352 The Upper Devonian Deposits of Maryland 



In the northern part of Garrett County are numerous loose blocks of 

 white quartz, flat pebble conglomerate, some of which, contain jasper 

 pebbles, as shown on the National Eoad about 5 miles from Frostburg on 

 the Graham farm, on the Frostburg-Salisbury Eoad near the Baker house, 

 and to the south of the jSTational Eoad on Pea Ridge near Avilton. The 

 pebbles in these blocks are evenly broken so that there is a smooth fracture 

 similar to that of the flat pebble conglomerate in the Oakland region and 

 the one found in place 1% miles south of Avilton opposite the house of 

 Mr. John Eobinson. The jasper pebbles, however, are infrequent in the 

 more southern localities just mentioned and the waiter is not certain that 

 the two conglomerates are identical. Professor Stevenson in the descrip- 

 tion of his upper conglomerate of Bedford County mentioned rounded and 

 flattened pebbles of white quartz,^ but apparently none of jasper; while 

 Dr. I. C. White in describing what he considered as the same conglomerate 

 in Huntingdon County distinctly called attention to " its red jasper ( ?) 

 pebbles." '' Professor Stevenson also stated that the upper conglomerate 

 in Bedford County had " films of quartz in the joints " ^ which the writer 

 believes is likewise true of the Garrett County conglomerate and Dr. Mar- 

 tin has noted that the joints of the Maryland conglomerate " are frequently 

 coated with drusy quartz." * It is not improbable that further study 

 may show that the flat pebble, jasper conglomerate of Garrett County 

 is identical with Stevenson's upper conglomerate of Pennsylvania. 



The flat pebble, jasper conglomerate of northern Garrett County is 

 named the Avilton conglomerate on account of its occurrence near the 

 post-office of that name on Pea Eidge. The flat pebble, white quartz con- 

 glomerate found farther south on Pea Eidge, frequently in the Oakland- 

 Mountain Lake Park district and to the south of Mountain Lake Park 

 and Oakland probably belongs to the same horizon although the writer was 

 unable to demonstrate it to his satisfaction. These conglomerates appar- 

 ently occur much below the top of the Jennings formation and their bould- 

 ers as stated by Dr. Martin " are found along a more or less distinct line of 



" T^ p. 79. 

 ' T», p. 93. 

 » T^ p. 79. 

 *Md. Geol. Surv., Garrett Co., p. 87. 



