38 IOWA ACADEMY OF SCIENCES. 



fragments they occur in the gravels of nearly all the region and in the beds of the 

 streams and brooks of the area covered by the Tertiary. Occasionally whole trunks 

 of trees are found, often partially buried in the sands or deeply imbedded in the 

 gravels which cover the flood plains of the creeks and ravines within the Tertiary 

 area and especially along Crowley's Ridge, from Helena to the Missouri line. 

 Specimens have been obtained from logs or stumps in sitit and in undisturbed Ter- 

 tiary beds at the following points: Hope, Hempstead county ; Camden, Ouachita 

 county; near Red Land, Cleveland county; at Red Bluff, Jefferson county; at 

 Helena, Forrest City. Wittsburg, Wynne, Harrisburg, Jonesboro, Gainesville, 

 Boydsville, and St. Francis in the country traversed by Crowley's Ridge in the 

 eastern part of the State, All of these localities have furnished examples of silic- 

 ified wood from large logs or stumps in place and always imbedded in Tertiary 

 sands or gravels. It is a remarkable fact that hitherto, in Arkansas, silicified 

 woods have been seen but very rarely in the Tertiary clays. At all the localities 

 mentioned above, except one, the wood is found only in gravels or sands in situ, 

 or in redeposited gravels and sands in the low valleys. 



The geological section of the Crowley's Ridge region, to which area this paper 

 especially refers, shows the following sequence, seen in the generalized section in 

 St. Francis county, which is characteristic for the southern portion. 



GENERALIZED SOUTHERN SBCTION ON LITTLE CROW CREEK. 



1. A loess soil, with enough sand to render it decidedly siliceous. This is the 

 surface member and is usually of but little depth. 



2. Typical loess, varying in depth froai thirty to ninety feet, eroding rapidly, 

 and presenting a characteristic loess top:graphy. This member caps the ridge 

 even at its highest points. 



.3. A clayey, pebble-bearing, bluish or otherwise dark colored loess clay which 

 forms the base of the typical loess deposits and probablv marks the first stage in the 

 loess deposition. This member varies somewhat in different localities, being often 

 quite thin and is even sometimes wanting. The pebbles are most abundant in the 

 lowermost portion. 



4. Orange-colored gravels, irregular in thickness, rudely stratified, sometimes 

 well assorted so that only coarse gravels, or vice versa, are seen ; there are occasional 

 pockets or lenses of sand derived from the underlying member. In rare instances 

 this bed lies directly under the clays. Silicified coniferous wood often occurs in 

 this member. 



5. Party-colored sands, of variable fineness, often quite irregularly stratitied, 

 sometimes overlying the pebble bed, but usually occurring underneath it. The 

 sand grains are well rounded. There are occasional masses or pockets of red, 

 drab, white, or yellow pipe clay. 



6. Blu(!, black ordrab clays, horizontally stratified, with small, sometimes larger,, 

 pieces of coniferous lignite. This member constitutes the greater portion of the 

 body of the ridge. Along its margin it is to be seen only in the deepest ravines, or 

 along the St. Francis and such of its small tributaries as flow from the ridge. _ It 

 is often penetrated in deep wells, as at Forrest City, and underlies the whole region. 

 The lower exposed portion is fossiliferous. the fossils are marine, and Claibornian 

 in age. The clays are, therefore, Eocene Tertiary. 



Slight differences in the section appear in various portions of the ridge, but are 

 not worthy of remark in this connection. The generalized section for the northern 

 portion of the ridge, made at a point seventy-five miles north of St. Francis 

 county, shows the following sequence: 



GENERALIZED NORTHERN SECTION NEAR G AINIiSVILLE, GREENE COUNTY. 



1. A humus, largely siliceous, or a soil mainly sand. At the highest hilltops 

 this soil contains gravel or may be entirely replaced by waterworn gravel. 



2. Gravel bed, commonly removed by erosion. 



