Art. XC.—On the Reptilian Beds of New Zealand.
[Read before the Wellington Philosophical Society, 4th November, 1876.]
In March last, I received instructions to proceed to the Amuri Bluff for the purpose of making further collections and a measured section of the northeast face of the bluff. In my official report I confined myself to a statement of the facts observed by me; and now, with the permission of Dr. Hector, I contribute my views in the form of a paper to the Society.
Before doing so I propose to shortly sketch the progress of the geological exploration of the Waipara and Amuri Bluff beds, as the views held as to the age of these vary considerably.
In 1861 a notice of the first discovery of saurian remains, at the Waipara, by Mr. T. H. Cockburn Hood, was given by Professor Owen in a paper read before the British Association, from which it is to be inferred that he considered the fossils to indicate a jurassic age for the formation period. *
In 1864 Dr. Haast, in a paper dated, June, 1869, states that he examined the Waipara beds, at which time he considered the saurian beds to be of lower tertiary age. † In the same year Mr. John Buchanan, of the Geological Survey Department, examined and made collections from the Amuri Bluff beds, considering the Amuri limestone and overlying marls at that place as lower tertiary. ‡
In the same report, from an examination of Mr. Buchanan's collections, Dr. Hector was enabled to classify the beds as below:—
A—Chalk marls, the upper parts of which are now known as the grey marls; the lower as the Amuri limestone.
[Footnote] * Proceedings of the British Association, 1861.
[Footnote] † “Trans. N.Z. Inst.,” Vol. II., p. 189, 1866.
[Footnote] ‡ “Geol. Reports,” 1866–7, p. 39.
B—Ferruginous clays, with septaria and leda marls, containing upper secondary fossils (the greensand group and saurian beds of later classification).
C—Sandstone and grit, with plants representing the West Coast coalfield. Now known as the Amuri group. *
This, the first proposed, will, there is no doubt, prove to be the true classification of the beds, and may be applied equally to the Amuri Bluff and the Waipara sections, minor sub-divisions being in places adopted with advantage.
In 1867 Dr. Hector examined the Waipara section, and, as remarked by Dr. Haast, was the first to point out the true relation of the saurian beds to the overlying Weka Pass limestone. †
In 1868 Mr. Hood made a second collection from the Waipara, and during the same season Mr. R. L. Holmes made in this district a collection for the Colonial Museum. During the same year Dr. Haast made a survey of the Waipara district, and in his report argues at considerable length the question of the age of the saurian beds; considering the whole series, including the coal beds of the Waipara and Malvern Hills, to be of lower tertiary age. ‡
During the latter part of the year 1869 and in the beginning of 1870, Dr. Haast, for the New Zealand Geological Survey Department, examined the Amuri Bluff and surrounding district. In his report he describes the Amuri Bluff beds as being altogether distinct from the saurian beds at the Waipara, and notes a total disagreement between the fossils of the two localities. §
In 1871 Mr. H. H. Travers made a collection for the Colonial Museum, at Amuri Bluff; and in 1872 the writer made a large collection from the Waipara for the Canterbury Museum; and in 1873, at Amuri Bluff, another collection for the Colonial Museum, but none of these visits had any reference to the stratigraphical relations of the beds.
During December, 1872, and in the early part of 1873, Captain Hutton, as assistant to the Geological Survey Department, made an examination of the north-east part of the South Island, with a special view to the relations of the saurian beds.
In his report he considers the Amuri limestone, and underlying beds of the same series, as belonging to the very uppermost part of the cretaceous formation. The overlying beds at Amuri Bluff he refers to the upper
[Footnote] * “Geol. Reports,” 1866–7, p. 17.
[Footnote] † “Trans. N.Z. Inst.,” Vol. II., p. 189. See also “Geol. Reports,” 1868–9, Progress Report, p. 11.
[Footnote] ‡ “Geol. Report.,” 1870–1, p. 5–19.
[Footnote] § “Geol, Reports,” 1870–1, pp. 25–46.
miocene period. The same beds at the Weka Pass and upper part of the Waipara section are by him considered to be of upper eocene age. *
In 1874 I made an examination, for the New Zealand Geological Survey Department, of a part of the Waipara district, with the object of ascertaining the extension of the lower beds of the series in a westerly direction, the collection of fossils, and to determine the relation of Weka Pass calcareous greensand to the underlying Amuri limestone and the overlying grey marls.
