GEOL 106- Lab Final

Extinction likely caused by rapid environmental change

- A very large igneous eruption could damage the ocean environment enough to cause mass extinction, triggering a series of major changes that lead to extinction. - But - major outpouring of magma on the Earth surface has happened many times during Earth history without causing major extinctions. Something else has to have occurred in addition to huge igneous eruption to produce the P/Tr mass extinction event. - Assuming that the P/Tr extinction was caused by collapse of phytoplankton production, the additional trigger would seem to cause killing off of most plankton, leaving suspension feeders to starve. - Possible factor: phytoplankton was so specialized to limited environmental conditions that they could not survive rapid environmental change. - One possible reason: Blooms of phytoplankton occurred rapidly and generated vast amounts of cells that soon die. The decay of these cells consume all available oxygen in 'dead zones' and kills off animals. - Also, some phytoplankton produced toxins (red tides} that animals could not tolerate, causing animals to die. - If this occurred on a vast scale, or if it severely disrupted the ecosystem, suspension feeders could fall into rapid decline leading to extinction.

PALEOZOIC CLIMATE

- After the wild times of Snowball Earth, climate change continues to produce major changes in Earth surface temperatures - CO2 content of the atmosphere suggests rapid increase in temperature in early Paleozoic followed by great decrease in late Paleozoic (then another cycle of high and low in Mesozoic-Cenozoic)

END ORDOVICIAN MASS EXTINCTION

- At the end of the Great Ordovician Diversification Event and high diversity a mass extinction event occurs - The end Ordovician mass extinction event occurs in the middle of a long-term hothouse climate event spanning the early Paleozoic. Documented by paleotemperature determinations from fossils and by calculations of high levels of CO2 content in the atmosphere. - Early Ordovician temperatures are thought to be many times present levels of CO2. This presents a paradox, showing we do not have enough data to understand Ordovician climates. - The end Ordovician mass extinction is assumed to be related to the end Ordovician glaciations; but the onset of continental glaciation in the Carboniferous and the late Cenozoic did not produce comparable mass extinction. - The cause of end Ordovician mass extinction remains obscure

ORDOVICIAN CLIMATES

- At the end of the Ordovician there was a short interval of low temperatures. This occurred during a time of glaciation on Africa - The thick black line is a record of average global temperature during the Ordovician

THE ICE AGES

- Athabasca glacier, Jasper Nat. Park, Alberta, Canada - Glacier in fjord, Alaska

CAUSE FOR END-PLEISTOCENE EXTINCTIONS

- CAUSES: 1. very rapid climatic changes at end Wisconsinian (last Ice Age event) 2. hunting, disturbance by humans - In Americas, extinctions correspond to time of human dispersal and major climate change However, major climate change had occurred many times before - Extinctions occurred when humans arrived and spread out to colonize a continent (North America, South America, Australia). Therefore, human presence is cause of End Pleistocene extinctions. - In Europe, few animals go extinct and the extinctions occurred earlier (at the time of arrival of H. sapiens in Europe)

BIOTIC RECOVERY

- Carbon isotope record shows a million year time for oceans to restabilize, but marine biotic recovery occurs within ten thousand years. -On land plants are little affected and vertebrate changes (except dinosaurs) are mostly change in dominance. Atmospheric carbon cycle on land recovers within 5000 years.

FEASIBILITY OF METHANE RELEASE CAUSING PETM

- Carbon isotope record shows shift in composition compatible with methane carbon composition - Volume of isotope change requires huge amounts of negative carbon isotope added fast; melting of methane ice could do it - Occurs during time of major volcanic magma outpouring in north Atlantic Ocean area

HOTHOUSE to ICEHOUSE

- Climate change over the last 100 million years has been an irregular pattern of global cooling. - Peak heating occurred in mid Cretaceous, ~95 million years ago, followed by continued decline to Ice Ages

TEMPERATURE AND CARBON DIOXIDE LEVELS

- Close correspondance for past 350,000 years - During the Ice Ages global temperature is closely related to CO2 content of atmosphere

BERING STRAITS ICE-FREE ZONE

- Cold climate in Alaska and Siberia, but low levels of precipitation preclude glacier buildup - Humans migrate into Americas during Wisconsin marine lowstand

ORDOVICIAN COLONIES

- Colonial organisms diversified during the Ordovician, but most are bryozoans, not corals. - Corals do not become common until the end of the Ordovician. - Colonial organisms feed mostly on small plankton food particles

FORMATION OF OZONE LAYER

- Colonization of land is possible only after the protective shield of an ozone layer is present in the atmosphere - Some O2 and water vapor in upper atmosphere becomes ozone (O3) Ozone layer forms barrier to ultraviolet radiation -Organisms living on land need protection from UV radiation. UV radiation kills cells and without protection, organisms will die from exposure A layer of water provide protection from UV radiation, but organisms exposed to sunlight need ozone layer protection - Higher concentration of O2 provides stronger ozone layer - The co-occurrence of increased O2 in atmosphere and appearance of multicelled organisms at end of the Proterozoic appears to be linked.

CONTINENTAL GLACIATION ON ANTARCTICA

- Continental glaciation first occurs in basal Oligocene lasts only for about 300,000 years (33.9-33.6 m.y.) - cooling of Antarctic ocean waters and appearance of glacial sediments in oceans; disappearance of land plants on Antarctica - Climates warm in late Oligocene and glaciers retreat

OCEAN CURRENT SYSTEMS

- Deep ocean currents - Formed by sinking of dense cold waters at high latitudes and flow over ocean bottom - Surface currents - Formed by atmospheric winds and flow on ocean surface

RISE OF LAND PLANTS

- Devonian rise of vascular plants colonizes the land surface Forests appear and peat (= coal) deposition begins. - The plant-arthropod association begins; origin of insects and tetrapods (4-legged vertebrates) leads to vast radiation of land biota.

