eurasia and Africa about 18 million years ago severed the once more extensive Tethyan seaway, and the western part evolved, after being cut off from the world ocean for a relatively brief time, into the modern-day Mediterranean Sea (see above). Finally, the emergence of the Isthmus of Panama about 3 million years ago and concomitant changes in ocean circulation patterns led to the formation of a polar ice cap shortly thereafter in the late Pliocene. The history of the Earth over the past 2.5 million years has been intimately linked with repeated oscillations between glacial advances and retreats. Biotic events reflect changes in paleogeography and climate. Among mammals the earliest equids (horses) and primates appeared during the early Eocenea time of diversification of mammals. In the middle Eocene free land-mammal faunal migration between North America and Europe was interrupted by the severance of the land-bridge connection that had existed prior to this time. Although Europe was cut off from North America, Asia (especially Siberia) remained in contact with the latter in the late Eocene, and repeated migrations occurred throughout the Oligocene and Miocene. In the early Miocene, the first wave of immigration from Europe occurred, bringing bear-dogs, European rhinoceroses, weasels, and a variety of European deerlike animals to North America. In the early Miocene, mastodons escaped from their isolation in Africa, and by the middle Miocene they had reached North America. Rodents and early anthropoids evolved in the middle Eocene and the first elephants (Proboscidea) in the early Oligocene. Immigration of African mammalian faunas, including proboscideans, into Europe occurred about 18 million years ago (early Miocene). The earliest apparent hominids have been reported in East Africa at about six to five million years ago and the subsequent australopithecinehominid evolution in East Africa has been traced over the past three million years. In the late Pliocene, the Panamanic land bridge allowed porcupines, armadillos, and ground sloths to migrate from South America and live in the southern United States. A much larger wave of typically Northern Hemispheric animals, however, moved south and drove most of the South American endemic mammals to extinction. These North American invaders included dogs and wolves, raccoons, cats, horses, tapirs, llamas, peccaries, and even mastodons. In the deep sea several major biotic events stand out. A major extinction event at the boundary between the Mesozoic and Cenozoic eras, 66.4 million years ago, affected dinosaurs, large marine reptiles, marine invertebrate faunas (rudists, belemnites, ammonites), and planktonic protozoans (foraminiferans) and phytoplankton (see above). On the other hand, deep-sea benthic protozoans suffered no effect until about 10 million years later at the boundary between the Paleocene and the Eocene, when more than half of all species suffered extinction under conditions that still remain unexplained but may be linked to changing deep-water circulation patterns. The present-day psychrospheric (i.e., cold), benthic fauna evolved in the deep sea in the late Eocene about 36 to 35 million years ago, concomitant with significant cooling of oceanic deep waters of some 35 C. The closure of the Tethyan seaway in the late early Miocene about 15 million years ago resulted in the disappearance of many of the larger tropical nummulitid-type foraminiferans that had ranged from Indonesia to Spain during most of the Tertiary. Although the descendants of these forms can be found today in the Indo-Pacific region, they show much less diversity. The marine faunas of the eastern Pacific and West IndiesCaribbean region were similar throughout the Tertiary until about three million years ago. The elevation of the Isthmus of Panama at that time created a land barrier between the two regions that resulted in faunal provincialization. Tertiary life The end of the Mesozoic Era marked a major transition in Earth history. Major extinctions took place among marine and terrestrial animals; plant life suffered to a much lesser extent. The cause of this major event, whether single or multiple, is still being widely debated among specialists. In any case, the net result in the oceans was a marked reduction in diversity, primarily of calcium carbonate-secreting organisms (i.e., coccolithophorids and planktonic foraminiferans), followed by a gradual recovery and radiation of new forms within a few hundred thousand years. The present-day ecosystem is for the most part populated by animals, plants, and single-celled organisms that survived and redeployed after the great extinction event at the end of the Mesozoic. Deep-sea benthic foraminiferans, mollusks, and teleost fishes survived and became prominent elements in the Paleogene seas. Following the extinction of the reef-building rudists at the end of the Cretaceous, reef-building corals recovered by the Eocene, and their low-latitude, continuous stratigraphic record is taken as an indicator of the persistence of the tropical realm. Whales (cetaceans) are descended from carnivorous terrestrial mesonychid Condylarthra; they had become adapted to the marine environment by the middle Eocene. Another enormous marine carnivore was the shark, which descended from an essentially similar form of the early Jurassic. Other new forms in the late Paleogene seas were the penguins, a group of swimming birds, and the pinnipeds, a group that includes seals, sea lions, and walruses. The CretaceousPaleogene transition was not marked by any significant change in terrestrial floras. Angiosperms continued the radiation that had begun in the mid-Cretaceous about 100 million years ago. Grasses were present by late Paleocene time, but they did not expand to form the upland grasslands and prairies that are intimately linked to expansion of grazing animals until late Oligocene and Miocene time. Evolution