Reviews — Mesozoic Igneous Rocks. 425 



was all red and mottled marls, faulted and broken for the first 

 100 yards, and over the second 100 yards dipping more regularly 

 at about 26 degrees. At 350 yards the heading passed through 

 another fault, and beyond this into red marl correlated with the 

 Keele Beds and having a still gentler dip of 16 degrees. 



This and the evidence from the other boundary faults shows that 

 they, like many other important lines of dislocation, are areas of 

 wide shattering and step faulting, partaking more of the nature of 

 broken folds than of clean fractures, a phenomenon which is well 

 seen in some other coalfields. 



Another point of interest about these faults is their throw in post- 

 Triassic time, which is large in comparison with that observed else- 

 where. This post-Triassic throw commonly amounts to 200 to 400 

 feet, while in two cases it exceeds 700 feet. The possibility of the 

 existence of workable coal between the two coalfields is reviewed, 

 but here the grounds on which the estimates can be made are far 

 from secure. The unconformable relations between the Trias and 

 the Coal-measures, the difficulty of determining the post-Triassic 

 throw of faults, and in the southern portion the possibility of uprising 

 of the pre-Carboniferous floor, all tend to render the formation of 

 definite opinions a very difficult task. The one fact which stands out 

 appears to be that the coal over a large part of this concealed coal- 

 field must be deep, in places as much as 3,900 feet. The most 

 promising areas appear to be in the northern j)art, where the Keele 

 Beds are absent, though here sinkings would have to pass through the 

 heavily watered Bunter. The surface of the area is in many places 

 thickly covered with drift which must have rendered surface mapping 

 very difficult, since in many places temporary exposures laid bare 

 in digging for sewers and foundations are all which can be obtained. 

 The ofiicers of the Geological Survey have, however, been very 

 fortunate in the co-operation of the colliery managers, and the 

 structure of the coalfields seems now to be established on a very 

 satisfactory basis. The map accompanying the memoir is not yet 

 published owing to causes connected with the War. 



W. H. W. 



A Contribution to the Knowledge of the Mesozoic Igneous 

 EocKS developed around the Tsushima Basin, Japan. By 

 Takeo Kato. Journ. Geol. Soc. Tokio, vol. xxvii, Nos. 316 

 and 317, 1920. 

 TN these two papers a description is given of a series of igneous 

 -*- rocks of late Mesozoic, probably Cretaceous, age, occurring in 

 the neighbourhood of the Straits of Tsushima. The series comprises 

 an extrusive phase of andesites and rhyolites, more or less meta- 

 morphosed pneumatolytically by a granitic intrusion allied to the 

 masanite of Professor Koto, the whole being subsequently penetrated 

 by a series of acid dykes similar to the granite. It therefore affords 

 an example of a complete normal sequence of eruptivity of Pacific 



