CenozoicCenozoic

GeologyGeology

CenozoicCenozoicIntroductionIntroduction

• Tertiary (66-1.6 Ma)– Paleocene– Eocene– Oligocene– Miocene– Pliocene

• Quaternary (1.6 Ma-present)– Pleistocene

• Present Earth features are Cenozoic

Cenozoic Cenozoic Plate MotionsPlate Motions

• Atlantic Ocean continues to widen• India to Asia

– Himalayas• Africa moves northward

– Mediterranean Sea – E. Africa Rift zone born

• Australia & Antarctic separate• North America & Greenland split

from Europe• Farallon Plate subducted

CenozoicCenozoicMountain BuildingMountain Building

• 2 zones of orogenesis– Alpine-Himalayan Belt – Circum-Pacific Belt

Alpine-Himalayan BeltAlpine-Himalayan Belt

• Began during Mesozoic– Most deformation Eocene to L. Miocene

• Africa-Arabian Plate hit Eurasia• India collided with Asia

– Himalayas

• Collision of Spain with France– Pyrenees, Alps, Apennines, Atlas Mtns. Evolved

HimalayasHimalayasIndia-Asia X-sectionIndia-Asia X-section

• Birth of Himalayas– Maybe evolved 40 to 50 Ma– Decreased spreading rates

(15-5cm/yr)– 2000 km of India beneath Asia

Swiss AlpsSwiss Alps

• Alps showing Nappes– Large, faulted overturned

folds

Circum-Pacific BeltCircum-Pacific Belt• Arc orogens – oceanic crust subducted

– Philippines, Japan, Aleutians form– Andes form – Nazca & Cocos plate subducted– Central America Arc connection develops

Japan EvolutionJapan Evolution

• Sea of Japan thought to have formed by back-arc spreading

Andes EvolutionAndes Evolution

• Passive margin changed to active margin

• Followed by continued deformation

North America CordilleraNorth America Cordillera• Complex mountainous region

• Extends from Alaska to Central Mexico

• Laramide orogeny (Late K-Tertiary)

• Intrusive and Extrusive volcanism

• Extension Basin & Range

• Uplift & Erosion Colorado Plateau

Laramide OrogenyLaramide Orogeny

• Begins in Cretaceous

• Orogenesis of Rocky Mtns.• Ends in middle Miocene

• Caused by subduction of Farallon plate beneath North America

Laramide OrogenyLaramide Orogeny

• Little volcanism or pluton emplacement

• Uplift is vertical– Little compressional

folding/faulting• Angle of subduction

decreases– Arc Magmatism shifts inland– Farallon subducted along with

mantle plume– Deformation occurs further

inland

Cordilleran VolcanismCordilleran Volcanism• Continuous through Cenozoic

• Varied Eruptive Styles & location– Columbia Plateau– Cascade ranges

Flood BasaltsFlood Basalts• Tertiary Extrusive Volcanism

– Eocene lavas in Yellowstone– Oligocene tuffs, flows,

calderas—Colorado– Pliocene to Quarternary

volcanism—San Francisco Mtns.

– Columbia River basalts—Pacific Northwest Issued from long fissures One flow covers 40,000 km2

May result from hot spot Flow young to northeast

Old Faithful

Columbia River Basalts

Cascade RangesCascade Ranges

• Built by andesitic volcanism during Pliocene, Pleistocene, & Recent

Mount St. Helens

Mount LassenCrater Lake

North AmericaNorth AmericaBasin & RangeBasin & Range

• Tensional forces caused crustal extension—Nevada mostly

– Crustal blocks moved up and down on normal faults

Basin & RangeBasin & RangePossible CausesPossible Causes

Subduction of East Pacific Rise

Mantle plume Back-arc spreading

Colorado PlateauColorado Plateau• Deep canyons, broad mesas, volcanic mtns

– Near sea level – Cretaceous Deposition of Red Beds

– Early Tertiary No deep canyons

– Late Tertiary uplift and erosion Deposition ceased Erosion of canyons began

Pacific CoastPacific CoastSan Andreas FaultSan Andreas Fault

• Results from Pacific-Farallon ridge collision with North America

• Subduction ceased– Continental margin bounded by transform fault

• Continued subduction – Juan de Fuca & Cocos plates– Continued volcanic activity in Cascades and Mexico

QuaternaryQuaternary

PleistocenePleistocene

CenozoicCenozoic

• Tertiary (66-1.6 Ma)– Paleocene– Eocene– Oligocene– Miocene– Pliocene

• Quaternary (1.6 Ma-present)– Pleistocene

QuaternaryQuaternaryPleistocene EpochPleistocene Epoch

• The Ice Ages include glacial and interglacial periods

– Glacials Widespread ice

– Interglacials Less ice Today’s climate

PleistocenePleistoceneIce AgeIce Age

• The last glacial maximum– 30% of Earth covered with ice– Sea level was about 100 m (300 ft)

lower than today

Ice Age Ice Age Erosional EvidenceErosional Evidence

• Yosemite Valley– U-shaped valley– Hanging valleys (glacial tributary)

• Striations – grooves

• Abrasions – smooth, polished surface

Ice AgeIce AgeDepositional EvidenceDepositional Evidence

• Glacial till– Poorly-sorted

• erratics• drumlins

Ice AgeIce AgeEffectsEffects

• Sea level change

• Pluvial Lakes• Isostacy

Carbon DioxideCarbon DioxideIPCC ReportIPCC Report

• Atmospheric CO2 concentration has increased from pre-industrial value of about 280 ppm to 379 ppm in 2005– Atmospheric CO2 concentration increased by only 20

ppm over 8000 years prior to industrialization

• Since 1750, CO2 concentration has risen by nearly 100 ppm

• Annual CO2 growth rate larger during last 10 years (1995–2005 average: 1.9 ppm yr–1) than since continuous direct measurements began (1960–2005 average: 1.4 ppm yr–1).

Classic CO2 GraphClassic CO2 Graph

• Carbon Dioxide has steadily increased—anthropogenic cause– Probably began in

industrial revolution

• Superimposed are variations with seasons– More CO2 in winter, less

in winter

– Due to photosynthesis

Globally Go Forth and Multiply!

World Population CO2

World Population vs. CO2

The concentrations and radiative forcing by (a) carbon dioxide (CO2), (b) methane (CH4), (c) nitrous oxide (N2O) and (d) the rate of change in their combined radiative forcing over the last 20,000 years reconstructed from Antarctic and Greenland ice and fi rn data (symbols) and direct atmospheric measurements (panels a,b,c, red lines). The grey bars show the reconstructed ranges of natural variability for the past 650,000 years (IPCC)

Pleistocene GlaciationPleistocene GlaciationCausesCauses

• Axis wobbles • 23,000 yr cycle

• Milankovich Theory

• Shape of Earth’s orbit• 100,000 year cycle

• Angle of Earth’s axis changes• 41,000 year cycle

– Eccentricity

– Obliquity

– Precession

The Future?The Future?