398 Transactions. 



of the land which follows the great deformations means a contemporaneous 

 filling of the sea-basins by transferred matter, and hence a slowly advancing 

 sea-edge, which is thus brought into active function as a base-levelling 

 agent. " The water-movement is essentially contemporaneous the world 

 over, and is thus a basis for correlation. The base-levelling process involves 

 a homologous series of deposits." It is further pointed out that dia- 

 strophism lies back of both stratigraphy and palaeontology, and furnishes the 

 conditions on which they depend. The relationship is not reciprocal in any 

 radical sense. The life does not in any appreciable way affect diastrophism, 

 nor does deposition control diastrophism except by exercising a localizing 

 influence. ' Diastrophism therefore seems to be the idtimate basis of 

 correlation. The criteria of this correlation include at once its own specific 

 criteria, the criteria of stratigraphy as dependent on diastrophism, and the 

 criteria of palaeontology as modified by the direct and indirect effects of 

 diastrophism." 



Chamberlin recognizes four stages produced by diastrophism — " (1) the 

 stages of climacteric base-levelling and sea-transgression; (2) the stages 

 of retreat which are the first stages of diastrophic movement after the 

 quiescent period ; (3) the stages of climacteric diastrophism and of greatest 

 sea-retreat; and (4) the stages of early quiescence, progressive degradation, 

 and sea-advance." For stratigraphical purposes it appears useful to intro- 

 duce a grouping of them, and to recognize in a diastrophic cycle two main 

 periods — one of climacteric deformational activity, and one of relative in- 

 activity, including the stages of sea-retreat which are the first stages of a new 

 deformation, and the stage of early quiescence. During the period of climac- 

 teric activity the land is greatly extended and its surface diversified, and 

 inequalities of climate and such extremes as aridity and glaciation are liable 

 to occur. The deposits of such a period include clastic deposits in land basins 

 and on low slopes, wind deposits such as loess, glacial deposits, and clastic de- 

 posits on the sea-margins. The terrestrial deposits of this period are largely 

 destroyed during the subsequent base-levelling, while the marine deposits 

 lying on the outside of the continental slopes are seldom likely to be raised 

 above sea-level. The deposits of the period of relative deformational in- 

 activity are dominantly marine, and furnish the main deposits of the strati- 

 graphical record. The cycle of marine sedimentation as opposed to the 

 diastrophic cycle includes a series of deposits formed during a period of 

 gradual sea-advance followed by gradual sea-retreat, the land surface which 

 supplies the sediments being at first diversified and later base-levelled, 

 so that the sediments of the later stages of sea-retreat are marked by the 

 increased erosion of the deep soil-mantles accumulated in the base-level 

 period. The succession of sediments given by Marshall as characteristic 

 of the younger rocks of New Zealand is an excellent example of such a sedi- 

 mentary cycle. The first deposits are gravels and sands, marking the early 

 base-levelling process. Then follow greensands, the formation of the glau- 

 conite in which is believed to be conditioned by a scanty supply of sediment 

 to the sea-floor, indicating that base-levelling was well advanced or the coast 

 distant. These are followed by limestones, during the formation of which 

 there was a nearly complete absence of sediment, corresponding to very dis - 

 tant or low-lying (peneplained) coasts. Greensands succeed, and then follow 

 mudstones arising from the erosion of the thick soil-mantles accumulated 

 on the peneplains, and finally sands and gravels, indicating that the' sur- 

 face of the peneplains has been destroyed by erosion due to sea-retreat. 

 j\[arshall and his colleagues, it should be noticed, did not recognize the 

 physiographic implications of their theory, and supposed that depression 



