Changes

Family II & III rocks are formed in low-energy settings and show poor reservoir quality. They usually formed in deep water and restricted settings where the current is not strong enough to winnow away the lime mud.[g] [h]     

Family II & III rocks are formed in low-energy settings and show poor reservoir quality. They usually formed in deep water and restricted settings where the current is not strong enough to winnow away the lime mud.[g] [h]     

===Spectral Subdivision of Limestones===  

===Spectral Subdivision of Limestones===

In 1962, Folk proposed the spectral subdivision. He subdivided the 3 major families into eight types forming a sequential transitional spectrum of energy level in which the first type represents the lowest energy, and the last type represents the highest energy (Figure 11).

In 1962, Folk proposed the spectral subdivision. He subdivided the 3 major families into eight types forming a sequential transitional spectrum of energy level in which the first type represents the lowest energy, and the last type represents the highest energy (Figure 11).

Criteria

====Criteria====

• For rocks dominated by lime mud, Folk considered the percentage of allochems presented.   

* For rocks dominated by lime mud, Folk considered the percentage of allochems presented.   

• For rocks dominated by sparry calcite cement, Folk considered the sorting and rounding of allochems presented.  

* For rocks dominated by sparry calcite cement, Folk considered the sorting and rounding of allochems presented.  

Subdivisions

 

====Subdivisions====

Folk proposed a total of eight types representing a gradational transition of energy level from low to high.  Considering, for instance, fossils to be the major allochems in the system[i], the sequential subdivisions are:     

Folk proposed a total of eight types representing a gradational transition of energy level from low to high.  Considering, for instance, fossils to be the major allochems in the system[i], the sequential subdivisions are:     

1. Micrites and dismicrites: rocks consist entirely of lime mud.

# Micrites and dismicrites: rocks consist entirely of lime mud.

2. Fossiliferous micrites and dismicrites: rocks consist of 1-10% allochems.

# Fossiliferous micrites and dismicrites: rocks consist of 1-10% allochems.

3. Sparse biomicrites: rocks consist of 10-50% allochems floating in the matrix.

# Sparse biomicrites: rocks consist of 10-50% allochems floating in the matrix.

4. Packed biomicrites: rocks consist of > 50% packed allochems.  

# Packed biomicrites: rocks consist of > 50% packed allochems.  

5. Poorly washed biosparites: rocks consist of almost equal amounts of lime mud and sparry calcite cement in which the current was not strong enough to winnow away all lime mud particles.  

# Poorly washed biosparites: rocks consist of almost equal amounts of lime mud and sparry calcite cement in which the current was not strong enough to winnow away all lime mud particles.  

6. Unsorted biosparites: poorly sorted rocks in which the current was strong enough to winnow away lime mud particles, but the allochems are still not sorted.  

# Unsorted biosparites: poorly sorted rocks in which the current was strong enough to winnow away lime mud particles, but the allochems are still not sorted.  

7. Sorted biosparites: well-sorted rocks in which the allochems are still not well-rounded and abraded.

# Sorted biosparites: well-sorted rocks in which the allochems are still not well-rounded and abraded.

8. Rounded biosparites: well-sorted and well-rounded rocks in which the allochems underwent intense abrasion.

# Rounded biosparites: well-sorted and well-rounded rocks in which the allochems underwent intense abrasion.

==Dunham Classification==  

==Dunham Classification==