LONG TERM DROP INTO ICE AGES

- During early Pleistocene (2.6-0.9 m.y.) climate changes occur on 41,000 years cycle basis - Major glacial variation in late Quaternary (0.9 m.y.-0) - continental glaciers in northern hemisphere form and decay about every 100,000 years - The cyclic variations in temperature shown on the temperature records reflect climate change produced by variation in heat retention as the Earth circles the Sun. Heat retention corresponds with Milankovich orbital variation and polar tilt variation of the Earth. - Starting 2.5 million years ago the climate started on a nearly regular 41,000 year cycle, then at 0.9 million years ago changed to a 100,000 year cycle with larger swings from cold to warm intervals. This allowed larger continental glaciers to form and spread over much more of the land surface before metling back. - This period of major advance and retreat of continental glaciers is what characterizes the Ice Ages. - THE QUATERNARY O18 STAGES - Note change from 41,000 year to 100,000 year cyclicity and longterm decline in mean annual temperatures

CLOSURE OF MEDITERRANEAN SEA

- During the early Miocene, the eastern end of Sea closed, then opened again during mid Miocene. - During the late Miocene, both ends were closed with land barriers, creating a closed sea. - Arid climate caused water level to drop and produce huge brine lakes

GLACIATION ON GONDWANA

- Early Carboniferous - early Permian continental glaciation (280-230 m.y.) - Early Carboniferous - center on South America Late Carboniferous - centered on South Africa Early Permian - centered on Australia - Recorded by tillites, striated pavements, peri-glacial deposits, dropstones, etc. - The presence of striated pavement beneath tillite gives data on the direction of ice flow

OLIGOCENE GLACIATION

- Early-Mid Oligocene (34-29 m.y.) cooling event - Results in formation of continental glaciers on Antarctica - Follows rifting of Australia from Antarctica (last breakup episode of Gondwana breakup) - Glaciers or icecaps present on Antarctica from that time to now

MID and early CENOZOIC CLIMATES

- Early: when climate experienced two scales of cyclic variation - a long term cycle of 20-30 million years change between cooing and warming and a shorter term cyclicity of ~ 400,000 years superimposed on the longer cycles. The 400,000 year cyclicity is very evident during the Early Eocene. These variations are well documented with paleotemperature proxies, primarily oxygen isotope measurements, providing a detailed record of climate change. The longterm cooling trend leads to the recent Ice Ages when climate variation is dominated by 100,000 year cyclicity that is accompanied by formation of large continental glaciers interrupted by melting away of the glaciers, a pattern that has persisted for 1 million years. - Mid: A time of longterm climate cooling trend

END CRETACEOUS EXTINCTIONS

- End Cret extinctions: dinosaurs ammonites ocean plankton (planktic forams; coccoliths) - Late Cretaceous extinctions (not end-Cretaceous) pterosaurs (flying reptiles) plesiosaurs & mosasaurs (swimming reptiles) rudist bivalves (coral-like clams) - Land plants not much affected by K-T extinction event. Full biomass recovery estimated to occur within 10 years. (Elevated CO2 promotes growth)

END-EOCENE GLOBAL COOLING

- End Eocene (34 m.y.) abrupt cooling event resulted in formation of continental glaciers on Antarctica. - 1. Produced formation of cold deep ocean bottom waters. 2. Beginning of grasslands in mid latitudes - Expansion of temperate climate zones

END-EOCENE GLOBAL COOLING

- End Eocene (34 m.y.) abrupt cooling event resulted in formation of continental glaciers on Antarctica. Also produced formation of cold deep ocean bottom waters. And, beginning of grasslands in mid latitudes - A time of slowdown in plate motion and decreased volcanic activity, resulting in net drawdown of CO2 from atmosphere as weathering removes it from atmosphere - The appearance of continental glaciers on Earth at end Eocene is related to a global shift in plate tectonics. The North Atlantic opened up and Australia separated from Antarctica. The isolation of Antarctica over the south pole allowed continental glaciers to form and cool the Earth several degrees. This is the end of the Mesozic Hothouse and beginning of the newCenozoic Icehouse.

TRIGGER EVENT FOR EXTINCTION?

- End Permian extinctions correspond with time of major flood basalt volcanism - Extrusion of Siberian Traps flood basalts volcanism releases CO2 (greenhouse gas) - Stable isotope event (C and O) - carbon13 excursion at boundary - oxygen18 event - Also occur during formation of Pangaea land areas produce extremes in climate and major drop in sealevel - Oxygen isotope reveal 8°C increase in temperature just before extinction horizon; appear to be result of CO2 release of volcanic Siberian Traps flood basalt eruptions

EAST GONDWANA BREAKUP

- Eocene rifting of Australia from Antarctica is last fragmentation event of Gondwana - They move apart and Antarctica moves back to position over south pole and Australia moves north - Eocene is a time of global tectonic change (also time of India collision with Asia) - A global re-organization of tectonic plates occurs during the Eocene. - 1. Australia and New Zealand split away from Antarctica 2. India collides with Asia 3. North America splits away from Europe as the midAtlantic spreading axis extends to North Pole 4. North America begins override of mid-Pacific spreading axis 5. Yellowstone hotspot pushes through North America continental crust

PETM

- Event has 1) Rapid C excursion 2) Strong global warming 3) Biotic extinction 4) Increase of hydrologic cycle 5) Widespread ocean anoxia - Linked to rapid release of methane from methane ice, caused by activity in a large igneous province - May have been start of an Ocean Anoxic Event (OAE)

SIBERIAN TRAPS FLOOD BASALTS

- Extrusion of Siberian Traps flood basalts releases CO2 (greenhouse gas) and oxygen isotope data reveals 8°C increase in temperature just before extinction horizon - Many volcanic ash layers in latest Permian strata of same age as Siberian Traps flood basalts - Rapid increase in release of volcanic gases could raise temperature and cause ocean acidification; damaging plankton production

FLOWERING PLANTS

- Flowering plants (Angiosperms) - Cret. to present appear in early Cretaceous (135 Ma) dominant plant group from mid Cretaceous faster growing than Jurassic conifers & cycads - Life cycle: produce flowers to attract pollinators and fruit to spread seeds - Egg and sperm produced in flower, pollen spread to other flowers and eggs fertilized to produce seed; many species are dependent on animals for reproduction: pollination and seed dispersal. Develop plant-animal associations where each species is dependent on the other for reproduction - Insect pollination and co-evolution of plants and insects (especially beetles and bees) leads to Cretaceous evolutionary radiation of insects and angiosperms - The appearance of flowering plants led to a major change in land biotas. Flowering plants produce much more nutritious food for herbivore animals. The result was great a great radiation of herbivores and of the carnivores that fed on plant eaters. - The Cretaceous was a time of great abundance of herbivore dinosaurs and of insects that fed on plants or the nectar and pollen they produce. There was a tremendous development of the plant-insect association that leads to insects being the most diverse group of animals on Earth.

