The Cenozoic: The Tertiary Tertiary or Paleogene & Neogene Tertiary: G. Arduino (1760) Paleogene: K.F. Naumann (1866) Neogene: R. Hornes (1835) The Epochs of the Cenozoic • Proposed by Charles Lyell in 1833 • Based on the work by Cuvier and Brongniart; description of fossils from the Paris Basin • Fossil description based on relative ratios of living vs. extinct species • Originally 4 epochs, Eocene, Miocene, Pliocene and Pleistocene and Recent (Holocene) • Later the Oligocene was recognized between the Eocene and Miocene and Paleocene before Eocene Eocene Paleogeography (50+/-5 my) The Earth Today Red Sea Rift Formed 30 my Oligocene Cenozoic Regional Events: East Coast • Appalachians reduced to a peneplain (Schooley Peneplain) by Paleocene • Only monadnocks [low domal structures](Stone Mountain) remain • Several episodes of uplift and renewed erosion of Appalachians (Miocene) • Thick sequence of Carbonate deposition in Florida-Bahamas platform Florida-Bahamas Carbonate Bank Cenozoic Regional Events • Gulf Coast: Continued clastic deposition (marginal marine and fluvial) up to 40,000 ft vs. 20,000 in the Atlantic coastal plain Gulf Coast Accumulation of Tertiary Sediments Cenozoic Regional Events: Western North America • Paleogene: Laramide Orogeny: volcanic belts and fold and thrust belts to the east (deformed most strata of the Cretaceous seaway) • Central W. US Colorado Plateau is quiet • East of CO Plateau, basement uplifts continue to form Rocky Mts. Cenozoic Regional Events: Western North America • Neogene: Miocene Subduction creates Cascade Range • Faulting and mountain building in California • Development of San Andreas Fault • Initiation of Basin and Range topography> Extentional, pull-aparts • Columbia Plateau forms -massive fissure eruptions of basaltic lava 500,000km2; 2800m thick • Uplift of Colorado Plateau (Grand Canyon), Rocky Mts. and Sierra Nevada Cenozoic Basins of the Western Us Eocene erosional detritus and stream discharge filled basins and formed extensive shallow water lakes One notable lake was the Green River Fm. A series of lacustrine deposits 600 m of freshwater limestones and shales (varves) 6.5 my of deposition was 0.1mm/yr or 9.2cm/1000 yrs Very well presrved fish, insects and plants Oil shales> petroleum reserve Interaction of Pacific, Farallon and North American Plates > Transform Boundary Grand Tetons: Normal Fault uplift with displacement of over 6000m Extentional Tectonics Pull-aparts Columbia Plateau: Eruption of basaltic lava buried 500,000km2 under 2800m Cenozoic Life • Diversity of Scleractinian Coral Reefs • Molluscs – Multi-tiered suspension & deposit feeders • Diversity of Planktic Organisms – Forams as Index Fossils • Fish • Birds DIATOMS FORAMINIFERS GREEN RIVER FORMATION Teleost Fishes- Ray-Fin Fishes 20,000 species Teleost Oligocene Tuffs near Florissant Colorado Late Eocene-Early Oligocene volcanic activity in the area around Yellowstone National Park >> White River Fm., famous for mammals in flood deposits with ash beds seen in the Badlands National Park of South Dakota Diatryma stood 2m Most primitive birds are large flightless ones In the Cenozoic South American Predatory birds were important Birds: 27 orders of modern birds Land and Water Birds Cenozoic Life • Advent of Mammals – Archaic Mammals> Paleogene – Modern Mammals> Neogene • Diversity of Mammals – Marsupial > earliest > pouched – Placental > Advanced > direct birth • Carnivores • Ungulates > Hoofed Herbivores, Most abundant and diversified (primitive) – Perissodactyles (odd-toed)> horse, rhino – Artiodactyles (even-toed, cloven hoofed)> cattle, pigs, sheep, goats, deer, antelope Marsupial vs Placental Mammals Evolution of the Horse Hyracotherium ancestral horse, ancestor of all perissodactyls, small 4, 3 toed animal to Equus, large complex enamel molars, one toe The Pleistocene • Pleistocene, the time period that spanned from 1.8 million to ~10,000 years ago. • Pleistocene biotas were extremely close to modern ones — many genera and even species of Pleistocene conifers, mosses, flowering plants, insects, mollusks, birds, mammals, and others survive to this day. • Pleistocene was also characterized by the presence of distinctive large land mammals and birds. • Mammoths and their cousins the mastodons, longhorned bison, sabre-toothed cats, giant ground sloths, and many other large mammals characterized Pleistocene habitats in North America, Asia, and Europe. • Native horses and camels galloped across the plains of North America. Great teratorn birds with 25-foot wingspans stalked prey. Mammoths had ridged molars, primarily for grazing on grasses, mastodon molars had blunt, cone-shaped cusps for browsing on trees and shrubs. Mastodons were smaller than mammoths,, and their tusks were straighter and more parallel. Mastodons were about the size of modern elephants Primates and Human Evolution • Primates, meaning first • Hominids, Family Hominidae, upright posture • The Order Primates is one of the