FOSSIL REEFS: TRIASSIC 435 



Ladinian. The masses are often of great thickness, that of the 

 Schlern-dolomite reaching over 3,000 feet (1,000 meters), and they 

 are commonly of Hmited horizontal extent. Tongue-like offshoots 

 of the "reef rock" extend into the surrounding bedded strata as is 

 the case with modern coral reefs. The reef character of these 

 masses was first pointed out by von Richthofen {72), and they 

 were subsequently more fully described by Mojsisovics (64). 

 This author calls attention to the fact that the position which these 

 isopic masses occupy with reference to the heteropic strata enclosing 

 them is that of a reef mass growing upon a basis of volcanic or 

 other origin, but rising above the level of the sea floor on whidi 

 the heteropic deposits were forming. The latter, therefore, have 

 their bases at a lower level than the reef masses, which always 

 project above the synchronous bedded deposits surrounding them. 



Fig. 92. Section of the Schlern-massif, showing the relationship of the dolo- 

 mite "reef rock" to the bedded formations, South Tyrol. (After 

 Mojsisovics.) 



The chief structural characters pointing to the reef origin of these 

 masses are : the resemblance of the isolated dolomite masses to 

 upraised reefs ; the great concentration of the dolomite masses 

 thousands of feet thick tailing off laterally into marly deposits of 

 much less thickness, but formed during the same interval of geo- 

 logic time and often showing inclined bedding near the reef; the 

 absence of bedding in the "reef masses" ; and the occurrence of 

 intei"fingering masses and of blocks of the dolomite material on the 

 slopes of the "reefs" and apparently intercalated among the sur- 

 rounding sedimentary deposits. (Figs. 91, 92.) On the other hand, 

 many observers (Ogilvie-70, Diener and Artharber-24 and others) 

 hold that the structural features are due to faulting and that the 

 dolomite masses are fragments of once continuous deposits of 

 marine origin. They do not deny, however, that they constitute 

 distinct facies of the Cassian, Wengen and Buchenstein or even 

 earlier beds. 



Corals are very rare in the dolomite, calcareous alga; and echino- 

 derms constituting the chief organic remains. This has forced the 



