Phillips used toe Cretaceous terminal extinction to mark end of Mesozoic and beginning of Cenozoic

Old division of periods recognized just two; holdovers from the Neptunian philosophy: Tertiary and Quaternary,
But, because of the work of Lyell (mid 1800s) the epochs always assumed greater important anyway than in other systems:

Paleocene, Eocene, Oligocene, Miocene, Pliocene were all assigned to the Tertiary)

 Pleistocene and Holocene were assigned to the Quaternary or "ice age"

This is a very unequal division of time: (65-0 Ma vs. 0-1.8 Ma)

So an alternate scheme has begun gaining acceptance:

Quaternary:  Pleistocene, Holocene (1.8-0 Ma)

Neogene: Miocene, Pliocene (24-1.8 Ma) (some include Pleistocene too)

Paleogene: Paleocene, Eocene, Oligocene (65-24 Ma)

Time of climatic change:  from greenhouse in early Cenozoic Paleocene-Eocene when very warm conditions extended far poleward

To icehouse world, culminating in Quaternary glacial episodes

Tectonics were extremely active in Cenozoic;

Continued opening of north and south Atlantic;  Australia-Antarctica split

Subduction to transform margin along much of Pacific "ring of fire";

Continued compressional tectonics in western America, then extension

Closure of Teethes by clockwise rotation of Africa-India toward Eurasia produced Alpine and Himalayan orogenies

PALEOGENE (PALEOCENE, EOCENE, OLIGOCENE;  65- 24 Ma)
 
Name: Nauman's  term for more ancient part of Cenozoic; classic exposures are in Europe, where Lyell originally coined Eocene ("dawn of the Recent" and Oligocene (" slightly recent"  London Clay which is youngest unit of the London Basin syncline, plus classic exposures in the Paris Basin

Climate:  Very warm, lush; tropical rain forests in England; warm , moist forests in western North America intermontane basins; gradual cool down recorded in O isotopes and leaf margin studies during later Eocene into Oligocene; chilling of poles;  icehouse world conditions

Isolation of Antarctica creates circum-polar circulation, chilling of the South Polar area;

production of deep Antarctic bottom water; chilling of deep sea psychrosphere

Sequence Stratigraphy and Sea Level

Sea level relatively low at end Cretaceous; then rise in Paleocene; "Cannonball Sea"  last remnant of marine waters in Western Interior; flooding of Gulf Coast gave rise to Sloss’s concept of the Tejas Supersequence the last  and relatively minor

In Gulf sea rise and fall of sea level Paleocene to Oligocene;  large Oligocene drop may  signal formation of ice in Antarctica

Tectonics:

Atlantic opening; South America becomes an isolated "island continent"
in Eocene a new rift develops between Ireland-Scandanavia and Greenland;

East side of Americas plate overriding a mantle plume ("hotspot") continuing the trend from White Mountain granites to New England

Along west coast continued low angle subduction of Farallon Plate continues compressional tectonics

Some arc magmatism now extending farther east; Absaroka volcanics of western Wyoming,  (fossil forests of Specimen Ridge; etc.) but large region of magmatic null beginning to develop in western Interior

In northern interior and also see a continuation of Sevier style tectonics, thin skinned thrusting in Canadian Rockies;

But further south see thick-skinned uplift of Laramide Orogeny  foreland basin block uplifts of  Wyoming Colorado:  Wind River, Laramie, Bighorns, Front Range etc.;  intermontane basins filling with sediments like Eocene Wasatch Formation; large lake basin develops in Colorado-Utah-Wyoming, the Green River Basin; model: flat slab subduction and clockwise rotation of Colorado Plateau which acted as a stable block (explains odd orientations of some of the Laramide uplifts around Colorado Plateau

Uplifts were largely peneplaned and intermontane basins filled by Oligocene; Great Plains pediment forms (includes presently dissected area of Badlands; Eocene-Oligocene terrestrial sediments with excellent mammals

In "Old World" major theme is closure of Tethys and incoming of Alpine Orogeny (Eocene to Miocene) which folded rocks of south central Europe and created giant nappes and thrusts: Penninic, Helvetic flysch, Juras, molasse basin in north
Atlas Mountains of north Africa are the counterpart

General model is clockwise NE rotation of  Africa toward Europe during Eocene time compression of microplates in Tethys (Mediterranean) region

Most notable is Adriatic Plate (Italy Greece) which was subducting northward under the old Hercynian Europe with Penninic ocean in between; Penninic Ocean closed and accretionary wedge was thrust northward, as Pennninic nappes forming peripheral foreland basin or Flysch Basin in southern Europe; Eocene Oligocene flysch this then thrusts northward as Helvetic nappes; forming Molasse Basin; Balkans formed to the east

