Volume 88, (Quarterly Issue), Part 4.

Issued February, 1961.

Published by the Royal Society of New Zealand,

Victoria University of Wellington. P.O. Box 196,

Wellington, New Zealand

Editor: J. T. Salmon, D.Sc., F.R.S.N.Z., F.R.E.S.

Associate Editor:

Sir Charles Cotton, D.Sc., Hon. LL.D., A.O.S.M.,

F.G.S., F.R.S.N.Z.

London Agent:

High Commissioner for New Zealand, 415 Strand, London, W.C.2.

Printed by Otage Daily Times and Witness Newspapers Co., Ltd.,

Dunedin, New Zealand.

The Stratigraphy and Structure of the Blair Atholl—Ben
a' Gloe Area, Perthshire, Scotland

By H. M. Pantin

The rocks of the area have been affected by several phases of folding and faulting. These phases appear to have taken place in the following order:

On a broad scale, the rocks are in normal stratigraphical succession over the whole area, although they are inverted in the overturned limbs of the isoclinal folds. The general order of succession was determined in Zone I by the direct observation of plunge in the resistant contact rocks at the Crochton, and in Zone II by observations on the plunge of minor folds in the Ben a' Gloe Quartzite. Numerous isoclinal fold cores can be recognised in Zone I, but none are of sufficient importance to receive separate names. The fold cores in Zone II are fewer and larger, and form a structural succession consisting of two synforms separated by an antiform, for which the following names are proposed: Ben a' Gloe Synform; Glen Fender Antiform; Meall Bhlair Synform.

These three fold cores can be recognised in Zone III, but no major isoclinal fold cores have been delineated in Zone IV.

This interpretation partially disagrees with that put forward by Bailey (1925), who concluded that in the part of the area called “Zone II” by the present writer, the rocks were in reversed succession. Bailey interpreted the Ben a' Gloe, Glen Fender, and Meall Bhlair-Meall Gruaim fold cores respectively as an antiform, a synform, and an antiform (Bailey, 1925, p. 696, and map with diagrammatic sections).

The folds of phase (1), or “primary major folds”, together with the slides of phase (2), have been considerably distorted by the movements of phases (3) to (5). The larger structures developed during phases (3) to (5) will be termed “secondary major folds”; these have played an important part in determining the present form and trend of the various lithological outcrops.

Contents

I. Introduction and History of Previous Work

The area to be described (Figs. 1 and 2) lies in the north Perthshire Highlands, and extends from the River Garry, in the region of Blair Atholl, to Glen Loch, about nine miles to the north-east. The north-western boundary of the area follows the River Tilt from the mouth of An Lochain southwards to Gilbert's Bridge, and continues west of the Tilt across lower Glen Banvie to Woodend, two miles west of Blair Atholl. The south-eastern boundary of the area is formed by the type outcrop of the Killiecrankie Schist.

Much of the ground is high moorland, the main exceptions being the Ben a' Gloe range in the north, where there are three main summits over three thousand feet in height, and the deep glen of the Tilt.

The rocks of the district were first mapped and described by the Geological Survey. Most of the present map area lies in the northern part of Sheet 55, but a small part overlaps on to Sheet 64. The rocks within this area belong very largely to the Dalradian series, but the Struan Flags (Moinian) are encountered in the west. Both pre-tectonic and post-tectonic igneous rocks occur, but are minor in bulk and will not be described here.

The earliest stratigraphical and structural interpretations covering the area under discussion were put forward by the Geological Survey in the Memoirs to Sheets 55 and 64. Bailey, in his 1925 paper on the Loch Tummel, Blair Atholl, and Glen Shee district, also covered the present area and proposed a new stratigraphical succession with several modifications. At a later date, he was also able to confirm his earlier views on the age relationships of the various members (1930, p. 92). His main stratigraphical divisions and their relative positions in the sequence are now generally accepted.

In the Schiehallion district, E. M. Anderson (1923) followed by Bailey and McCallien (1937) subdivided the two lowest members of the Dabradian as follows:

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

In the Blair Atholl-Ben a' Gloe area Bailey (1925) correlated various outcrops with the Schiehalhon Quartzite and others with the Killiecrankie Schist, but no rocks north-west of the type Killiecrankie Schist outcrop were referred to the Carn Mairg Quartzite. He also divided the Blair Atholl Series into a Pale Group (next to the Quartzite Series) and a Dark Group, but did not subdivide these further. His map indicates the mutual boundary of the Pale and Dark Groups over much of the area, but shows a few zones in the Blair Atholl Series that are not definitely allocated to either division. A later small-scale map by Bailey and McCallien (1937, p. 92) shows the Pale Group outcrop divided into White Limestone and Banded Group, but the Dark Group remains as a unit. The subdivisions of the Quartzite Series and the Blair Atholl Series in the present area, and their relationship to the Schiehallion succession, will be discussed in this paper.

The structure of the area was interpreted by Bailey as consisting essentially of a single large recumbent fold, with secondary folds superimposed on the limbs. The type outcrop of the Killiecrankie Schist, together with the underlying Blair Atholl Series immediately to the north and west, were taken to represent the upper, normal limb. The quartzite outcrops of Ben a' Gloe and Meall Gruaim were interpreted as secondary antiforms overturned towards the north-west and superimposed on the reversed limb of the mam recumbent fold. The latter was assumed to close below ground to the south-east of the type Killiecrankie Schist outcrop. The work on which this paper is based made it clear that the structural as well as the stratigraphical problems of the area needed some reconsideration.

Regional metamorphism of all rocks in the area has progressed well beyond the garnet isograd, both kyanite and staurolite occurring sporadically within the pelitic formations.

The writer remapped the area on a scale of six inches to a mile. The exposures are usually moderately good, but vary from crags and scars in which the rocks are almost completely exposed to drift-covered moorland with no outcrops except in a few stream-sections.

Maps of the western and eastern parts of the area are presented in Figs. 1 and 2.

II Stratigraphy

sistently dip to the south or east at a moderate angle, and it is evident that they are involved in strong isoclinal folding.

On the basis of lithological mapping, the rocks have been divided by the writer into a number of different formations, some of which correspond to formations recognised by Bailey (1925) while others do not. The writer has renamed some formations on the basis of type locality rather than lithology alone, as purely lithological names take no account of any variations which may be found as the formations are traced across country, and do not allow for the possibility (borne out in practice) of similar rock-types being found at more than one stratigraphical horizon.

The general characteristics of the various formations will now be summarised.

2. Description of Formations.

3. Stratigraphical Relationships and Correlations Between the Ben a' Gloe, Tulach Hill and Schiehallion Areas

a. Blair Atholl Series: Shierglas Limestone and Tomnabroilach Schists. These formations can be recognised with confidence in all three areas. They are synonymous with the “Grey Limestone” and “Dark Schist” in the Tulach Hill area across the Garry (cf. McCallien, 1943), and are undoubtedly equivalent to the Grey Limestone and Dark Schist of the Schiehallion area.

b. Blair Atholl Series: subdivisions younger than the Shierglas Limestone. In the Schiehallion area, the Blair Atholl Series occurs in three main belts:

(i) The northern belt, running from the north side of Schiehallion to Ben a' Chuallaich and Trinafour. This is the type area for the subdivisions of the Blair Atholl Series in Bailey and McCallien's Schiehallion succession.