CAUSE OF PETM?

- Heating of ocean bottom waters by igneous activity could result in sudden release of methane needed to change carbon isotope signal. - Problem: ocean bottom waters at end-Paleocene were several degrees warmer than modern ocean bottom waters and there was minimal methane clathrate present in ocean bottom sediments at that time. - Alternative explanation is that igneous intrusions create methane from carbon-rich source rock and coal beds. - The PETM is well documented and it effects on the biota is obvious all over the Earth. The carbon cycle record shows there was a large release of methane (a greenhouse gas) within a very short time. Ocean bottome sediments today contain a large amount of methane locked into methane ice clathrate, which could be released rapidly if heated. But - ocean bottom waters were warmer in the early Cenozoic and it is doubtful there was enough clathrate present. - A more reasonable interpretation is that basalt magma of the north Atlantic hotspot intruded North Sea sediments with much coal and carbon source rock, cooking it to produce methane. That is consistent with seismic work showing sheet intrusions of basalt into sediments of the region. - The effects of the PETM on biotas were great. Several degrees warming resulted in shift of climate zones toward the poles. During the PETM subtropics extended to the US-Canada border. The Arctic Ocean was in a temperate climate zone. Comparable change occurred elsewhere. - At that time North America and Europe had a land connection and the result was a great migration of Eurasian animals across the connection into North America. Many North American animals were driven to extinction by the arrival of Eurasian migrants that displaced them. - This huge change was mostly restricted to North America. South America remained isolated and kept its Gondwanan land animal biota dominated by marsupial mammals (like Australia). They were later driven to extinction when a land connection (Panama Isthmus) formed in the Pliocene.

HOLOCENE CLIMATE HISTORY

- Holocene interglacial - 12,000 years - Early Holocene ~ 1°C warmer than late Holocene - but decline in temperature is slower than during past interglacials - Human-produced deforestation for agriculture (rice) stabilized temperature over past 5000 years, by releasing enough CO2 to counter cyclic temperature decline - However, modern rapid rise in CO2 is much greater than natural variations

CONTINENTAL GLACIER ICE CORES

- Ice cores are formed of annual layers of snowfall and can be dated like tree rings. Have a half-million year record of climate. - Ice layers contain dust and tiny bubbles of atmospheric gases. - Ice formed during glacials shows there there was much more dust in the atmosphere than during interglacial times.

Land Plants

- Important group is vascular plants. Ancestry: evolve from charophyte green algae - A revolution in plant history: Vascular system - Have characters needed for survival on land: -vascular system - plumbing system to transport fluids water from roots (xylem) & food from leaves (phloem) -cutin - waxy covering on stem and spores to prevent water loss by drying -support - woody cells with lignin -roots & leaves - roots gather water and nutrients (and support tree) and leaves increase area for photosynthesis -surface growth - growth occurs on surfaces - Alternation of generations - with spore-producing life stage dominant

CLIMATE CHANGE -LAST 30,000 YEARS

- In western North America: Maximum extent of Wisconsin glaciers - 18,000 ybp -- begin deglaciation - Ice margin lakes - temporary meltwater lakes - Maximum pluvial lake levels - 15,000-13,500 ybp -- vegetation indicates wetter climate - Rapid melting of glaciers - 12,000-9000 ybp -- brief colder event (Younger Dryas) - 11-10,000 ybp - Early Holocene warm climate - 8000-5000ybp - Modern climate regimes established - 4000 ybp

PALEOCENE-EOCENE THERMAL MAXIMUM (PETM)

- Increase in temp of 5°C in mid latitudes and 6°C in Arctic, lasting about 200,000 years, return to pre-PETM conditions occur over another 250,000 years - Addition of >1500 gigatons of C13-depleted methane or CO2 to oceans and atmosphere - Possibly caused by release of methane from coal-bearing land basins, due to igneous intrusions, or from seabed clathrates (methane ice) in oceans - Coincident with massive volcanism in North Atlantic (NAIP) and opening between Europe and Greenland (55.5 Ma) - Extinctions, followed by migrations and radiations - Recovery results from marine carbon storage (phytoplankton blooms) and continental rock weathering

ICE MARGIN LAKE AGASSIZ

- Lake Agassiz overflow to Gulf of Mexico, to St. Lawrence River and to Hudson Bay at different times, as ice retreats and rebound changes gradient - Catastrophic flood (draining the lake) to Arctic at 8000 bp release 100,000 cubic km of water and raise sealevel ~ 1 foot; stop N.Atlantic deep water current and produce cold climate Younger Dryas event

LAKE MISSOULA FLOODS

- Lake Missoula: an ice-dam lake - Glacial Lake Missoula formed on south edge of Cordilleran glacier sheet, in the deep valleys of northwestern Montana. - 1. Dam of glacial ice blocking rivers in north Idaho - created lake with about 2200 km3 of water - exist from 18,600 -15,900 years before present 2. Catastrophic (total) failure of ice dam and flood - bouyant lifting of ice dam and subglacial draining - ~2200 km3 of water released; peak flow rate of 1 km3/hour 3. Create channeled scablands of SE Washington - deep troughs cut into ground and rock; huge gravel bars - floods empty into Columbia River, then to Pacific 4. Refilling of lake and many huge floods - at least 89 floods; floods separated by 100's years - Overflow channel with falls, Dry Falls, Washington - Gravel dunes ('current ripples') on channel floor, Washington

PLUVIAL LAKE HISTORY

- Lake levels low at 30,000 ybp - Lake levels highest at 15,000 ybp - Lake Bonneville & Lahontin 10 times larger - wetter climates and different plant communities - Bonneville overflow flood at 14,500 ybp -lake level abruptly dropped 108 m as outlet cut at Red Rock Pass, releasing 1500 cubic km of lake water - new shoreline cut at lower level (Provo shoreline) - Water level drops 180 m in lakes -14,000-13,500 ybp Very low Bonneville lake levels 13,000-12,000 ybp - Minor rise in Bonneville lake level at 11,000 ybp (30 m rise; Gilbert shoreline)

PLUVIAL LAKES

- Lakes that fill with water during times of wet climates, then shrink or dry up during times of dry climate. - Form in basins with internal drainage. Rivers are unable to maintain permanent flow out of basin. - Note the large area formerly covered with water. The presence of water had a huge effect on regional climate.

