Maryland Geological Survey 445 



LOCAL SECTIOXS OF THE UPPER DEVONIAX ' 



THE JENXINGS FORMATION 



The Jennings formation outcrops in a nmnber of narrow areas, the 

 longer axes of which trend northeast and southwest, jiarallel to the Ap- 

 palachian Mountains. At least one and where possible several sections 

 have been studied in each area.'' 



Marked differences exist between the strata east and west of Wills 

 Mountain. In the following discussion, therefore, the sections east of 

 Wills Mountain have been grouped in one division and those west of 

 Wills Mountain in another. The various sections of each area are brought 

 together, while the areas are considered in order from east to west."" 



Sections East of Wills Mountain 



I. Section East of Millstone* 



An extended section of the Jennings is exposed east of the village of 

 Millstone, beginning at the Eomney-Jennings contact in the village and 

 extending eastward along the National Road and in the cuts of the 

 Western Maryland Railroad which parallels that road, for a distance of 

 6500 feet. It ends at the axis of the syncline in which the strata are con- 

 tained. The lower part of the section is partially concealed and is so 

 complicated by minor folds that the measurements of it are not deemed 

 trustworthy and hence are not employed in the discussion. A bed 

 occurring 2706 feet east of the beginning of the section and abounding in 

 Caviar otceckia congregata var. ■par'kheadensis is taken as a datum plane 

 and is placed at an altitude of 1600 feet above the base of the Jennings, 



* Contributed by Charles K. Swartz. 



^ Graphic sections are shown on pi. vi (In pocket at end of volume). 



' The writer is greatly indebted to D. W. Ohern, T. P. Maynard, and J. T. 

 Singewald, Jr., for assistance in the study of the sections described in this 

 chapter. The sections in large part were first measured, described, and the 

 fossils collected by Ohern and Maynard. The critical points were then studied 

 in detail by the writer, who alone is responsible for the conclusions presented. 



'Measured by pacing. The strike of rocks is taken as N. ."55° E. through- 

 out the entire calculation. 



