4<02 Mr. Murchison on the Tertiary andSecoiidary Rocks 



Apennines they fully rival in thickness our most important 

 secondary formations in England. This particular group, 

 however, near Bassaiio, is not offered as a type of all the other 

 tertiary deposits of the north of Italy, where their variable 

 characters may still form the subject of other communications 

 from Mr. Lyell and myself. 



The tertiary or subalpine deposits, which to the west of the 

 Brenta are so much traversed by basaltic and trap rocks, are 

 entirely free from them in this district between the rivers Brenta 

 and Piave, where they swell into hills of considerable impor- 

 tance, occupying between Asolo and Possagno a breadth of 

 four or five miles. Here, as in many other parts of the north 

 of Italy, they form two great natural divisions : — 



1st. An exterior zone composed of conglomerates, with sub- 

 ordinate beds of yellow sand and blue marl, containing shells, 

 the greater number of which are found in the subapennine 

 formations described by Brocchi, and amongst which a con- 

 siderable pi'oportion of the species are identical with those of 

 the present sea*. 



2ndly. An inferior system of green and yellow calcareous 

 sandstone, blue shell marl and compact limestone, some of 

 which are distinguished by nummulites. These latter beds rest 

 upon the scaglia (or equivalent of the chalk), which rising into 

 the Alps passes into a dolomitic limestone of the oolitic series. 



Explanatory of these relations, I now proceed to detail two 

 sections in a descending order : the first from Asolo f to Pos- 

 sagno at the foot of the Alps ; the second from Bassano to Cam- 

 pese at the mouth of the Canal di Brenta, where that river 

 issues from the Tyrol. 



I. The tertiary conglomerates rise from the plains of Venice, 

 about a mile and a half south of Asolo, at an angle of about 

 20° to 25°, dip S.S.E. ; and to the north of that place they 

 reach to the height of at least seven hundred to eight hundred 

 feet above the level of the Adriatic. The angle of their in- 

 clination increases with their altitude ; and the mountain tor- 

 rents flowing from north to south, expose many of these beds 

 dipping even as high as 40° S.S.E. 



The boulders contained in these rocks are of very great size 



* This zone is the equivalent of the subalpine conglomerates and marls 

 near Nice, which Mr. Risso was the first to identify with the subapennine 

 formations of Brocchi. 



f Fortis in his" Memoires," vol. i. p. 144, gives a slight sketch of the 

 district of Asolo, but without any attempt to explain its geological relations. 

 He however describes " Madrepora fungites" in blue marl atCastel Cucco; 

 Turbinites terebra and editus of Brander, fig. 47 ; Dentalium, Murex of 

 ditto; Helix rautabilis, Brander, fig. 58; and other shells in theVal d'Ur- 

 gana. His figures of the Madrepora fungites are very characteristic. — P.147. 



towards 



