Abstract:
The present study is focused on the origin and demarcation of the various types
of concretion and non-skeletal grains, depositional environments and their significance.
The area under study lies in the vicinity of the Abbottabad region of the Khyber
Pakhtunkhwa province Pakistan. The study area being topographically close-to-theMBT has been under intense deformation. The_study_area is marked by South East
moving thrust faults, and North-East Trending Anticlines. The Samana Suk Formation
consists of well bedded limestone which is light brown to grey in color.
The.Samana.Suk.Formation includes brachiopods, belemnite guards, micritic beds and
Oolitic limestone.
The Concretions and non-skeletal grains interpreted.are; 1) Ooids grains have
been further divided into 6 types which are Micritic Ooids, Concentric Ooids, Radial
Ooids, Superficial Ooids, Broken Ooids, Deformed Ooids. These Ooids are
characterized by well-rounded to sub-rounded and differ from each other on the basis
of number of cortices and the structures of the Ooids, the environment of deposition for
the ooids range from a lower intertidal to lagoonal shallow marine environment. 2)
Aggregates, grains have been characterized as grapestones based on the stage of
transformation. Grapestones grains are sub rounded and moderately sorted. The
features indicate a platform to marginal reef marine environment. 3) Peloids grains
have been further divided into 2 types which are Fecal Pellets and Bioerosional Peloids.
These are characterized by elongated rod like to angular shaped grains formed by
burrowing of micro-organisms. The present features indicate upper to middle intertidal
shallow marine environment. The depositional environments for the concretions and
non-skeletal grains range from inter tidal zone to marginal reef zones. The significance
of these concretions and non-skeletal grains are such that they’re presence of absence
can indicate Sea level fluctuations, these grains can be used for correlations on a
regional scale, Specific depositional settings can be interpreted on the basis of
abundance and type of grains present, carbonate concretions and grains are of high
economic importance and their geometries have a significant influence on the reservoir
qualities of carbonate rocks.
