SECTIONAL TRANSACTIONS.— C. 347 



discontinuous ring about the basin and initiated the tectonic depression of 

 Strangford Lough and that south of Co. Down which continues into the 

 Solway. The Carboniferous Limestone sea was in some respects the 

 precursor of the present Irish Sea, for the mountains of Wales, Wicklow, 

 the Lake District and the Isle of Man rose above its surface though the Coal 

 Measure swamps largely surmounted them. Hercynian folding and faulting 

 again emphasised the morphological difference between hill and plain 

 which the Keuper Marls and Jurassic strata later did so much to minimise. 

 The close of the Cretaceous coincided with the beginning of the present 

 drainage. 



During the Tertiary Era that witnessed the birth of the Mournes the basin 

 was the scene of fracturing, as in the North Channel and Carlingford Lough, 

 and of intermittent elevation, for levels of planation, three at least in number, 

 are still preserved. The last of these, of early Pliocene age, was succeeded 

 by further uplift which initiated the ' buried valleys.' 



Pleistocene ice sculptured the uplands and deposited its load on the sea- 

 floor and the surrounding plains, converting parts of the floor into dry 

 land, obliterating the ' buried valleys,' and largely obscuring the ' preglacial ' 

 shoreline. In recent times, the sea withdrew into a narrow channel and 

 expanded subsequently to inundate the ' submerged forests ' and separate 

 Ireland and the Isle of Man from Great Britain. 



Dr. E. Greenly. 



On the floor of the sea to the east of Anglesey are sheets of Mesozoic 

 rocks, with an outlier of Chalk ; so this is the site of a Neozoic syncline. 

 Anglesey (before base-levelling) was the core of an anticline. But it was a 

 mere lobe. For Snowdonia is carved out of a plateau, whose last base- 

 levelling seems to have been in Late Cretaceous time. Now raised into a 

 very gentle dome, it is the core of a far loftier anticline. Further, the valleys 

 of Snowdonia cannot have existed at the time of the intrusion of certain 

 dykes, which are of Neozoic age. Consequently, the mountains, as 

 mountains, must have begun to develop at some stage of Neozoic time ; 

 probably Oligocene, possibly Miocene. For the Menaian Platform cannot 

 be later than Pliocene. Thus, none of the major features of the south-east 

 part of the Irish Sea Basin can be anterior to Oligocene time. They are the 

 work of prolonged erosion acting upon gentle Neozoic folding. 



Mr. R. Kay Gresswell. — The south-eastern portion of the Irish Sea 

 Basin. 



Having found that foreshore drifting occurs on the south-west Lancashire 

 coast away from Formby Point in both directions (see paper to Section E 

 at this meeting), the conclusion is reached that material is brought from the 

 sea floor to the beach at Formby Point, and also since the bottom to the 

 10-fathom line is more or less pure quartz sand, this indicates that sub- 

 marine contours to this depth will be controlled by present-day currents. 

 From the 10- to the 30-fathom line in an east-west direction is about 43 miles, 

 giving an average gradient of 3 ft. a mile or 1 in 2,000 approximately. The 

 submarine contours here are intricate but indicate possible post-glacial 

 estuaries for the rivers Ribble, Mersey and Dee between the 16- and 

 25 -fathom lines. The Mersey and Dee appear to unite at 25 fathoms. The 

 presence of submerged forestal remains on the Formby to Liverpool and 

 Wirral coasts shows that in post-glacial times the land stood higher than 

 to-day, 120 ft. having been suggested by De Ranee. Thus the determina- 

 tion of the post-glacial coastline is of importance. It is, however, possible, 