During April, May, and June of 1876, I made the collections and examinations already alluded to, the results tending to confirm the view that the entire series as seen at the Amuri Bluff follow in unbroken sequence, of which, with the Waipara beds, the following is a comparative statement:—
|1. Mount Brown Limestone.||1. Wanting.|
|2. Grey Marl.||2. Grey Marls.|
|3. Weka Pass Calcareous Sand-stone.||3. Weka Pass Calcareous Sand-stone.|
|4. Greensand Conglomerate.||4. Greensand Conglomerate.|
|5. Amuri Limestone, embracing||5. Amuri Limestone.|
|a. Tucoidal Limestone.||a. "|
|b. Flaggy "||b. "|
|c. Flinty "; and||c. "|
|d. Chalk Marl or Leda Beds.||d. "|
|6. Teredo Limestone wanting, or merged in 7.||6. Teredo Limestone.|
|7. Concretionary Greensand.||7. Concretionery Greensand.|
|8. Boulder Sands, Saurian Beds.||8. Boulder Sands, Saurian Beds.|
|9. Glance Sandstone.||9. Black Grit.|
|10. Conchothyra Beds.||10. Aporrhais Beds.|
|11. Trigonia Beds.||11. Trigonia Beds.|
|12. Grey and Rusty Sands.||12. Belemnite Beds.|
In the section at Amuri Bluff the grey marls are not overlaid, as in the Waipara section, by the Mount Brown limestones; these beds, if ever present at Amuri Bluff, having been removed by denudation. The grey marls are here the highest beds, and have partially been removed by denudation. They are present both to the east and west of the older rocks, which divide the two wings of the cretaco-tertiary formation at Amuri Bluff. On the eastern wing, Dr. Haast calls them Leda beds; on the
[Footnote] * “Geol. Reports,” 1872–3, p. 47, and Sec. 5.
[Footnote] † The three last beds are distinguished by the abundance of the fossils from which they take their names.
western, Scalaria beds—these latter being, according to him, uncomformable to the Amuri limestone. Captain Hutton, on the other hand, describes the beds on the eastern wing as unconformable to the Amuri limestone, but makes no mention of the scalaria beds of Dr. Haast. These same beds in the Waipara section are referred by Dr. Haast to the Awatere formation, a′nd by Captain Hutton to the trelissaic group of his Oamaru formation. None of these arrangements agreeing with the classification here adopted, which regards the grey marls as the higher beds of the cretaceo-tertiary formation, leaving for future determination the relation of the Mount Brown limestone. That these beds, as seen at Amuri Bluff, belong to the chalk group, there can be no doubt, their conformable sequence to the Amuri limestone, and the contained fossils alike being evidence in this direction. In the upper part they are unfossiliferous, but in the middle and lower part they contain a few bivalve shells, besides abundance of Foramenifera shells, which characterise the same marls in other localities. The lower part is also characterized by the great abundance and beauty of the fucoidal impressions contained therein. Downwards, they pass into a calcareous greensand, harder, but presenting the same composition as do the same beds at the Weka Pass and at the Waipara Gorge. These beds are parted from the Amuri limestone by a rubbly bed of calcareous greensand occurring as nodules in a greenstone matrix, which, according to Captain Hutton, contains, at the Weka Pass, rolled pebbles of Amuri limestone.
When I examined the Weka Pass section, in 1874, I observed the pebble-like pieces of limestone, but doubted the evidence of their shape, as proving that they were water-worn.
While yet undecided how to account for them in the position in which they occur, I discovered, in the upper part of Weka Creek, where it breaks through the limestone range and in the underlying greensands, pebbles of Amuri limestone in every way resembling those which occur in the higher greensand parting the Amuri limestone from the Weka Pass stone. I concluded, therefore, that these pebbles are of a concretionary character, as those in the underlying greensands could not possibly be the proceeds of the denudation of the Amuri limestone.
