abstracts: geology is:; 



GEOLOGY. — Geology and underground waters of northeastern Texas. 

 C. H. Gordon. Water-Supply Paper U. S. Geological Survey 

 No. 276. Pp. 78, with maps, sections, and views. 1911. 



Geologic formations that outcrop are (1) upper Cretaceous, 

 (2) lower Tertiary, and (3) surficial deposits. In addition there are 

 sands, silts, and clays of Pleistocene age and the flood-plain deposits 

 of the present streams. Seven water-bearing horizons have been recog- 

 nized, ranging in age from lower Cretaceous to Eocene. 



Warping of the old Jurassic land-surface, which preceded and accom- 

 panied the deposition of later formations, gave the beds a gentle slope 

 toward the Gulf of about 55 feet per mile. 



Upon the upper Cretaceous beds in the south half of the district, 

 without recognized stratigraphic break, lie sands, clays, and ferruginous 

 sandstones belonging to the Eocene. At the beginning of the Eocene 

 slight warping enlarged the Mississippi embayment, causing overlap 

 of early Eocene beds upon the Cretaceous contemporaneous with marked 

 change in fauna. During Eocene time near-shore or swampy condi- 

 tions prevailed with an occasional submergence by the ocean. No Oli- 

 gocene or Miocene deposits have been recognized. The Miocene was 

 essentially a period of erosion, and if deposits of Oligocene age were laid 

 down they were afterwards removed. During the Pliocene a mantle 

 of sand, silt, and gravel was* spread over the eroded surface, and was in 

 turn eroded. Further Pleistocene deposition succeeded, giving rise 

 to marine and fluviatile (Port Hudson formation) deposits. Erosion 

 followed again, leaving the present flood plains and principal terrace-. 



H. D. McCaskey. 



GEOLOGY.— Sewickley, Pa., Folio. M. J. Munn. Geologic Atlas of 

 the United States, No. 176. Pp. 16, with maps and sections. 

 U. S. Geological Survey. 1911. 



Outcropping formations include the Allegheny, Conemaugh and Mo- 

 nongahela, of the Pennsylvanian series of the Carboniferous, and 

 aggregate about 800 feet in thickness. Deep borings indicate 

 1200 feet of underlying Devonian and Carboniferous strata. The 

 dip is south-southeast, at about 50 feet to the mile. Detailed study 

 of the oil sands indicates greater folding in the older buried beds 

 than in those above. It is suggested that the pre-Pottsville rocks were 

 slightly folded during the early Pottsville uplift, developing lines of 

 weakness followed by the post-Carboniferous folds. The Pleistocene 

 is represented by four terrace formations, of which all but the oldest 

 are outwash glacial gravels. H. D. McCaskey. 