longest surviving (Eocene) and generalized group of mammals • 2 suborders – Prosimii and Anthropoidea • Superfamily Homonoidea (3 Families; includes chimps, gorillas, orangutans and humans) Primate Evolution • As a result of the change in climate and vegetation, adaptive radiation occurred among the Old World primates. • During the late Miocene, primates appeared that gave rise to the pongids (orangutan, chimpanzee, and gorilla) and the hominids (human family). • A new group, the dryomorphs (formerly dryopithecines) appeared in the Miocene. Australopithicines • Australopithecus africanus was discovered in 1924 by Raymond Dart in South Africa. Since then, many specimens have been discovered in East Africa, particularly in Olduvai Gorge by Mary and Louis Leakey. • East African fossil sites have yielded hundreds of hominid bones, documenting human evolution over the past 4 million years. • Interbedded volcanic ash allows radiometric dating of the hominid fossils. Australopithecus africanus • Australopithecus africanus skull replica. The original of this replica was discovered by Robert Broom in Sterkfontein, Transvaal, South Africa in 1947. 2.5 million years old. "Lucy" Australopithecus afarensis • Discovered by Donald Johanson in 1974 and nicknamed "Lucy". • Lucy was an erect-walking hominid in East Africa about 3.5 million years ago. Posture is determined from analysis of pelvic and leg bones. Hominids • During the Pleistocene the hominid tendency to increase brain size and hence intelligence continued. • Homo erectus, Homo neanderthalis, and finally modern man (Homo sapiens) succeeded each other in time (although modern man and neanderthals lived alongside each other in Europe for a short period The Earliest Humans • Fossil evidence from along the Omo River in southern Ethiopia shows that modern humans, Homo sapiens, lived in Africa as much as 195,000 years ago, according to an article published in February 2005 • Previously, modern humans were thought to have appeared in Africa about 160,000 years ago • Humans appeared in Africa many thousands of years before our species appeared on any other continent The Quaternary • The Pleistocene 1.8 Ma-10,000Ka – The term Pleistocene ("most recent") was coined by Charles Lyell in 1839, on the basis of a section of type strata in eastern Sicily, according to the proportion of extinct to living species of mollusk shells in the sediment. – Strata with 90 to 100% present day species were designated Pleistocene. • The Holocene 10,000 Ka- Present Mt. St. Helens eruption May 18, 2000 Cascade Range>> Subduction Zone (trench) Columbia Plateau and Cascade Range Volcanism • West of the Columbia Plateau, more viscous lava produced the volcanoes of the Cascade Range. • Volcanism is caused by the North American plate overriding the Juan de Fuca plate in the eastern Pacific. Volcanoes of the Cascade Range • • • • • • • Mt. St. Helens Mt. Rainier Mt. Adams Mt. Hood Mt. Jefferson Mt. Lassen Mt. Shasta Mt. Rainier • Mt. Rainier is considered to be the most dangerous volcano in the range. • Major eruption about 2000 years ago, and minor eruptions in 1800's. Crater Lake Crater Lake, Oregon formed from the eruption and collapse of Mt. Mazama in the Cascade Range about 6000 years ago. Origin of Crater Lake In the last 30 years evidence from deep sea drilling has shown that about 25 million years ago the earth's climate began to cool and the polar ice caps began to expand steadily. The cause of this slow change in global environment is still unknown but adjustment of atmospheric chemistry, possibly due to increasing volcanic activity may have been the trigger. Volcanic dust in the upper atmosphere and the chemical changes wrought by massive releases of sulfur dioxide from certain volcanoes can cause large climatic changes. Global Surface Cooling • Temperatures dropped by about 8-13o C (roughly 22o F) near the Eocene-Oligocene boundary, as indicated by isotope data from brachiopods from New Zealand. • Antarctic sea ice began to form by 38 m.y. ago. • Greenhouse conditions were replaced by icehouse conditions. Worldwide cooling resulted in: 1. First Cenozoic widespread growth of glaciers in Antarctica about 38-22 m.y. ago. 2. Global sea level dropped by about 50 m in the Early Oligocene, as glaciers formed. 3. Cold, dense polar water flowed northward across ocean bottom. 4. Upwelling of cold bottom waters affected world climate. 5. Decrease in diversity and extinctions of many: – marine molluscs – planktonic and benthonic foraminifera – ostracodes 6. Extinctions were earlier and more severe at higher latitudes. 7. Reefs shifted toward the equator. 8. Calcarous biogenic deep sea sediments (foraminiferal ooze) shifted toward the equator and were replaced by siliceous biogenic sediments (diatom and/or radiolarian ooze) at higher latitudes. 9. Changes in pollen indicate long term cooling and drying. – Temperate and tropical forests shifted toward the equator. – Grasslands expanded. – Rainforests became confined to tropical, equatorial areas. 