Alay Desai (130420106060)

Jeet Donga (130420106061)

Sarvesh Khanna (130420106062)

Aalekh Shah (130420106063)

Kaushal Kathiriya

Nirav Deshmukh (120420106055)

Prof. Pratima Patel

Prof. Khushboo Berawala

Stratigraphy is the branch of Geology which deals with the

history of the rocks of the Earth’s crust with special

emphasis on their approximate time of formation and the

changes they have undergone since their formation.

Stratigraphy

Photo by W. W. Little

Photo by W. W. Little

Stratigraphy Records History

The stratigraphic record preserves details pertaining to major

geologic events, such as:

• Mountain-building (orogenies)

• Land-Sea Relation

• Climatic fluctuation

• Glaciation

• Epeirogeny

• Age of rocks

•Evolution and migration of plants

Principles of Stratigraphy

• Superposition

• Original Horizontality

• Lateral Continuity

• Crosscutting Relationships

• Faunal (biological) Succession

Sedimentary layers become progressively younger upward

through a stratigraphic sequence.

Principle of Superposition

At the time of deposition, sedimentary layers are horizontal. If they

are no longer horizontal, they have undergone some type of

deformation. The two most common types of deformation are folding

and faulting.

Principle of Original Horizontality

Tilting of Beds by Folding

Tilting of Beds by Faulting

At the time of deposition, sedimentary layers are continuous for long

distances. If they terminate abruptly, they have either undergone

deformation or they have been eroded. The two most common causes

of abrupt bed termination are faulting and unconformities.

Sedimentary layers can taper laterally into other sedimentary units.

Principle of Lateral Continuity

Bed Termination by Faulting

Bed Termination by Unconformity

An unconformity is a surface that represents an episode of missing

geologic time. During the formation of an unconformity, sediment is

either not deposited or it is deposited and subsequently removed by

erosion.

There are three types of unconformities based on the types of rocks

involved and their attitude with respect to each other.

Types of Unconformities

Disconformity (paraconformity) Nonconformity

Angular

Unconformity

Principle of Cross-cutting

Relationships

A rock body that is cut (crossed) by another rock body, structure, or

unconformity is older than what is cutting it.

Fossils are found in a consistent and predictable succession

everywhere on earth.

Principle of Fossils or Faunal

(biological) Succession

Fossils may be defined as remains or impression of ancient animals and plants which have been preserved

in sedimentary rocks by natural processes.

It is like the calendar of an year. As an year is divided into different months, weeks, days , geological time

scale is also subdivided into smaller and smaller unit to suit stratigraphical study and correlation. The

unconformities subdivide geological time scale into smaller units.

Geologic Time Scale

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Geotechnics and Applied Geology by Dr. R. P. Rethaliya