abstracts: geology 421 



In the location of oil pools from geologic examinations of the surface, 

 structure is the one factor, of the several controlling the accumulation 

 of oil, which can be determined. Other important factors are: (1) The 

 thickness, number, and positions of beds which contain or have contained 

 the organic material from which the oil and gas were derived; (2) the 

 stratigraphic relation of beds carrying salt water to those in which the 

 oil and gas originated; (3) the thickness, variability, and stratigraphic 

 positions of porous lenses, or irregular beds of sand, that may serve as 

 reservoirs; and (4) the structural changes through which these beds 

 have passed since they were deposited. The effectiveness of the combi- 

 nation of these various factors in the production of oil pools in any given 

 localitj^ can be determined only by the drill, but drilling is to be under- 

 taken only in localities at which the structure is favorable. 



The old anticlinal theory based on the idea that oil and gas accumu- 

 lations are due to differences in the specific gravity of gas, oil, and salt 

 water, seems inadequate to explain the facts as observed. It is believed 

 by the author that the accumulation of oil and gas in pools is due to the 

 action of large bodies of water moving under both hydrostatic and cap- 

 illary pressure. C. H. Wegemann. 



GEOLOGY. — Erosion and sedimentation in Chesapeake Bay around the 

 mouth of Choptank River. J. Fred. Hunter. U. S. Geological Sur- 

 vey Professional Paper 9Q-B. Pp. 7-15, with map and figure. 

 May 23, 1914. 

 This work is a result of a comparison of a small portion of two separate 

 topographic and hydrographic surveys of the Chesapeake Bay made by 

 the United States Coast and Geodetic Survey, one in 1847-48, and a 

 second, over a half century later, in 1900-01. A third supplementary 

 topographic survey of a part of the area studied was made in 1910 by the 

 author and C. C. Yates. It is demonstrated that very significant 

 changes, both in the topography and in the hydrography of the region, 

 have taken place, and quantitative data on the amount and rate of ero- 

 sion and sedimentation in a representative area of the bay are presented. 

 The three islands at the mouth of Choptank River are being rapidly 

 cut away and Sharps Island, whose north end has suffered a loss of 1 10 feet 

 per year during the last ten years, will probably be entirely effaced before 

 1950. Practically all the erosion has been on the west and north sides 

 of the islands; that is, on the shores which are most open to the attack 

 of the southerly bay currents and the westerly winds and their waves. 



