A confined-aquifer model of meteoric flow through the oolitic grainstones of the upper Smackover explains the systematic variation in early diagenesis and porosity from updip to downdip in the Smackover trend.

Updip limestones have moldic porosity and isopachous rims of clear, bladed calcite cement (freshwater phreatic). Brittle-compaction features indicate dissolution after initial burial. Classic vadose textures are not observed.

Downdip limestones have primary porosity and minor micro-moldic porosity. Grain interpenetration is common, and poikilitic calcite cement and saddle dolomite formed during and after this intergranular pressure solution.

Dolomite predominates in upper Smackover in the middle of the dip trend of Texas, Alabama and Florida. Most common is medium-crystalline dolomite which replaces grains and occurs as cement. These rhombs are interspersed with updip freshwater cements and overlie sutured grain contacts in downdip Smackover. Similar dolomite is in the basal Smackover above thick Norphlet sands in Alabama and Florida. Finer crystalline dolomite occurs in the uppermost Smackover and in evaporitic deposits of the Buckner/ Lower Haynesville Formation.

Meteoric water in updip areas dissolved ooids and calcite cement reprecipitated. As groundwater flowed downdip, it mixed with interstitial fluids and dolomite precipitated and replaced grains. Meteoric flow slowed downdip, and marine pore fluids persisted in this area. Computer modeling suggests that hydraulic head for the meteoric flow was provided by falls in eustatic sea level and can be timed to three Late Jurassic sequence boundaries. Basal Smackover dolomites formed from meteoric fluids expelled from the Norphlet aquifer system. Dolomites of the Buckner/Lower Haynesville likely formed from evaporitic fluids related to sabkha deposition.

End_of_Record - Last_Page 11---------------