This greensand conglomerate, though never more than two feet thick, generally about ten or twelve inches, is of great importance, as from it fossils have been obtained which have an important bearing on the view here taken of the general sequence. I have not obtained any fossils from this bed at the Waipara or in the Weka Pass section, but at Amuri Bluff it contains in places abundance of fossil bones, and of these there seems to be a considerable variety, but on account of the peculiar character of the matrix they are very difficult of extraction. Some of these I believe to be saurian,
but as the bones only appear when the surface of the bed has been long exposed to the action of the sea, they are necessarily much eroded.
From this bed I succeeded in securing two or three recognizable fragments of the fossil Penguin (Palæeudyptes antarcticus, Huxley), found in the limestone of Fortification Hill, Oamaru, and at Brighton, on the West Coast of the South Island.
North of Amuri Bluff, at Kaikoura, and in the Clarence District, this horizon is represented as beds of greensand, interstratified with the upper part of the Amuri limestone; and further north, in the vicinity of Cape Campbell, this and the overlying Weka Pass stone is wholly represented by beds of greensand, with which the Amuri limestone itself is frequently interbedded.
In the Amuri limestone itself the fossils of the higher beds are found, and notable amongst these is a well known form of Pecten zettelii, which has never yet been found outside the chalk group of the cretaceo-tertiary formation in New Zealand. From the same bed whence the above comes I obtained Inoceramus, sharks' teeth, and other remains of fishes, which are equally to be had in the marls above the underlying teredo limestone. In the lower part of the teredo limestone, fossils are met with which characterize the upper beds of the Amuri group, for which reasòn it is separated from the leda marls and Amuri limestone, and classed as the highest member of the greensand group. It is followed by the concretionary greensands, which, together with the boulder sands, and sulphur or gypseous sands, make up the saurian beds. Although abounding with saurian remains, these beds have not yielded fossil shells to the extent which might have been anticipated, although boulders containing shells frequently occur in the higher beds, and, invariably yield highly characteristic forms. In the Waipara District, the saurian beds are far more productive of fossil shells than the same beds at Amuri Bluff.
The Amuri group, or lower division of the series, has for its highest member the black grit or pebble bed, rich in fossil remains, of which the greater number are found in the lower beds of this group. Yet many shells and most of the saurians are also to be had in the overlying greensand group. A considerable thickness of green and grey sands follows, in the lower beds of which small and irregular concretions, abounding in fossils, are to be had; from which point, to the lowest beds of this section, fossils are extremely abundant and in great variety. The very lowest beds, seen only on the western wing, are brown or grey sands, with abundance of silicified wood, fragments of trees 18 or 20 inches in diameter. The upper beds of this group are represented at Boby Creek, Waipara River, by the calcareous semi-crystalline sandstone, with Conchothyra parasiticum, and other fossils,
and in like manner the occurrence of the black oyster of the Waipara in the trigonia beds at Amuri Bluff affords us the means of comparing the very lowest beds in the two localities. Both the Amuri group and the saurian beds are much more indurated as they are followed north, and at Flaxbourne their lithological characters are very different to what they are either at Amuri Bluff or the Waipara; heavy beds of volcanic rocks, with beds of indurated green sandstone, playing a prominent part in the composition of the beds which underly the Amuri limestone.
Having reviewed the opinions entertained by former workers in this field, and in part given a description of the beds in localities where they have come under my own observation, I now venture to place before you the views held by myself as to the age and conditions under which they have been deposited, and the after movements to which the beds have been subjected.
As regards the question of their age, my labours in the field as collector to the Geological Survey Department have accumulated abundant evidence in the shape of fossil remains to prove the synchronism of the beds throughout, and also to indicate by means of highly characteristic forms, that all the rocks here specially treated of are of young secondary age; and if, as has been contended, some of the fossils obtained from the higher beds are also to be had in decidedly tertiary rocks, these beds thus objected to on account of their perfect conformity to the underlying and decidedly cretaceous rocks, cannot be considered as other than passage beds between it and the very lowest tertiaries; and hence the classification of whole series of beds under the term “cretaceo-tertiary,” as proposed by Dr. Hector, even in the objections of dissenters, receives its fullest verification. *
The middle and lower beds of the series have generally been considered as of secondary age. Although Dr. Haast is not alone in assigning a tertiary age to these beds, in certain localities where the more characteristic secondary fossils are less abundant than at Amuri Bluff; as Captain Hutton considers the Saddle Hill and Green Island coal beds near Dunedin to be of tertiary age, although many of the fossils from these beds are to be found associated with saurian remains at the Waipara and other localities, one or two cretaceous Cephalopods being common both to the Amuri Bluff and Otago deposits. As to the synchronism of the Waipara and Amuri Bluff beds, which Dr. Haast considers to be of different ages, at Amuri Bluff I obtained besides saurians of the same species many fossils common both to the Waipara and Malvern Hills; and at Flaxbourne and near Cape Campbell in beds that co-relate with the belemnite and trigonia
[Footnote] * Although I here make use of the term “passage beds” it is used in a palæontological sense only, a break occurring between these and our oldest tertiary rocks.