and distribution of foraminiferans Since about the 1960s detailed studies have shown that the calcareous planktonic protozoan foraminiferans (superfamily Globigerinacea) have evolved rapidly and dispersed widely, following a major extinction at the end of the Cretaceous. These organisms have proved to be extremely useful in regional and global correlation of oceanic sediments and uplifted marine strata found on land. Differential rates of evolution within different groups give rise to the greater utility of some forms in stratigraphic zonation and correlation than others. For example, conical species of the Paleogene Morozovella and Neogene Globorotalia have stratigraphic ranges that vary from one to five million years. The larger foraminiferansthe nummulitidswere a group of circular-to-elliptical, shallow-water, tropical, benthic forms that had complex, labyrinthine interiors and internal structural supports to strengthen their adaptation to life in high-energy environments. They contained symbiotic algae in life conditions and received nourishment from symbiosis performed by the entrained algae. The genus Nummulites occurred in massive numbers and large size (diameters up to 150 millimetres) during the great middle Eocene transgression and formed extensive limestone deposits in Egypt from which the pyramids were built. Nummulites lived throughout the Eurasian Tethyan province from late Paleocene to early Oligocene time but did not reach the New World. Following their extinction in the Oligocene, larger foraminiferans, the miogypsinids and lepidocyclinids, flourished during the Neogene. These forms are characterized by increased complexity in the internal part of the test (structural hard parts) by the addition of lateral chambers and changes in the geometry of the embryonic initial successive chambers. The miogypsinids ranged from the Oligocene to middle Miocene, while the lepidocyclinids disappeared in the early Pliocene, the last representative being recorded in Fiji. Tertiary rocks Types and distribution With the exception of the great Tethyan seaway, the basins of western Europe, and the extensive Mississippi embayment of the Gulf Coast region, Tertiary marine deposits are located predominantly along continental margins. They occur on all continents and are found in situ as far north as Alaska (Miocene), eastern Canada (Eocene), and Greenland (Paleocene). Deposits of Paleogene age occur on Seymour Island in the Antarctic Peninsula, and Neogene deposits containing marine diatoms (silica-bearing marine phytoplankton) have recently been identified intercalated between glacial tills on Antarctica itself. Global sea level is believed to have fallen gradually but inexorably about 300 metres over the past 100 million years, but superimposed upon that trend is a higher-order series of globally fluctuating increases and decreases in sea level with a periodicity of several million years. The resultant transgressions and regressions of the sea onto passive (i.e., tectonically stable) continental margins has left a record of interfingered marine brackish and continental sedimentary deposits in Europe, North Africa, the Middle East, southern Australia, and the Gulf and Atlantic coastal plains of North America. In most regions, the Paleogene seas extended farther inland than did those of the Neogene; in fact, the most extensive transgression of the Tertiary is that of the Lutetian Age (Middle Eocene), about 4945 million years ago, when the Tethys Sea expanded onto the continental margins of Africa and Eurasia and left extensive deposits of shallow-water carbonate rocks characterized by tropical foraminiferans of large size called Nummulites from Indonesia to Spain and as far north as Paris and London. Sediments of Tertiary age are widely developed on the deep ocean floor and elevated seamounts as well. In the shallower parts of the ocean above 4.5 kilometres, sediments are calcareous or siliceous (or both), depending on local productivity. Below 4.5 kilometres the sediments are principally siliceous or inorganic (i.e., red clay) owing to dissolution of calcium carbonate. Nonmarine (terrestrial, or continental, as they are called) Tertiary sedimentary and volcanic deposits are widespread in North America, particularly in the intermontane basins west of the Mississippi River. During the Neogene, volcanism and terrigenous deposition extended almost to the coast. In South America thick nonmarine clastic sequences (conglomerates, sandstones, and shales) occur in the mobile tectonic belt of the Andes Mountains and along their eastern front; these sequences extend eastward for a considerable distance into the Amazon Basin. Tertiary marine deposits occur along the eastern margins of Brazil and Argentina, and they were already known to Charles Darwin during his exploration of South America in 1833 and 1834. Volcanism and orogenesis Volcanism has continued throughout the Cenozoic on land and at the major oceanic ridges, such as the Mid-Atlantic Ridge and the East Pacific Rise, where new seafloor is continuously generated and carried away laterally by seafloor spreading. Iceland was formed in the middle Miocene, and it remains one of the few places where the processes that occur at the Mid-Atlantic Ridge can be observed today. Two of the most extensive volcanic outpourings recorded in the geologic record occurred during the Tertiary. The Deccan trap of India was the site of massive outpourings of basaltic lava near the boundary between the Cretaceous and Tertiary about 6766 million years ago, whereas massive explosive volcanism took place near the PaleoceneEocene boundary between 57 and 54 million years ago in northwestern Scotland, northern Ireland, and the Faeroe Islands and East Greenland, as well as along the rifted continental margins of both sides of the North Atlantic Ocean. This volcanic activity was associated with the initial rifting and separation of