THE TRANSITION TO LAND

- Land colonized by plants, then by animals - in mid Paleozoic first vascular plants - late Silurian first forests - late Devonian first tetrapod vertebrates - late Devonian - Land truly colonized by vascular plants With appearance of land plants, land areas provide food & shelter for animals & origin of tetrapods (4-legged) - Groups well adapted to land conditions 1) vascular plants 2) arthropods - arachnids; myriapods; insects 3) gastropods 4) worms -annelids; roundworms 5) vertebrates

LAST CONTINENTAL GLACIATION

- Last interval of continental glaciation known as: Wisconsin - in eastern & central North America maximum extent at about 20,000 years ago Wisconsin glaciation end at 10,000 years ago - Last interglacial (Sangamon) (O18 stage 5) lasted from 120,000 to 90,000 years ago and was slightly warmer than current interglacial interval

LATE EOCENE COOLING

- Late Eocene (38-34 m.y.) cooling event associated with formation of continental glaciers in Antarctica - A time of slowdown in plate motion and decreased volcanic activity, resulting in net drawdown of CO2 from atmosphere as weathering removes it from atmosphere

LATE MIOCENE CLIMATES

- Late Miocene cooling event starts at 14 Ma - Rapid growth in south polar ice sheets that cover continent with permanent ice cover - Beginning of present abyssal ocean current system (fully developed by 6.2 m.y. ago) - Drake Passage opens; begin circum-Antarctic current - The complete separation of Antarctica from other continents opens up an open path for ocean waters to flow around Antarctica and isolate it from warmer waters. This makes it colder, it becomes ice-covered, and chills surrounding sea water. - Higher density sea water sinks to bottom of ocean basins and starts flowing as a deep water current, cooling the world oceans. - This cools cliimates and leads into the Ice Ages.

"PIONEER" COLONIZER OF LAND

- Lichens - This type of organism is a symbiotic consortium of a photosynthesizer microbe (like bluegreen algae) and a fungus - Because fungi are land organisms that feed on decaying tissue, they depend on plants to be present - They would arise after the initial colonization of land, not be part of the early invasion

CASE STUDY OF EXTINCTIONS (END PLEISTOCENE EXTINCTIONS)

- Major extinction event among large terrestrial mammals (over 40 kg weight) at end Pleistocene -- both herbivores & carnivores -- does not affect plants or marine biota - Worldwide extinction of 200 large mammals genera - North America -- 33 of 45 genera (75%) extinct - South America -- 80% - Australia -- 94% - Few extinction in Eurasia (occur ~ 200,000 years bp) - Extinctions in Americas occur 12,000-8,000 years bp. - Extinctions in Australia occur ~40,000 years bp.

PLANKTON EXTINCTIONS

- Major extinctions of: Planktic foraminifera (90%)- zooplankton Coccolithophores (93%)- phytoplankton - Lesser extinction among: Dinoflagellates - phytoplankton Diatoms - phytoplankton - This is of huge importance because phytoplankton (coccoliths, dinoflagellates, diatoms) are the food producers of the ocean

DINOSAUR HERDING

- Many dinosaur species were social animals and the plant eaters probably moved in herds, especially ceratopsians and hadrosaurs. - Dinosaur herding is mostly associated with the spread of more nutritious plants during the late Cretaceous when flowering plants become the dominant land plants. - Dinosaur biology is a fascinating topic and one of continuing interest. Although reptiles and including the largest land animal known, both plant eaters and carnivores seem to have had life habits similar to large animals living today. - The discovery of nesting sites with hatchlings needing parental care and of group behavior shown by many trackway sites is as noteworthy as recent studies showing that dinosaurs maintained body temperature above background levels, although not as high as mammals. - The discovery of many feathered dinosaurs suggested those animals could probably use the feathers to keep the body warm. This also proves the ancestral relationship to living birds. - Very large sauropod fossils also occur in concentrations and many places have sauropod trackways showing several animals moving in the same direction in a group - The famous trackway site at Glen Rose, Texas (Dinosaur Valley State Park) has sauropod tracks that show animals moving in the same direction

CE AGES CLIMATE FLUCTUATIONS

- Marine record of climate change during last 120,000 years (Sangamon interglacial and Wisconsin glacial) is determined from: Ice cores from Antarctica and Greenland, Loess sequences in central Asia - Show synchronous millenial scale variations in climate. - Indicates linkage of climate systems around the globe.

MASS EXTINCTION EVENTS

- Mass extinction events: times when species extinction rates much exceeds species origination rates - Several "mass extinction" events in the Sepkoski data end Ordovician late Devonian end Permian end Triassic end Cretaceous ("K-Pg boundary") - The P/Tr is the greatest mass extinction event - it is also poorly documented because of the scarcity of sedimentary deposits spanning the Permian-Triassic boundary - Mass extinction events are infrequent and associated with many extinctions occurring within a short time period. Extinction of species occurs all the time but times of great extinction usually involve the disappearance of all the species of a major group of organisms. Such examples include extinction of trilobites (end Permian) and dinosaurs (end Cretaceous). These were common and important parts of biotas before their extinction. - Why did such successful organisms go extinct? That is the question that fascinates biologists and paleontologists. Even with good data it is very hard to identify why groups of organisms went extinct. - The greatest mass extinction event known is the end-Permian event but the best documented ancient mass extinction is the end-Cretaceous.

ROLE OF VOLCANISM

- Massive eruption of basalts started ~1 million years before the Chicxulub impact and continued for 500,000 years after, releasing much CO2 to atmosphere. The Deccan Traps large igneous province (LIP) in India. - This produced pulses of climate change and short intervals of global warming, but did not cause the KPg ocean extinctions - The role of this igneous event in causing end-Cretaceous extinctions is a big debate at present, with a few workers claiming it is the main cause of extinctions. - However, most of the Deccan Traps volcanic activity occurred in latest Cretaceous before the big extinctions and during a time of moderate change in biotas. In contrast, the ocean plankton extinctions occur exactly at the time of the meteor impact event. The impact appears to be the trigger for extinction among the already stressed ecosystems of the oceans. - Dating of the dinosaur extinctions is not precise enough to know if they died out in the latest Cretaceous or were still living at the time of impact. Most people want to believe that dinosaurs were killed by the meteor impact, but data isn't good enough to prove it.

