THE 



GEOLOGICAL MAGAZINE 



NEW SERIES. DECADE III. VOL. IX. 



No. IV.— APRIL, 1892. 



I. — Preliminary note on the Sequence and Fossils of the Upper 



Triassic Strata of the Neighbourhood of St. Cassian, Tyrol. 



By Miss Maria M. Ogilyie, B.Sc. (Lond.). 



DURING the past autumn, at the kindly suggestion of Prof. 

 Baron von Richthofen, I spent some months in the study of 

 the strata and fossils of the neighbourhood of St. Cassian. My object 

 was to endeavour, if possible, to determine the most natural sub- 

 divisions of these classic strata, and to fix their characteristic fossils. 

 As the results I have obtained are somewhat novel, and may prove 

 of interest to those who are familiar with the enigmatical character 

 of the stratigraphy of the beautiful region of the Dolomites, I may, 

 perhaps, be permitted to give in this place a short summary of my 

 conclusions, in anticipation of a detailed paper upon the subject. 



In 1860, von Eichthofen ' published the first detailed examination 

 of the Triassic strata in South Tyrol ; and in this work he sought 

 to explain the geological features of the Upper Trias by application 

 of Darwin's theory of the conditions attending the growth of Coral- 

 reefs. In the well-known work of Mojsisovics ("Die Dolomit-Riffe 

 von SiJd-Tirol und Yenetien," Wien, 1879) the Upper Triassic strata 

 of the region are grouped in five main divisions in ascending order. 



ilSforic Strata = 1. Buchensfeiit Beds. 2. TFengr en Beds. \ 



Karnic Strata = 3. Cassian Beds. 4. RaiblBeda. 5a. Bachstein ( 

 Kalk (in part). I 



Rhmtic strata = 5 J. Bachstein Kalk (in part). ) 



This succession of Upper Trias is but slightly modified from 

 Eichthofen's ; one main point of difference is that Eichthofen places 

 between the Cassian and Eaibl Beds the SMern Dolomite, which he 

 holds (1) to be younger than the Buchenstein, Wengen, and part of 

 Cassian strata, and (2) in some cases to rest unconformably, as at 

 Schlern mountain, on Mendola Dolomite (Muschelkalk) ; (3) to be 

 of local occurrence. Mojsisovics, on the other hand, states that the 

 three groups of the Buchenstein, Wengen, and Cassian Beds are 

 normally stratified, but that all three are locally represented by 

 massive non-stratified dolomitic reefs of the same age. He draws 

 attention also to the appearance of thinner lenticular beds of dolomite 

 at any horizon in the Wengen and Cassian strata. 



^ Geognostiche Beschreibung der Umgegend von Predazzo, Sanct Cassien und der 

 Seisser Alpe in Siid-Tyrol. 4to. Gotha. 



DECADE III. VOL. IX. NO. IV. 10 



