On the Probable Events which succeeded the Close of the Cretaceous Period
Authors: Wood S. V. 
Published: October 2009

T
he
object of this paper was to show that the close of the Secondary period was followed by the formation of a continent having a great extent from east to west, and at that time chiefly occupying low latitudes; that this direction of continent prevailed throughout the Tertiary period; and that in certain portions of the southern hemisphere, particularly in Australia and New Zealand, there have been preserved portions of the Secondary continent with isolated remnants of the Secondary Mammalia and Gigantic Birds.

These conclusions were arrived at by a consideration of the direction of the principal volcanic axes in the Secondary and Tertiary periods. The Secondary continent was (the author considered) mainly influenced by volcanic axes which came into action at the close of the Carboniferous, and continued through the Secondary Period. These axes were (in the northern hemisphere) that of the Oural, that of the north of England prolonged into Portugal, and that of the Alleghanies, having all a north and south direction; and (in the southern hemisphere) those of eastern Australia and New Zealand, having a similar alignement. From this circumstance an inference was drawn that the Secondary continents had generally a trend from north to south, governed by volcanic bands having this direction; while, as the Secondary formations indicate a great extent of sea over the northern hemisphere, the bulk of the Secondary continent lay in the southern hemisphere.

The elevation of the bed of the Cretaceous sea, it was inferred, was due to volcanic forces acting from east to west; and the author adduced evidence, of this action having become perceptible during the later part of the Cretaceous period. He considered that the direction of all the Post-cretaceous lines of volcanic action governed the direction of the continent during the Post-cretaceous period, and pointed out that these were nearly all in an easterly and westerly direction, coincident with the existing volcanic band which extends from the Azores to the Caspian, and thence (with an interval of intense earthquake-action between the Caspian and Bengal)extends to the Society Isles. He concluded that they gave rise to a continent extending from the Caribbean Sea to the Society Isles,—many reasons uniting to show a land-connexion between America and Europe at the dawn of the Tertiary period, the submerged continent of Oceanica also indicating the easterly extension of Southern Asia; and that, since this continent receded to the north at the dawn of the Tertiary period before the inroad of the Nummulitic Sea (which stretched from the south-east through Western Asia and Southern Europe, and was, as the author conceives, the oceanic equivalent of the Eocene basins of Europe), thc greater portion of the deposits formed in the interval between Cretaceous and Eocene times must be now under the Southern Oceans.

The author then adverted to the circumstance that the recent great wingless Birds and the nearest living affinities of all the Secondary Mammalia yet known occur only in the Southern hemisphere. From this, and from some considerations as to the Vegetation, he concluded that, while parts of the Secondary continent yet remain in that hemisphere incorporated more or less into the Post-cretaceous continent, other parts of it, such as Australia and New Zealand, have remained isolated up to the present time to an extent sufficient to preclude the migration of Mammalia and wingless Birds, the terrestrial fauna of those lands being the isolated remnant of that of the Triassic or the Oolitic period. He inferred that the wingless Birds, excepting the swift Struthionidæ, have been preserved solely by isolation from the Carnivora, which do not appear as an important family until the Pliocene age; and he instanced the
Gastornis
of the Eocene (which had affinities with the Solitaire and Notornis) as evidence that the apterous birds had survived until that period, at least when the true Carnivora had not appeared.

An inference was then drawn that the remains of the Secondary continent, accumulated to the southward, caused cold currents to flow to the southern shores of the Post-cretaceous continent, causing the extinction of the bottom-feeding and shore-following Tetra-branchiata, to which Mr. Wood attributes the destruction of the Cestracionts which fed on them, and that of the marine Saurians that fed on the Cestracionts. The preservation of the Dibranchiata, on the contrary, was attributed to their being ocean-rangers. The extinction of the Megalosaurians he attributed to the effect produced on vegetation by the alternation of dry seasons during the year, brought about by a great equatorial extent of land,—the extinction of the herbivorous Megalosaurians, by this cause, involving that of the carnivorous.

Tne author also alluded to the contiguity of volcanos to the seas or great waters, which he considered to admit of explanation by every volcanic elevation causing a corresponding and contiguous depression, which either brings the sea or collects the land-drainage into contiguity with the volcanic region; and in conclusion he alluded to the law of natural selection and correlation of growth lately advanced by Mr. Darwin, in the soundness of which he asserted his belief.