NORTH ATLANTIC LARGE IGNEOUS PROVINCE (LIP)

- Massive outpour of basaltic lava and igneous intrusion in latest Paleocene and early Eocene (PETM time) - Related to presence of a mantle plume hotspot - Note alignment of exposed volcanics on west & east Greenland, Iceland, and Scotland

METHANE CLATHRATES

- Methane molecules become trapped in water ice when molecules form a clathrate ice structure; a common occurrence in seafloor sediments under freezing conditions - Methane burning when released from under Arctic lake ice - Methane ice

CHANGING CLIMATE & OCEAN CURRENTS

- Mid Miocene - open Drake Passage; new circum-Antarctic current isolates continent, with growth in Antarctic glaciers - Deep ocean currents driven by heat flow. Solar heating (insolation) greatest at equator and is modified by reflection (albedo) and heat is lost from the poles. Ocean and air currents move heat to cold polar areas. - These differ from wind-driven surface currents (gyres)

CAUSES OF QUATERNARY CLIMATE FLUCTUATIONS

- Milankovich cycles: Gravitational influence of Jupiter and Venus on Earth orbit produces oscillation in orbit shape (eccentricity). - Orbital variations -- eccentricity - 413,000 year cycle -- eccentricity - 100,000 year cycle - this is the dominant cycle affecting Earth climate over past million years - Rotational variations -- Axial angle variation - 41,000 year cycle -- Precession of equinoxes - 26,000 year cycle

MAJOR DRAINAGE CHANGES

- Missouri River system - TeaysOhio River system

PLANKTON EXTINCTIONS

- Most extinction occurred among specialist species adapted to stable, oligotrophic environments. - Survivor species were wide-ranging and hardy, common in high latitudes, or had shallow shelf distribution, prone to blooms as nutrient levels changed. Survivor species are common among groups that can produce resting (encystment) stages - a form of hibernation. Brown, 2005, Geology, p.653 for nannoplankton PLANKTON EXTINCTIONS - Short term decline in ocean phytoplankton, collapsing ecosystem leads to extinctions. Impact is so disruptive that specialist taxa go extinct, leading to collapse and more extinctions. - The end-Cretaceous extinctions show that mass extinction events may be selective and cause some groups to die out but other groups continue on with relatively small change. The less affected groups maintain normal species origination rates while experiencing only moderate increase in extinction rate. - The animal groups snails and clams were only slightly affected by the end-Cretaceous mass extinction. Other groups started declining during the latest Cretaceous

NAUTILUS

- Nautiloids are the first group of cephalopods to appear and were became very large during the Ordovician (they precede the ammonites and coleoids). - Their time of greatest abundance was in the Ordovician, declining in importance in the marine biota with only the genus Nautilus remaining today

CONTINENTAL COLLISION: AFRICA - EUROPE/ASIA

- Northward movement of Africa results in convergence with Europe - Closes connection of Atlantic Ocean with Indian Ocean in warm latitude; produces Mediterranean Sea - The initial breakup of Gondwana left Africa as an isolated continent that moved slowly. It gradually moved northward towards Europe and began to close up the intervening ocean, hitting Europe near Spain and in the Middle East. - This movement led to fragmentation of crust into several tectonic plates in the region that rotate in different directions. - The collision formed the Alps mountain chain, but also created some small spreading zones on small tectonic plates south of the Alps. that form basins of the Mediterranean Sea. - World ocean connections to these basins has varied, leading to alternation from ocean to fresh waters and at one point isolating the Mediterranean enough to dry up. - This is the most dramatic event of the late Cenozoic

END CRETACEOUS EXTINCTIONS

- Occurs at time of METEOROID (BOLIDE) IMPACT - Evidence of iridium-rich layer in sediments at boundary - this element rare in Earth crustal rocks, more abundant in meteorites and mantle rocks. - Impact of large (10 km diameter) meteoroid-comet - would generate shock waves, tsunami waves, wildfires, enormous dust clouds to cause "impact winter". Produce physical disruptions. - Site at Chicxulub in Yucatan identified as impact site. - This is an extinction where the trigger mechanism is well determined. The trigger event set off several major environmental changes that caused some groups of organisms to decline and some groups to go extinct - What is remarkable about this extinction is that the trigger mechanism was very abrupt: a large meteoroid collision with Earth. The environmental disturbances developed very fast, within days, weeks, years. - This is the only mass extinction event that can be shown to be triggered by such a sudden event.

PERMIAN LIFE

- Ocean biota changed dramatically - Land biota was much less affected

CHANGE IN ORBITAL VARIATIONS

- Orbital eccentricity variations (100,000 years), with superimposed obliquity (41,000 years) variations, control glacial cyclicity and climate changes during last 0.9 million years. - Mid Pleistocene climate change: Earlier (2.8 to 0.9 million years) glacial cyclicity and climate dominated by 40,000 axial angle obliquity cycles.

PALEOGENE CLIMATES

- Paleocene & Eocene: warm climate, like Cretaceous - warmest temperatures in early Eocene (high latitude oceans 10-12° warmer than today) - warm ocean bottom waters reach to polar seas - Paleocene-Eocene boundary: PETM hyperthermal event - sudden warming event (5-6°); carbon isotope spike - global increase in temp, several degrees C, lasting about 200,000 years -probably caused by release of methane from seabed clathrates (methane ice)

INTO THE ICE AGES

- Pliocene-Pleistocene boundary (2.6 m.y.) cooling event - formation of continental glaciers in Arctic regions - tundra vegetation established - Panama isthmus forms and Gulf Stream flows north - Quaternary: cyclic fluctuations in temperature - episodes of continental glaciation in northern hemisphere - major changes in global ice volume (start 0.9m.y.)

HEINRICH CLIMATE EVENTS

- Short term climate disruptions during late Pleistocene and Holocene, produced by changes in ocean currents and associated effects on climates (12,17,24,31,38,45 Ka) -global in extent -they are triggered by floods of fresh water and icebergs into ocean; this triggers breakup of sea ice -alters formation of cold deep ocean waters and shifts warm surface water currents (e.g., Gulf Stream) -results in change in rainfall and global temperatures - Illustrates how change in one area can affect climate elsewhere, becoming a global event.