(ii) The central belt, running from the south side of Schiehallion to Foss and Kynachan. This belt appears to represent the continuation of the Blair Atholl Series in the Tulach Hill area across the Loch Tay Fault.

(iii) The southern belt, in the neighbourhood of Loch Kinardochy. This belt will not be discussed here.

Bailey and McCallien (1937, p. 91) correlated the Banded Group of the northern belt with the Coire Fhiann Group of the Ben a' Gloe area, and their view is almost certainly correct. Whatever may be the precise correlation of the Ben a' Gloe Quartzite, it must belong to the lower part of the Quartzite Series; and this means

III. Minor Structures

schistosity surface. This “normal” type of lineation appears to have developed at the same time as the schistosity, and is generally directed towards the E or SE (Fig. 4). The less common type takes the form of corrugations up to several millimetres in width, which affect the schistosity and were clearly formed at a later stage. This second type of lineation has no obvious preferred orientation.

The Coire Rainich Phyllites are exceptional in possessing two groups of “normal” lineations, one group plunging to the NE and the other plunging to the E or SE. Usually only one lineation is present, but in a few localities the phyllites carry two distinct lineations, one lying in the NE quadrant and the other in the SE quadrant.

Schistosity is rare in the limestones and the Ben a' Gloe Quartzite, except in pelitic partings. Lineation also is rare in the limestones (except in pelitic partings), but is relatively common in the Quartzite, notably in the Ben a' Gloe outcrop itself, where two kinds of lineation are present. The first kind, found mainly in quartzites with pelitic partings, takes the form of rodding associated with minor folds, and usually plunges towards the NE or ENE; it is clearly a b-type lineation. The second kind, found mainly in massive and pebbly quartzites, consists of a striation on the bedding surfaces, accompanied by a conspicuous elongation of relict pebbles parallel to the striation. This is almost certainly an a-type lineation, and it is nearly always directed towards the E or SE.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Fig. 5. —Characteristic styles of synchronous minor folding. A—Shierglas Limestone. B—Ben a' Gloe Quartzite. C—Coire Fhiann Group. D—Struan Flags. Thick lines = lithological banding. Thin lines = general schistosity. Scale × 1/25.

2. Minor Folding

Minor folds in the pelitic, semipelitic, and calcareous formations may be divided into two groups. The great majority appear to be synchronous with both schistosity and the “normal” type of lineation, which runs parallel to the minor fold axes and is thus a b-lineation. The minor folds of this group affect only the lithological banding, and do not disturb the schistosity. They are typically incompetent, and grade from gentle monoclinal flexures into small recumbent folds (Fig. 5). They have the same general orientation as the “normal” lineation, plunging dominantly to the E or SE at moderate angles. The second and very subordinate group of

IV. Major Structures

striking NW-SE; probably it was more or less horizontal, with the same orientation that it possessed during the earlier stage of primary major folding.

2. Slides and Faults

(a) Slides. The Carn Liath and Luib Mhor Slides are the most important structures of this type in the present area, and the evidence leading to their recognition will now be summarised.

At the south-western foot of Carn Liath, the Monzie Limestone-Schist assemblage, bordered to the north by an outcrop of the Limestone, cuts diagonally from the Ben a' Gloe Quartzite across the Coire Fhiann Group and the Shierglas Limestone of Zone II on to the Tomnabroilach Schists. The northern contact of the Monzie Limestone is clearly tectonic, and this is confirmed by the presence of cross-bedding in the Quartzite, which occurs quite near to the margin and youngs towards the Blair Atholl Series. The Monzie Limestone runs westward to the Fender, remaining in contact with the Tomnabroilach Schists, and finally dies out in the Fender section south of Tomnaguie. Exposures farther west are very poor, but the slide is probably represented by the junction between Shierglas Limestone and Coire Fhiann Group just above Old Bridge of Tilt.

The south-eastern margin of the Ben a' Gloe quartzite outcrop is bordered wholly by the Monzie Limestone-Schist assemblage. If the latter are both older than the Tomnabroilach Schists, as suggested by the writer, there must be an important discontinuity running along the whole margin of the quartzite. In any case, the obvious discontinuity south-west of Carn Liath would be expected to persist some distance to the north-east. The slide is therefore continued along the margin of the quartzite as far as Loch Loch. The name Carn Liath Slide is proposed for this structure.

The numerous variations in the lithological succession which take place in the sector between Allt na Caillich and An Lochain, in the northern part of Zone II, show that in this area the Blair Atholl Series and the Quartzite-Phyllite assemblage are separated by an important discontinuity, presumably tectonic. The name Luib Mhor Slide is proposed for this structure. Its presence was noted by Bailey (1925, p. 683) and it is shown on his map.

Both these slides are apparently later than the primary major folds: the Luib Mhor Slide cuts obliquely across several fold cores which presumably belong to the primary major fold system, while the Carn Liath Slide truncates the southern end of the Glen Fender Antiform. On the other hand, the slides are certainly earlier than some, at any rate, of the secondary major folds. The Luib Mhor Slide is affected by secondary folds of type (ii) around Allt na Caillich, and the Carn Liath Slide is affected by a secondary fold (probably a dextral “twist”) at the southwestern foot of Carn Liath itself. The time sequence of the various fold systems and the slides therefore appears to be as follows:

The various faults in the area (infra) are clearly later than all these episodes of folding and sliding.

(b) Faults. The only faults of major importance in the district are those of the Loch Tay Fault System. In the Loch Tay area itself, the dislocation consists of a single fault, which runs obliquely across a zone of steep-dipping rocks near Fortingall. From the lateral displacement of the steep-dipping zone it can be shown that the fault has undergone a sinistral transcurrent displacement of 4½ miles. The more gently-inclined formations on either side of the steep-dipping zone show that a minor vertical displacement has also occurred, the upthrow being to the northwest. In the present area, the total relative displacement between Zone II and Zone IV is probably similar to that between the south-eastern and north-western blocks around Loch Tay.

The transcurrent displacement of Zone III relative to Zones II and IV cannot be determined with certainty, owing to the general lack of structures running at wide angles to the fault outcrops.

However, the relative vertical displacement of Zones II and III can be estimated, on the assumption that the quartzite outcrop just east of Croftmore does in fact correspond to the Meall Bhlair and Meall Gruaim outcrops. Using the uppermost margins of these quartzites as reference planes, it is clear that Zone III is down-thrown relative to Zone II: the amount of downthrow appears to be about 1,000 feet Zone III must also be downthrown at least. 1,500 feet relative to Zone IV by the western branch of the fault, but the amount of vertical displacement cannot be estimated more closely, since there are no lithological reference planes that can be identified in both Zone III and Zone IV.

Along most of the minor faults in Zones I, II and III, the predominant displacements appear to be vertical, although a sinistral transcurrent component may also be present in some cases.

3. Tectonic Comparisons with Adjoining Areas

The results described in this paper correspond fairly closely with the general observations of King and Rast (1956) on the Central Highlands, and with the results obtained by Rast (1958) in the Schiehallion area. King and Rast divide folds in the Central Highlands into two classes, “Main” or “Caledonoid” folds on NE-SW (or NNE-SSW) axes, and “Cross-folds” on NW-SE (or WNW-ESE) axes. The major Caledonoid folds obviously correspond to the primary major folds of the present paper, and the writer agrees with King and Rast (1956, p. 257) that “on a regional scale, the trend of the formations indicates that the major direction of fold axes is NE-SW.” However, the statement that “minor folds on these (Caledonoid) axes are ubiquitous” (King and Rast, 1956, p. 257) does not appear to be true for the Ben a' Gloe area. While the “Caledonoid” direction is dominant in the Quartzite this is not the case in the limestones and schists, where the dominant minor folds trend WNW-ESE and are clearly the cross-folds of King and Rast. A similar association of quartzite with Caledonoid minor folds and limestone with cross-folds has been observed around the hill Morrone, near Braemar (King and Rast, 1956, p. 263).