India was beginning to contact southern Asia in Oligocene times
 Beginning Himalayan Orogeny

Paleogene Life History:

 Marine Ecosystem

Plankton rediversify include diatoms, which now also invade fresh water;
Planktic foraminifera
Benthic include scleractinian corals which, again form reefs, mollusks diverse clams and snails formed the basis for Lyell’s recognition of the epochs of Cenozoic; first sand dollars
Abundant sharks and teleost fishes; first whales evolve (Pakicetus)

Terrestrial Ecosystem:  Paleogene rediversification
Angiosperms now becoming dominant vegetation, by Oligocene times the first grasslands; rise of rodents and grazing mammals coevolution

Associated with rise of insects, especially butterflies, beetles, bees, flies
Beautiful insects in fresh water lake deposits of Green River and Florrisant Colorado; Baltic ambers

In fresh water; teleost fishes; famous fossil fish localities in Eocene Green River oil "shale" of Wyoming-Colorado’ also crocodiles, snakes, mammals
Also beautifully preserved Messel oil shales of Germany

Major theme is adaptive radiation of mammals
Following disappearance of larger dinosaurs (but not birds!) enabled sudden (19 million year) adaptive diversification of mammals
In Paleoecene few mammals larger than cat or dog size, primitive marsupials, placentals, include creodont forerunners of carnivores;

Marsupials diversify on island continents of South America and Australia;
Elsewhere placentals take over; by Eocene over 30 mammalian orders:

Insectivora  ancestral stock, gave rise to
Chiroptera: bats
Rodentia: rodents; Lagomorpha: rabbits;
Primates perhaps already present in Cretaceous
Carnivora:  creodonts plus, weasel, dog, cat families and semi aquatic pinnepeds (seals and kin)
Hoofed mammals:
Perrissodactyls: (odd toed) tapir, horse, rhinos include largest land         mammal ever, Indrichotherium (17' high at the shoulder)
Artiodactyls: (even toed or cloven hoof) pigs; camels, ruminants (cattle, sheep, deer, giraffes)
Whales evolved from group of hoofed mammals known as mesonychids
Poboscideans: first elephants were Eocene
Minor mass extinctions of both terrestrial mammals and some marine species at end Eocene; associated with tektite horizons
 

NEOGENE PERIOD (24-1.8 Ma)

Name:  Hoernes’ name for late Cenozoic

Climate:  Distinct trend toward cooling; several sources, probably most important are: a) isolation and chilling of Antarctica; b) slowed seafloor spreading (compared to Cretaceous or early Cenozoic); c) regression
Icehouse climate and return to aragonite oceans; aragonite is dominant carbonate phase precipitated, reef formers

Messinian Event:  involved increasing aridity in Mediterranean basin during late Miocene time (Messinian Stage); basin became cut off from free circulation at Gibraltar straits (due to Alpine tectonism: in increasingly arid climate, water boiled off, drawing sea-level down to near the bottom of basin; vast evaporite deposits accumulated (now these are beneath the Mediterranean and forming salt domes in places); Nile entrenched to new base level, an arm of the Tethys remained (Paratethys); it drained through a series of channels near Turkey;
Finally, sea level rise caused flooding of Atlantic water across the Gibraltar straits with what must have been a colossal cataract of sea-water that would dwarf any known waterfall; gradually Mediterranean basin refilled `

Sequence Stratigraphy: generally low sea-level; cyclic inundation of continental shelves; in North America this is the regressive phase of  the weakly developed Tejas Supersequence; there are excellent Miocene and Pliocene deposits on the Coastal Plains of Maryland (near Chesapeake Bay, Virginia, and North Carolina; unconsolidated sands and muds carry diverse mollusks, as well as shark teeth and whale bones (Salisbury Embayment was a larger embayment associated with Chesapeake. Bay area)

In Gulf area Mississippi Embayment receiving lots of sediment; Miss. Delta prograding; salt domes forming; deep burial of older Jurassic Louanne salt beginning to cause upward rise of salt in diapirs or Salt Domes; these ultimately provide migration routes and traps for petroleum;

Atlantic Ocean now opening to full extent
 
 
 
 
 
 

Tectonics:  Almost unprecedented tectonism globally; entire Pacific margin surrounded by "Ring of Fire" as plates are actively being subducted

North America saw continued subduction to northwest where Aleutian arc formed under Alaska and subduction continues along Pacific northwest of US where a remnant of old Farallon Plate-the Juan de Fuca plate continues subducting magmatic arc thus formed is the Cascades-an active andesitic volcanisms; also subduction continues in Mexico and Central America where arc volcanism persists

But, in the region of California the margin changes from convergent to transform as a result of oblique collision with a segment of mid-ocean ridge; the initial short transform fault between two segments widened to connect Mendocino triple junction with Baja; Baja is being rifted away from rest of Mexico by still active spreading ridge