10. Glaciation occurred in other areas in Pliocene (and younger) deposits - Sierra Nevada, Iceland, South America, and Russia. http://www.museum.state.il.us/exhibits/ice_ages/images/laurentide.mpg Pleistocene Glaciations 30% of Earth’s surface covered by glaciers Glacial Erratic. Lopez Island, Washington This granitic boulder is a long way from the nearest possible source area--too far to be carried by anything other than ice. Willow Lake and moraines on south flank of the Wind River Mtns, 9 miles NNW of Pinedale, WY. View to the northeast. Note one or more recessional moraines and the different morphological ages of the lateral moraines (i.e. pitted or smooth). Outwash channel in foreground. (14Apr66) Lou Maher Glacial Lake Missoula (ice dam 800 m high) 500 km3 water Okanogan Glacier lobe dammed Columbia River, deflected flood waters flood waters spilled across southeastern Washington, stripped off loess, created giant ripples most floods occurred after [14C ] 19 ka 13 floods were after 13 ka, two > 6 X 106 m3/s (Benito O'Connor, 2004) Advance of the Ice Sheets • The Late Pliocene and Pleistocene had strong, rapid, climatic fluctuations. • Ice ages are characterized by glacial expansions separated by warmer interglacial intervals. • Before the mid-1970's, the Pleistocene was divided into four glacial stages with intervening warmer interglacial stages. • More recent investigations have shown that there may have been as many as 30 glacial advances over the past 3 million years (roughly every 100,000 years.) Milankovitch Cycles • The overriding controls in climate that has occurred during the Quaternary are three predominant characteristics of the earth's astronomical position relative to the sun, which vary cyclically over time on different wavelengths • This theory, first adequately proposed by a Serbian mathematician, Milutin Milankovitch, who spent over 30 years perfecting it -publishing detailed accounts in the 1930s and 40s. • It is these astronomical variables that have been forcing our climate during the Quaternary and the sudden reversals in trend and the step like pattern is the product of vast positive and negative feedback systems operating in the climate system. • The effect of these climatic changes is spatially dissimilar (i.e. in different parts of the World the climate has reacted differently -perhaps becoming wetter or drier rather than colder and warmer) and also their periodicity has altered over time during the Quaternary. Milankovitch Cycles • In northwestern Europe the last 750,000 years have been characterised by long periods (c.100,000 years) of cold climates interspersed with shorter periods (c.10-15,000 years) of warmer conditions. • Viewed against current fears of global warming (currently believed to have been less than 1oC in the last 100 years) then it gives us a chilling insight into the actual geological evidence which suggests that over 90% of the last 750ka has been very cold at our latitude (with mean annual air temperatures dropping well below zero). • It is thought by some that any trend in global warming will be easily outweighed by much more important overlying trends and climatic feedback systems. Milankovitch Cycles 1. Precession - Earth's axis wobbles or moves in a circle like a spinning top over 26,000 years, affecting the amount of solar radiation received at the poles. Milankovitch Cycles 2. Orbital eccentricity - Earth's orbit around the Sun changes from more circular to more elliptical by about 2% over about 100,000 years, moving the Earth closer to or farther from the Sun, and varying the amount of solar radiation received by the Earth. Milankovitch Cycles 3. Angle of tilt of Earth's axis currently about 23.5o, this tilt angle causes the seasons. Tilt angle varies from about 21.5o - 24.5o over about 41,000 years, changing length of days and amount of solar radiation received at the poles. The Little Ice Age • Cold spells recurred periodically into the Holocene. • The “Little Ice Age” lasted from 1540 – 1890. Temperatures were several degrees cooler than today. • Loss of harvests, famine, food riots, and warfare in Europe. • Cold conditions correlate with periods of low sunspot activity. • A time of extremely low sunspot activity from 1645 -1715 is known as the Maunder Minimum. The Little Ice Age – cont’d • Heightened volcanic activity occurred during the Little Ice Age. • Volcanic ash and aerosols in the atmosphere caused temperatures to drop by blocking out incoming solar radiation. • The eruption of Mount Tambora in Indonesia in 1815 was followed by the “Year Without A Summer”. • Frost and snow were reported during June and July of 1816 in New England and Northern Europe. End of the Little Ice Age • Human-induced warming may be the reason for the end of the “Little Ice Age”. • Greenhouse gases associated with the Industrial Revolution are the major factors influencing global warming and climate change today.