118 Ziegler — Siliceous Oolites of Central Pennsylvania. 



All of the oolite layers in this horizon are fairly definite, and 

 are exposed for about ten or fifteen feet along the bedding 

 planes. Over this distance they maintain a fairly uniform 

 character and thickness. Layers Nos. 1, -4, and 6 show con- 

 temporaneous erosion of some oolite horizon, and its redepo- 

 sition in a limestone matrix in layer No. 1, and in an oolite 



Fig. 



Fig. 3. 



- . - , I — . — i II 



1 1 ; 1 1 — ! 



— II — 1 - i - |— | — |- 



1 — 1 ! ~3f 1 ' - 1 1 1 



^7- 1 1 



1 1 I /» / 1 1 



e e o o o oeoo© ~ o o oo G o°eo G G 



i i \/y i i i i 



ll \ rJ \ i i i 



ii \k c i \ ii 



-1 - i ; L a / I - I I I 



1 1 ii 1 II 1 



1 V 1 1 1 1 



II 1 1 1 1 1 



1 II 1 1 



1 1 1 1 1 1 



1 1 1 1 III 



1 II III 



1 1 1 1 1 1 



III 1 III 



1 1 \ 1 1 1 



Fig. 2. Siliceous oolite layer on Spring Creek. 



Fig. 3. Fragment of siliceous oolite, coarse, showing included fragment 

 of limestone and of fine-grained siliceous oolite. 



horizon in the other two. No. 11 also shows contemporaneous 

 erosion, in this case, of one of the limestone layers. Fig. 2 

 shows the occurrence of oolite in No. 31, and fig. 3 a specimen 

 from layer No. 4, and shows the association of the two differ- 

 ent oolites. 



Petrographic description of the Oolites. — Several distinct 

 types of siliceous oolite exist in this area, and they will be de- 

 scribed in order. As may be noticed from the accompanying 

 map, the name of the locality is applied to the occurrence. 



Type One : the Filinore phase. — The specimens were col- 

 lected about one-and-one-half miles south of Filmore, and occur 

 here as loose fragments, and in one doubtful exposure. 



The oolites are here fairly variable in size and in shape, and 

 as a rule are mixed with many flat and lense-like grains, which 

 appear essentially like lentils, are somewhat imperfectly 

 cemented, and consist of quartz. The nucleus is in nearly all 

 cases a grain of quartz, usually of irregularly, rounded, and 

 elongated shape. Sphericity of grains is notably absent, and 