FIRST EVIDENCE

- Spores (reproductive bodies) and cuticle from probable land plants are known from late Ordovician and Silurian sediments, although no complete remains of land plants have been found so far - These come from Gondwana continents, a land mass that remained high during the early Paleozoic

DEVELOPMENT OF PLANTARTHROPOD ASSOCIATION

- Terrestrial arthropods appear mid Devonian (mites - insects; myriapods; arachnids) - Plant-living arthropods feed on decaying vegetation, sap, fungi, spores & pollen - Plants evolve complex spores and bark for protection - Lead to great evolutionary radiation of insects, first appearing are detritivores and carnivores, then herbivores become common in Cretaceous

ISOTOPE STRATIGRAPHY

- The Cenozoic was a time of irregular but persistent cooling, shown by oxygen isotope record. - There were several major short term or abrupt changes in climate.

END-CRETACEOUS FLASH HEATING

- The Chicxulub impact event released enough energy to warm Earth several degrees Celsius - Much heat was lost by atmosphere blasted into space; heating of Earth surface by blast wave and fires rapidly lost by radiation and minimal - CO2 added to atmosphere CO2 added from vaporization of limestones quickly reprecipitated as carbonate accretionary spherules that fell to surface and buried - minimal impact on Earth heat budget

CRETACEOUS TERRESTRIAL RADIATION

- The Cretaceous was a time of rapid radiation of flowering plants, producing major changes in floras. Flowering plants (angiosperms) replace conifers and others as dominant plants on land. - Flowering plant tissue and fluids are more nutritious than that of other plants. This leads to major radiations among herbivores of all types (esp. insects and vertebrates), social insects, dinosaurs, birds and mammals. This begins the rapid rise in diversity toward modern levels. (see Sepkoski curve).

ETM2 HYPERTHERMAL

- The ETM2 hyperthermal is a small version of the PETM, occurring at 53.7 Ma, about 1.3 million years after the PETM - Like the PETM, this occurred for only about 200,000 years - Other hyperthermals can be recognized at 53.6 Ma (H-2), 53.3 Ma (I-1)m 53.2 Ma (I-2), and 52.8 Ma (ETM-3) - These occur on a frequency related to the 405 thousand year extended eccentricity orbital cycle of Earth - The PETM ended after ~450,000 years, but it was followed by a series of shorter and less disruptive hyperthermal events, the ETMs. These fairly closely occur in synch with Earth's longterm Milankovich orbital cycles and reflect periodic increase in global warming and cooling produced by changes of the Earth's orbit around the sun. - Milkanovich orbital cycles produce systematic changes in climate that can be recognized in sediment deposits. These cycles have a known duration obtained by using orbital dynamics calculations. When a complete record of cycles is present, the record can be tied to the geologic time scale. This is a dating method know as astrochronology. It can be used to date strata with an accuracy of a few centuries (for very young strata) to several thousand years (for older Cenozoic and Mesozoic strata).

ICELAND ON MANTLE PLUME HOTSPOT

- The NW to SE trend suggests plate movement over a mantle plume hotspot, but at a slow rate. - The mid-Atlantic ridge straddles a mantle plume hot spot. Mantle plume probably developed when spreading axis developed, producing a hot spot fixed on spreading axis

ORDOVICIAN ARTHROPODA

- The Ordovician biota contained a high diversity of arthropods, but most were of small to moderate size - Trilobite fossils are common fossils because they produced a mineralized skeleton, but other arthropods were also common

CRINOIDS OF THE ORDOVICIAN

- The Ordovician was a time of proliferation of crinoids (echinoderms) that lived attached to that seafloor and fed on tiny food particles (suspension feeder); they look like plants but are animals - This group remained common throughout the Paleozoic

Mass extinction events

- The Paleozoic record of life shows episodic crises with mass extinctions. The greatest are 1) end Ordovician 2) Late Devonian 3) End Permian - These presumably relate to major environmental disturbance, but exact cause is not known for these mass extinctions. - The end Permian mass extinction is the greatest one known in the fossil record of life. Many groups go extinct or have only a few survivors that produce offspring quite different from the ancestors. - Mass extinction events: times when species extinction rates much exceeds species origination rates - Several "mass extinction" events in the Sepkoski data end Ordovician, late Devonian, end Permian, end Triassic, end Cretaceous ("K-T boundary") - The P/Tr, Tr/Jr, and K/T are major mass extinctions; The O/S and late Dev are not major.

PARA-TETHYS SEA BASINS

- The Para-Tethys seas are a series of basins produced between uplifted mountain blocks north of the Turkish and Arabian tectonic blocks that moved north and east. - Contains the Pannonian, Black, Caspian, and Aral sea basins. They gradually became more restricted and changed from marine to fresh water.

CHICXULUB IMPACT

- The classic set of indicators of Chicxulub impact Iridium anomaly (ppb) Spherules (bubbly glass spherules) ('tektite') Shocked quartz grains (bedrock) Extinctions (planktics) Tsunamites (seismites) - Calculated results of Chicxulub bolide impact Revised estimates: 1) crater size 100 km 2) firestorm local only 3) CO2 release minor 4) acid rain minor-minimal 5) dense cloud cover brief, minor

What made colonization possible

- The colonization of land by animals was possible only when food resources appeared in the form of land plants. In oceans, rivers and lakes algae could provide food for animals, but on land there was little food available until vascular plants appeared in the Devonian. - Land (vascular) plants radiated and spread rapidly, providing a huge new supply of food for animals. This led to the origin of animals adapted to land conditions: spiders and relatives, centipedes, millipedes, and especially INSECTS! - Insects are fundamentally adapted to life on land and are nearly all confined to life on land.

COAL DEPOSITION

- The deposition of coal represents a huge storage of carbon into the rock reservoir of the Earth - A transfer of carbon (hence CO2) from the atmosphere to the lithosphere and a decrease in greenhouse gas content - This occurs at the beginning of longterm Gondwana continental glaciation and the start of late Paleozoic Icehouse Earth - The beginning of coal deposition is of great importance to global climates because it was a new process of removing CO2 from the atmosphere and storing it in the rock reservoir. Vascular plants produce large volumes of cellulose and lignin that are most resistant to decay and easily transfer into sediment deposits. - As more plant carbon is stored in coal the effect is shown with the start of major Gondwanan glaciation - a pattern of repeated continental glacier growth alternating with glacial melting. This lasted for nearly 50 million years before warming conditions returned and ended Gondwanan glaciation. That is a very long time duration for glacial conditions. - The return to warmer climates reflects increased volcanism and probably involved the start of recycling (by volcanism) of some of the buried coal deposits.

