Cenozoic Earth

      Mesozoic ended with a mass extinction

      Mammals become dominate

      More development of the West coast

            Cascade mountains

            Basin and Range

            Colorado Plateau

            Columbia River Basalts

            Continued uplift of Rockies and Sierras

            San Andreas fault system forms

      Another meteor hits earth

      Ice age returns

 

West Coast Mountain Building

      Mesozoic:

            Nevadan Orogeny

                  Subduction zone with LOTS of granite emplaced

            Sevier orogeny

                  Thrust Faulting East of Sierra Nevada Mtns

            Laramide orogeny

                  Low angle subduction “wrinkles” plate and modern Rocky Mountains start to form—  continues into the Cenozoic

      Cenozoic:

            Subduction angle increases and Laramide deformation stops

            Increase in subduction angle cause volcanism on west coast

                  John Day volcanics (~65-45 mybp)

                        John Day is known for world class fossils from 60 million years ago

 

            Subduction changed off and on throughout the Cenozoic.

                  Changes in Subduction zone caused off and on volcanism and mountain building

                        Cascade mountains

                              1st stage of building ~35 mybp (Eocene)

                              2nd stage of building ~ 7mybp

                              Current mountains ~1 mybp

            Cascades part of the Circum-Pacific mountain building of the Cenozoic

 

            Columbia River Flood Basalts

                  Miocene age 17-6 mybp

                  Created due to extension of NW

 

            Basin and Range formed during the Miocene

            Colorado Plateau Uplifted and eroded during Miocene to Pliocene

            Coast range develops: Eocene to  Pliocene

                  Willamette valley forms as coast range begins to uplift during Miocene

                        Much of the Willamette valley was underwater until the miocene

                        Fossils of clams etc. are found throughout the region

 

      Other notable events:

            Arabia and Africa separate opening the red sea (~20 mybp)

            India and Asia collide

            Antarctic and Australia completely separate allowing a circumpolar ocean current

            Temperatures drop (more in a minute)

            Land bridge between N. and S Americas appeared

            Meteor hit E. Coast ~ 35 mybp

 

Cenozoic Climate

      Beginning to mid-Eocene

            Warmest temperatures of Cenozoic

      End Eocene

            Circumpolar circulation begins

            Climate begins to cool

      Cooling in Oligocene

            Ice sheets form

      Warming at beginning of Miocene

      Cooling at end of Miocene

      Ice caps form in Pliocene

            Cooling trend ever since (till now)

            Coolest earth has ever been

      Pleistocene—Ice age

            Start about 2 million years ago

            Large ice sheets

 

Ocean sea levels are very low compared to the history of the planet

 

Meteor impact

      Occurred ~35 million years ago (Eocene)

      Located under ~400 m of sediments in Chesapeake  bay

      Discovered in 80’s through studies on aquifers in this area

      Deep drilling project just completed December 2005

            Drilled down 1.1 miles

 

Summary of Cenozoic

      Radiation of Mammals

      Development of NW

      Cascades, CRBs, Coast range, Willamette Valley, John Day

      Uplift of Co. Plateau, Rocky Mts and Sierra Nevada

      Development of Pacific ring

      Cooling of Climate over all due to changing locations of continents

      Ice age and lower sea levels