XIV 



BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Page 

 Stose and Jonas : 



Figure 4 — Solution crevice in white marble of the Ledger dolomite 

 tilled with limestone breccia at base of Conestoga 



limestone 512 



" 5 — Closer view of limestone breccia at base of the Cones- 



toga limestone in solution crevice in white marble of 



Ledger dolomite. 512 



6 — Rapid change in character of sediment of the Conestoga 



limestone ; also bed of conglomerate 513 



" 7 — Thick-bedded granular dolomite passing into finely lami- 

 nated impure ribbed limestone typical of the Cones- 

 toga limestone 513 



" 8 — Thick bed of limestone conglomerate with underlying 



thin-bedded dark calcareous slate of the Conestoga 

 limestone unconformable on massive Ledger dolomite. 515 

 " 9 — Thinly laminated impure limestone characteristic of the 



Conestoga limestone 515 



" 10 — Closely folded and fluted gray and white banded mica- 

 ceous marble of the Conestoga limestone in a small 



overturned syneline 516 



" 11 — Fossiliferous beds in the Conestoga limestone 516 



'' 12 — Geologic map of Chester Valley in the vicinity of Coates- 



ville 518 



" 13 — Geologic map of Chester Valley in the vicinity of Down- 



ingtown 519 



" 14 — Early sedimentation'. 522 



" 15 — Early uplift and erosion 522 



" 16 — Later Ordovician sedimentation and overlap 523 



" 17 — Later folding, uplift, and erosion 523 



Nelson : 



Figure 1 — Geologic section across Missionary Ridge 529 



2— Bed of bentonite 530 



" 3 — Diagrammatic sketch of west side of Isabella Stewart 



bauxite mine 531 



" 4 — West side of the present Isabella Stewart bauxite mine 532 



Gould : 



Figure 1 — Location of occurrences of crystalline rocks on the 



Plains 542 



" 2 — Relation of hypothetical Balcones-Arkansas-Ohio Valley 



line of weakness to adjacent masses ; also exposures 



of igneous rock 546 



" 3 — Location of buried granite ridges in Kansas. Oklahoma, 



and Texas ; also location of wells which have reached 



granite 554 



Ugix)w : 



Figure 1 — Key map of area studied 563 



" 2 — Sketch map of portion of North Thompson Trench 565 



" 3— North Thompson Trench from Skull Hill 566 



" 4 — North Thompson River at Chu Chua 567 



