Lithostratigraphy is the subdivision of rock layers based on their lithology or rock type. Rock layers are divided into standardized units including supergroups, groups, formations, and members. Lithostratigraphic units are defined solely based on distinct rock compositions and types. Boundaries between lithostratigraphic units are placed at points of clear lithological changes, either where rock types sharply differ or where gradational changes allow arbitrary boundaries. The basic hierarchy of lithostratigraphic units ranked from highest to lowest includes supergroups, groups, and members.

1. Lithostratigraphy
Lecture #9

2. LITHOSTRATIGRAPHY
• Subdivision of rock successions into units on the basis
of lithology or rock type
• Lithostratigraphical standard units:
• Supergroup
• Group
• Formation
• Member
• Bed

3. • Lithostratigraphic classification is the
subdivision, classification, and organization of
rock strata on the basis of their lithologic
characters

4. • Lithostratigraphic unit :
• based on the type of rock,
• may consist of sedimentary, igneous-, or metamorphic
rocks, or of an association of two or more of these
• defined and distinguished solely by lithologic feature
(primarily rock composition) suplemented by
stratification/succession
note : such features should
normally be of such-a
nature that they can be
readily recognized in the
field by a knowledgeable
geologist

5. Boundaries of
Lithostratigraphic Unit
• Boundaries of lithostratigraphic unit, or boundaries
between adjacent (either laterally or vertically)
lithostratigraphic units:
• are placed at points of lithologic change
• will be placed at naturally occurring sharp or
distinct contact between differing lithologies,
• may be fixed arbitrarily within zones of lithologic
gradation

6. Boundaries of Lithostratigraphic Unit
• …placed at points of
lithologic change
• placed at naturally
occurring sharp or
distinct contact between
differing lithologies
Sandstone unit
Claystone unit

7. Claystone unit
Sandstone unit
…fixed arbitrarily
within zones of
lithologic gradation
..this interval can be consider as
another lithostratigraphic unit
and known as … claystone -
sandstone unit…
…or boundary of claystone
unit and sandstone unit
“fixed arbitrarily” (red line)
in the gradation boundary

8. Basic Hierarchy of
Lithostratigraphic Unit
• Basic hierarchy of ranks of formal
lithostratigraphic units (from highest to lowest)
are: supergroup, group, and member

15. 1,2,3, etc. : similar
time gap
A, B, C, etc. :
lithostratigraphic
unit boundary
10 m
0