508 



LOCAL SECTIONS 



From Davenport to Rockingham the white compact limestone prevails nearly the 

 whole distance, forming sometimes low perpendicular walls, four to ten feet high, 

 and sometimes gradually sloping banks down to the margin of the Mississippi. 



The shores are here frequently lined with boulders, some of which are four feet 

 in diameter. The hills rise to the height of one hundred and fifty feet, presenting 

 a gentle inclination, with vegetation extending down to the water-level ; so that no 

 rocks are visible except in the above quarry. 



It is not until reaching a creek,, half a mile below Rockingham, that the rocks 

 can be studied. Here an argillaceous limestone crops out in thin shaly layers, nine 

 feet above the water, disintegrating by exposure. In the debris, many good fossils 

 can be found, of the following species : Atrypa reticularis, A. aspera, Terebrahda 

 concinna, Spiri/er eurutein.es, S. granulifera, S. heteroclites, Ortlvis resupinata, Lep- 

 tcena inequistriata (?), Ghonetes nana, Phacops rnacrqphihalina, Favosites spongites, 

 and F. polymorplia. 



At the mouth of the next creek emptying into the Mississippi, along with many 

 of the above species occur, Olivanites Yerneuilii, Pliacops crassimarginata, Pleuro- 

 rhynchus alaiformis, Astraa ananas, and A. hexagonum. 



About three hundred yards up the first of these creeks is an outcrop of coal, 

 enclosed between ledges of limestone of Devonian date, thus : 



/. Devonian limestone] eighteen feet, c, <;'. Coal, nine feet above creek. Talus, s. Sbale. V. Devonian liineptoue, eleven feet. 



The limestone is hardly twenty feet from the coal, and rises, a little below, to the 

 height of twenty-three feet. The coal is two and a half feet thick, and reposes on 

 ash-coloured clay, with dark, thinly-laminated shale over it, six to eight inches thick. 



Fifty to sixty yards above this place, there is another coal exposure, occupying a 

 similar fault in this limestone formation. At both localities the limestones contain 

 fossils, the same as those previously enumerated as occurring in the ledges at the 

 mouth of the creek. 



The coal is of inferior quality, being much impregnated with pyrites. Outcrops 

 of the same seam of coal have been discovered at several other places in the vicinity. 



At New Buffalo, these limestones of the Devonian System are again to be seen, 

 and are exposed for about five miles on the north side of the Mississippi, varying 

 from five to twelve feet in height, the hills back from the river being from seventy 

 to one hundred feet in elevation ; and one mile above Pine Creek, coal appears 

 again, twenty inches in thickness, in the following relation to the associate rocks, 

 No. 1 being the lowest. 



Feet. Inches. 



1. Limestone (ferruginous), containing Atrypa reticularis, A. aspera, 



Spiri/er eiiruteines, and other Devonian species, . . 20 



2. Light yellow clay, ...... 15 



3. Dark, thinly laminated shale, ..... 1 



4. Coal, ........ 20 



5. Coarse and fine sandstone, thickness not seen. 



