Of course, in all this we are dealing only with relative time. When we find one bed or stratum lying above another in their natural position, the lower one is of course the older of the two; but whether laid down ten minutes earlier, or ten million years earlier, how are we to determine? Ignoring the matter of the fossils they contain, must we not own that, though there is no way of telling just how much longer the lower one was deposited before the next succeeding, yet if the two are conformable to one another, and the bottom one shows no evidence of disturbance or erosion before the other was fitted upon it, the strong presumption would seem to be that no great length of time could have elapsed between the laying down of the two layers. To say that we have here a geological example similar to that of a modern American having been personally acquainted with Julius Caesar, would seem to be quite "inexplicable," as Herbert Spencer used to say.
But if the life succession theory be true, we have just such a conundrum in our Fact Number Two, which is that any formation whatever may rest conformably upon any other "older" formation.
The lower may be Devonian, Silurian, or Cambrian, and the upper one Cretaceous or Tertiary, and thus according to the theory millions on millions of years must have elapsed after the first, and before the following bed was laid down, but the conformability is perfect, and the beds have all the appearance of having followed in quick succession. Sometimes, too, though less frequently, these age-separated formations are lithologically the same, and can only be separated by their fossils!
But before going into the minute description of any of these cases, we must notice some general statements. Thus as long ago as the date of the publication of "The Origin of Species," Darwin, in speaking of the "Imperfection of the Geological Record," could speak of "The many cases on record of a formation conformably covered, after an immense interval of time, by another and later formation, without the underlying bed having suffered in the interval by any wear and tear."[20]
Also Geikie,[21] in speaking of how "fossil evidence may be made to prove the existence of gaps which are not otherwise apparent," says that "It is not so easy to give a satisfactory account of those which occur where the strata are strictly conformable, and where no evidence can be observed of any considerable change of physical conditions at the time of deposit. A group of quite conformable strata having the same general lithological characters throughout, may be marked by a great discrepance between the fossils of the upper and the lower part." In many cases he says these conditions are "not merely local, but persistent over wide areas.... They occur abundantly among the European Palaeozoic and Secondary rocks," and are "traceable over wide regions."
We have seen how Dana admits that "A stratum of one era may rest upon any stratum in the whole series below it, ... the intermediate being wanting." He classes this under the head of the "Difficulties" of the science, quite naturally as it would seem, though he does not expressly assert that these age-separated formations are often conformable to one another, as Geikie and Darwin have said in the above given quotations.
The literature really teems with illustrations of these facts, and the more detailed accounts contained in the various Geological Reports are often quite charmingly naive in their description of the conditions. Two examples, however, must suffice, both from the Canadian North West.
The first is from the Report on the region about Banff, in Alberta, near the line of the Canadian Pacific Railway, and just east of the Rockies.
"East of the main divide the Lower Carboniferous is overlaid in places by beds of Lower Cretaceous age, and here again, although the two formations differ so widely in respect to age, one overlies the other without any perceptible break, and the separation of one from the other is rendered more difficult by the fact that the upper beds of the Carboniferous are lithologically almost precisely like those of the Cretaceous (above them.) Were it not for fossil evidence, one would naturally suppose that a single formation was being dealt with."[22]