LOUISIANA. 



COAST FORMATION. 



In the extreme soutliejistoi-n and in the 

 ex;reuu' soul li western portions of tliis 

 Btate. iiiciiuiing a part of tlie parishes of 

 St. Taniinauy, Tangipahoa and Livingston 

 in the east and Calcasieu in the west, 

 occur low "pine flats, ' or 'meadows," 

 the exact geological position of which is 

 not yet fully determined. Field examina- 

 tions are now being made, with a view 

 of throwing some light on this subject. 

 This formation may be anterior to the 

 '•blue clay" (ChampUiin) period, or coin- 

 cident with it. The entire country is 

 covered with small, scattered lonii-leaf 

 pines. Most of it is covered with "orange 

 sand," which overlies a partly marine and 

 partly fi-esh water fornuition. consisting 

 mainly of gray, mossy clays, wliich gives 

 the imiiervious stra+um to which these 

 "pine tl.its" owe their peculiar features. 

 To the eastward they extend beneath the 

 littoral allnvium of lakes Maurepas, Pont- 

 chartrain and LSorgne. and perhaps form 

 the clay bottoms of these '.akes bevoud •rtie 

 sand and clay deposited by the tides and 

 streams running into them. This forma- 

 tion is found along the entire Mississippi 

 coast, and is reached at moderate depchs 

 in many of the wells, rendering the water 

 therefrom unrtrinkabie. In the west, in 

 Calcnmieu parish, it is covered on the 

 south by the silty prairie, a subse- 

 quent form.ition, as explained above. 



THE BLUE CLAY. LOESS AND 

 BLUFF. 



may togetlier be classified as the Cham- 

 plain formation. 



Striiriy .speakiug, all of the soils of the 

 larse 'bottoms of this state are not 

 alluvial. The rivers have cut their way 

 through a thick deposit made long be 



fore the existence of our present chan- 

 nels. From Memphis and Shreveport to 

 the gulf the entire bottoms are underlaid 

 by a stiff clay of variable depths, 

 through which the present rivers have 

 carved their channels. This deposit was 

 made at a time when the entire valleys 

 were depressed belo.v their present 

 levels and were stagnant, continuous 

 swamps. By subsequent elevation sutii- 

 cient fall was given to produce currents 

 strong enough to establish channels, 

 tlirough which the rivers liave been ever 

 since enii)tying their floods. Ui)on this 

 clay (blue in the Mississippi l)ottouis) 

 these rivers liave ever s'nce been deposit- 

 ing their alluvium. Freiiuently, however, 

 large areas are found still uncovered, and 

 when cultivated give us the famous 

 "buckshot" soils. These buckshot clays 

 are the lowest strata of the ChamiWaiii 

 formation, whose higlior ones give ns the 

 "loess" and "bluft" of the cane hills on 

 both sides of the Missi!'S;i)pi and of the 

 southwestern prairies. 



The bluff region in this state is under- 

 l£ id by a calcareous silt belonging to 

 the loess formation, and this in turn is 

 overlaid by a rich brown loam, the lime 

 bluff formation varyiiig in thickness fi-om 

 a few inches to S or 10 feet. At Port 

 Hudson tliese formaticns are together 

 well exposed, superimposed the one above 

 the other. At the foot of the blulf occurs 

 dark-colored clays, with calcareous and 

 ferruginous concretions, fossil wood, 

 stumps, cypress knees, etc. From these 

 clays the buckshot soils already men- 

 tioned are derived. Above these clays oc- 

 cur the calcareous silts of tlie loess, 

 while nearer the surface are 7 feet or 

 more of brown loam, the thin surface soil 

 of the bluff formation. 



The following conuensed table will give 

 the geological ages and groups found in 

 Lo-iisiaiia and the material and fossils of 

 each ; 



GEOLOGY OF LOUISIANA. 



AGE NAME OF GROUP 



CHIEF MATERIALS. 



Alluvium. 



Second b()lt(mis. 



Bluff lands. 



Loess. 



Blue Clay, 



Drift. 



Yellow sand.v clays 



Coast formation." 



^ Grand Gulf group. 



K \ Vicksburg group. 

 2 J Jackson's group. 

 H \ Arcadia clays. 

 g / Upper Lignitic. 

 ^ I CI:iiborne 



V Lower Lignitic. 



g J Uipley. 



Soils. 



Soils. 



Brown loams. 



Calcareous silts. 



Clays. 



Sands, pebVdes, etc. 



Sands, loams and clay 



Sands and clay. 



Light clays and white 



sandstones. 

 Marls and limestone. 

 Marls and limestone. 

 Gray clays. 

 Dark-colored clays. 

 Marls. 

 Dark-colored clays. 



Marls and limestone. 



KIND OF FOSSILS FOUND. 



Living plants and animals. 

 Living plants and animals. 



Living shells and trees. 

 Living shells and trees. 

 Living shells and trees. 



Plants partly oxtiuot. 

 Marine anim tis. 

 Marine animals. 

 No fossils. 

 I'lants— Lignite. 

 Marine animals. 

 Plants— Lignite. 



Marine animals. 



Only three of the principal geological periods are here represented, and one of 

 these by its uppermost group, with only an occasional outcrop. 



While all of these gro ips are represented in Louisiana very few -^f them occupy 

 excessive surface development, and therefore take but little part in the formation 

 of coils. 



