I ( .h; /•." W. Skeats — The Formation of Dolomite 



exception to this condition which the writer can find in the 

 literature of the subject, is in the island of Faxoe off the Dan- 

 ish coast. This has been the subject of papers by F. .lohn- 

 strup,* translated into German by A. Stelzner, and by E. M. 

 Xoerregaard.f 



In these papers it is shown that the Faxoe chalk, of Danian 

 age, is of specially shallow water origin since it is in part coin- 

 posed of coral reefs and of bryozoan limestones and it is stated 

 that the coral reefs are in part dolomitized. That is to say 

 dolomitization of the chalk is only recorded where the indepen- 

 dent testimony of the organisms shows that the chalk has been 

 formed in shallow water and not, as is customary, in water of 

 moderate depth. In the Keuper marls of Britain, a rock 

 clearly of shallow water origin, Cullis^: has described the 

 occurrence of minute rhombs of dolomite. In the West of 

 England Sir A. Geikie§ states, "At the base of the Keuper 

 series in the region of the Mendip hills a remarkable littoral 

 breccia or conglomerate occurs. ... Its matrix being some- 

 times dolomitic it has been called the Dolomite conglomerate. 

 ... It represents the shore deposits of the Trias salt lake or 

 inland sea." Perhaps the Carboniferous Limestone of the 

 British Isles provides the best authenticated illustrations of 

 "contemporaneous" dolomites associated with independent 

 evidence of shallow water conditions. 



References to some of these were made in a discussion on 

 the author's paper to the Geol. Soc. of London, 1905. E. L. 

 Dixon referred to the evidence that some dolomite in the Car- 

 boniferous Limestones of Pembrokeshire and Caermarthen- 

 shire is associated with shallow water conditions. Prof. Watts 

 drew attention to the probably shallow water dolomites near 

 Charnwood Forest, and to the base of the Carboniferous Lime- 

 stone in Ireland, frequently either a dolomite or a conglom- 

 erate or grit cemented by dolomite. 



The writer remembers asking the late Dr. Vaughan, who did 

 such valuable paleontological and field work in the zoning of 

 the Carboniferous Limestone in the West of England, during 

 the course of his w r ork, whether he found that the fossil evi- 

 dence showed specially shallow water conditions where the 

 limestone had been dolomitized. Pie replied that his results 

 definitely supported that conclusion but expressed surprise that 

 it should be known as his results were still unpublished. 



Frequent references will be found in his papers as well as in 

 those of other writers like Sibly and Dixon among the same 



* F. Johnstrup, translation by A. Stelzner, Neues Jahrb., xxxviii, 542-575, 

 867. 

 fE. M. Noerregaard, Meddel. dansk. Geol. Forch. No. 10, 1904, pp. 85-106. 

 JC. G. Cnllis, Rep. Brit. Assoc, 1907, pp. 506-507. 

 S A. Geikie, Text Book of Geology, 1903, vol. ii, pp. 1092-1093. 