Further north San Andrea transform allows Pacific plate (western California) to slip past Americas plate (including rest of California; this piece is gradually moving to NW causing much friction in coastal California

Along with stoppage of subduction came many other changes to the tectonics of western North America these basically can be summarized as:

A  change from
a)  flat slab subduction of Farallon plate and compressional tectonics, to

b) transform motion; regional uplift-rejuvenation of entire Cordillera belt (especially Colorado Plateau, Sierras and Coast Range) and extensional tectonics

Several regions affects thus, starting in about Miocene:

a) Rockies re-uplifted and rejuvenated;  in the process some streams became superimposed on Laramide uplifts and forced to entrench canyons through hard rock; subsequently the intermontain basins which had been filled with sediments were partially re-excavated as low areas between ranges;  Rockies scenery is result of this rejuvenation NOT directly of Laramide

b) Colorado Plateau was regionally uplifted as a coherent block;  starting in the Miocene rivers began entrenching this rising land creating wonderful erosional scenery in Four Corners area. these include:

 1) Grand Canyon: (Arizona) over deeply entrenched  cut in   Proterozoic to Permian strata (with many gaps)

 2) Canyonlands, Natural Bridge, Goosenecks of San Juan (S.  Utah) cut into Penn., Permian  sandstones

 3) Deadhorse, Needles; canyons cut into red Triassic strata

 4) Zion Canyon: entrenched Jurassic Navajo Sandstone

 5) Bryce Canyon: entrenched and wind sculpted pinnacles of  Eocene non-marine sediments

c) Sierra Nevada,  Jurassic-Cretaceous granitic batholiths uplifted rapidly along faults in Pliocene time and sculpted by Pleistocene mountain glaciers

d) Coast Ranges; old Jurassic-Cretaceous accretionary prism and melange uplifted rapidly along faults in Pliocene time and cut by transform faults of San Andreas system

e) Basin and Range: one of the most remarkable areas in US separated by bounding Wasatch and Hurricane faults from Colorado Plateau and by large fault from Sierras; includes Rio Grande rift extending into New Mexico; this vast territory of Nevada, Arizona, Utah, Idaho is being rifted in Neogene; great extension (~100 km) normal faulting horsts and grabens (along listric faults that taper and become sub horizontal at depth; lots of Miocene and Pliocene volcanism; mainly Paleozoic -early Mesozoic rocks thrusted and then cut by the normal faults

Why all of this activity?  Must be associated with stoppage of subduction

Models:
a) subduction of a mid ocean spreading center (probably not true)

b) shear associated with transform action of San Andreas

c) subsidence of subducted Farallon slab and perhaps coupling and tearing away of base of lithosphere beneath Basin and Range

In central America a tab of Farallon Plate  extended eastward between North and South America forming the Caribbean Plate; lateral strike-slip faults on either side slicing off Jamaica and Cuba from south end of Mexico and moved east  and moving Nicaragua piece southeastward

Antilles arc develops at east end of Caribbean Plate as Americas plate dives beneath Caribbean. Plate producing an island arc

In the Pliocene a new subduction zone develops along western margin of Caribbean plate as Pacific ocean dives down eastward isolating  Caribbean plate off as separate microplate and creating an island arc on west side- the Panamanian isthmus

This Panamanian land bridge then connected North America with South America which had been an isolated "island continent"' this caused the great American Interchange of Mammals: largely a one way flow from North to South America;  led to wave of extinction of primitive South American mammals

In Mediterranean region, aftermath of Alpine Orogeny;  Alpine folding and thrusting largely completed but Molasse Basin to north filling with sediments during Miocene; failed rifting in Rhine Graben; Spain rotated  to SE opening Bay of Biscay and forming the Pyrenees Mtns.

East Africa a new triple junction forming; three rifts are Red Sea-Gulf of Aden-East African rift belt; meet at Afar Triangle in Ethiopia; Arabian  subcontinent is rotating NE,  counterclockwise and compressing Middle East;  Persian Gulf is foreland basin, Zagros Mountains of Iran represent fold and thrust belt

Farther east, the northeast rotation of the Australia Plate carried Indian subcontinent from Africa northward to collide with Asia; during Oligocene to Miocene the collision was complete; Himalayan Orogeny

two slices sheared off north edge of India along 1) Main Central Thrust (foothills suture) and later 2) Main Boundary thrust; Himalayas are formed of these slabs

India is now tucked beneath these two slabs having partially subducted;  in turn this pushed up Tibetan Plateau to north and depressed crust of India to south forming the Sawalik foreland basin, now filled with molasse famous for Neogene mammal fossils;

Himalayas still pushing upward as compression continues highest most active mountains and largest volumes of sediment to oceans, have affected oceanic Sr budget and produced climatic shift to monsoonal seasonality

In South Pacific;  northern Australia subducting beneath Timor Trench;  major island arcs including parts of  Japan, Indonesia, Phillipines,

Hawaiian chain represents nematath or hotspot from Pacific plate overriding a hotspot from Cretaceous to present

 Neogene Life

Marine Ecosystem:

Very modern in aspect; scleractinian coral reefs including Great Barrier reef over 1200 km long; Pacific atolls on seamounts, etc.

