Cenozoic Earth and Life History

1
Cenozoic Earth and Life History
2
Introduction

• The Cenozoic began 66 mya and continues until the
  present
• Cenozoic rocks are more easily accessible and
  less deformed than older rocks
• divided into the Tertiary and Quaternary

3
Cenozoic Plate Tectonics and Orogeny - An Overview

• Orogenic activity concentrated in two areas
• Alpine-Himalayan belt deformation began in the
  Mesozoic and remains geologically active
• circum-Pacific belt deformation occurred
  throughout the Cenozoic

4
The North American Cordillera

• Complex mountainous region of the circum-Pacific
  orogenic belt
• continuously deformed during Late Jurassic
  through Early Tertiary
• the Laramide orogeny took place further inland
  than most, and deformation was mostly vertical
  uplift, with little volcanism
• shallow subduction angle helps explain these
  observations

5
The Interior Lowlands

• Sediments eroded from the Laramide highlands were
  deposited in the Zuni sea
• terrestrial deposits are also found, but much of
  this area was experiencing erosion
• igneous activity was significant in some areas -
  New Mexico, Colorado, Wyoming, and others
• east of the Great Plains, deposits other than
  glacial are rare

6
The Gulf Coastal Plain

• The Tejas epeiric sea transgressed briefly over
  the Atlantic and Gulf coastal plains
• eight minor transgressive-regressive sequences
  are recognized as sea level fell in general

7
Eastern North America

• Passive margin sedimentation dominates
• rocks form a seaward thickening wedge that dips
  gently seaward
• Cenozoic uplift and erosion produced the present
  topography of the Appalachians

8
Life of the Tertiary Period

• Angiosperms continue to dominate land plant
  communities
• Present-day groups of birds evolved
• Marine invertebrates diversify to todays fauna
• Mammals rapidly diversify

Marine Invertebrates and Phytoplankton

• Coccolithophores, diatoms, and dinoflagellates
  recover from K-T
• Foraminifera diversify
• Corals become dominant reef-builders
• Bivalves and gastropods are two major groups
• Echinoids evolve new forms and diversify

9
Tertiary Mammals

• Ungulates
• artiodactyls are even-toed mammals and are the
  most common
• perissodactyls are odd-toed
• grazers and browsers
• The miacids were ancestors to all later mammalian
  carnivores
• saber-toothed cats, bears, seals
• Elephants and whales evolve

10
Primate Evolution

• Several trends in the evolution of the Primate
  order help to define them
• changes in skeleton and mode of locomotion
• increase in brain size
• shift toward smaller, fewer, and less specialized
  teeth
• evolution of stereoscopic vision
• grasping hand with opposable thumb
• Homonoids diverge from Old World monkeys prior to
  the Miocene in Africa

11
Hominids

• Hominids are bipedal, show a trend toward a large
  brain, reduced face and canine teeth, and are
  omnivores
• five species of Australopithecines are recognized
• A. anamensis (Lucy) is a 4.2 myo bipedal species
  from Kenya
• earliest member of Homo lived 2.5 to 1.6 mya.
• H. erectus migrated to Europe about 100,000 ya
• Cro-Magnons resembled modern humans closely and
  lived in France until about 10,000 ya

12
Pleistocene Glaciation

• The Pleistocene began 1.6 mya and ended about
  10,000 years ago
• several intervals of widespread glaciation took
  place, separated by warmer intervals

13
The Effects of Glaciation

• The effects of glacial erosion and deposition are
  evident worldwide
• lowering of sea level affected base level of
  streams
• pluvial lakes
• proglacial lakes

14
Pleistocene Extinctions

• Many terrestrial mammals became extinct near the
  end of the Pleistocene
• affected mostly mammals over 40kg, and more so in
  N. and S. America
• may not have been able to adapt to rapid climate
  changes at the end of the Pleistocene
• may have been killed off by human hunters