327 



APPENDIX. 



Notes on the Correlation Table of British with Continental Tertiary 

 Strata. By George F. Harris, P.G.S. 



WnEX commencing to draw up the accompanying Table it was the writer's 

 intention to indicate the limits of the main divisions, as Eocene, Oligocene, 

 Jliocene, and Pliocene ; but as the work progressed this was abandoned, because 

 so few authorities were found to be in accord with each other as to the precise 

 position occupied in the series by so many beds along the border-lines. This 

 difKculty has been felt by all who have essayed at correlating European Tertiaries 

 on a large scale. Thus, Prof. Fallot says*, "Rien n'est plus difficile en effet 

 que de fixer une delimitation precise et rationnelle entre I'Eocene et I'Oligocene, 

 entre le IMiocene et le Pliocene." With respect to the correlation of the British 

 Tertiary strata with those on the continent, the chief difficulty, perhaps, consists 

 in assigning those portions which are usually known as Oligocene to their proper 

 places. This arises mainly from the circumstance that the strata are so largely 

 made up of freshwater and estuarine beds of more or less local value only. 



The Table does not profess to deal in detail with the stratigraphy of the whole 

 of the Tertiary basins of Europe ; hut it correlates upwards of 300 of the best^ 

 known (local) formations. In order to bring the size of the Table within rea.son- 

 able limits, it has been necessary to include more than one basin iu each column, 

 with the result that, in some instances, it has not been possible to indicate 

 homota.\ial relations as precisely as could be desired. Thus, in cases where it 

 has been clearly shown that a certain bed in one basin was laid down contem- 

 poraneously with another bed in an adjacent basin, one would, in drawing up a 

 correlation Table of the two basins, usually place the names of the two beds 

 referred to in a line with each other in two columns ; but by including the two 

 basins in one column these names must, of necessity, come one above the other, 

 so that the exact' relationship of the two beds cannot be correctly expressed. 

 Again, to adequately display the relative positions of the different horizons, the 

 columns would have to be at least twice their present length. Nevertheless the 

 Table indicates the approximate homotaxis of every bed mentioned, with its 

 position in the Tertiary series, as near as possible. 



* Ann. Geol. Univ. t. v. (1888) p. 425. 



