SECTIONAL TRANSACTIONS.— C. 321 



for the great expansion of the Permian sandy beds in the former area and the corre- 

 sponding reduction of the limestones. It will be shown in a subsequent paper at this 

 meeting that there was no physical barrier between these areas in Permian and 

 Triassic times, and in these circumstances the replacement of a great thickness of 

 limestone by sandy deposits suggests lateral passage. At least, there is nothing to 

 indicate a Permo-Triassic break. In my opinion the essential continuity of the 

 Permian and Trias in this country must be accepted as a fact in the discussion. 



Since they are continuous, and the sandy facies of both groups is usually quite 

 unfossiliferous and lithologically indistinguishable, it is no matter for surprise that 

 mistakes have been made in correlation, and it may be affirmed with little hesitation 

 that many isolated sandstones in this country can never be strictly correlated. This 

 affords no argument either for or against the abolition of the Permian system ; it 

 does urgently demand the adoption of some such term as ' undifferentiated Permo- 

 Trias ' (or New Red Sandstone) for beds which cannot be definitely correlated — 

 especially by the official Geological Survey. 



The above are matters which have led to this discussion — but the subject is much 

 wider, namely, whether the Permian fulfils our conception of a system. Examination 

 of the well-established systems readily shows that their delimitation rests on no 

 logical basis whatever, other than that they cover a substantial portion of the geological 

 record, and are more or less naturally bounded in the region where they have been 

 originally defined. They are commonly stated to be bounded by physical or 

 palseontological breaks. The two supposed criteria are fundamentally one. Without 

 physical interruption, either locally or elsewhere, there can be no palseontological 

 break, and it is yet far from being established that any but possibly the very greatest 

 unconformities are of world-wide effect. Experience proves repeatedly that the systems 

 which are naturally bounded in one region are difficult of application elsewhere. 

 Under these circumstances, close adhesion to the original definition of any system 

 is the only alternative to chaos. 



The Permian and Trias together cover one great epoch of widespread continental 

 extension. The great length of this interval is amply attested by the enormous 

 evolutionary progress which occurred within it, the development of nearly every 

 great group of reptiles and of the larger stegccephalia ; wide changes in the fish fauna ; 

 the major portion of the evolution of the ammonites ; and many more changes of 

 similar magnitude. It is clearly the enormous contrast between the floras and faunas 

 above and below these rocks which led to the conclusion that the break between the 

 Palaeozoic and Mesozoic must lie within them. The contention that these rocks should 

 form one S3^stem would be logical, and open to objection only on the ground that the 

 system would be unwieldy. Their union, however, would do nothing to diminish 

 the difficulties of correlation which gave rise to this debate, but would merely hide 

 them under a comprehensive name. It should be recognised that the Permian and 

 Triassic rocks are very incompletely represented in this country and in Central Europe. 

 The Lower Permian in particular appears to be very slightly represented. The 

 Zechstein alone (probably mostly Upper Zechstein) is represented by adequate fossil 

 evidence. 



Prof. W. S. BouLTON. — No system, perhaps, has given rise to more discussion than 

 the Permian. Difficulties and problems have arisen wherever its rocks have been 

 investigated. The Period bridging the gap between the Palaeozoic and Mesozoic eras 

 was marked by powerful crustal movements, notably in Europe and North America, 

 and its rocks accumulated for the most part in continental areas with an arid climate. 

 In consequence the rocks are abnormal, fossils are absent or scarce, and correlation of 

 deposits in separate or distant regions becomes difficult or impossible. 



I would urge, however, that these Permian problems ought not to be shirked 

 because they are difficult and not immediately resolvable. By abolisliing the name 

 ' Permian ' and substituting some other, such as Permo-Carboniferous or Permo- 

 Trias, or by linking up the whole or part of its deposits with the Carboniferous or with 

 the Trias, we do not thereby solve the Permian problems. 



Fiurther, I would stress the unwisdom of attempting to settle the validity of the 

 Permian as a system chiefly from a study of British stratigraphy. To decide whether 

 or no there shall be a separate system which we call Permian, it is not sufficient to go 

 back to the time of Murchison and his contemporaries, and discuss the propriety of 

 adopting the old name New Red Sandstone or some other in order to rid us of the 

 troublesome name Permian. The Permian system is now recognised by most foreign 



1930 Y 