BRAZOS RIVERBED

- The event deposits produced by the Chicxulub impact - Cottonmouth Creek: The lower white band is a volcanic ash bed 20 cm below the light gray mass flow bed - Large mudstone blocks in mass flow bed, capped by spherule sand and cemented quiet water settling layer - Cemented sandstone beds overlying thick layer of spherule sand (to right) - Two units of sand overlying spherule bed - Hummocks produced by oscillating water - The basal Paleocene beds containing a recovery biota

END-ORDOVICIAN MASS EXTINCTION

- The first land plants (moss; liverworts) occupying the land might have removed enough CO2 from atmosphere during Ordovician to cause the short duration end-Ordovician glaciation. - But a glaciation is not enough to explain a mass extinction that is documented entirely with species living in continental shelf marine environments. - The cause is unknown.

PIONEER COLONIZERS OF LAND

- The first multicelled organisms to occupy the land surface were probably non-vascular plants - Mosses; liverworts; lichens - These are small and have a surface layer resistant to drying and stiff organic structure to support cells and maintain position

COLONIZERS OF LAND - NEEDS

- The first multicelled organisms to occupy the land surface would need protection from: 1) desiccation (drying), 2) UV radiation, and 3) a support system to counteract the force of gravity - Support is a problem not encountered by organisms living in water (they usually have a density similar to water). - The main function of a skeleton for organisms living in water is to protect against predators or to provide structural support for muscle attachment - The first organisms to occupy the land surfaces would be microbes and protists living in wet places and in areas sheltered from radiation. These could be diverse and similar to organisms living in the oceans. - When multicelled organisms appear, they could live in fresh water environments, but probably few could survive on land

END PERMIAN MASS EXTINCTION

- The greatest extinction event of multicelled organisms ~90% extinction of marine species (75% extinction of genera) Less change in land biotas, but that is not as well documented - Extinction greatest in the tropics and among plankton-feeding animals - Extinction (total) of trilobites fusulinid forams rugose & tabulate corals - Severe extinction of brachiopods bryozoans (several orders) echinoderms (several orders) - Near extinction of ammonites , a group that extinction-prone, subject to near extinction 4 times before a final crisis caused total extinction at the end of the Cretaceous - The end-Permian mass extinction results in the disappearance of most of the dominant animal groups of the Paleozoic, marking the end of the long-lasting Paleozoic biota, dominated by trilobites, brachiopods, crinoids, corals, and bryozoans. - The groups most affected by extinction are the plankton suspension feeders (brachiopods, crinoids, corals, bryozoans). There were few survivors of these groups and the survivors changed fast to produce new types that radiate to high diversity again. - The extinction of suspension feeders indicates a huge loss of phytoplankton (plant plankton) species and resultant loss of food for animals and zooplankton.

MINOR CLIMATE WARMING

- The late Oligocene and early Miocene was a time of moderate warming that led to shrinkage of continental glaciers on Antarctica and global warming conditions - Time of evolutionary radiations of land and marine biotas when more nutrients enter ocean waters and promote phytoplankton growth

BIOTIC RADIATIONS AND MASS EXTINCTION EVENTS

- The record of animal life from the great radiation of multicellular life to the present day contains several time of mass extinction and two time of great radiation of life. - The Cambrian Explosion (Radiation) and Great Ordovician Biodiversification Event (GOBE) are the early and late stages of the first great radiation of multicellular life.

Animal Diversity

- The tabulation of animal diversity shows a leveling off of animal diversity by the end of the Ordovician and an apparent leveling off of maximum diversity through through the entire Paleozoic Era (Cambrian to Permian). - This leveling of maximum diversity is unusual, suggesting there was a limit on the ability of the marine environment to support additional growth of life. It may be related to the amount of food available, with established groups utilizing all available food, but the primary source of food is phytoplankton which we can assume could increase growing (making more food) available. - If phytoplankton growth was limited, it would be because of limited nutrients in the water. -Were less nutrients available for plant growth during the Paleozoic? (Was weathering on continents less intense during the Paleozoic?) -Was there little food available in the shorezone setting at those times? (Shorezone currently are nurseries for much marine life) - A factor to consider is that there were no plants growing in shorezones before the Devonian

TRILOBITES

- These were the most abundant skeleton-forming organisms of Cambrian but by the Ordovician they were one of several shell-forming groups of animals - Trilobites molted (shed exoskeleton) regularly, producing large amounts of skeletal debris - Related to crustaceans (shrimp, crabs, lobsters, etc); had multiple appendages with gills and antennae, but lacked claws - Name is a reference to 3 fold division of body

END-DEVONIAN "MASS EXTINCTION"

- This second Sepkoski mass extinction event occurs in 3 separate steps of moderate extinction among several groups of shallow marine organisms. - It is not comparable to the big mass extinction events and is really a case of rapid species turnover and change and disappearance a few groups of reef-dwelling organisms. It is better considered to be an example of rapid evolutionary change. - The species turnover occurs during a time of cooling global climate that leads to episodic advance and retreat of Gondwanan continental glaciers.

MID-MIOCENE CLIMATE OPTIMUM

- Time of short duration of higher temperatures during the middle Miocene; lasts for a few million years - The brief interval of warming is the warmest time of the last 30 million years of Earth history

PLUVIAL EVENTS

- Times of lake formation in arid regions , associated with episodes of "wetter" climates and glacier melt. - Pluvial lakes in Great Basin area of western states: Lake Bonneville (largest), Lake Lahontin, Searles Lake, Mono Lake - Pluvial events and lakes (in North America) are probably result of southward deflection of jet stream, producing cooler temperatures and lesser evaporation, as well as minor increase in rainfall. - Pluvial lake formation coincides with early part of melting of Wisconsin continental icesheets. - Some pluvial lakes show record of overflow and draining into adjacent basin or drainages. - Lake Bonneville flood into Snake River drainage - Mono Lake (& others) overflow into Searles Lake

AMMONITE EXTINCTION

- Total extinction of ammonites occurs - Ammonites are common in marine environments to the end of the Cretaceous - The types were commonand were plankton feeders

DINOSAUR EXTINCTION

- Total extinction of dinosaurs - Dinosaurs present up to the latest Cretaceous - not common, but a few genera - Dinosaur bones occur in strata only a short interval below the end Cretaceous; not known if they were actually living at the time of the meteoroid impact event, but any still living would be very prone to dying

TRIGGER EVENTS FOR MASS EXTINCTIONS

- While extinctions follow great disturbance of the environment, the environmental evene does not necessarily produce extinction, it is the changes produced by the event that degrade environment and reduces food supply that can lead to great extinction - Small numbers, loss of food supply, long time to reproductive maturity, adaptation to limited set of conditions - all can lead to extinction during rapid change in environment - Specialists go extinct, but generalists may prosper or evolve rapidly to new conditions. This is certainly the case with end-Cretaceous marine species.