Eurasia and North America between Scandinavia and Greenland and left a stratigraphic record in the form of distal ash deposits as far south as the Bay of Biscay and the marine sedimentary basin of England. In both instances, comparable volumes of extensive basalts in the amount of 1 to 2 by 10,000,000 cubic kilometres were erupted. The well-known volcanics of the Massif Central of south central France, which figured so prominently in early (18th-century) investigations into the nature of igneous rocks, are of Oligocene age, as are those in central Germany. The East African Rift Zone preserves a record of mid-to-late Tertiary rifting and separation of the East African continent that eventually led to the formation of a marine seaway linking the Indian Ocean with the Mediterranean. During the Early Tertiary, volcanism occurred in the Caucasus Mountain region but was essentially absent elsewhere in Asia. The circum-Pacific Ring of Fire, an active tectonic belt that extends from the Philippines through Japan around the west coast of North and South America, was subject to seismic activity and andesitic volcanism throughout much of the Tertiary. The extensive Columbia Plateau basalts were extruded over Washington and Oregon during the Miocene, and many of the volcanoes of Alaska, Oregon, southern Idaho, and northeastern California date to the Late Tertiary. Active volcanism occurred in the newly uplifted Rocky Mountains during the Early Tertiary, whereas in the southern Rocky Mountains and Mexico volcanic activity was more common in the mid- and late Tertiary. The linear volcanic trends, such as the Hawaiian, Emperor, and Line island chains in the central and northwestern Pacific, are trails resulting from the movement of the Pacific Plate over volcanic hot spots (i.e., magma-generating centres) that are probably fixed deep in the Earth's mantle. The major island groups such as the Hawaiian (which has been active over the past 30 million years), Galpagos, and Society islands (Miocene) are volcanoes that rose from the seafloor. Finally, Central America, the Caribbean region, and northern South America were the sites of active volcanism throughout the Cenozoic. In contrast to the passive-margin sedimentation on the Atlantic and Gulf coastal plains, the Cordilleran (or Laramide) orogeny in the Late Cretaceous, Paleocene, and Eocene produced a series of upfolded and upthrusted mountains and deep intermontane basins in the area of the modern Rocky Mountains. Deeply downwarped basins accumulated as much as 8,000 metres of Paleocene and Eocene sediment in the Green River basin of southwestern Wyoming and 14,000 metres of sediment in the Uinta Basin of northeastern Utah. Other basins ranging from Montana to New Mexico accumulated similar but thinner packages of nonmarine fluvial and lacustrine sediments rich in fossil mammals and fish. In the Oligocene and Miocene, Cordilleran influences on what is now the western United States had ceased, and the basins were gradually filled to the top by sediments and abundant volcanic ash deposits from eruptions in present-day Colorado, Nevada, and Utah. These basins were exhumed during the Pliocene-Pleistocene with renewed uplift of the long-buried Rocky Mountains, along with uplift of the Colorado Plateau, producing steep stream gradients that resulted in the cutting of the Grand Canyon to a depth of more than 5,000 metres. Volcanism along the Cascade Mountain chain was active from the late Eocene to today, as evidenced by the 1980 eruption of Mount St. Helens. This volcanism was gradually shut off in California as the movement of plate boundaries changed from one of subduction to a sliding and transform motion (see also Earth: The major geologic features of the Earth's exterior: The surface of the Earth as a mosaic of plates; Types of plate boundaries). With the development of the San Andreas Fault system, the western half of California started sliding northward. The CascadeSierra Nevada Mountain chain began to swing clockwise, causing the extension of the Basin and Range Province in Nevada, Arizona, and western Utah. This crustal extension broke the Basin and Range into a series of northsouth-trending fault-block mountains and downdropped basins, which filled with thousands of metres of upper Cenozoic sediment. These fault zones (particularly the Wasatch Fault in central Utah and the San Andreas zone in California) remain active today and are the source of most of the damaging earthquakes in North America. The Andean mountains were uplifted during the Neogene as a result of subduction of the South Pacific beneath the South American continent. Complex tectonic activity occurred in Asia and Europe during the Tertiary. The main Alpine orogeny began during the late Eocene and Oligocene and continued throughout much of the Neogene. Major tectonic activity in the eastern North Atlantic (Bay of Biscay) extended into southern France and culminated in the uplift of the Pyrenees in the late Eocene. On the south side of the Tethys, the coastal Atlas Mountains of North Africa experienced major uplift during this time, but the Betic region of southern Spain and the Atlas region of northern Morocco continued to display mirror-image histories of tectonic activity well into the late Neogene. In the Middle East the suturing of Africa and Asia occurred about 18 million years ago. Elsewhere, India had collided with the Asian continent about 45 million years ago, initiating the Himalayan uplift that was to intensify in the late Neogene (i.e., Pliocene and Pleistocene) and culminate in the uplift of the great Tibetan Plateau and the Himalayan Mountain range. Major orogenic movement also occurred in the Indonesian-Malaysian-Japanese arc system during the Neogene. In New Zealand, which sits astride the Indian-Australian and Pacific plate boundary, the major tectonic uplift (the Kaikoura orogeny) of the southern Alps began about 10 million years ago.