10 



ON THE GEOLOGY OF LOWER LOUISIANA 





THE ^I^^c i.sx.a:nds, 



COAST or liOUISIAls^A. 



COTE BLANCHE. 



Of these Islands, Cute Blanche affords on its sea-face the best exposure of the 

 lower strata of the series. It is a regular mammillary elevation, somewhat elliptical 

 in outline ; its highest point, near the centre, rises one hundred and eighty feet 

 above mean level of the Gulf, according to the Coast Survey determinations. Its 

 area embraces about two thousand acres of excellent upland, possessing an amber- 

 colored loam subsoil. It was originally covered with a fine growth of Magnoha, 

 Ash, Live and Black Oak, as well as tall cane; but it is now almost entirely denuded 

 of timber, and under cultivation for sugar-cane and cotton. About three-fourths of 

 a mile of its southern and southwestern front is washed, and continually encroached 

 upon, by the sea; on all other sides it is bordered by sea marsh. A causeway three- 

 fourths of a mile long connects it with the mainland, i. c, the cypress swamp of 

 bayou Cypres Mort. 



The southern face, towards the sea, presents a perpendicular bluff about fifty 

 feet high, with but little talus; from its foot there extends seaward at low-tide 

 level, for some forty to sixty yards, a shelving terrace of blue clay dotted with 

 cypress stumps and small patches of lignitic matter. The cypress roots are in 

 rather a better state of preservation than at Port Hudson, though when dry they 

 become as light as cork. Wherever exposed, the teredo and barnacle, as well as 

 occasionally the oyster, have taken possession of them. 



The following section shows the strata exhibited; which, however, vary greatly 

 in character at different points, and are no doubt continually changing, as at Port 

 Hudson, in consequence of the rapid encroachment of the Gulf waters upon the 

 "caving" land; the entire area of the clay-shelf, now covered by the tide, having 

 within the memory of the inhabitants formed part of the upland. The section 

 is taken at about the middle of the exposure. 



