The Calm Before the Storm- Ice Age Approaching -

Jarðsaga 2

-Saga Lands og Lífs –

-Ólafur Ingólfsson

Glaciers start to form on N Hemisphere highlatitude and high altitude areas during Pliocene.

Seasonal sea ice cover appeared in the Arctic basin

Pliocene onset of N Hemispherehigh-latitude glaciations

Ocean Drilling Program record of N Hemisphere glaciations

• ODP long sediment cores fromthe Greenland- Norwegian andNorth Pacific Seas recognizes input of Ice Rafted Material (IRD) as early as 5-6 MY ago, interpreted to signify the presence of annual sea ice and calving valley glaciers.

• There is a significant increase inIRD about 2.6 MY ago, whis is interpreted to show that ice sheets had started to form at high latitudes

http://www.usssp-iodp.org/PDFs/Greatest_Hits/Rhythms/KrissekKud.pdf

Closing a land bridge – openingthe Bering Strait makes for

marine fauna interchangeThe migration of Atlantic-Arctic mollusks intothe Bering Sea and North Pacific occurred when the Bering Strait first opened at ca. 5.5 MY ago. The opening of the Bering Strait caused cooling in the Arctic basin.

The abrupt appearance of North Pacific mollusks in the North Atlantic at 3.6 Ma postdated the first opening of the Bering Strait by 1.2–1.9 MY.

The BeringStrait

The Bering Straitseparates Alaska and E Siberia by only 85 km. The strait averages 30-50 m in depth. There are numerous islands in the strait, including the two DiomedeIslands (about 16 km2), and to the south of the strait lies St. Lawrence Island.http://eosweb.larc.nasa.gov/HPDOCS/misr/misr_html/bering

_strait.html

The Bering Land Bridge – very important for

Ice Age migrations of

animals

Life in the Oceans adaptsto increased seasonality

Nowhere is this more obvious than at high latitudes: Packice at both poles is constantly on the move, freezing solidin winter. In spring, with the retreating ice and lightreaching the water, life explodes. Plankton blooms feed vast hordes of migrating invertibrates, fish, birds, whales, seals and polar bears. Walruses rake the seabed for clams. Minke and humpback whales gorge themselves on gigantic swarms of krill.

The origin of bird migration

Why do birds migrate? The reasons are complex and not fully understood. But a simple explanation is food and a safe place to breed. Bird migration probably originated in late Tertiary as a response to increased seasonality...Annually, as many as 4 to 5 billion birds worldwide migrate from north to south and back again. This involves >200 species...

http://www.audubon.org/bird/puffin/virtual/arte.html

Longest migrations 1• The Arctic tern (kría) migrates the longest distances of any animal. It flies over 35,000 km each year - almost the circumference of the Earth.

•The whale that migrates the longest (and the longest-migrating mammal) is the Gray Whale, which migrates from California to Alaska (~20,000 km) each year.

Blue Whales (steypireyður) undertake extensive north-southmigrations each year, travelling from winter grounds in low latitudes to summer feeding grounds in the Arctic or Antarctic high latitudes.

Longest migrations 2

• The insect that migrates the longest is the desert locust (Eyðimerkurengisprettan), which travels about 4500 km. • The butterfly that migrates the longest is the Monarch(Konungsfiðrildi), which migrates up to 3000 km, flying from Canada to central Mexico in the fall.

Longest migrations 3

•The land animal that migrates the longest isthe caribou (villt hreindýr), which travels about 1100 km.

Seasonal migrations of African savannah wildlife –also caused by Late Cenozic climate changes

Many African mammals migrate 500-700 km between rainy-dry cycles

Where the prey goes, thepredators and scavengers follow...

...and the increasing Late Conozoic seasonality andcontinental aridity - which caused the grasslands/ savannahs to expand - led the hominoids on the trail of walking. It is not a coincidence that the Australopitecans (Lucy) appeared in late Pliocene, ~3.2 MY ago.

Short migrations and otheradaptations to seasonality...

Many ground-dvelling animals migrate downwardsin soils when winter comes, while other animals hibernate to survive winter...

The Great Faunal InterchangeFor tectonic reasons, a land bridge formedbetween North and South America in Pliocene, ~3.5 MY ago. At that point began what is known as the Great American Faunal Interchange.

Earlier in Tertiarytimes animals mayhave migratedthrough island-hopping over volcanic islands in the Caribbean...

CaribbeanCaribbean plateplate margin margin summarysummaryhttphttp://://wwwwww..mtsumtsu..eduedu/~/~cdcdharris/honors/caribharris/honors/carib--tectonics/caribtectonics/carib--tectonics.htmtectonics.htm

The GreatAmerican Faunal

InterchangeThis was a gigantic ex-periment in evolutionarybiogeography, involvingthe effects of dispersal, evolution and extinct-ion. It permitted an encounter between two continental biotas that had been evolving in isolation for >100 MY

The effects of the exchangeMammals going North:

Only few groups of South American mammal colonised theNorth American continent: porcupines (broddgöltur),armadillos (beltisdýr) & opossums (pokarottur) contributed species; ground sloths (letidýr) and glyptodonts (skjalddýr) did colonise southern USA and survived until the last few thousand years, but they are now extinct everywhere. http://www.bbc.co.uk/beasts/factfiles/quicktimefactfile.shtml?doedicurus

Flightless killer-birds went North too – but got killed...

• This bird sacrificed the abilityto fly in order to become bigger and a more efficient killer

• It could run at least 60 km an hour to catc its prey.

• Titanus was larger than its South American cousinAndalgalornis, which was 1.6 m tall, >50 kg and a beak that could slice through bone.

