6 ON TUE GEOLOGY OP LOWER LOUISIANA 



bluish or whitish clay; while around their tops, alternating layers of muck and clay 

 deposit mark the annual fall of leaves, and succeeding overflows. Some of these 

 stumps are of large dimensions, and their wood remains sufficiently solid to render 

 it troublesome to detach a large chip with the hatchet. Few retain more than 

 twelve inches of trimk above the junction of the roots. 



The stump stratum emerges from the talus at the lower steamboat landing, ten 

 feet visible above low water; then gradually sinks, and a quarter of a mile below 

 disappears under the wate^. 



Stratum No. 2, the main clay deposit, varies but little in its general character. 

 Altliough at many points so solid and tenacious as to render it difficult to detach 

 a specimen, it cleaves and crumbles into prismatic fragments upon the least 

 change from wet to dry. It is unsafe to walk near the edge of the vertical face 

 washed by the ripple of the river, and it is rarely necessary to wait more than 

 a few minutes for the splash which announces the fall of another prismatic frag- 

 ment. At a point about a quarter of a mile above Fontania, exfoliation by drying 

 takes place to such an extraordinary extent, as to raise the level surface of the 

 stratum into dark-tinted hillocks of loose material, which excite the curiosity of 

 passers-by on the river. There occur in this stratum flattened ferruginous concre- 

 tions, of mcnilitic forms, smooth and of concentric structure — a ferruginous clay- 

 stone; also a few very distinct impressions of leaves. 



In the upper portion of this stratum, near the southern end of the exposure, there 

 occur abundantly, chiefly on the stratification lines, strings of calcareous nodules. 

 These are sometimes hard and crystalline, but mostly rather of the character of 

 Agaric mineral ; of a flattened shape, and often of concentric structure, and quite 

 diff'erent from the contorted "Loess puppets" of the Bluft' formation. Fragments 

 of sticks and impressions of leaves occur occasionally, hut so far as observed, no 

 trace of zoogene fossils. 



No. 3, the interesting fossiliferous stratum, is extremely variable both in com- 

 position and thickness. It first appears near the northern end of the outcrop, as 

 a narrow band of purplish-gray, semi-indurate silt, containing lignitized sticks and 

 leaves. As its thickness increases, its composition becomes more variable, and at 

 tlie first of the profiles given above, it is clearly an ancient sandbar. Farther 

 south, near the upper steamboat landing, it takes the character of a swamp deposit, 

 consisting of heavy, dark-tinted clays and lignite bands, regularly stratified, and 

 about eight feet thick. Again, at the locality of the second profile, we find it 

 formed of a white, indurate silt, without a trace of vegetable remains. But lower 

 down, a dark-colored band appears at its base, and in this we find, imbedded in a 

 mixture of sandy clay and swamp muck, the acorns of Quercus aquadca, nuts of 

 Far/us sylvatica' iind Carya aquatica? burrs of Plnus twda, Taxodium distichum and 

 Llquldamhar styracifitia., the most abundant trees of the present swamps. The 

 leaves (except some of the bottom pine) are too much decayed to be recognized. 



Still farther down, near Fontania, the stratum resumes the character of a river 

 alluvion — sandy deposits showing the sandbar bedding-lines, filled with drift-wood 

 of large size and a great variety of species. Amongst these, the cypress is perhaps 

 the most abundant ; but oaks, pine, hickory, Cottonwood, ash, and beech appear all 



