The Forest Hill Formation

Introduction
The Forest Hill Formation is a geological area that mainly stretches from west-central to southeastern Mississippi, but thins right at the border of and barely touches Clarke County, Alabama (Echols, et al., 1893). Geologist Ephraim Nobel Lowe originally proposed the name Madison Sands for this formation, due to the fact that he had studied it in Madison County, Mississippi. The name was later changed to Forest Hill by Charles Wythe Cooke. The Forest Hill Formation overlies the Red Bluff Formation in eastern Mississippi and disconformably overlies the Yazoo Formation in western and central Mississippi (MacNeil, et al., 1984). In southeastern Mississippi and southwestern Alabama this formation overlies the Red Bluff Clay and the
Forest Hill’s type locality is badly weathered and slumped, making accurate descriptions of the lithology and measurements of the thickness difficult. A pilot hole was drilled to a depth of 100 feet at Forest Hill. A second hole was cored to a depth of 78 feet piercing weathered Glendon limestone, Mint Spring marl, and the Forest Hill and bottoming in the upper part of the Yazoo clay. The core can be seen in figure 1. The thickness of the Forest Hill Formation varies from around 72 to 145 feet in the west-central to southeastern Mississippi area. The thickness in the Wayne County ranges from 45 to 128 feet. Forest Hill’s variable thickness is an attribute that holds true throughout its outcrop belt in Mississippi. The Forest Hill abruptly thins at the Alabama state line from 104 feet thick to 9 feet thick. The formation is absent in the Jackson, Alabama area (SEGSA,
Rees property north of Cleary in the SE/4, SE/4, SW/4, NW/4, Section 22, T. 4 N., R.1 E., Rankin County, Mississippi. Here the Mint Spring Formation is a nine-foot thick, fossiliferous, calcareous, glauconitic, moderately clean, massive sand. This facies is very different from the two-foot thick, soft, sandy limestone facies occurring in Wayne County as shown in Figure 2. Mary Dockery, 5’ 8”, for scale. Arrows mark the upper and lower contacts of the Mint Spring Formation. Photograph taken in January of 1984 (MacNeil, et al.,