Thomson. — Geoloyii of Midtlle Clarence and Ure Valleys. 297 



The evidence for a later major period of diastrophism is afforded by 

 the displacements which the whole Notocene series has experienced subse- 

 quent to the cessation of its deposition. A great fault runs along the 

 south-eastern base of the Kaikoura Mountains, along which all the Notocene 

 rocks are deeply involved. For the most part they have experienced a 

 strong tilt, and dip at steeji angles to the north-west against the fault, the 

 north-west side of which is occupied by pre-Notocene rocks. From the 

 Swale Valley north-east the Notocene rocks are strongly folded and com- 

 pletelv overturned in the upper limb of a recumbent syncline which is 

 truncated by the fault. The production of such structures proves the 

 existence of very considerable earth-pressures after the conclusion of the 

 Notocene deposition, and there are good reasons, as will be shown below, 

 for believing that the Looker-on and Kaikoura Ranges owe their uplift 

 to such orogenic movements of post-Notocene date, which Cotton (1916) 

 has termed the Kaikoura orogenic movements. 



Between these two epochs of major diastrophism there ensued a period 

 of relative diastrophic inactivity — the Notocene — during which a great 

 thickness of accordant sediments was laid down. The presence of a thick 

 series of basalts near the base of the Clarentian in the south-west part of 

 the Middle Clarence doubtless points to crustal instability at this period, 

 and there are locally evidences of slight discordance and of disconformity 

 at higher horizons ; but such earth-movements as occurred throughout the 

 Notocene, with a single exception outlined below, were epeirogenic and not 

 orogenic in nature, and the general accordance of the whole Notocene is 

 most marked. 



The nature and distribution of certain members of the Notocene leads 

 to the belief that these rocks had formerly a much wider extension, and 

 prior to the Kaikoura orogenic movements formed a cover to the pre- 

 Notocene rocks, a cover which has since been removed by denudation 

 where the movements carried it to higher elevations, leaving only a narrow 

 strip in the valley-bottom, w4iere it has been until recently below the 

 effective action of erosive agents — in other words, that the Kaikoura and 

 Looker-on Ranges did not exist as such at the time of the deposition of 

 the rocks in question. If they had so existed, and a long fiord had occupied 

 the site of the Middle Clarence Valley, the deposits of this fiord would have 

 been of the nature of river-delta deposits, mainly conglomerates and sand- 

 stones, so long as the mountains existed — i.e., throughout the whole Noto- 

 cene, since the mountains still exist. Instead we find conglomerates and 

 sandstones only poorly represented in the lower beds, which consist mainly 

 of mudstones, while the middle beds consist of limestones which are in part 

 argillaceous and in part of an indurated chalky and siliceous nature and 

 exceedingly fine-grained. The limestones are succeeded by more or less 

 calcareous mudstones, also fine-grained, and it is not till near the top of the 

 Notocene that coarse detrital matter reappears in the mudstones and in an 

 overlying conglomerate. This in turn is followed by further mudstones. 

 The whole series of sediments, except the conglomerate, has the characters 

 of the deposits of an open continental shelf {cf. Cotton, 1918), and not 

 those of delta deposits in a narrow fiord. 



The lower and greater part of the limestone may be correlated on litho- 

 logical and stratigrapliical grounds with the Amuri limestone, the upper 

 part of the limestone and the succeeding mudstones with the Weka Pass 

 stone and the " grey marls " respectively of the Waipara district of North 

 Canterburv. These three rocks maintain the same lithological characters 



