Uzair Shah Department Of Geology Abdul Wali Khan University Mardan

2. DUNHAM CLASSIFICATION
Introduction
 The Dunham classification system for carbonate sedimentary rock was
originally devised by Robert J Dunham in 1962,
 And subsequently modified by Embry and Klovan in 1971 to include
coarse-grained limestone and sediments that had been organically
bound at the time of deposition.
 The modified Dunham Classification has subsequently become the
most widely employed system for the classification of carbonate
sedimentary rocks with 89% of workers currently adopting this system
over the alternative Folk classification scheme.

3. ROBERT J DUNHAM published his classification system
for limestone in 1962.
The original Dunham classification system was developed in
order to provide convenient depositional-texture based class
names that focus attention on the textural properties that are
most significant for interpreting the depositional environment
the rocks.
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4. DUNHAM CLASSIFICATION
The Dunham classification is based on the concept of
grain support. The classification divides carbonate rocks
into two broad groups
 Those whose original components were not bound
together during deposition and
 Those whose original components formed in place
and consist of intergrowths of skeletal material. The
latter group are called boundstones.

5. The former group is further subdivided as to whether or not the grains
are mud-supported or grain supported.
If the rock consists of less than 10% grains it is called a Mudstone.
If it is mud supported with greater than 10% grains it is called a
Wackstone.
a grain-supported fabric containing 1% or more mud-grade fraction
, it is called a Packstone.
If the rock is grain supported, that contain less than 1% mud-grade
materials, it is called a Grainstone.
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6. Floatstone is a type of limestone which displays 10% or more of the
grains larger than 2 mm in diameter and there is Mud (matrix)
between the grains.
Rudstone is a type of limestone which displays 10% or more of the
grains larger than 2 mm in diameter and there is Spar between the
grains.
Boundstone is a carbonate deposits in which the sediments are
bound during deposition by organisms such as corals or algae.
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7. Bafflestone is type of carbonate rock that exhibited any evidence of the original
components being organically bound together at the time of deposition.
Bindstone matrix-supported sediments that have been stabilized by encrustation
and binding.
Framestone sediments with a rigid fossil-supported framework.
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8. Diagram

9. Original Dunham classification (Dunham 1962)[1]
Depositional texture recognizable Depositiona
l texture
not
recognizabl
e
Original components not bound during deposition Original
component
s were
bound
during
deposition
Contains mud Lacks mud
and
is grain-
supportedMud-supported Grain-
supported
Less than
10% grains
More than
10% grains
Mudstone Wackestone Packstone Grainstone
Bound
stone
Crystalline
Carbonate