Annona Chalk

Annona Chalk Stratigraphic range: Cretaceous
Outcrop east of Clarksville, TX (c. 1910)
Type	Formation
Sub-units	Austin Group
Underlies	Ozan Formation
Overlies	Brownstown Marl
Thickness	30 Meters
Lithology
Primary	Chalk
Location
Region	Arkansas
Country	United States
Type section
Named for	Annona, TX

Annona Chalk overlying Brownstown Marl at White Cliff, Howard County, AR (c. 1910)

The Annona Chalk is a geologic formation in Arkansas, Texas, Louisiana, and Oklahoma.^[1] It preserves fossils dating back to the Cretaceous period. The formation is a hard, thick-bedded to massive, slightly fossiliferous chalk. It weathers white, but is blue-gray when freshly exposed. The unit is commercially mined for cement. Fossils in the Annona Chalk include coelenterates, echinoderms, annelids, bivalves, gastropods, cephalopods, and some vertebrate traces.^[2] The beds range in thickness, up to over 100 feet in depth in some areas (such as the White Cliffs).^[3] There is a gradual transition between the Annona chalk and the underlying Brownstone formation, where chalk and marl are interbedded.^[4]

See also

• List of fossiliferous stratigraphic units in Arkansas
• Paleontology in Arkansas

References

1. USGS Geolex, Annona Chalk/Formation
2. R. T. Hill. "ANNONA CHALK/FORMATION". Arkansas Geological Survey. v. 5: Arkansas Geological Survey. p. 308. Retrieved 25 May 2015.
3. Veatch, Arthur Clifford (1906). Geology and Underground Water Resources of Northern Louisiana and Southern Arkansas. U.S. Government Printing Office.
4. "http://pubs.usgs.gov/bul/0619/report.pdf" (PDF). pubs.usgs.gov. 1916. p. 21. Retrieved 2015-05-25. External link in |title= (help)

• Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 8 July 2014.
• http://www.jstor.org/stable/1298209?seq=1#page_scan_tab_contents

8http://pubs.usgs.gov/bul/0619/report.pdf