King and Rast (1956, p. 263) also conclude that the Caledonoid and cross-fold systems developed simultaneously. This does not appear to be strictly true in the Ben a' Gloe area, but the writer agrees with their conclusion that “the two systems of folds were developed during the same general epoch of folding” (p. 262), and that “all the movements formed integral phases of one period of orogenesis” (p. 263). There is no reason to suppose that the two trends represent two distinct orogenic episides, separated by an interval of quiescence. Rast and Platt (1957) have recognised the widespread occurrence in orogenic areas of cross-folds, formed during the same orogenic episode as the main series of folds but running at a considerable angle to the main trend.

The tectonic sequence at Schiehallion (Rast, 1958, p. 40) is very similar to that at Ben a' Gloe. The various episodes are compared in Table IV.

V. Summary and Conclusions

The rocks of the Blair Atholl-Ben a' Gloe area consist mainly of metasediments (quartzites, limestones, and schists), accompanied by subordinate igneous intrusions. The metasediments (together with the pre-tectonic igneous intrusions) have been extensively folded and faulted: the most important result of these movements has been the formation of a series of strongly compressed isoclinal folds, with planes dipping towards the south-eastern quadrant.

The area can be divided into four tectonic zones, bounded by the Carn Liath Slide and the branches of the Loch Tay Fault System. In each zone, the metasediments form a characteristic lithological succession, and the successions in the four zones are as shown in Table V.

Zone IV

• Glen Banvie Series

• Struan Flags

These series represent stratigraphical successions modified by folding and sliding. There is little doubt that the formations listed are in stratigraphical order, with the youngest at the top.

Proposed correlations with the Schiehallion succession are shown in Table VI.

The “White Limestone” of the Schiehallion sector does not appear to be represented around Ben a' Gloe; the white “Monzie Limestone” likewise appears to be absent from the Schiehallion sector, and is probably older than, the adjacent Tomnabroilach Schists.

The differences between the zonal successions at Ben a' Gloe are closely paralleled by lithological differences between the various structural zones at Schiehallion. These differences can be explained in terms of facies variations in the original sediments, and it is not necessary to attribute all the discrepancies to tectonic processes.

The rocks of the area have been affected by several phases of folding and faulting, which probably took place in the following order:

On a broad scale, the rocks are in normal stratigraphical succession over the whole area, although they are inverted in the reversed limbs of primary major folds. Numerous fold cores can be recognised in Zone I, but none are of sufficient importance to receive separate names. The fold cores in Zone II are fewer and larger, and form the structural succession:

Ben a' Gloe Synform
Glen Fender Antiform
Meall Bhlair Synform

These three fold cores can be recognised in Zone III. but no primary major folds have been delineated in Zone IV.

Acknowledgments

In conclusion, the writer wishes to express his best thanks to the University of Glasgow for financial assistance in meeting the expenses of field-work; to Professor J. G. C. Anderson, Mr. J. W. Brodie and Dr. W. A. Watters, for reading the manuscript critically; and to Mr. C. T. T. Webb (Chief Cartographer, New Zealand D. S. I.R.) and his staff, for drawing the maps and diagrams.

Mass Movement and Landform in New Zealand and
Hong Kong

By Leonard Berry and Bryan P. Ruxton

yellow on poorly drained sites, but numerous sections show grey or brown shades characteristic of local weathered volcanic rocks.

Contacts between the hillslope deposits and sedentary weathered material are usually very sharp and well defined and they often rest on Zone IIa (Ruxton and Berry, 1957, p. 1269) of the weathered granite. No fossil soils have been found between the hillslope deposits and bedrock or between the two layers of such a hillslope deposit. Thus, if a soil had formed, sub-surface corrasion has been sufficient to remove it as well as an unknown amount of weathered bedrock.

This outline account indicates the many points of resemblance between the hillslope deposits in Hong Kong and geliflual debris in New Zealand. The photographs used by Te Punga of “frost-riven fragments of greywacke set in a matrix of silty sand” are indistinguishable from many sections we have studied in Hong Kong. It is well known that deeply weathered igneous rocks and associated superficial deposits in humid tropical regions were first mistaken for boulder clays (Belt, quoted in Romanes, 1912, p. 133, in Costa Rica; Ansted, quoted in Kingsmill, 1862, in south China; Agassiz and Hartt, quoted in Derby, 1896, p. 530, in Brazil), because of their angular boulders, unsorted nature and clayey matrix. Moreover, as noted by Sharpe (1938, p. 56), “it is probable also that certain deposits resembling till may be in reality old mudflows, for both consist of heterogeneous or poorly sorted material and may contain striated pebbles or boulders.”

Te Punga (1955, p. 1007) stated that “angularity of large fragments of rock and of many mineral grains cannot be explained other than as frost riving”. The hillslope deposits in Hong Kong often have these characteristics, however, and frost riving has not occurred. Dominance of simple mineral grains and their angularity are also common features of weathered debris in tropical semi-arid, savannah, and humid regions. Comminution of grains of quartz is intensely active in the migratory layer on the pediment slope at Jebel Qasim in the savannah region of the Sudan (Ruxton, 1958, p. 373).

The proportion and grain size of the minerals in the hillslope deposits compared with that of the weathered and fresh source rock might be a significant factor in climatic correlation. Even then, with no additional evidence, a large proportion of unaltered minerals in a superficial deposit could be due to derivation in an arid climate or from a low weathering zone in a humid tropical climate. Most of the geliflual debris at Wellington was derived from deeply weathered greywacke. An earlier period of intense chemical weathering had already decomposed and disintegrated the rock, and it would be very difficult to recognise extra comminution and disruption caused by frost riving and heaving from that caused by the movement of a migratory layer.

Mass Movement

The slow downslope movement of rock waste saturated with water was termed solifluction by Andersson (1906). In the initial definition there was no climatic limitation to the term, but later it was restricted to movement occurring over a frozen subsoil. The latter, Baulig (1957, note 21, p. 926) now terms gelifluxion, and he implies that solifluxion should be used for all other conditions. Penck (1953, p. 107) claimed that flowing rock waste is widespread in frost-free regions, especially when the surface mantle is moistened. Peltier (1950) pointed out that mass movement of saturated or lubricated surface material should be common in several climatic zones, becoming a relatively important factor in denudation in periglacial, maritime, and selva (humid-tropical) landscapes. Saturation of surface layers because of impeded drainage is undoubtedly the greatest single factor causing gelifluxion in periglacial regions. Saturation of the surface layers is also common in areas receiving numerous short periods of very intense rainfall, when drainage to the subsoil cannot keep pace with precipitation.

sub-surface corrasion may occur. This leads to a renewal of exposure on the upper slopes. But on pediments, valley-side strips, and plains removal of surface material causes a downward extension of the surface influences which promote creep. Sedentary weathered rock is thus gradually incorporated into the migratory mantle. Removal from above is compensated by renewal from below. If corrasion is defined as a freeing of loosened rock fragments from their place of origin (cf. Penck, 1953, p. 112) then sub-surface corrasion can be said to occur under both active mass movement and slow creep. If corrasion is defined as the mechanical wearing of surfaces by rock waste in transit (cf. Malott, 1828, p. 158) then sub-surface corrasion will be practically confined to hillslopes.

