Cenozoic Geology

Cenozoic Introduction Tertiary ( Ma) –Paleocene –Eocene –Oligocene –Miocene –Pliocene Quaternary (1.6 Ma-present) –Pleistocene Present Earth features are Cenozoic

Cenozoic Plate 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

Cenozoic Mountain Building 2 zones of orogenesis –Alpine-Himalayan Belt –Circum-Pacific Belt

Alpine-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

Himalayas India-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 Alps Alps showing Nappes –Large, faulted overturned folds

Circum-Pacific Belt Arc orogens – oceanic crust subducted –Philippines, Japan, Aleutians form –Andes form – Nazca & Cocos plate subducted –Central America Arc connection develops

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

Andes Evolution Passive margin changed to active margin Followed by continued deformation

North 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 Orogeny Begins in Cretaceous Orogenesis of Rocky Mtns. Ends in middle Miocene Caused by subduction of Farallon plate beneath North America

Laramide 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 Volcanism Continuous through Cenozoic Varied Eruptive Styles & location –Columbia Plateau –Cascade ranges

Flood 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 km 2  May result from hot spot  Flow young to northeast Old Faithful Columbia River Basalts

Cascade Ranges Built by andesitic volcanism during Pliocene, Pleistocene, & Recent Mount St. Helens Mount Lassen Crater Lake

North America Basin & Range Tensional forces caused crustal extension— Nevada mostly –Crustal blocks moved up and down on normal faults

Basin & Range Possible Causes Subduction of East Pacific Rise Mantle plume Back-arc spreading

Colorado 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 Coast San 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

Quaternary Pleistocene

Cenozoic Tertiary ( Ma) –P–Paleocene –E–Eocene –O–Oligocene –M–Miocene –P–Pliocene Quaternary (1.6 Ma-present) –P–Pleistocene

Quaternary Pleistocene Epoch The Ice Ages include glacial and interglacial periods –Glacials  Widespread ice –Interglacials  Less ice  Today’s climate

Pleistocene Ice Age The last glacial maximum –30% of Earth covered with ice –Sea level was about 100 m (300 ft) lower than today

Ice Age Erosional Evidence Yosemite Valley –U-shaped valley –Hanging valleys (glacial tributary) Striations –grooves Abrasions –smooth, polished surface

Ice Age Depositional Evidence Glacial till –Poorly-sorted erratics drumlins

Ice Age Effects Sea level change Pluvial Lakes Isostacy

Carbon Dioxide IPCC 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 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 Glaciation Causes 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?