Lithostratigraphic

LithostratigraphyLecture #9

LITHOSTRATIGRAPHY• Subdivision of rock successions into units on the basis

of lithology or rock type

• Lithostratigraphical standard units:

• Supergroup

• Group

• Formation

• Member

• Bed

• Lithostratigraphic classification is the subdivision, classification, and organization of rock strata on the basis of their lithologiccharacters

• 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

• 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

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

Boundaries of Lithostratigraphic Unit

Sandstone unit

Claystone unit

..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

…fixed arbitrarily

within zones of

lithologic gradation

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

Basic Hierarchy of

Lithostratigraphic Unit

1,2,3, etc. : similar time gapA, B, C, etc. : lithostratigraphicunit boundary

10 m

0