210 The American Geologist. March, 1894 
which, from their lithological character and the few fossils collected, 
would appear to correspond to Gabb's mesa sandstones and to be of 
probable Eocene age. Though not observed in immediate superposi- 
tion over the Chico-Tejon beds, the general altitude of both series leads 
to the opinion that no considerable movement could have intervened 
between the periods of their respective depositions. 
The mesa sandstones and possibly also the Chico-Tejon beds once 
extended entirely across the peninsula, covering all but the highest 
peaks of preexisting mountain ranges. Since the emergence of these 
beds there has been extensive erosion, and during a subsequent sub- 
sidence later beds of Pliocene or post-Pliocene age have been deposited 
in the canons and interior valleys, and the tops of the plateaus have 
been baselevelled at a slight angle with the bedding of the older beds. 
Evidence of recent elevation of the peninsula is found in delta plains 
and wave-cut terraces along the coast at various elevations, strewn 
with recent marine shells. 
The underlying or buried mountain ranges, as far as shown by erosion, 
disclose a general structural resemblance to the Peninsula Sierra 
further north, as described by Lindgren. They consist of a western 
range formed of porphyries, diabases, diorites and dioritic granites break- 
ing through steeply upturned and highly metamorphosed sedimentary 
beds, and an eastern range with a short and abrupt descent to the gulf 
coast, consisting of granite andmetamorphicsedimentaries, with broad, 
elevated, longitudinal valleys separating the two ranges. The strike of 
the sedimentaries and the trend of the minor orographic features of 
the ranges appear to run more to the west of north than the general 
trend of the peninsula. 
It is suggested therefore that in the broader features of orographic 
structure, the Peninsula Sierra is a representative of the Sierra Ne- 
vada,-set off en echelon to the southwest, and gradually passing out 
into and sinking under the ocean. The present depressions of the Gulf 
of California and the deserts to the north appear to be representatives 
of the Great Basin of Nevada, and like that to have been once elevated 
regions separating the Mesozoic seas of the west from the Gulf of 
Mexico, thus accounting for the faunal differences in the Cretaceous 
rocks of California and of Mexico. 
29. Origin and classification of the greensands of New Jersey. 
William B. Clark, Baltimore, Md. (Read in abstract by Prof. W. M. 
Davis.) This paper embodied a discussion of the conditions under 
which greensand is formed upon the floor of existing seas and a descrip- 
tion of such deposits. The striking resemblance which the New Jersey 
strata bear to them was pointed out. together with certain physical 
changes which took place during the period of their deposition. A 
classification, based upon a study of four type sections across the state, 
was suggested for the several formations represented, although the 
older terms were retained as economic equivalents. (The same author 
somewhat fully discusses this subject in his "Preliminary Report on 
the Cretaceous and Tertiary formations of New Jersev," forming pages 
167 245 in the Annual Report of the Geol. Survey of N. J. for 1892.) 
30. Crustal adjustment in the upper Mississippi basin. Charles 
R. Keyes, Des Moines, Iowa. (Read by title.) Attention was called to 
the fact that throughout the Iowa coal field there exist numerous faultR 
of small throw. Many of these are quite close together and form well 
marked step-faults. Ordinarily it would be impossible to recognize 
most of these ruptures and slippings except when disclosed bv fortunate 
excavations. Through the extensive working, however, of compara- 
tively thin beds they are capable to be made out. From a careful ex- 
amination of the large number of these faults it would anpear that th« 
adjustment of the tension in the flat-lying strata of the Mississippi 
basin is, as in mountainous regions, carried on largely by means of many 
