Table 1 Diagenetic features and interpretations of the Lower-Middle Eocene carbonates.
Diagenetic feature | Description | Interpretation |
|---|---|---|
Micritization | Skeletal particles exhibit micrite envelopes, often with microborings; thickness 18–46 μm | Occurs in marine-phreatic environments under tranquil water conditions; stabilizes carbonate grains and prevents further diagenetic alteration |
Glauconitization | Dispersed yellowish to reddish-green glauconitic grains; partial replacement of biogenic materials | Indicates sub-oxic, mild reducing conditions; formed through glauconitization of fecal pellets or biogenic materials in restricted marine environments |
Cementation | Includes fibrous calcite, granular spar, and blocky calcite cements | Fibrous calcite formed in marine-phreatic settings; granular and blocky spar precipitated in meteoric-phreatic and burial diagenetic environments |
Dolomitization | Two modes: matrix-replacive and void-filling dolomites; euhedral to subhedral crystals | Early dolomitization occurred in marine-phreatic environments; void-filling dolomites formed during shallow burial diagenesis |
Neomorphism | Micritic matrix recrystallized to neomorphic spar; skeletal allochems partially replaced | Indicates stabilization of metastable aragonite and high Mg-calcite in meteoric-phreatic diagenetic conditions |
Silicification | Silica occurs as pore-filling material and partial replacement of skeletal grains | Derived from terrestrial sources; precipitated during regression periods under meteoric-phreatic diagenesis |
Compaction | Mechanical compaction caused grain deformation, fracturing, and reduced porosity | Reflects burial diagenesis; initiated shortly after deposition and progressed during shallow burial |
Fracturing | Macroscopic and microscopic fractures occur in all formations | Indicates late diagenetic processes, including tectonic stress during uplift and meteoric-vadose diagenesis |
Dissolution | This affected matrix, cements, and skeletal grains, creating secondary porosity | Occurred during meteoric-phreatic and meteoric-vadose conditions; dissolution facilitated later cementation |
Iron oxides | Occurs as brown to reddish-black patches, often coating allochemical constituents | Represents epidiagenetic processes in oxidizing meteoric-vadose conditions; linked to subaerial exposure and weathering |
