746 ABSTRACTS OF PAPERS 



Triassic deposits of eastern and western North America, though those of west- 

 ern Europe may perhaps come in part under the first group. 



The distinction between marine and continental types of cross-bedding is 

 not easy, chiefly because our observations are too limited. We have, how- 

 ever, the following: Hobbs has shown that cross-bedding of a torrential de- 

 posit, such as the Guadix and related formations of comparatively recent ori- 

 gin, consists of a series of diagonal and horizontal beds many times repeated, 

 and the diagonal beds all dipping in some one direction, while the successive 

 horizontal and diagonal series are of moderate thickness, perhaps not over 6 or 8 

 feet, and not much less. Such cross-bedding has not yet been described from 

 undoubted marine strata, nor is it conceivable how it can be formed under the 

 sea. Walter Huntington and others have shown that the cross-bedding, with 

 the successive series dipping in all directions and separated by erosion planes, 

 is characteristic of eolian deposits due to migrating ripple-marks, and can pro- 

 duce this structure on a large scale under the sea, except in sand-bars, when it 

 would have only a linear extent. So far, then, as we now know, cross-bedding 

 on a large scale, except when of only lineal or limited extent, is character- 

 istic of continental deposits. Fossiliferous eolian deposits are illustrated by 

 the Lunegarth limestone. 



STRUCTURE OF ESKER FANS EXPERIMENTALLY STUDIED 

 BY T. A. JAGGAB, JR. 



(Abstract) 



Deltas formed by miniature cavern torrents were shown and cross-sections 

 made by slicing them. The conclusions arrived at concern the effects of sheet- 

 floods, of a raised or lowered lagoon level, of variation in load of detritus and 

 variations in velocity and volume of current. These effects appear in the sym- 

 metry and asymmetry of ground plan of deltas and in the relations of topset 

 and foreset beds. 



EFFECT OF RAPID OFFSHORE DEEPENING ON LAKE-SHORE DEPOSITS 



BY RUFUS MATHER BAGG, JR. 

 (Adsti'OCt) 



Local beach pebble deposits on the shore of Little Sister Bay, near Ephraim, 

 Wisconsin, on the east side of Green Bay. consist of Silurian (Niagara) lime- 

 stone pebbles beautifully rounded by wave action in a protected cove, where the 

 water grows deep very rapidly offshore. No similar occurrence is to be found 

 anywhere in the immediate neighborhood along this shore where similar con- 

 ditions prevail. In all other sections the flat limestone fragments remain in 

 more or less of their original condition or but slightly water-worn. 



STRUCTURE OF THE IIELDERBERG FRONT 

 BY A. W. GRABAU 



(Abstract) 



The Ilelderberg front is the northern extension of the westernmost belt of 

 the Appalachian folded area, left after extensive erosion. The former extent 