beds at Amuri Bluff, the lower sands of the Waipara and the coal beds of the Malvern Hills; Belemnites, Inoceramus, and other characteristic shells, besides saurian remains closely associated with volcanic rocks, occurring under like conditions as the trachitic conglomerate described by Dr. Haast as interbedded with coal seams in the Malvern Hills.
It might be gathered from the authorities I have already cited that this series has already been traced to its very lowest beds. With this conclusion in the main I agree, but am still prepared for the discovery in the South Island of local deposits of still older date; and in the North Island, along the east coast, of a large development of rocks conformably underlying the saurian beds.
At all points where seen, the Amuri group lies highly unconformable on what appears to have been a very uneven surface, and this character of the old land seems to have been but little modified during the depression of the area over which the younger beds have been deposited.
The consequence is that the lower beds often appear as though deposited in bay-like indentations, a fact which appears to have been particularly noticeable to Dr. Haast during his earlier examinations of the Waipara district. A larger acquaintance with the beds in the adjoining district showed him that the Waipara beds could not have been so deposited, and this difficulty is overcome in his later reports by gradually increasing the dimensions of this imaginary bay, till eventually what, in the first instance, was of very moderate size, now, according to him, extended from the Looker-on Mountains in the Marlborough district to Otago Peninsula.
Captain Hutton seems to lay considerable stress on the apparent fact that “many of our vallies were formed in jurassic times.” And in support of this view, points to the occurrence of outliers of the Waipara beds in the Upper Waipara, Waimakariri, and Rakaia Rivers.
The occurrence of cretaceous rocks in the localities indicated, I do not consider as at all proving that the vallies in which they are now found were then excavated.
It might as well be contended that, because these same rocks are to be found at an elevation of over 4,000 feet on the neighbouring ranges, that the mountains in question are thus proved to date back to jurassic times.
Dr. Haast, with a reasoning similar to that of Captain Hutton, would place the excavation of some of our vallies at a period long prior to jurassic times, as the following extract from his Amuri report will show:—It may be truly said that after the mostly sub-ærial-denudation of these mountains, probably after the deposition of the triassic beds in New Zealand, the skeleton form of this portion of the South Island was already fixed, and that subsequent volcanic action, and the deposition of extensive younger
beds, changed little the characteristic features the country had then assumed. In any case, it is apparent that the country had already received its present orographical main configuration, in so far that the broad valley of the present Kahutara and its connection with the Upper Conway already existed, through which an arm of the sea flowed to the south before the marl stones and the succeeding beds were deposited.”*
The marl stones here mentioned as being deposited after the excavation of this valley belong to the Mataura series, which, in the South, Captain Hutton finds to be conformable to the Kahiku series. Are we then to consider this valley as having been formed prior to the deposition of the Kahiku beds?
In his paper “n the Kaikoura District” † Mr. Buchanan notices the anticlinal arrangement of the young secondary rocks, and clearly shows that the movements whereby this was effected was not confined to the younger beds, but extended over a very large district, and involved in its action all the older rocks.
My attention thus attracted, I consulted the reports of Dr. Haast and Captain Hutton on this subject, but, further than that they note the beds as frequently standing at high angles, and occasionally forming synclines, no mention is made of the greater movements in which these beds have participated; wrapping round spurs, deposits in bays and vallies between mountain ranges, being the favourable theories advocated by them.