• It went extinct in Pleistocene

Titanus walleri – a birdthat is almost a rever-sal to the dinosaurs. It had clawed hands instead of wings...

Mammal migration from N to S

Many groups of N American mammals colonised S America, 17 families in all: rabbits, mice, foxes, bears, raccoons(þvottabjörn), weasels (hreysiköttur), cats, peccaries(pekkarisvín) & deer still have close living relatives in N America; tapirs & camels are still alive in South America but they went extinct in their original home; mastodons & horses went extinct on both continents.

Great impact on S American fauna

Jaguar

Maned Wolf

About half of all species of today's South Americanmammal fauna derives from this influx from north.• Having colonised South America, many of thesenorthern groups diversified greatly, so that nowadays, most of the families have more species in the south than remain in the north.• There are more species of wild dog and cat species inSouth America than on any other continent, even though they got there less than 4 MY ago.

Migration of other animal groups

Among reptiles and amphibians, the pattern israther the reverse of that shown by mammals: the majority of colonization was south to north. Treefrogs (left) and toads (karta, padda) (right) are now widely distributed in North America; yet they derive from South America.

Results of the GFI

3227Families at present45Families that went extinct

816Families that spread to other continent and survived on both

06Families that survived on different continent

1621Families that survived on same continent

3032Mammal families before 4 MY ago

SouthAmerica

NorthAmerica

Closing of the Panama Strait caused reversal of waterflow

through the Bering StraitResearch on fossil mollusks in the North Pacific, Arcticand North Atlantic oceans shows that the direction of seawater flow through the Bering Strait gateway musthave changed from a southerly flow to a northerly onearound 3.6 MY ago. This reversal in flow direction was caused by formation of the Isthmus of Panama as a land barrier where a broad tropical seaway between North and South America had existed for millions of years.

This caused drastic shifts in Northern Hemisphere ocean currents, and initiated the flow of the Gulf Stream

The closing of the Panama Strait/seaway

The closing of thePanama equatorialseaway drasticallychanged oceano-graphic conditionsin the Atlantic. It opened the path towards thermo-haline circulation and Pleistocene cooling...

Diatom data showconsiderable coolingof N Pacific waters towards the end of the Pliocene

http://www-odp.tamu.edu/publications/167_SR/chap_04/chap_04.htm

The Pliocene-Pleistocene transition in

Iceland

The Pliocene-Pleistocene transition is recorded in the Tjörnes strata, where the relaively warm Pliocene mollusc fauna is replaced by colder elements, and major till horizons occur in the strata

• The Tjörnes strata spans the time from Pliocene and up to Late Pleistocene, with some gaps: Lava flows, fluvial sediments, lacustrine sediments and fossiliferous marine/glaciomarine sediments alternate with glacial tillites.

• Altogether the Tjörnes strata is >1200 m thick

Tjörnes stratigraphy

The Serripes layers: Sudden cooling...• The Serripes layers are associated with Serripes grönlandicus. • At the base of the Serripes layers most warm-loving molluscs have disappeared. The fauna is similar to present-day fauna.

• Of about 100 different species of molluscs in the Serripes layers, about 25% originate in the Pacific.

• Lava on top of the Serripes layers dates to ~2.5 MY. Their age is 3-2.5 MY

Buchardt & Símonarson, 1991

Thermohaline circulation (simplified)

The Pliocene comesto an end...

The boundary between Plioceneand Pleistocene is defined on thebasis of marine faunal changes in marine sediments in Italy suggesting cooler waters.

In the real world, theP-P transition means a step further away from the greenhouse and closer to the ice house.

Summing up the Pliocene• By the end of Pliocene, continental configuration is largely modern.

• The single most important Pliocene tectonic event is the closing of the Panama seaway.

• The Pliocene fauna and flora is largely modern, with 50-90% of present species already in place.

• Life adopts to cooler and drier climates, and increased seasonality

• Cooling and onset of glaciers at high Northern latitudes.

• Pliocene saw the evolution of primates towards the genus Homo.

References used when preparing this lectureStanley: Earth System History. Arnold, LondonFortey: Life. A Natural History of the First Four Billion Years on Earth. Vintage, New York.Einarsson, Þ. 1991. Myndun og Mótun Lands. Jarðfræði. Mál og Menning.Buchard, B. & Símonarson, L.A. 2003: Isotope paleotemperatures from the Tjörnes beds in Iceland: Evidence of Pliocene cooling. Palaeogeography, Palaeoclimatology, Paleoecology 189, 71-95. http://www.crystalinks.com/mollusks.htmlhttp://www.giss.nasa.gov/research/paleo/pliocene/page3.htmlhttp://www.arthurgrosset.com/http://publish.uwo.ca/~handford/zoog2.htmlhttp://www.naturia.per.sg/buloh/birds/migration.htmhttp://elephant.elehost.com/About_Elephants/Stories/Evolution/evolution.htmlhttp://www.bbc.co.uk/beasts/factfiles/quicktimefactfile.shtml?doedicurushttp://www.bbc.co.uk/beasts/factfiles/index_all.shtmlhttp://www.ivry.cnrs.fr/deh/geraads/aao/wcont.htmhttp://www.esd.ornl.gov/projects/qen/pliocene.htmlhttp://www.palaeos.com/Cenozoic/Pliocene/Piacenzian.htmlhttp://www.science501.com/PTPliocene.htmlhttp://www.geosci.usyd.edu.au/research/marinegeophysics/Resprojects/Platekinematics/Caribbean/caribbean_paper.htmlhttp://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v425/n6956/abs/nature01892_fs.htmlhttp://jan.ucc.nau.edu/~rcb7/globaltext2.htmlhttp://www.stratigraphy.org/pliple.htm