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Published online by Cambridge University Press: 01 May 2009
From no part of the world have we of late years derived more additions to the Geological Record than from North America. Besides important additions to the earliest pages of that record, the rich collections made by the United States Surveyors, both of fauna and flora, from the Cretaceous, Eocene, and Miocene deposits, have thrown much light upon the life history of the Earth; and it is even contended that they have bridged over the interval which, notwithstanding the Maestricht beds, the Pisolitic, and the Faxoe Limestones, still remains sharply marked between the Cretaceous and Tertiary formations of Europe so far as they have yet been examined.
page 481 note 1 The map of Yorkshire with sections will appear with Part III.
page 482 note 2 Considering that the term “Primary” had long become obsolete, and that the term “Secondary” was fast becoming so, we might have been spared the absurdity of “Quaternary.” However, as Crinoline has done so, I suppose, it will go out of fashion in time. The separation of Geology into “solid” and “superficial” officially lade by the late Director of the Geological Survey of England, and on the basis of which the maps of the National Survey are to be delineated, is, to my mind, also an bsurdity; but in deference to the leaders of fashion, I have adopted the term of Surface Geology” in the title of this paper.
page 482 note 3 The Surface Geology of Ohio, by J. S. Newberry (Columbus, 1874).
page 483 note 1 If, as some American geologists say, unstratified morainic clay has been found overlying the forest surface in sitû, then these would seem to me to be instances of dropping from floating ice; for if the ice passed over the forest, it must have destroyed it. Some of our Norfolk geologists are now coming to the opinion that the longknown Forest-bed of Cromer is not in sitû, but transported; and if they are right, the theories based upon the occurrence of peats and freshwater shells in the midst of Glacial clay will require much reconsideration. This, however, does not apply to the Pakefield and Kessingland root-indented bed, which is clearly in sitû. If it should turn out that the Cromer Forest and freshwater deposits associated with it are not in sitû, but stripped from some distant land-surface by ice, and transported, analogy for such a thing may be found in some peaty masses which I have observed imbedded in the midst of the marine-formed Contorted Drift in the Cromer cliff itself.
page 484 note 1 In objecting in my paper, “On the Climate Controversy.” in this Magazine for September, 1876, to the extreme thickness assigned to the ice of Britain during the Glacial period, I spoke of the existing Antarctic ice being at least 5000 feet thick. In this I was led away by the instances of bergs of tabular form having been met with in Southern seas which rose more than 500 feet or 600 feet above the sea, given by Dr. Croll in his work on “Climate and Time.” From the description of the Southern bergs, however, given by the Challenger Expedition, I do not see how the Antarctic ice can at its sea termination much exceed 2000 feet, even if it reaches that. It seems probable, however, so far as Greenland and Spitzbergen disclose the case, that land-ice is of less thickness at the glacier terminations than where it lies in greater masses further inland.
page 485 note 1 Quart. Journ. Geol. Soc. vol. xxiv. p. 148; and Palæontographical Society's volume for 1871Google Scholar; Introduction to Crag Mollusea, Supplement, p. xxv. They are also shown in the section which accompanies the sequel of the present paper under the letter b.
page 486 note 1 See paper by myself and MrHarmer, on the later Tertiary Geology of East Anglia, in Quart. Journ. Geol. Soe. vol. xxxiii. p. 74.Google Scholar
page 486 note 2 vol. xxiii. p. 84. Instead of this action on the Liteham chalk having (as represented in the paper quoted) taken place during the formation of the Contorted Drift, I should now refer it to the time when, after the elevation of part of the Upper Glacial into land, the inland-ice pressed on the west of Norfolk, as explained in the sequel of the present paper: the bed b of the section in the paper quoted not being, apparently, the Contorted Drift.
page 487 note 1 Brown, Journal of the Geographical Soc. for 1871, p. 351. Mr. J. W. Tayler, also, in the same journal for 1870, p. 228, says that numerous fiörds in Greenland have been so filled up by the moraines extruded by the glaciers, that boats hardly find depth of water enough to ascend them, while one of the glaciers, that north of Frederickshaab, which is 15 miles wide, and ends, not in a fiörd, but on the open coast, has formed a beach at its base with the moraine it extrudes.
page 489 note 1 This, as described further on in the present paper, has been the case with the Lower Glacial deposits in England. Mr. Geikie seems to see no difficulty in glacierice passing over forest-surfaces without destroying them, although to such ice is attributed the excavation of great valleys and rock-basins, but I do not believe in the possibility of such a thing, the two resulting actions appearing to me irreconcilable with each other. According to Prof. Dana the thickness of the ice which passed over the northern part of the United States was 6000 feet, exerting a pressure of 300,000 Ibs. to the square inch, while it was double this on the watershed between Canada and Hudson's Bay. I am, however, very sceptical of these vast thicknesses of ice anywhere.
page 492 note 1 It must not be, however, forgotten that the doubts which are being raised as to whether the Forest-bed of the Norfolk coast is in sitû apply with greater reason to the forest-beds over the Erie clay which appear to have been only encountered in sinkings, and therefore not open to so rigorous an examination as the Norfolk forest; so that if the latter should turn out to be a land-surface ploughed off and removed by the agency of ice, it would be difficult to resist a similar explanation for the Ohio forest-bed; and in such case the beds 3a would probably prove to be only a continuation of the Erie clay formation itself.
page 494 note 1 Prof. Newberry observes that only patches of the Erie clay occur on the waterparting which is the region of these Kames, and in the details of sections that he gives, these Kame gravels do not rest on the Glacial deposits, but on the rock surface. Mr. Geikie, in the second edition of his “Great Ice Age,” similarly suggests that the Ohio Kames were due to the action of water flowing from the glacier-ice when it reached to the centre of Ohio, but he does not of course recognize such a distinction as I have endeavoured to draw between the deposit formed by the subaërial extrusion of the moraine and that formed by its subaqueous extrusion.
page 495 note 1 The line up to which this formation, and also the Middle Glacial and earliest part of the Upper, have been destroyed by the subsequent ice is defined in a note to the sequel of this paper.
page 495 note 2 This, at least, is my impression, from the works to which I have had access. If the facts are otherwise, then my argument to that extent fails.
page 496 note 1 In reference to this suggestion it would be interesting to learn to what extent rock-fragments have been found in the Mississippi valley which can be identified with rocks in sitû in the St. Lawrence area. Prof. Newberry speaks of large quantities of gravel and boulders having been carried through the waste weirs, penetrating the water-parting, and deposited in lines leading towards the valley of the Ohio, so that I infer such rock-fragments of lake-basin origin do abound within the limits of the Mississippi valley, and up to the line of Northern drift limit shown in the map.