Ripley Sands. Providence, Eutaw, and Blufftown Formations

1. Ripley Sands. Providence, Eutaw, and Blufftown Formations Lithology, Characteristics, etc.

2. Ripley Formation Backgroud Cretaceous strata was first recognized by Sir Charles Lyell on his second trip to North America E.W. Hilgard proposed the name Ripley in 1860 to distinguish strata in Tippah County, Mississippi that lays between the Rotten Limestone that he encountered, which is now given the name Selma Chalk, and lignite formation, now know as the Porters Creek Clay.

3. Ripley Background The Cretaceous strata of the Ripley was first divided into the Eutaw Group and the Ripley Group The Eutaw Group includes the Tuscaloosa and Eutaw Formation, and the Ripley Group is known as the Ripley Formation and the Prarie Bluff Chalk In 1909 the Ripley Formation was subdivided into the Lower Marl (Blufftown), Middle Sand (Cusetta), Upper Marl ( Renfroe), and the Upper sand (Providence) The Renfroe Formation was later dropped, and known as the Perote Formation, which is situated between the Cusetta and the Providence Formation

4. Ripley Formation The extent of the beds that the Ripley have been named extend from Twiggs County, in central Georgia to central Alabama The Selma chalk interrupts the formation synchronously, forming the top of the Upper Cretaceous between central Alabama, and Houston County, Mississippi Selma Chalk also occurs in Cretaceous stratagraphic units extending from Tennessee to Georgia

5. Ripley History The extent of the Ripley Formation was better defined after paleontology studies better defined the limits of the formation and the subdivisions are still being redefined Sediments of the Ripley Formation and Providence Sand were deposited during the Maestrichtian, meaning the latest Cretaceous (65-70 Mya.) During this period transgressive-regressive deposition cycles occurred Sedimentary cycles throughout the Upper Cretaceous represent a period of rapid transgression followed by progradation (sediments build in the basin in areas of progradation) Progradation- The accumulation of sequences by deposition in which beds are depostited successively basinward because sediment supply exceeds accommodation. The shoreline migrates into the basin during episodes of progradation, known as regression

6. Extent of the Ripley Formation The entire Ripley Formation extends from Northern Alaska, through the Central USA, down to South Georgia, then up through the northern U.S. to the southern part of Greenland Towards the east of Georgia, and east of the Chattahoochee basin, the Ripley Formation is thought to be around one thousand feet, and thins in Georgia, where it becomes a littoral sand (littoral sand- sand transported by erosion), then thins to 400 feet in Wickcliffe, Kentucky, and has been measured to be 50 feet in Cairo, Illinois according to well logs In Georgia, outcrops of the Ripley are known to be between ten to fifteen miles wide

7. Composition of the Ripley Formation In Georgia, the Ripley is predominately massively bedded dark grey to greenish black marine sands of mainly calcareous, micaceous, pyritiferous, glauconitic, and argillaceous, depending on the conditions of sedimentation in different parts of the Ripley Sea Some contain enough fossils to be considered Marls (metamorphosed limestone)

8. Eutaw Formation In west Georgia, it is characterized by facies of estuarine origin The central deposits are dominated by mud shales It is exposed in Columbus, Georgia and have fine-grained sand beds that reflect deposition during long occuring or intense storms, thus showing hummocky cross-stratification The Eutaw is mildly bioturbated, including funnel and disk-shaped structures, back-filled cylindrical burrows, and escape structures, and are composed of a diverse assemblage of trace fossils, which include assemblages of Ophiomorpha, Asterosoma, and Planolites. These ichnofossils occur mainly occur in mud, and can be attributed to deposit feeders that colonized the sands.