FEATHERED DINOSAURS

- small ground-dwelling theropod dinosaurs - Give rise to birds, that survive the end Cretaceous extinction event - The following animal groups were large reptiles that were common during the Cretaceous but died out in the late Cretaceous, as climates began to cool from a mid Cretaceous hothouse climate climax. - It is remarkable how reptiles radiated to be the dominants of the land, the oceans, and the atmosphere (flying).

MID-EOCENE CLIMATE OPTIMUM

A stable isotope event associated with global warming and the last warm event before the plunge into an icehouse world

ORDOVICIAN BRACHIOPODS

Brachiopods were the dominant shelly benthic animal They fed on tiny food particles (suspension feeders)

MARINE REPTILES: MOSASAURS

Common during the last 20 million years of Cretaceous - but probably extinct a million years before impact event

NORTH HEMISPHERE GLACIERS, PLEISTOCENE

Concentration of land just below Arctic Circle provide good conditions for growth of continental glaciers

RUDIST REEF EXTINCTIONS

Cretaceous reefs were made by clams growing like reef corals (rudist bivalves) They live until a few million years before end Cret

CARBONIFEROUS SWAMP

Dominated by lycopsids, ferns and horsetails

MESSINIAN SALINITY CRISIS

Evaporite deposits of the latest Miocene (Messinian) in the Mediterranean Sea basin - In late Miocene (7 m.y. ago) Africa and Iberian Peninsula (Spain) joined, forming a land bridge, while Africa joined with Asia at Sinai - As sealevel drops Mediterranean basin is isolated from open ocean; isolations lasts 300,000 years - Med basin dried up - forming the Messinian evaporites Water levels dropped 1500 m, forming brine lakes in low areas and depositing salt beds - Rivers cut deep gorges (Nile, Rhone, Danube) in basin margins - Begin of Pliocene - sea flows in at Gibralter -Gibralter falls -gravel sheet a record of flood

NORTH EUROPEAN ICE CAP

Extent of continental glacier ice at last glacial maximum (LGM) reflects the moisture gradient more than temperature - The distribution of glaciers in Eurasia illustrates the dominant control of precipitation over mean annual temperature in producing continental glaciers. The coldest temperatures of the northern hemisphere occur in central Siberia, but central and eastern Siberia had very little continental glaciation. There wasn't enough snowfall for glaciers to form. Winter snow would evaporate in the dry air. - Big continental glaciers formed in Europe and in north and eastern North America, on both sides of the Atlantic Ocean. Gulf Stream waters flow into the North Atlantic, producing high precipitation. During cold intervals the snow accumulates year after year, forming glaciers. - This did not happen in most of Siberia. Very cold but too dry.

MID-CRETACEOUS HOTHOUSE

Hothouse peak in mid Cretaceous, then long climate cooling trend to end Cretaceous

SEA LEVEL LOWSTAND

Last glaciation dropped sea level 130 m; shoreline moved out to edge continental shelf (black line)

MOST RECENT ICE AGES GLACIATIONS

Major increase in continental glaciers occurred at intervals of 100,000 years, alternating with episodes of deglaciation, responding to climate control

NAUTILOIDS OF THE ORDOVICIAN

Nautiloid cephalopods radiated during the Ordovician and became the largest predators

ORDOVICIAN PREDATORS

Nautiloids were the great predators of the Ordovician - nautiloids are relative of octopus and squid

ORDOVICIAN TRILOBITES

Ordovician trilobites were common crawling animals of the seafloor. They fed on organic debris and small animals

NCISED CANYONS OF THE MESSINIAN

Rhone, Nile river valleys

CENOZOIC CLIMATE EVENTS

Several short term hyperthermals occur in the early Cenozoic

BONNEVILLE LAKE LEVEL HISTORY

Short drops in lake level between 21,000 and 14,000 years correspond to Heinrich (and Younger Dryas) climate events. Short term climate events associated with fresh water floods, ice breakup and change in ocean currents.

ORDOVICIAN GLACIATION

Short time of glaciation at end of Ordovician, associated with sea level fall and extinction event

BRAZOS RIVER K/Pg SECTION

The best studied example of K/Pg impact event deposits

MID PALEOZOIC CLIMATE

The middle Paleozoic was a time of cooling global temperatures that preceded the late Paleozoic Gondwanan glaciations. It corresponds to the time of colonization of land surfaces with land plants and associated major radiation of land biota.

MID-PLEISTOCENE TRANSITION

The transition occurs abruptly at 900,000 years ago. It coincides with major expansion of ice sheets in Antarctica, that are probably related to changes in ocean bottom water flow patterns.

MARINE REPTILES: PLESIOSAURS

Time of extinction 80 million years ago - 14 million years before impact event

ICHTHYOSAURS

Time of extinction 95 million years ago - 30 million years before impact event

PTEROSAURS

Time of extinction not known - probably few million years before impact event

EARLY EOCENE CLIMATE OPTIMUM

Time of long duration high temperatures during the Eocene; a period of several million years

MID-EOCENE CLIMATE OPTIMUM

Time of short duration of high temperatures during the middle Eocene; lasts for a million years, peaking at 40 Ma

THE GIBRALTER FALLS

Waters flow across the Betic corridor and into the Valencia gorge

ORDOVICIAN BIOTA

the Great Diversification Event (GOBE) saw the occurrence of high diversity, appearance of all phyla, large animals, large predators, and proliferation of colonial organisms