Vol. 67.] THE CARBONIFEROUS SUCCESSION IN GOWER. 537 



from earth-movements. The shallowing may be due to accumula- 

 tion of material, but, for several reasons, has more probably resulted 

 from movements of elevation (negative movements). Thus, in two 

 of the cycles it appears to have been progressive and intermittent ; 

 and in one (if not two) it has been completed in parts of the South- 

 western Province by emersion. 



(4) If we knew the exact depth in feet at which each uniform 

 group of the series had been deposited and the time occupied in 

 the deposition, by adding, for each group in turn, depth to total 

 thickness of deposit already formed, we could construct a curve 

 with these totals as negative ordinates and total times as abscissas. 

 This curve would show the movement of the base of the Car- 

 boniferous throughout Avonian time. It would then be seen that 

 the negative movements above mentioned have been mere incidents 

 in a prolonged spell of depression (positive movement). Thus, 

 although the incoming of oolites in S 2 has, doubtless, been accom- 

 panied by a certain amount of negative movement, their deposition 

 to the thickness which they attain can have been conditioned only 

 by a renewal, and for a long time, of depression. In this case, 

 where the thickness of the deposit is enormous relatively to any 

 possible range of depth during its formation, depression has been 

 approximated isostatic (in the sense in which that term is used on 

 p. 528). 



(3) Relations between the Different Districts of Gower at 

 Successive Times ; Conclusions ; Earth-Movements. 



The following interpretation is placed on the differences and 

 resemblances between the three districts, summarized in Table I 

 (facing p. 505). 



(i) Of K little is known, but during the deposition of Horizon /3 

 the facies of sedimentation was practically uniform over the whole 

 area. 



(ii) During the interval, Z and the lower half of the Laminosa 

 Dolomites, dolomitization was much more extensive in Eastern and 

 North- Western Gower than in South-Western Gower; this differ- 

 ence accords with the view of Prof. Skeats l and others that within 

 certain limits shallowness favours dolomitization, for the Avonian 

 sea is known from other evidence to have shallowed northwards 

 in the South-Western Province. 



(iii) The facies of sedimentation of the rest of C 1 was practically 

 uniform over the whole area, though the ratio of the two rock-types 

 formed, dolomite and oolite, varied. 



(iv) The fact that lagoon-conditions were established at the base 

 of C 2 in Eastern and North-Western Gower but not in South- 

 Western Gower was doubtless due to the southward deepening of 

 the Avonian sea. At this period, however, part of the Eastern 



1 Q. J. G. S. vol. lxi (1905) pp. 133-38. 



