232 J. C. Branner — Paleozoic Sediments in Arkansas* 



Beginning at the base of the Lower Coal Measures rocks 

 southwest of Little Kock where they rest directly upon the 

 Silurian novaculites, and going across the strike, nearly due 

 north, to the Big Rock syncline whose axis crosses the 

 Arkansas River two miles above Little Rock, we have a series 

 of sandstones and clay shales, the latter predominating. The 

 rocks all have very steep, almost vertical north dips except 

 near the axis of the syncline ; this belt is from three to four 

 and a half miles wide. If they are not faulted or overturned, 

 these beds have a thickness of something more than 16,000 

 feet. It is not improbable that they are faulted, however, for 

 they are mostly clay shales, with an abundance of large quartz 

 veins, and the beds exposed at the " little rock " on the river 

 bank at Little Rock are much crushed aud distorted ; faulting 

 in this case must have tended to conceal a part of the true 

 thickness of the rocks. 



About four and a half miles north of the Big Rock axis is 

 another syncline whose uppermost beds are at about the same 

 horizon as those at Big Rock. The same beds are again 

 exposed in a third syncline — the Cato syncline — fourteen miles 

 north of Little Rock. The Cato synclinal axis is shown on the 

 accompanying plate (p. 233). It lies east-west, and at its west- 

 ern extremity turns northward and ends in the Round Mountain. 

 The rocks exposed at the axis of this syncline are at or very 

 near the same horizon as those at the axis of the Big Rock 

 syncline, so that we are here apparently no higher geologically 

 than at Big Rock. Fortunately the geology hereabout and 

 especially from Cato north to the Bayou Meto anticline, west 

 to Round Mountain and thence to the Cadron anticline, north 

 of Con way, is so plain that there can be no serious doubt about 

 the thickness calculated for the several beds. An examination 

 of the accompanying figure will, I believe, make this evident."^ 



The rocks are alternate beds of sandstone and shale, and 

 erosion has developed a striking system of sandstone ridges and 

 shale valleys : in some places these valleys and ridges may be 

 traced for fifty miles, doubling back and forth upon them- 

 selves. The directions and continuity of the many sandstone 

 ridges show that there can be no considerable faults or over- 

 turns. 



From the top rocks of the Cato syncline (A on map, p. 

 233) to the bottom rocks of the Bayou Meto anticline (B on 

 map) the rocks exposed have a total thickness of 14,900 feet. 



But the top of the syncline at the starting point has been 



* The details of the geology in the region represented on the figure were 

 worked out by Mr. John B. Means and the figure was taken from his vahiable map. 

 Mr. Means has prepared a report upon the Lower Coal Measures area of Arkan- 

 sas, but thus far the State has not published it. 



