ABSTRACT

The name Heterostegina sp. is becoming synonymous with limestone. "Het lime" is here used for a hard limestone in which fractures go through the imbedded fossil.

A dip section by means of electric logs from northern Harris County, Texas, to southern Galveston County, Texas, is presented. In the most updip well, Heterostegina sp. occurs at a depth near 3000 feet. The lithology in this instance is a calcareous sand. The fauna consists of large Eponides ellisorae, Amphistegina sp., and Heterostegina sp. Bryozoa are also present.

In the middle portion of the section, the lithology is shown to be calcareous mudstone at a depth of 5000 feet. Heterostegina sp. is fairly common. Bolivina perca appears in this type of environment. At the extreme southern end of the section, at a depth of 8000 feet, the mudstones are only slightly calcareous. Heterostegina sp. is rare while Bolivina perca is common.

Another dip section through Calcasieu Parish, Louisiana, is presented. The portion of the section in this area containing Heterostegina sp. appears to be more calcareous as Bolivina perca occurs some distance below this fossil. Some of the wells in this section are located on shallow domes but no true "Het lime" was observed.

A strike section from St. Bernard Parish, Louisiana, through Orleans, St. Tamany and Livingston Parishes is shown. On this section, a Heterostegina limestone reef is suggested. Since this probable reef ceases near the Mississippi River, it is postulated that domes from the Mississippi River westward into Texas to Matagorda County on which a true Heterostegina lime is found were uplifted prior to the occurrence of Heterostegina sp.

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