Convex Profiles in Headwater Streams

Waters (1953, p. 72, fig. 2) noted that the breaks in slope on Dartmoor streams are composite and convex. An upper knick on unconsolidated gravel has migrated upstream more rapidly than a lower knick on the underlying granite. The convex knick thus owed its form to a break in the physical mobility (the ease of removal by mass-wasting or erosion) of the affected material. In a similar way, if a surface is mantled with a thick, complete, gradational weathering profile, then in general the physical mobility of the material will decrease steadily downwards, with a further sudden decrease at the basal surface (Ruxton and Berry, 1959). An old age surface developed in a humid climate usually bears an old age weathering profile with thick upper zones resting abruptly on the basal surface. After uplift revival of weathering below the former basal surface will thicken the lower zones, especially near the upland margins (Fig. 2). A thick mantle of upper weathering zones will then rest abruptly on a complex of lower zones (IIb, III and IV, Ruxton and Berry, 1957) and there will be a considerable break in the physical mobility between them. A convex valley profile may then develop around the upland margin, as the resistant lower zones hold up retreat, while the physically mobile upper zones allow the ready removal of debris and the development of a normal concave profile above the knick. On Dartmoor, Waters (1957) noted that, while the valley sides at the breaks of slope were steep and narrow, wide basins were formed above them.

If the upland margin is much dissected, as in Wellington, New Zealand, headwater streams will rise on the margins of the upland remnants, starting their courses with a convex profile as there will be insufficient catchment above them to allow the development of the upper courses. In Hong Kong convex knick points and convex headwater streams are common on the weathered granite, volcanic, and

Fig. 2. —The profile of a headwater stream and the axis of a dell-like hollow in relation to the zones of weathering on the margin of a deeply weathered upland surface. The diagram is an idealised version of relationships observed on weathered granite and weathered ignimbrite in Hong Kong.

sedimentary rocks. Above them the floor may broaden out into a basin form with a continuation of the stream, as in Dartmoor, or it may end with a dell-like hollow near a ridge top as in New Zealand.

Dell-like Hollows

Dell-like hollows in Hong Kong frequently have a swampy floor with no trace of a stream course. Artificial sections in these basins show an upper migratory layer resting on well-weathered sedentary debris sometimes with a stone line between them. The migratory layer is moving slowly downhill while its upper surface is being eroded by sheet and rill wash.

Mass movements in Hong Kong, as elsewhere (cf. Cotton, 1958a, 1958b), tend to soften the relief and to coarsen the drainage texture. There is a sharp contrast between the morphology on the granite and on the volcanic rocks. The former weathers to a clayey sand which is remarkably stable, whereas the volcanic rocks yield a silty clay which is very unstable, and slips, slumps, and flows are common. The drainage texture on the volcanic rocks is much coarser and the surface contours much smoother than on the granite, though a layer of migrating rock waste occurs en both. There is a detailed adjustment to structure both in the weathering profile and in the surface form on both the granite and the volcanic rocks (cf. Cotton, 1943, p. 239).

Cotton (1955, p. 1017) has described V-shaped gullies cut into deeply weathered rock which are now partly infilled by strips of peat swamp up to 10–20ft wide. The change from cutting to filling was assumed to be due not to deforestation but to some recent micro-climatological change. Similar features occur in Hong Kong. The floors of some side valleys are aggraded with a reddish-brown silty clay with a marsh vegetation, while the side slopes and nearby spurs are intensely and deeply gullied (Ruxton and Berry, 1957, Pl. 1, Fig. 3). The development of these features seems to be partly due to the advanced stage of the gully cycle and partly to deforestation. In the Kowloon Hills where gully development is extreme with only narrow walls of weathered debris between adjoining gullies, some of the larger gullies have aggraded floors with marshy bottoms. Here aggradation appears to be part of the normal cycle of gully development and destruction.

Conclusion

The products of mass movement in similar geological environments appear to be comparable in monsoonal and in periglacial conditions, and they must be used with caution in climatic deductions. Common factors in several areas are thick weathering profiles and conditions favouring saturation of the surface layers of rock waste. Geliflual corrasion by saturated thaw debris moving over the frozen ground in dell-like hollows in New Zealand is paralleled in Hong Kong by permissive incorporation of the sedentary weathered debris into the migratory layer by “removal and renewal”. But, whereas in Hong Kong intense chemical weathering at the base of scarp slopes is coupled with the progressive removal of the finer and more physically mobile material and collapse of the upslope debris to form hillslope deposits, it is difficult to understand how a slope can be undermined in such a way under periglacial conditions.

It seems that deeply weathered areas under many climatic regimes are very susceptible to mass movements provided sufficient relief and concentration of water are available. The Massif Central (Beaujeu-Garnier, 1953); Devon and Cornwall (Waters, 1957); Wellington (Cotton and Te Punga, 1955); Portugal (Guilcher, 1949); Brazil (Tricart, 1958), and Hong Kong all have thick weathering profiles which are affected by mass movements.

We are grateful to Professor Sir Charles Cotton, Professor W. J. McCallien, and Dr. L. Curtiss for their reading of the manuscript and their many helpful suggestions.

On the Definition, Date, and Character of the Ross Glaciation,
Early Pleistocene, New Zealand

By Maxwell Gage

Evidence for Glaciation

The beds under consideration unconformably underlie the extensive piedmont moraines of Westland, which show morphologic as well as textural evidence for their glacial origin, but with which we are not concerned in this paper. The evidence for the earlier glaciation at Ross comes from the two members of the succession formerly designated “R6” and “R7” (Gage, 1945, pp. 144–7). Glacial conditions of deposition are inferred for R7 for the following reasons: (i) it includes a typical till made up of boulders and pebbles unsorted as to size or shape and embedded in tough fine blue silt; (ii) the boulders and pebbles (many of them since found to be striated) include angular fragments of schist and hornfels, for which there is no known or likely source within 9 or 10 miles; (iii) the till is overlain by laminated, graded, fine silts indistinguishable from a type of sediment common in modern ice-margin or proglacial lakes. Large angular blocks of schist also occur in the upper part of the underlying R6 conglomerate, equally remote from the nearest source. At least the upper part of the conglomerate may therefore be interpreted as proglacial outwash from advancing ice, which eventually reached the Ross area and deposited R7.

It has been tacitly assumed that the ice advanced towards Ross from an elevated tract roughly coincident in position with the present South Island mountain axis. There is no evidence from striated rock surfaces, but a westward or north-westward direction of ice flow is demanded by the lithologic composition of the glacial deposits. New Zealand has been totally isolated from lands to the west since long before the Pleistocene, and so no suggestion of ice invasion from the west need be entertained.

Evidence for Age

Younger glacial deposits at Ross were described as “R9: High-level Terrace Gravels” (now regarded as glacial; Gage and Suggate 1958, p. 594) and “R10: Piedmont moraines and associated gravels and silts”. The age of these deposits, which rest unconformably upon the Lower Pleistocene beds, is accepted as late Pleistocene and will not be discussed further here.