Not seeing my way clear to accept these as the true explanations, I submit some further evidence in support of Mr. Buchanan's theory, convinced that it alone fully explains the scattered occurrence of the Waipara beds from Southern Canterbury to Cape Campbell.
From the mouth of the Waiau River, and running parallel to the coast, the Hawkeswood Range is continuous until the Conway River is reached, north of which it loses the character of a range, and an assemblage of rocky peaks of inconsiderable elevation form the older rocks between the Conway and the north-east face of the Amuri Bluff. The line of higher elevation is yet, however, to be traced as far as Kais Hill, and fully a mile out to sea at the Hapuka Rocks.
The same line continued cuts the Kaikoura Peninsula at the centre of the anticline, where the older unconformable beds are exposed. Continuing this line to the north, the coast range south of the Clarence River is reached, consisting also of older rocks.
Thus from the mouth of the Waiau to the south bank of the Clarence
[Footnote] * “Geol. Reports,” 1870–71, p. 28.
[Footnote] † “eol. Reports,” 1866.
River, we have a well-marked line of elevation, to the east and west of which, at intervals, outliers of the Waipara beds are to be found. For example, to the west, in the Valley of the Eden, and in the Lower Conway, and thence extending a few miles inland from the Amuri Bluff to the coast at the mouth of Oaro Creek.
Though at considerable distances, the limestones and saurian beds in the Kaikoura Peninsula west of the anticline, and the Waipara formation as exposed near the source of the Hapuka River, are evidently a continuation of this western division.
At the Amuri Bluff only are any portions of the Waipara beds continuous, so as to connect the eastern and western wings of the anticline. On the east side none of the Waipara rocks appear south of the Conway River, while at the Kaikoura Peninsula the whole have been removed on the crown of the anticline to the underlying beds, while east of the source of the Hapuka River the Waipara beds are not present, the older rocks reaching to the sea level. They are, however, to be found on the right bank of the Clarence River, extending some distance south along the coast.
To the east of this line of elevation the Waipara beds are nowhere observed to form a syncline (the Kaikoura Peninsula excepted), but on the west or inland side, this is invariably the rule.
From the point where it crosses the Waiau, this same line of elevation may be traced south (a slight interruption occurring at Cheviot Hills), and still dividing the younger beds, as in the north, into an east and west division, the easterly seldom presenting a synclinal arrangement, the westerly invariably doing so.
Further west, another belt of these younger rocks, often accompanied by tertiary beds, may be traced from Kaikoura up the valley of the Kahautara River, to the Upper Conway, thence across the Whale's Back to the Waiau Township, and at intervals along the borders of the Hurunui Plains, till, at the upper end of the Weka Pass, the two westerly divisions join. Tracing these south, they are found covering a considerable area in the vicinity of Heathstock, occurring as patches on the high ground dividing the south branch of the Waipara from the Okuku River, reported as occurring in the Upper Ashley, present in the Waimakariri basin west of Mount Torlesse, forming the coal basin west of the Big Ben Range, present in the Rakaia Valley near the mouth of the Acheron, crossing which at Redcliff they are next seen on the Smythe River, and at Clent Hills near Lake Heron. They are next seen in the Moorhouse Range on the north bank of the Rangitata, crossing which they appear in Coal Creek, and at Raincliff, west of Mount Four Peaks, uniting with the eastern division in the low country between Burke Pass and Timaru. These western divisions, in most cases,
stand at high angles, and in two places present the phenomena of an overturned section. The first in the country, between the Clarence and Kaikoura, where the whole series, including the leda marls, are overturned 20° beyond vertical. The second, near Heathstock, where the Awatere beds are also involved; the beds here are for the most part nearly vertical, and it is only the greensand group which, in the section seen, is overturned.
And thus, when these facts are taken into consideration, it does not appear to me that, at the time when these beds were being deposited, the outlines of the present configuration of the area within which their remnants are now found, was then determined; or that this series, at least the higher beds of it, were deposited in a large bay, with inlets penetrating the mountain ranges, wherever these rocks are now found. I rather think that the evidence points to the subsidence of a very wide area until deep-sea deposits were formed and a subsequent upheaval of mountain chains, between which, and in the folds of which, the younger beds have been preserved to the present day.