Mollusks, crustaceans, echinoderms highly diverse

Abundant sharks, teleost fishes, and whales

Terrestrial Ecosystem:

Neogene is usually called part of age of  mammals but could be called ; Age of Angiosperms (C4 plants) , Age of Insects, Age of Frogs, Age of Rodents, Age of Snakes, or Age of Songbirds

Coevolution with flowering plants led to unparalleled diversity, both of the angiosperms and of the insects

In turn, abundant insects give rise to adaptive radiation of frogs and insect feeding song birds (first appearance) and mammals; abundant  snakes

 With rise of grasslands the ungulates or hoofed herbivores plus small rodents Still some rhinos and horses getting larger and more specialized

artiodactyls taking over from perrisodactyls; include diverse pigs, odd antelope relatives (some with horns on nose)

large proboscideans by Miocene including shovel tusked mastodons
 
 

QUATERNARY PERIOD (1.8-0 Ma)

Name:  Desnoyers named "fourth age" long after Neptunists gave up; synonymous with Ice Ages (though glaciation started in Pliocene or even Miocene)

Climate: Global cooling; icehouse typical example; cyclic oscillation of glacial buildup and melt down on 20,000, 41,000, and 100,000 time scale;
(precession, obliquity, and eccentricity signals of Milankovitch); as many as 18 major advances and retreats of ice plus many small stadial-interstadial; Wisconsin and Illinoisian recorded locally are just the last two, separated by Sangamon Interglacial

Cause of glacial onset unclear but is final phase of long cool down begun in late Eocene; glacial onset in northern Hemisphere may have been brought on by heat conveyor of Gulf Stream deflected by Panamanian Isthmus

Laurentian iced mass extended in lobe southward down to Ohio Valley ( a few areas escaped glaciation; Driftless Area in Wisconsin)

Ice over a mile thick from evidence of ancient nunataks; exposed mountain tops like Mt. Monadnock, NH

Glacial Evidence/Effects:

a) erosional sculpting; u-shaped valleys like Yosemite; glacial grooves and striae; valleys of great Lakes and Finger Lakes scoured out;  Ohio River formed

b) deposition; moraines very important in modifying topography; huge erratics scattered around; outwash and loess deposits plus varved glacial lake clays

c) glacial depression and rebound; Hudson Bay still depressed but rising; some areas have rebounded by over 30 m

d) sea level lowstands during glacials; Bering Land bridge allowed influx of animals and humans into North America via Asia; Britain connected to the mainland

e) disrupted drainages and rerouting of streams; e.g. Licking River;  Niagara River formed; hanging tributaries created

f) pluvial lakes in Basin and Range; during locally more humid times large lakes formed in Basins; now partially evaporated remnants (e.g. Great Salt Lake)

g) catastrophic flooding; Channeled Scablands of Washington apparently created by massive flooding when ice "cork" that dammed giant Lake Missoula (Montana-Idaho) was floated up; dam burst enormous volumes of water flowed westward to Pacific clearing bedrock; cutting canyons (Grand Coulee in Washington) huge dunes /antidotes; greatest flood known in Earth history; may have occurred repeatedly

Quaternary Life:

Cold adapted species move southward; compression of floral and faunal belts some disruption

Large mammals flourish in North America then go extinct; woolly rhinos and mammoths/mastodons in north

La Brea tar pits provide glimpse of Pleistocene life in California; mammoths, horses, wolves, giant sloths, sabertooth cats (predators over represented here)

Perhaps the most dramatic event of late Neogene-Quaternary is evolution of humans; Hominidae arose in Africa perhaps 4.5 Ma;

Australopithecus (include A. afarensis) appears in rift sediments of Ethiopia; "Lucy" small, semi-upright, bipedal (Laetolil trackways); small brain;

Australopithcines gave rise to larger and smarter Homo around 2.5 Ma; Homo habilis  handy man; made Olduvan tools
Homo erectus evolved about 1.6 Ma and spread out of Africa into Eurasia

H. sapiens evolved from H. erectus in Africa and moved out; in Eurasia H. erectus gave rise to H. neanderthalensis.; ultimately H. sapiens has taken over; migrated to North America around 13 to 14,00 years BP and may have beneath cause of demise of large mammals by "overkill";  now for first time a single species is controlling the entire biosphere

Quo Vadis??