The older glacial beds at Ross were inferred by Gage (1945, p. 155) to be Pliocene. From studies of migrations of marine molluscan faunas Fleming (1944) concluded that the seas in the New Zealand region cooled during the Lower Nukumaruan Stage (then regarded as mid-Pliocene) and subsequently became warmer. Finlay (1947, p. 352) correlated the Opoitian and Waitotaran stages with the Plaisancian stage of Europe. During the next few years the use of plant fossils, especially pollen and spores, developed rapidly in New Zealand, so that Fleming, in a paper presented in 1953 (published 1956), was able to quote Couper as supporting the correlation of a carbonaceous band at the base of R6 with the Lower Nukumaruan. While recognizing that direct faunal evidence was still lacking for correlation of the New Zealand stages above the Waitotaran with the Calabrian or Villafranchian, Fleming (1953) recalled that the Commission of the XVIIth International Geological Congress (London, 1948) when recommending that the base of the Pleistocene be fixed at the base of the Calabrian stage, had noted that the first indication of climatic deterioration in the Italian Neogene succession begins to appear at this horizon. In New Zealand, climatic deterioration setting in at the end of Waitotaran time thus provides reasonable grounds for drawing the Pliocene-Pleistocene boundary between the Waitotaran and Nukumaruan stages. Couper and McQueen (1954, table, p. 416) confirmed the Lower Nukumaruan age of the cool-flora lignitic bed at the base of R6 at Ross, and thus the older Ross glacial beds found themselves in the Lower Pleistocene.

Stratigraphic Terminology

Investigations by Gage (1945) and Wellman (1945) at Ross, which lies within the Mikonui Subdivision of the New Zealand Geological Survey (Morgan, 1908), showed the necessity for revising Morgan's stratigraphic classification in the light of recent paleontological advances, but in accordance with views then held with regard to overloading of the nomenclature with provisional terms (Gage and Wellman, 1944, pp. 352–3), Gage designated his divisions of the Ross succession merely by mapping symbols R1, R2, etc. The terms “Ross Glaciation” and “Ross Advance” came into use later, without precise formal definition, but by inference they were based upon R7 by Wellman (1951, p. 30) and upon R6 to R8 inclusive by Fleming (1956, p. 926). “Ross Glacial Stage” was introduced nominally and with local application by Wellman (1951, fig. 2, following p. 24), but was later adopted into a proposed scheme for a glacial chronology of the New Zealand Pleistocene by Gage and Suggate (1958, p. 593). By implication, R8 was excluded on the grounds that it lacks distinctively glacial characters.

Report 6 of the American Commission on Stratigraphic Nomenclature (Richmond, et al., 1959) advises against using evidence of climate change for the defining of time stratigraphic units. The writer, on the other hand, agrees with Suggate (1960) that important reversals of trend in climate change are probably world-wide and virtually synchronous and therefore are acceptable as criteria for time-stratigraphic definitions. A “Ross Stage” of the New Zealand succession might therefore be typified by the beds between the first indications of the Ross cooling and the first indications of post-Ross warming, but no such unit is required since the time-interval concerned appears to be covered by the existing time stratigraphic classification, with which the Ross sequence can be correlated reasonably by paleontological means. It would therefore be advisable to discontinue using the term “Stage” in connection with the Ross glacial beds, and instead to re-define “Ross Glaciation” as a climatic event (not as a stratigraphic unit, the recommendation of Richmond et al., 1959, Table I, p. 666) recorded by the character and sequence of certain beds at Ross. The beds themselves should now be properly defined as rock-stratigraphic units, especially in view of the greater significance which they have assumed since they were first described.

It is now proposed to establish the Jones Formation¹to include that part of the Lower Pleistocene succession at Ross described by Gage (1945, pp. 144–6) under the headings: “R6: Lower Decomposed Conglomerate” and “R7: Laminated Fine Silts and Boulder Clay”. Henceforth, the Ross Glaciation may be considered to be based upon the evidence for climate-deterioration leading to glacierization that is shown by the Jones Formation.

The sections undoubtedly should eventually be re-traversed to fix the formation boundaries precisely, but until this can be done, the sequence as described in Jones Creek upstream from the site of Ross United Claim, in the north-western branch of Jones Creek and along the former Mount Greenland water-race are offered as a provisional composite type locality.

It is intended, for the present at least, to exclude the R.8 beds from the Jones Formation, but the possibility is recognized that less well-sorted conglomerate in the upper part may represent outwash from a glacier which failed to reach the Ross area, or for some other reason failed to leave a positive record. Meanwhile, for convenience, the name Mont d'Or Formation (from an old sluicing-claim of that name) is proposed for the beds previously designated “R8: Upper Decomposed

may be interpolated with reasonable approximation on the existing small-scale map (Fig. 1). Wellman's interpretation of the Coal Creek section (1945, fig. 1) has been adopted.

Structure and Deformation of the Lower Pleistocene Strata

Mount Greenland consists of an elevated mass of ancient greywacke and slate (Greenland Group) of Lower Palaeozoic or pre-Cambrian age surrounded by Tertiary and Quaternary deposits. Thin outliers and a basal fringe on three sides are composed of Pliocene and Lower Pleistocene beds which are deformed into sharp north-east-plunging folds and faulted in at least one place, and which show a general periclinal arrangement. The outliers are probably more extensive and more numerous than the forest cover has allowed us to discover, but the whole Mount Greenland range may be regarded as an irregularly elevated and almost completely denuded mass of ancient rocks, its relief being due directly to comparatively recent tectonic movement on a large scale. Greenland Spur and Malfroy Spur thus appear to be denuded cores of anticlines or differentially-elevated sub-blocks of the Greenland mass.

In these circumstances it is held justifiable to extend the Greenland and Malfroy anticlines (Fig. 1) beyond the known limits of surviving Pliocene-Lower Pleistocene cover in order to demonstrate the character of the later deformation. The trends of these folds conform generally with the locally very uniform north-westerly strike of the steeply-dipping greywacke basement rocks. The undermass may therefore have been deformed by the mechanism of shear-folding or closely-spaced bedding-faults, while the incompetent covering strata accommodated themselves to the displacements largely by folding. But this cannot be the whole story, for Wellman (1945, pp. 10, 12) showed that the Lower Tertiary rocks in Coal Creek were sharply folded in mid-Tertiary times about an axis transverse to the trend of Greenland Group rocks.

The timing of the later deformation at Ross may be given approximately in terms of the glacial chronology. Our knowledge of the regional paleogeography is insufficient to confirm the possibility of earlier localized emergence which is suggested by overlap of Waitotaran beds upon greywacke at Ross, but there is no doubt that the climax of the disturbance occurred after the Ross Glaciation (Lower Nukumaruan) and was, therefore, part of the major paroxysm of the Kaikoura movements in early Pleistocene times. Deposits from the Otiran Glaciation (Gage and Suggate, 1958: correlated with “Last Glacial” of the northern hemisphere) are warped and faulted at several places along the Alpine Fault (e.g., see Wellman, 1955, p. 38, “Paringa Formation”; Bowen, 1954), but are not perceptibly deformed near Ross. Gravel remnants on benches on the valley sides high above the lower gorge of the Mikonui River, and ascribed to glacial deposition during the Waimaungan Glaciation (Gage and Suggate, 1958, p. 594; probably equivalent to “Penultimate Glacial”), are more than 2,000 feet above sea-level at a distance of six miles from the coast. Moreover, a distant view of the benches gives an impression of upwarping about a north-easterly axis. Additional altitude data are required to verify this impression which, if confirmed, would mean that the uplift of Mount Greenland continued into the earlier part of the late Pleistocene.

