SCIENCE. 



[N. S. Vol. V. No. 107. 



Notes on the Structure of the Cranberry District 

 in North Carolina. Arthur Keith, Wash- 

 ington, D. C. 



The paper opened with a sketcli of the 

 topography, drainage and geology of the 

 district. The latter involves seven mem- 

 bers below the Siluro-Ca.mbrian limestones. 

 Thej' are in general schists and gneisses 

 and Pre-Cambrian volcanics. A sketch 

 map was used to illustrate the faults of the 

 region. Great folds also intervene. Faults 

 occasionally show breccias and slicken- 

 sides, but these are not marked. Pressure 

 has caused metamorphism and schistosity. 

 Remarkable cases of sheared conglomerates 

 of quartz porphyry and granite pebbles 

 were exhibited. The phenomena gave 

 accurate data for determining the depths of 

 zones of crushing and flowage. A great shear 

 zone in an east and west line, with a pas- 

 sage of the southern part beyond the north- 

 ern, was described. The curious behavior 

 of sediments regarding the hard crystallines, 

 and their strange relations to them, if we 

 assume a simple case of compressive stress, 

 transmitted by the sediments, leads the au- 

 thor to believe in the upthrust of the crys- 

 tallines through and over the sediments. 



Note on the Stratigraphy of Certain Homogenous 

 Bocks. C. H. Hitchcock, Hanover, N. H. 

 The object of the note was to call atten- 

 tion to recent discoveries of obscure planes 

 of stratification cutting the cleavage at large 

 angles, as noted in two formations in the 

 upper Connecticut Valley. These discov- 

 eries will make it necessary to question the 

 reliability of many of the observations hith- 

 erto made as to the positions of the strata. 

 The speaker described an argillite and a 

 quartzite at Thetford, near Hanover, whose 

 true bedding he had been unable to dis- 

 cover until lately. Finally the true strati- 

 fication was identified in manj^ lines nearly 

 at right angles with the cleavage and as in- 

 dicated bjJ^ little quartz veins. Quartzite in 



another locality was also shown to have 

 suffered so much change that its stratifica- 

 tion was obliterated. Various examples 

 were further cited to bring out the rela- 

 tions of cleavage and stratification. In 

 discussion, Mr. Lane asked if the observa- 

 tions of Prof. Hitchcock and Mr. Keith 

 carried out Van Hise's rule that cleavages 

 cutting stratification at right angles indi- 

 cated the presence of synclines and anti- 

 clines. Messrs. Hitchcock and Keith re- 

 plied that so far as their observations went 

 they did. 



Unconformities in Martha's Vineyard and Block 

 Island. J. B. Woodworth, Cambridge, 

 Mass. 



Beginning below, plant-bearing beds of 

 Cretaceous age appear in both islands with- 

 out their base being exposed. On Martha's 

 Vineyard marine Cretaceous strata overlie 

 the plant beds; but contact has not been 

 worked out. Above the Cretaceous and on 

 an eroded surface rests the Miocene of Lyell 

 and Dall, composed of (a) the osseous con- 

 glomerate, (h) the green sand, (c) the yel- 

 lowish green sand. There was erosion in 

 the area between (a) and (6), probably 

 also between (6) and (c). Fragments of a 

 Pliocene formation have been detected at 

 Gay Head, but little is known regarding 

 it. A marked unconformity now appears 

 on Gay Head and Block Island at the base 

 of the lowest Pleistocene boulder formation. 

 The Miocene has been locally swept away 

 at Gay Head. On Block Island this early 

 Pleistocene rests upon the surface of the 

 Cretaceous white clays, the Miocene being 

 entirely unknown. There was probably 

 some folding of strata at Gay Head before 

 the deposition of this boulder bed. After 

 the deposition of from 25 to 50 feet of com- 

 pound gravels and sands, more folding took 

 place over Martha's Vineyard and Block 

 Island. The Mohegan Blufi" beds on Block 

 Island and the Tisbury beds on Martha's 



