SECTIONAL TRANSACTIONS.— C. 319 



are still dependent on the eoral-brachiopod sequence. Similarly in the Middle and 

 Upper Coal Measures of the Midland Province of England and the equivalent beds 

 abroad we are dependent for zonal analysis mainly on the freshwater mollusca 

 and the flora. 



It would, however, appear that, taking the Midland Province of Gibson as a whole, 

 and including in it all the Pennine area south of the Craven Faults, we delimit area 

 extremely suitable for use as a type area. Not only is the sequence approximately 

 complete (including beds not yet recognised elsewhere), but the goniatite-yielding 

 phase is a widespread one, and affords a most delicate index for correlation purposes. 

 Also the exposures at the junction of this phase with the coral-brachiopod phase of 

 the Northern Province are excellent, and offer the most promising avenue yet dis- 

 cernible for a more accurate correlation and explanation of the two great marine facies. 



Miss Emily Dix and Dr. A. E. Trueman. — Marine Horizons in the Coal 

 Measures of South Wales and the North of England. 



The importance of marine bands as datum planes in the correlation of the Coal 

 Measures has been recognised for some years, and in Nottinghamshire and Yorkshire, 

 and North Staffordshire, several marine bands have been much used in determining 

 the structure of the coalfields. The two most noteworthy are the Mansfield Marine 

 Bed (the Gin or Speedwell band of North Staffordshire) and the First Marine Bed 

 (the Lady Coal band of North Staffordshire). These appear to indicate widespread 

 submergences which affected simultaneously a wide area in the North of England. 



In the South Wales Coalfield there has been little information concerning marine 

 horizons, but an examination of cores of recent borings has revealed the existence of 

 several well-marked horizons, two of which may be compared with the Mansfield and 

 First Marine Beds. They agree closely in fauna, and they likewise occur near the top 

 of the Anthracornya pukhra Zone. They appear to have been the latest marine 

 episodes in all these areas. Earlier marine horizons are known in South Wales in the 

 Carbonicola ovalis Zone and possibly in the A. modiolaris Zone. 



Mr. W. S. Bisat. — The Junction of the ' Upper' and 'Lower' Carboniferous 

 Strata. 



The view that the deposition of the Carboniferous beds formed everywhere an un- 

 broken sequence from bottom to top has long since been exploded, but the exact 

 status of such break or breaks as occur in the succession has still to be determined. 



It is by no means clear that a twofold division has any physical basis when 

 Western Europe is viewed as a whole. 



In Yorkshire a considerable break occurs at the junction of the Mountain Limestone 

 and the basal beds of the Millstone Grit, but this break is associated with, and is prob- 

 ably largely caused by, a median ridge in the Carboniferous geosyncline of Northern 

 England. This ridge, elusive though its character may be, served as an effectual 

 barrier between the Midland Province of Gibson, and a Northern Province which 

 included Garwood's North-western Province and the Northumberland-Durham area. 



From the researches of Tonks and Hudson on this break in Yorkshire at the 

 junction of the Yoredale rocks and the Millstone Grits, it would appear that the 

 barrier itself moved northwards in Grit times, and that the Midland Province increased 

 in area at the expense of the Northern Province. Apart from this median ridge with 

 its attendant though obscure phenomena of knoll-reef bmestones, breccias and 

 facies-changes, there appears no important break in the North of England succession, 

 except perhaps at the margins of the basins and around the Lake District and the 

 Derbyshire Peak. 



In S. Wales and Somerset there is a much more important break at the junction 

 of the Limestone and Grits, and perhaps to a lesser extent the same is true of 

 Westphalia, though here it is difficult to know how much of the apparent non-sequence 

 is due to lack of exposure or barrenness of the strata. 



Mr. W. S. Bisat Some Episodes in the ' Millstone Grit ' Period. 



Thanks to the detailed zonal analysis of the Millstone Grits, it is now clear that 

 there were several major outwashings of coarse grit into the deltaic area of the Mid- 

 land Province, with intercalated marine periods of considerable extent. The earliest 

 such grit invasion appears to be that of the Grassington and Pendle Grits, which form 



