Geological time scale

1. Geological Column & Geological Time Scale
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

3. ❑ The geologic time scale is broken up into:
•Eons: Longest expanse of geologic time.
•Eras: Next longest expanse of geologic time.
•Periods: Third Longest expanse of geologic time.
•Epochs: Shortest expanse of geologic time.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

4. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

5. Fossils From Precambrian Age: Ediacara Fauna
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

6. Fossils From Cambrian Age: Trilobites
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

7. Fossils From Ordovician Age: Brachiopods
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

8. Fossils From Silurian Age: Eurypterids
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

9. Fossils From Devonian Age: Fish
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

10. Fossils From Carboniferrous Age: Glossopteris Flora, Amphibians
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

11. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)
Fossils From Permian Age: Reptiles

12. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)
Fossils From Triassic Age: Lizard, Dragon

13. Fossils From Jurassic Age: Dinosaurs
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

14. Fossils From Cretaceous Age: Dinosaurs
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

15. Fossils From Cenozoic Era
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

16. Mass Extinctions in Geological Time Period
A sharp decrease in the number of species in a relatively short period of time. There different ways a
mass extinction can occur including…
▪ Asteroids
▪ Comets
▪ Global warming
▪ Ice age
▪ Climate Changes
▪ Disease
5 mass extinctions recorded in geological time..
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

17. Ordovician-Silurian extinction
Late Devonian extinction
Permian-Triassic extinction
End Triassic extinction
Cretaceous-Tertiary extinction

18. 1. The Ordovician-Silurian Extinction
▪ 439 million years ago
▪ Caused by a drop in sea level as glaciers formed, then by rising sea levels as glaciers melted.
▪ Killed about 25% of marine families
▪ Killed 60% of marine genera
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

19. 2. Late Devonian extinction
• About 364 million years ago
• About 22% of marine families were killed
• About 57% of the genera were killed
• Suggested that a asteroid impact was the prime cause
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

20. 3. Permian-Triassic extinction
▪ Informally called the “Great Dying” . It was the most severe extinction .
▪ Occurred about 251 million years ago
▪ 96% of all marine species were killed, 70% of terrestrial vertebrate were killed
▪ Most likely due to volcanic eruption, an asteroid impact or a near by super nova.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

21. 4. End Triassic extinction
▪ 199 million to 214 million years ago
▪ Caused by massive floods or lava erupting from central Atlantic province – an event that triggered the
opening of the Atlantic Ocean
▪ The volcanism may have lead to deadly global warming
▪ 22% of Marine families, 52% of marine genera
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

22. 5. Cretaceous-Tertiary extinction
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)
▪ Caused Forest fires to start and ignited volcanic eruptions all over the globe as well as tidal waves,
severe storms that would eliminated all sunlight. It would be six months before sunlight would reach
the ground after such a blow. The dinosaurs, even in their prime, stood no chance without sunlight
and plant life, ending the dinosaurs 165 million year reign.

23. ▪ One of the other theories is that climate change killed all of the plant eating dinosaurs due to lack of
food from the climate change. The cretaceous period was tropical and so were almost 50 percent of
the plants. If the temperature was to change drastically the plant eater’s food would slowly dwindle.
With the plant eaters becoming extinct the carnivores would soon run out of food as well.
▪ The first and the most favored theory is that an asteroid hit somewhere in the golf of Mexico in the
Yucatan Peninsula 65 million years ago. The Asteroid impact is site is called the Chixclub and is
approximately 200 Kilometers across making the asteroid itself about 9 miles wide
5. Cretaceous-Tertiary extinction
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

24. The Big Five
• Ordovician-Silurian extinction -
439 million years ago,
• Late Devonian extinction - 364
million years ago
• Permian-Triassic extinction - 251
million years ago
• End Triassic extinction, - 199
million to 214 million years ago
• Cretaceous-Tertiary extinction,
about 65 million years ago
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

25. The sixth mass extinction?
This extinction is referred to as the Holocene extinction.
This is named after what geologists call the period we as
humans have been in.
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

26. A Journey through time
Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

27. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

28. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

29. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

30. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

31. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

32. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

33. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

34. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

35. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

36. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

37. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

38. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)

39. Md. Yousuf Gazi, Lecturer, Department of Geology, University of Dhaka (yousuf.geo@du.ac.bd)