308 G. Stefanini — Outline of the Geological History of 



earlier Miocene, are found forming a part of the intra-alpine 

 deposits, in central and western Yenetia. Thns, it is toward 

 the end of the middle Miocene that the peripheral region of 

 the gnlf underwent an elevation which carried it well above sea 

 level, while the central part of the gnlf was only filled up in 

 the upper Miocene with sediments which the young streams 

 brought into it in large part from the recently emerged region. 



Age and nature of the Miocene Displacements. 



As to the duration and the nature of the movements whicli 

 affected the region at the time of the emergence, one must be 

 warned lest he believe that the succession of facies, everywhere 

 not so thick as are observed during the middle and upper Mio- 

 cene, is an indication of a slow and general elevation of the 

 bottom. On the contrary, the Tortonian alone measures 700 

 meters in Friuli. Now these lower beds exhibit already a 

 strictly littoral character and could never have been deposited 

 in a depth of several hundred meters. Upon as good grounds 

 this same reasoning could be continued for the complete series 

 of middle and upper Miocene beds, a thickness of 1800 to 2500 

 meters. 



There is no doubt in my mind that the deposition of this 

 enormous quantity of clastic material, corresponding to the 

 emergence and the erosion of the Alpine continent, was accom- 

 panied by a slow but general and continuous sinking of the 

 bottom; a subsidence, however, which was not sufficient to pre- 

 vent the formation of deltas which continued until the com- 

 plete filling up of this part of the basin. 



A gradual sinking of the bottom is, according to the studies 

 of Barrell, an indispensable condition for the formation of 

 delta deposits of enormous thickness, such as the sub-Himalayan 

 formations, which suggest, in many I'espects, resemblances to 

 the subalpine formations of Yenetia. 



In conclusion, during the middle and upper Miocene, the 

 Pj'eadriatic gulf was the seat of two opposite movements. 

 While the peripheral region underwent the emergence of which 

 I have spoken above, other areas farther seaward, and especially 

 those which corresponded to the central part of the gulf, the 

 sinking of the bottom, begun throughout the entire region at 

 the beginning of the period, continued, and the materials 

 which the youthful streams tore from the recently emerged 

 country contributed largely to the filling of the basin which 

 persisted in the extra-alpine zone. 



The Pliocene transgression. 



The geocratic* period just mentioned was not of long dura- 

 tion. At the beginning of the Pliocene the sea returned, bear- 



* Geocratic = uplift, or a negative movement of the strand. 