Nature of the Ross Glaciation

The Pliocene-Lower Pleistocene succession at Ross embodies the record of a complete cycle of glacier advance and shrinkage complicating the record of final expulsion of the sea from the North Westland region. The coastline migrated north-wetswards partly as a direct result of emergence, and partly as an indirect result through progradation promoted by the abundant transfer of waste from the rapidly

rising alpine region. In some places at least the material was contributed in the form of pro-glacial outwash gravels. The coincidence cannot be ignored, and one must count the growing elevation of the land as a direct factor promoting the first Pleistocene glacierization of New Zealand, but not the sole cause, for the Ross glacial cycle begins with the floral indications of cooler conditions in the basal R6 lignite which was deposited near sea-level. Allochthonous angular bounders near the top of R6 have been taken to indicate proximity of glacier ice, while the till and sub-glacial or ice-contact water-laid deposits at the base of R7 mark the actual invasion by the glacier. Laminated silts at the top of R7 indicate recession of the ice, leaving a pro-glacial lake impounded probably by terminal moraine. The cycle is completed with the infilling of the lake, and sufficient amelioration of climate to encourage recolonization of the region by plants, as indicated by a peaty layer at the base of the Mont d'Or Formation.

Correlatives of the Jones Formation are recognized elsewhere in the region, but so much has been eroded or covered by younger deposits that we cannot picture either the details of the early Pleistocene landscape, or the character of the Ross Glaciation. It is not known, for example, whether the ice responsible for the Jones glacial beds was at any stage continuous with that responsible for similar Lower Pleistocene glacial beds farther north at Humphreys Gully and Findlay Creek (Bowen, 1957) and if so, whether continuity would imply a Ross ice-cap or merely piedmont coalescence of valley glacier tongues such as developed in Westland later in the Pleistocene. One can, however, visualize an early stage in the mountain-building when dissection was incomplete, the relief less severe, and the scenery less strongly alpine in aspect than in the later Quaternary,^* so that there may have been extensive plateaus upon which ice-caps or plateau-glaciers could have been generated.

References

Bowen, F.E., 1954. Late Pleistocene and Recent Vertical Movement on the Alpine Fault. N.Z. J. Sci. Tech., B 35, pp. 390–7.

Bowen, F. E., 1957. Early Pleistocene Glaciation in Westland. Austr. N. Z. Assoc. Adv. Sc., 32nd Meeting, Dunedin, Sec. C, Abstr. C 26.

Couper, R. A., and McQueen, D. R., 1954. Pliocene and Pleistocene Plant Fossils of New Zealand and their Climatic Interpretation. N.Z. J. Sci. Tech., B 35, pp. 398–420.

Finlay, H. J., 1947. The Foraminiferal Evidence for Tertiary Trans-Tasman Correlation. Trans. roy. Soc. N.Z., 76, pp. 327–52.

Fleming, C. A., 1944. Molluscan Evidence of Pliocene Climatic Changes in New Zealand . Trans. roy. Soc. N.Z., 74, pp. 207–220.

— 1953. New Evidence for World Correlation of the Marine Pliocene. Austr. J. Sci., 15, pp. 135–6.

— 1956. Quaternary Geochronology in New Zealand . Actes IV Congr. Internat. Quaternaire, Rome-Pisa, 1953, pp. 925–30.

Gage, M., 1945. The Tertiary and Quaternary Geology of Ross, Westland. Trans. roy Soc. N.Z., 75, pp. 138–59.

— 1959. Ross Glacial Stage, in Lexique Stratigr. Internat., 6 (Océanie), (4) New Zealand: Paris.

— and Suggate, R. P., 1958. Glacial Chronology of the New Zealand Pleistocene. Geol. Soc. America Bull., 69, pp. 589–98.

— and Wellman, H. W., 1944. The Geology of Koiterangi Hill, Westland. Trans. roy Soc. N.Z., 73, pp. 351–64.

Hutton, F. W., 1872. On the Date of the Last Glacier Period in New Zealand, and the Formation of Lake Wakatipu. Trans. N. Z. Inst., 5, p. 384.

Contributions to the Mineralogy of New Zealand—Part V

By C. Osborne Hutton

a-axis zero-layer Weissenberg film. Two lines at d = 1.218 and d = 0.902 Å that result from reflections from (314) and (534) respectively have not been recorded by Swanson et al., although they are both permitted by the space group for zircon, and have been observed on the writer's Weissenberg and powder films.

In one of the powder patterns listed for comparative purposes by Swanson et al., viz. the British Museum pattern, there is a diffuse line at 1.217 Å with an intensity of 20. This has been dismissed by these writers as alone due to monoclinic form of ZrO₂, or baddeleyite. They are justified, in the main, since the British Museum pattern also exhibits a strong line at 2.76 Ź that is undoubtedly due to baddeleyite, but the writer believes that they are incorrect in considering the line at 1.217 Å as solely due to baddeleyite.

Again it should be noted that, although Swanson et al. do not record a line at 0.902 Å ca, the United Steel Companies pattern listed by them does contain this line; the intensity, however, is given as 50 on their scale, although the corresponding reflection due to (534) is faint in both the present writer's powder pattern and a-axis 3rd-layer Weissenberg film. Inspection of the scale of intensities listed with d-spacings by the United Steel Companies, suggests that their films have been heavily over-exposed; this would permit fainter lines to assume greater densities.².

Table. I —X-ray Powder Diffraction Data for Hyacinth

Snowy River, south-western Nelson, New Zealand (x-ray films Nos. 1123, 1124). Nickel-filtered copper radiation (CuK_a = 1.5418 Å). Camera diameter = 114.59 mm; cut-off at 18.5 Å ca. Spacings corrected for film shrinkage. Disordered form:

a_o = 6.625 Å, c_o = 6.010 Å. Ordered form a_o = 6.605 Å, c_o = 5.978 Å.

Samarskite in Hyacinth

Table II —X-ray Diffraction Powder Patterns of Samarskite.

Nickel-filtered copper radiation (CuK_a = 1.5418 Å) Camera. diameter = 114.59 mm. Cut-off at 18.5 Å ca. Intensities determined visually and films corrected for shrinkage.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Explanation of Table II.

A. Samarskite heated in air to 1130–1140° C. for three hours. Spruce Pine, Mitchell Co., North Carolina . X-ray film No. 255. The lines at 2.517 and 2.497 Å and those at 1.436 and 1.426 Å are bracketed together because these pairs of lines are only barely resolved. Resolution is somewhat less in films yielded by material that has been heated to 1000° C., still less so at 950° C., and was unrecognized in films yielded by samarskite that has been heated to 860° C. (column B).

The line at 1.560 Å represents the sharp shoulder of a band that fades off imperceptibly towards lower angles of 2θ. The band is approximately 0.03 Å in width. A number of very diffuse lines have been noted in the film following the last spacing (1.018 Å) listed.

B. Samarskite as for A, but heated in air to 860° C. for 30 minutes. X-ray film No. 1150. The lines that are bracketed signify barely resolved reflections, and in the case of lines at 1.914, 1.888, and 1.859, although resolution is quite evident, the lines are enveloped in a fairly strong diffuse band.

