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DAVENPORT ACADEMY OF NATURAL SCIENCES. 



Geolog"ical Section of the Bluff at East Davenport. 



BY \V. H. PRATT. 



At the foot of Mississippi avenue, East Davenport, the street ex- 

 cavations and quaiTving have exposed a section which has attracted 

 some attention, especially on account of the fossils found there. 



a. Upper Helderberp Limestone. 



b. Gravel bed. 



c. Clay and saud. 



1. Low water level Missi-ssippi Uiver. 

 li. High water level, 

 s. Front street. 



[SCALE, fid KEKT TO THK IXr-H.] 



The hard non-fossiliferous Upper Helderberg limestone, (a) which 

 there forms the river bed, extends upward to a heiarht of about Ho 

 feet above low water mark. 



Front street passes this point (jn a terrace of this njck, covered by 

 three or four feet of soil, at the height of 37 feet above the same line, 

 and the top of the ledge is 25 or 30 feet higher. 



The upper portion of the rock is much broken, containing water- 

 worn cavities and crevices filled with clay and sand, but lower down 

 it is more solid and regular, exhibiting, however, scarcely any seams 

 tf) facilitate the quarrying. 



Immediately overlying this rock (the upper surface of which is un- 

 even) is a bed of gravel (b) of perhaps an average thickness of eight 

 or ten feet, and over this a mixture of sand and clay, (c) the lower 

 part being more sandy and the upper more clayey, to the depth of 

 30 to 40 feet, forming a ridge extending thus abruptly toward the 

 the river (southward) and sloping off at a short distance both east and 

 west. 



The upper surface of the gravel bed is not well defined but consid- 

 erably intermingled with the clay and interstratified in small beds. 

 The gravel drift contains a considerable variety of carboniferous fos- 

 sils, of which we have identified the following, viz : 



