Herbert Spencer has laid it down in his First Principles that no hypothesis is capable of more than partial proof, and that of two rival hypotheses the one that approaches nearest the truth is that which does least violence to fundamental principles. I venture to think that Cotton's titanic faulting and stupendous walls of weak, unconsolidated sediments (vide fig. 2, Cotton, 1913) postulate conditions that appear almost impossible. Moreover, his and Thomson's contention that the post-Miocene conglomerate is conformable to the “grey marls,” notwithstanding that it is composed of material derived from all the underlying formations, is opposed to all the canons of stratigraphical geology. The view of conformity did not even suggest itself to Hector, McKay, or myself.
According to Cotton's hypothesis, the faulting was a single catastrophic movement of such magnitude as to expose the Tertiary and Cretaceous strata in a stupendous fault-scarp from the steep face of which blocks and vast slabs of the different beds, under the influence of gravity, fell or slid into the valley below, forming the “pell-mell” so well described by McKay. But the blocks are contained in a matrix of fluviatile drift composed mainly of the basement Juro-Triassic rocks. Evidently the Clarence Valley was already drained by a well-established river-system. It seems incredible that the titanic dislocation required by Cotton's view could have taken place without causing serious disarrangement of the pre-existing drainage-system.
If it be conceivable that the faulting proceeded by a series of catastrophic displacements that exposed in a steep escarpment first the Tertiary and
afterwards the Cretaceous strata in the order to their superposition, we should expect to find the Awatere rocks, as the first exposed to shattering and crumbling, predominating in a stratum towards the base of the great conglomerate. Above this stratum there should appear a succession of layers dominated by blocks of “grey marl,” Amuri limestone, and Cretaceous rocks, and in the inverse order of their superposition. But the blocks of the different formations do not occur in this orderly succession: they are mingled in a confused jumble. Clearly this conception also fails.
It is generally recognized that all great faults are of slow growth. If the growth of the Clarence fault were slow, the denudation of the newly uplifted covering strata would result in the formation of the slopes normal to weak strata, and there would be no dislocation of the established drainage-system.
The Tertiary strata were laid down on the floor of the sea, and elevated before the process of shattering and denudation began. Surely this uplift and the geographical changes which it brought about must represent a time-break between the post-Miocene conglomerate and the underlying Tertiary strata which figure so conspicuously in its composition.
I do not know of any natural agency other than ice that could transport and leave stranded among fluviatile drifts slab-like masses of soft friable rock ranging from a few feet up to 70 ft. in length; and I can see nothing unreasonable in my suggestion that high chains like the Kaikouras could support ice-fields during the period of Pleistocene maximum refrigeration. I do not suggest that my view is the obvious truth. My contention is that it is a reasonable interpretation of the known facts. The obvious truth may often resemble a truism, which Carlyle has defined as an invention for concealing the real truth. The uplifted hand may obscure a landscape; and a simple truth may be presented in such a manner as to hide a whole gospel.