The document provides information about the geological time scale. It defines the geological time scale as a system used to date geological strata and relate Earth's history. The time scale is divided into eons, eras, periods, and epochs based on significant geological events. In the 18th century, Steno established principles of geological timescales. Hutton later proposed theories of plate tectonics and the rock cycle that were foundations of modern geology. By the 19th century, correlating fossil evidence across regions allowed precise division of Earth's history into standardized periods still used today.

1. Welcome
To
My Presentation

2. Palaeontology
Course Name: Palaeontology
Abu Reza
Islamic University, Kushtia

3. Contents
Definition
History of Geological Time Scale
Naming of Geological Time Scale
Geological Timing
Formulation of Geological Time Scale

4. Geological Time Scale

5. Geological Time
Scale
Definition:
The geological time scale (GTS) is a system of chronological
dating that relates geological strata (stratigraphy) to time. It is
used by geologists, paleontologists, and other Earth scientists to
describe the timing and relationships of events that have
occurred during Earth's history. The table of geologic time
presented here, agree with the nomenclature, dates and
color codes set forth by the International Commission on
Stratigraphy (ICS).

6. Geological Time
Scale
The geological time scale is based on the geological rock
record, which includes erosion, mountain building and other
geological events. Over hundreds to thousands of millions of
years, continents, oceans and mountain ranges have moved vast
distances both vertically and horizontally. For example, areas that
were once deep oceans hundreds of millions of years ago are
now mountainous desert regions.

7. History of Geological Time Scale
In Ancient Greece, Aristotle (384-322 BCE) observed that
fossils of seashells in rocks resembled those found on
beaches – he inferred that the fossils in rocks were formed by
living animals, and he reasoned that the positions of land and
sea had changed over long periods of time. Leonardo da Vinci
(1452–1519) concurred with Aristotle's interpretation that
fossils represented the remains of ancient life.
Early history

8. History of Geological Time Scale
In the late 17th century Nicholas Steno pronounced the
principles underlying geologic (geological) time scales. Steno
argued that rock layers (or strata) were laid down in succession,
and that each represents a "slice" of time. He also formulated the
law of superposition, which states that any given stratum is
probably older than those above it and younger than those
below it.
Nicholas Steno’s Time (1638–1686):

9. History of Geological Time Scale
Over the course of the 18th century geologists realized that:
• Sequences of strata often become eroded, distorted,
tilted, or even inverted after deposition.
• Strata laid down at the same time in different areas
could have entirely different appearances.
• The strata of any given area represented only part of
Earth's long history.

10. History of Geological Time Scale
The Neptunist theories popular at this time (1749–1817)
proposed that all rocks had precipitated out of a single
enormous flood. John McPhee asserts that "as things appear
from the perspective of the 20th century, James Hutton in those
readings became the founder of modern geology".
The Neptunist theories:

11. History of Geological Time Scale
Hutton proposed that the interior of Earth was hot, and that
this heat was the engine which drove the creation of new rock:
land was eroded by air and water and deposited as layers in the
sea; heat then consolidated the sediment into stone, and uplifted
it into new lands. This theory, known as "Plutonism", stood in
contrast to the "Neptunist" flood-oriented theory.
Proposal Hutton:

12. Naming of Geological Time Scale

13. Naming of Geological Time Scale
The geological time scale divides the history of Earth is divided into
eons, eras, periods and epochs.
Eons:
• Eons are the largest intervals of geologic time and are hundreds of
millions of years in duration.
• The history of Earth has been divided into three eons: Archaean,
Proterozoic and Phanerozoic.

14. Naming of Geological Time Scale
Eras:
• Eons are divided into smaller time intervals known as eras. In the time
scale we can see that the Phanerozoic is divided into three eras:
1. Cenozoic (recent life)
2.Mesozoic (middle life)
3. Paleozoic (ancient life)
• Very significant events in Earth's history are used to determine the
boundaries of the eras.

15. Naming of Geological Time Scale
Periods:
• Eras are subdivided into periods. The events that bound the
periods are widespread in their extent but are not as significant as
those which bound the eras.
• In the time scale we can see that the Paleozoic is subdivided into
the Permian, Pennsylvanian, Mississippian, Devonian, Silurian,
Ordovician and Cambrian periods.

16. Naming of Geological Time Scale
Epochs:
• Finer subdivisions of time are possible, and the periods of the
Cenozoic are frequently subdivided into epochs.
• Subdivision of periods into epochs can be done only for the most
recent portion of the geologic time scale. This is because older
rocks have been buried deeply, intensely deformed and severely
modified by long-term earth processes. As a result, the history
contained within these rocks cannot be as clearly interpreted.

17. Geological Timing
• This approach to the sweep of geologic time follows that in "The
Grand Canyon", C.Hill, et al., eds. to organize the different periods of
life since the beginning of the Cambrian period.
• The time data from radiometric dating is taken from that source. The
times are in millions of years.

18. Geological Timing
• Note that the dates in millions of years are representative values.
Research publications would give error bars for such division dates - it
is not implied here that these boundaries are known to 3 or 4
significant digits.
• The division of the geologic column into different periods is largely
based upon the varieties of fossils found, taken as indicators of a time
period in Earth's history.

19. Geological Timing

20. The first serious attempts to formulate a geologic time scale that
could be applied anywhere on Earth were made in the late 18th
century. The most influential of those early attempts divided the rocks
of Earth's crust into four types:
 Primary
Secondary
Tertiary and
Quaternary.
Formulation of Geological Time
Scale

21. Each type of rock, according to the theory, formed during a
specific period in Earth history. It was thus possible to speak of a
"Tertiary Period" as well as of "Tertiary Rocks." Indeed, "Tertiary" (now
Paleogene and Neogene) remained in use as the name of a
geological period well into the 20th century and "Quaternary"
remains in formal use as the name of the current period.
Formulation of Geological Time
Scale

22. The identification of strata by the fossils they contained,
pioneered by William Smith, Georges Cuvier, Jean d'Omalius d'Halloy,
and Alexandre Brongniart in the early 19th century, enabled
geologists to divide Earth history more precisely. It also enabled them
to correlate strata across national boundaries. If two strata contained
the same fossils, chances were good that they had been laid down at
the same time. Detailed studies between 1820 and 1850 of the strata
and fossils of Europe produced the sequence of geologic periods still
used today.
Formulation of Geological Time
Scale