526 IOWA ACADEMY OF SCIENCE Vol. XXV, 1918 



is seen outcropping at a nunil)er of places in the bank adjacent 

 the wagon road with a few exposures of the limestone ledge 

 above it. In tliis distance one of the rare exposures in the ]\Iis- 

 souri river bluffs of the Aftonian gravel bed was noted in the 

 ditch along the roadside. Besides the usual diabase and quartz- 

 itic gravel there were several bowlders of Sioux quartzite up to 

 six inches in diameter, and one of gray granite at least one foot in 

 its greatest dimension. The wagon road leaves the bluffs and 

 turns wesit and then north on the bottom lands tor three-fourths 

 of a mile before it again reaches the bluffs. In this distance the 

 , bluffs were carefully searched for outcrops but none were found. 

 In the l>luff at the residence of Chas. Bald^^^n at an elevation 

 of about twenty-five feet above the wagon road the same strata 

 traced for four miles from the Baylor farm are again found im- 

 mediately south of the fault line. Udden's Section XIII was evi- 

 dently taken at this place when the quarry was in operation. As 

 the strata were better exposed at that time than at present his 

 section will be given in full with his lithogical descriptions. 



XTII. SECTION OF THE UPPER PART OF THE EXPOSURE IN 



BLUFF NEAR THE NORTHWEST CORNER OF SEC. 26, 



SCOTT TOWNSHIP, FREMONT COUNTY. 



Feet 



4. A dark bluish limestone of fine texture along some layers 



ond along other seams almost wholly made up of very small and 



thin shell fragments, lying flat, barely visible under a good hand 



lens; thin and wavy plates of cone in cone and fibrous calcite 



occur in this ledge 2 



3. Shaly silt ■. 1 



2. Dark gray, in places brownish, limestone, with some fossils. 

 A ground specimen is seen to consist of thin pieces of shells, 1 

 to 3 millimeters across, lying fiat in a sparse matrix holding a 



few small quartz grains % 



1. An arenaceous and calcareous rock of fine texture and of 

 bluish color, consisting of a siliceous, well assorted silt or sand 

 imbedded in calcareous material. It contains frequent specimens 

 of a Cythere, also a Fenestella, other bryozoa, and fragments of 

 brachiopod shells 2 V^ 



Both the limestone and sandstone weather into irregular slabs 

 with a rough granular surfa<ie, a good example of which is shown 

 in figure 41 of Volume 17, Iowa Geological Survey, giving a view 

 of the retaining wall in front of Chas. Baldwin 's residence. This 

 ledge of limestone and sandstone was not named in Condra and 

 Bengtson's Nel)raska report. While reluctant to add to an over- 

 burdened terminology^ the writer would suggest the name Ne- 

 braska City ledge for this double ledge. The type section is the 



