376 The TJprER Devonian Deposits of Maryland 



The conglomerate or grit has also been called the top of the Jennings 

 formation M'hich indicates that there was a change in the deptli of water 

 and so a physical modification ; but it is not certain that all these conglom- 

 erates occur at precisely the same horizon. It is known that in Garrett 

 County there are at least two and probably other horizons. At least the 

 Chemung fauna continues above the conglomerates both in the western 

 part of Allegany County and Garrett County and since this shows that 

 the rocks succeeding a conglomerate for a thickness of about 550 feet are 

 of Chemung age it appears better to class this upper division in the 

 Jennings formation. Succeeding this horizon the rocks are mainly red 

 shales and sandstones which belong in the Catskill formation. The 

 first of the reds begins considerably lower in most of the sections 

 but as long as Chemung fossils occur in considerable abundance the 

 rocks have been classed in the Jennings formation. It will be seen 

 from the above statements that there is a gradual change in lithological 

 appearance between the Jennings and Catskill formations so that it is 

 difficult in this particular to draw a sharp line of division between them. 

 Again there is probably some difference of position in the horizons at 

 which the last Chemung fossils were collected; but upon the whole it is 

 thought that this method of division is the most satisfactory one that 

 can be used in separating these formations. 



Exposure on Braddock Run. — Four miles or more south of Jennings 

 Eun the Allegany Front is deeply cut by Braddock Eun in which gorge in 

 the cuts of the two railroads which follow it, are frequent exposures of the 

 same formations shown in Jennings Eun. That portion of the Allegany 

 Front to the north of Braddock Eun is known as Piney Mountain, and to 

 the south is Dans Mountain which when seen from the east is the most 

 conspicuous mountain slope in western Maryland. Unfortunately for the 

 geologist it is well timbered and the slope mostly covered so that the 

 several formations composing it are largely mantled. There are from the 

 crest line of both Piney and Dans mountains magnificent views of the 

 country to the south and east, and one of the most favorable and popular 

 localities is known as Dans Eock on Dans Mountain 5 miles southeast of 

 Frostburg. 