C. Samarskite inclusion in hyacinth, heated in air to 860° C. for 30 minutes. Snowy River, south-western Nelson, New Zealand . X-ray films Nos. 1130 and 1131A.

Bracketed lines have the same significance as those in columns A and B. The line at 1.431 Å, although rather broad, is not diffuse; it is probably a doublet.

D. Samarskite as for columns A and B, but heated in air at 560° C. for four hours. X-ray film No. 252.

The lines at 1.764 and 1.700 Å constitute a band, rather sharp at 1.764 Å but fading towards higher angles. The lines at 1.490 and 1.440 Å represent the limits of a very diffuse band.

E. Samarskite heated in air to 600° C. for five hours. The locality is given merely as N. Carolina (Lima-de-Faria, 1956, p. 128, Table I, 3rd column).

D, diffuse line. B, broad line. VD or VB, very diffuse or very broad line. VBD, very broad, diffuse line.

The temperature at which hyacinth with inclusions was heated—viz., 860° C., was chosen before it was realized that the inclusion material was samarskite. Accordingly, the x-ray diffraction pattern yielded by the phases so formed by the multiple oxide may not readily be compared to any recorded data, because powder patterns made available by other investigators (Berman, 1955; Lima-de-Faria, 1956, 1958) have been obtained from samarskites heated to temperatures of 600° C. and 1000° C. in air. For this and other reasons, x-ray patterns have been secured for Spruce Pine samarskite that had been heated in air to 560°, 600°, 750°, 860°, 1000° C. 1130–1140° C. The 600° and 1000° C. temperatures were chosen so that the films obtained by the present writer might be compared with the data recorded by Lima-de-Faria, and the other temperatures were chosen after inspection of differential thermal analysis curves of Spruce Pine samarskite. The curve obtained in this instance shows, after an initial endothermic dip, four exothermic peaks at 445°, 700°, 830°, and 1015° C. It would seem appropriate, therefore, to heat specimens of samarskite for subsequent x-ray study at temperatures which correspond to points on the differential thermal analysis curve that indicate a cessation of an exothermic reaction.

It should be noted that for temperatures in excess of 1000° C. a heating period of 30 minutes is quite adequate, and in fact in the study reported later in this paper it is stated that films yielded by euxenite that had been heated to 1000° C. in air for 10, 30, 60 and 180 minutes are identical in every way. A number of specimens of samarskite studied here were heated for a range of periods up to four hours, but careful inspection of the films yielded by materials so treated showed that longer periods of heating were no more effective than the shorter ones.

The x-ray diffraction powder patterns yielded by samarskite heated to 560°, 600°, 860°, and 1130–1140° C. are set out in. Table II, and a number of these are to be found in Pl. 44. The pattern secured for samarskite that had been heated to the latter temperature is listed here in place of that yielded by the same material after heat-treatment at 1000° C., because, although the two patterns are identical,

Euxenite-Polycrase

In heavy residues secured from gravels of the Nile or Waitakere River, just downstream from its junction with Awakari Stream¹, some particles were dismissed, at first, as anhedral grains of chromite or chromian spinel owing to deep brown colour, isotropic character, and marked conchoidal fracture surfaces, until a few

Fig. 3. —Slightly simplified drawings of euxenite-polycrase crystals from the Nile River, New Zealand. Magnification is approximately the same for all crystals, and crystal B is 2.1 mm in length. A and B: Crystals exhibit development of forms a {100}, b {010}, d {101}, and m {110}, together with satellites. Crystals are strongly striated parallel to [001]. C: Two striated crystals of similar form with a {100}, d {101}, and b {010} exhibit inter-penetration effect.

[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]

Explanation to Table III

• A.

  Euxenite-polycrase, Nile River, south-western Nelson, New Zealand. The specimen was heated, as fragments (average diameter = 0.5 mm ca.), in vacuo for one hour at 620° C. X-ray film No. 1034.

  • a.

    Several additional lines are to be observed at higher angles than the last line recorded here, but they are so faint and diffuse that no measurements were made.

• B.

  Euxenite-polycrase, Nile River, south-western Nelson, New Zealand. The specimen was was heated as fragments in air for three hours at 700° C. X-ray film No. 1045.

  • a.

    Strongly asymmetric line.

  • b.

    In comparison to the lines at higher and lower angles, this line is very precisely defined.

  • c.

    A. few additional lines are to be observed at higher angles than the last line recorded here, but they are extremely faint and very diffuse.

  • d.

    The lines from 1.34–1.03 Å are measured only approximately owing to the diffuseness of the reflections.

• C.

  Euxenite, south Norway. The specimen was heated in air to 700° C. for three hours (Lima-de-Faria, 1958, p. 938, Table I).

• D.

  Euxenite-polycrase, Nile River, south-western Nelson, New Zealand. The same specimen that yielded the pattern listed in column A of this table was heated as a fragment (0.1 mm in diameter ca.) in vacuo for 1¾ hours at 1130–1140° C. X-ray film No. 1036.

  • a.

    This is a broad band with a wide shoulder on the higher 2° side.

  • b.

    A slight shoulder on the high 2° side.

• E.

  Euxenite, Iveland, Setesdalen, Norway. The specimen was heated as fragments in air for 2¼ hours at 1130–1140° C. X-ray film No. 215.

  • a.

    This is a broad band of uniform density.

  • b.

    The 1.817 Å reflection consists of a sharp line superimposed upon a diffuse band that ranges from 1.802–1.825 Å. This situation is distinct from the more precisely defined lines at 1.814 and 1.834 Å in column D of this table.

  • c.

    The absence of a corresponding strong line in the pattern presented in column D of this table appears to be one of the outstanding differences between the patterns in columns D and E.

  • d.

    These two lines represent the two relatively sharp edges of a diffuse band; the latter is not evident in the pattern in column D, but instead two precise lines are present.

  • e.

    These lines represent the two relatively well-defined edges of a diffuse band. Resolution into two distinct lines has occurred in the pattern in column D of this table.

  • f.

    A broad diffuse band.

• F.

  The d-spacings listed here are the calculated values for euxenite-polycrase in column D in this table.

The letters in the intensity columns, B, VB, BD, VBD and D, indicate broad, very broad, broad and diffuse, very broad and diffuse, and diffuse lines respectively.

• a.

  Morphological axial ratio after W. C. Broegger.

• b.

  Ratio derived from x-ray data.

• c.

  Nefedov has a_o = 5.18, b_o = 14.70, c_o = 5.72Å, and this order does not correspond with the axial ratio derived therefrom by him; the present author has transposed Nefedo's values for a_o and c_o.

• d.

  Determined by single crystal work.

• e.

  Ratio derived from x-ray data and to be compared with morphological ratio already given—viz. a:b:c = 0.369:1:0.348.

