page_title: Dunham classification
section_title: Modification by Embry and Klovan (1971)
hierarchical_section_title: Dunham classification / History / Modification by Embry and Klovan (1971)
caption_attribution_description: English: Larger benthic foraminifera floatstone with a foraminifera grainstone matrix
context_page_description: The Dunham classification system for carbonate sedimentary rocks was originally devised by Robert J. Dunham in 1962, and subsequently modified by Embry and Klovan in 1971 to include coarse-grained limestones 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
context_section_description: Following the publication of the original Dunham Classification System a number of modifications were proposed. The most widely adopted of these has been that of Embry and Klovan (1971) who recognized that the Dunham classification scheme lacked detail when it came to the description of organically-bound and coarse-grained limestones.
  Embry and Klovan proposed the subdivision of the Dunham 'boundstone' category on the basis of the means by which the sediment was organically-bound, thus yielding three new classes within the Dunham boundstone class:
  Bafflestone 
  autochthonous organically- baffled sediments
  Bindstone 
  matrix-supported sediments that have been stabilized by encrustation and binding
  Framestone 
  sediments with a rigid fossil-supported framework
  Recognising that the identification of these structures is problematic at the limited scale of a petrographic thin section and typically requires examination of outcrop exposures or core, Embry and Klovan stated that where the mode of binding is not identifiable then the original Dunham classification term boundstone should be retained.
  To address the issue of coarse-grained allochthonous limestones (lithologies where >10% of the components are >2 mm in diameter), Embry and Klovan proposed the introduction of two further new classes:
  Rudstones 
  textures where the >2 mm grain-size fraction supports the framework
  Floatstones 
  matrix-supported textures with the >2 mm grains appearing to 'float' in a finer-grained matrix
  As with the original Dunham classification, modifiers should be employed to enhance the classification. Additionally, the class names should be employed as textural modifiers to describe the matrix. Embry and Klovan also redefined 'mud matrix' as material with a diameter of <30 μm.
  Following the wide adoption of the Embry and Klovan (1971) modifications, the Dunham Classification system is typically referred to as the 'modified Dunham Classification System' with both Dunham (1962) and Embry and Klovan (1971) being cited.
  It can be summarized as follows:
  .
caption: Thin section photomicrograph of Orbitolinid foraminifera floatstone with a fragmented bioclast packstone matrix, plane polarised light
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