|
|
Geologic Principles
|
Lecture 4
2/9/98
|
| | Last week we discussed what fossils are and the processes involved in their formation. |
| | This week will look at a primary use of fossils, building the Geologic Time scale. |
| | To start off the discussion we will look at some of the guiding principles of geology. |
| | Three principles form the basis for stratigraphic and paleontologic studies. |
| | These are principles, not laws. There are limitations |
| | Development of the Geologic Time scale relied heavily on these principles and their limitations. |
| | The present is the key to the past |
| | Modern processes operating over long periods of time produced the earth features. |
| | fossils or groups of fossils occur in distinct intervals of rock |
| | Correlation is possible based on fossil assemblages |
| | Subdivision of the rock record is possible based on fossil assemblages |
| Environmental considerations |
| | Depositional environments |
| | Laterally adjacent environments are stacked vertically |
| | environment specific fossils |
| | used to detail/confirm environmental conditions |
| | environment independent fossils |
| | used to delineate time units |
| | Time units cross rock units |
| | example: Beach progradation |
| | point out where principles break down. |
| | Rock units are based on environment |
| | Time units are based on fossils |
| | short period of existence |
|
|
