BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 11, pp. 207-216, pls. 18-19 April 6, 1900 



FAULT SCARP IN THE LEPINI MOUNTAINS, ITALY 



BY W. M. DAVIS 



{Read before the Society December 27, 1899) 

 CONTENTS 



Page 



The approach from Rome 207 



Local geology 208 



The mountain front 208 



The rock fans 209 



The piedmont slope 212 



The fault scarp 213 



The Approach from Rome 



The express trains from Rome to Naples begin their journey with an 

 oblique ascent of the long northern slope by which the ancient Alban vol- 

 canic group descends to the Campagna, and thus gain the flat pass near 

 Palestrina, between the old volcanoes and the limestone range on the 

 east. On the way, while crossing the radiating spurs and valleys of the 

 northern slope, fine views are opened on Rome and the Campagna from 

 the embankments, and excellent sections of lava flows and stratified 

 tuffs are shown in the cuttings. In two of the latter the lava beds may 

 be seen in section lying in a broad flat trough of tufaceous shale, and 

 thus indicating that since these lavas were poured down between low 

 radiating ridges on the flanks of the volcano, the ridges have been worn 

 away to produce the existing valleys — an inversion of topography well 

 known to be characteristic of such situations. 



The pass by Palestrina is crossed in a long and deep cut by which the 

 summit level is somewhat reduced ; then the train begins a rapid descent, 

 and as one looks forward on the right he may soon see the Lepini moun- 

 tains, a well dissected, plateau-like mass, rising in the distance. As the 

 journey is continued, the mountains are perceived to descend by a strong 

 northeastward slope to the broadly aggraded valley floor of the Sacco, a 

 rich agricultural plain, annually spaded over (plows seem to be unknown) 



XXX— Bull. Geol. Soc. Am., Vol. 11, 1899 (207) 



