Dunham classification presentation

Uzair Shah Department Of Geology Abdul Wali Khan University Mardan

1. Dunham classification By U zair Shah

2. Dunham Classification Introduction The   Dunham classification  system for  carbonate sedimentary rock  was originally devised by  Robert J Dunham  in 1962 , A nd 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 of the rocks. Continue

4. Dunham Classification The Dunham classification is based on the concept of grain support. The classification divides carbonate rocks into two broad groups T hose 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 M udstone . If it is mud supported with greater than 10% grains it is called a W ackstone . 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 . Continue

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. Continue

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. Continue

8. Diagram

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