The x-ray powder patterns obtained with Nile River material, after having been heated to 620°, 700°, and 1130–1140° C., are set out in Table III, columns A, B, and D, and the d-spacings of the two latter specimens are compared to those recorded by Lima-de-Faria (1958, pp. 938–939) for euxenite that had been heated

to 700° C. (Table III, column C), and to data obtained by the present writer for Setesdalen, Norway, euxenite¹ that was subjected to a temperature of 1130–1140° C. in air (Table III, column E). The d-spacings yielded by the Nile River sample and the Norwegian material, both of which have been heated to 1130–1140° C., are quite comparable, and any slight differences that do exist possibly result merely from compositional variation between the two specimens.² Furthermore, the similarities between the powder patterns yielded by Nile River euxenite-polycrase that had been heated to 700° and 1130–1140° C. are quite striking. Lima-de-Faria's x-ray pattern obtained from euxenite that had been heated to 700° C. is listed in Table III, column C, for the sake of comparison, and there is little obvious similarity between the latter and Nile River euxenite that had been heated to the same temperature. The only line in Lima-de-Faria's pattern that corresponds reasonably well is the most intense line at 2.92Å, but as for the other lines, if the d-spacings should correspond approximately, the intensities are out of all proportion to those listed in column B; note, for instance, the line at 1.79 Å (Table III, column C) with an intensity of 7, or 70 when compared with the same scale employed in column B, and the line at 1.77 Å in the latter column.

Accordingly, Lima-de-Faria's pattern of euxenite (Table III, column C) is much more comparable to that yielded by Pilbara, Western Australia, tanteuxenite, for instance, where a face-centred cubic pattern (uraninite or pyrochlore-microlite type) is obtained after the material has been heated to about 700° C. After a study of films yielded by a large number of specimens of euxenite that had been heated to about 700° C., the uraninite or pyrochlore-microlite type of pattern appears to be only occasionally developed. Instead, a pattern similar to that set out in Table III, column B, is the type more often obtained.

According to the studies of Komkov (vide Nefedov, 1956, p. 85) “the x-ray pattern of anisotropic euxenite is identical with that of the regenerated or heat-treated euxenite”. This statement is presumed to indicate that the powder patterns of anisotropic euxenite and of the heat-treated metamict mineral are identical. Nefedov (1956) found that similar circumstances obtained for an anisotropic euxenite from the Central Ural Mountains. Accordingly, determination of the dimensions of the unit cell of euxenite from the powder pattern of a heat-treated but originally completely metamict mineral would appear to have some value. The cell dimensions of the Nile River euxenite-polycrase have been calculated from the powder pattern after partial indexing of the more critical reflections (Table III, column F), and are as follows: a_o = 5.53, b_o = 14.63, c_o = 5.16 Å, which leads to an approximate x-ray axial ratio a: b: c: = 0.378:1:0.353.

These data may be compared with the unit cell dimensions of euxenite that are recorded by other writers, in Table IV.

Acknowledgments

The writer wishes to acknowledge the opportunities provided for this research by the award to him of a John Simon Guggenheim Foundation Fellowship during 1953–1954, and he is also indebted to the Shell Fund for Fundamental Research

The New Zealand Tertiary Genus Sectipecten Marwick (Mollusca)

By Anne U. E. Boreham, New Zealand Geological Survey

the Kapitean sequence in Kapitea Creek, from a rusty sandstone with thin greensand bands (GS 2888). The basal sandstone is followed by fine blue sandy siltstones containing typical S. wollastoni (GS 2630, 2631). Among the great majority of S. wollastoni individuals some slight variation can be seen in the detailed pattern of ribbing, also in the number of major ribs, but variation is consistent among individuals from any one area or province, and the range of variation differs in separate provinces, perhaps indicating an incipient geographic subspeciation.

Sectipecten wollastoni was replaced in the Opoitian by an incoming species of Chlamys (Phialopecten), which apparently occupied a similar ecological niche. Thus in central Taranaki, the Mangaotuku Shellbed contains abundant S. wollastoni, but the Wawiri Shellbed, approximately 125 feet stratigraphically above, contains Phialopecten n.sp. aff. triphooki (Zittel) and the two species have so far not been found to overlap (see Table I).

A representative of Sectipecten wollastoni is found at the Chatham Islands, in beds of Opoitian age at Momoe-a-toa. This species, described under the name of Sectipecten allani Marwick, appears to be a development from S. wollastoni, but it retains a greater variability than the mainland species and includes a few shells with less advanced rib pattern comparable to that of the early Kapitean Sectipecten cf. wollastoni at Kapitea Creek (GS 2888). Sectipecten allani, like its mainland counterpart, was short-lived, for it is absent from the (?) Waitotaran tuffs at Pitt Island and the Nukumaruan Shellbed at Titirangi (Marwick, 1928).

On the mainland, a single right valve of Sectipecten, comparable to S. allani, has been collected from Opoitian beds at Kaawa Creek, south-west Auckland. At three other localities of approximately the same age (Opoitian–Lower Waitotaran), namely Black Reef, Cape Kidnappers (GS 5308), Greek's Creek, Westland (GS 2875), and Arahura River, Westland (GS. 2987), occur shells that are quite unlike S. wollastoni and S. allani in sculpture but are nearer S. grangei, except that they have equal anterior and posterior ears and completely filled-in byssal notch, in contrast to Upper Tongaporutuan examples of S. grangei. There is no evidence that the highly specialised and distinctive S. wollastoni regressed to a more simple “grangei” form; it seems more likely that the S. grangei lineage persisted outside the New Zealand area during Kapitean times and returned in the early Pliocene, when the wollastoni branch of Sectipecten (including S. allani) disappeared from all but outlying areas such as the Chatham Islands and the more northern parts of the North Island.

The Chlamys (Phialopecten), which replaced Sectipecten wollastoni over the greater part of New Zealand in the Opoitian, did not reach the Chatham Islands or Kaawa Creek, but did eventually reach the Auckland area at Otahuhu in the Waitotaran, together with other groups of southern origin such as Aulacomya (Fleming, 1959, p. 167) and coarse-sculptured Tawera (Fleming, 1944, p. 211), and perhaps Laternula.

Sectipecten is not known anywhere after Lower Waitotaran times.

Systematics

Note: All primary types and figured specimens are in the collection of the New Zealand Geological Survey, except for the figured specimen of S. cf. allani Marwick from Kaawa Creek, which is in the collection of Mr. E. S. Richardson, c/o. Oruaiti School, Mangonui, Northland.

Family Pectinidae

Genus Sectipecten Marwick.

1928. Trans. N.Z. Inst. 58: 454.

Type species (by original designation): Pecten wollastoni Finlay (= Pecten sectus Hutton). Upper Miocene, New Zealand .

Sectipecten cf. grangei Boreham, Pl 46, f. 7.

Material. Figured specimen (TM 2760), a complete right valve from Black Reef, Cape Kidnappers (GS 5308); one incomplete right valve and fragments from Greek's Creek, Kanieri S.D. (G.S. 2875); a fragment from Arahura River, Kanieri S.D. (GS. 2987). All three localities are Pliocene in age, either Opoitian or Lower Waitotaran.

Discussion. The complete right valve from Cape Kidnappers, measuring 84 mm in height, has about 17 ribs, mostly grouped in pairs or threes, which tend to divide by grooving at various stages in growth. The riblets thus formed remain grouped to the ventral margin. Ribs are high, flat-or concave-topped. Ears are equal, with byssal notch totally obsolete in all but earliest growth stages. The specimen from Greek's Creek has about 19 rudely grouped ribs, a few of which tend to groove. Ribs are high and narrow but still nearly flat-topped. The specimens are very different in sculpture from S. wollastoni or S. allani but are similar to several individuals of the highly variable S. grangei. The only significant difference observed between Upper Tongaporutuan specimens of S. grangei and those from the Pliocene is that the latter have completely equal ears and obsolete byssal notch, indicating a decreased period of attachment in the life of the individual.

Summary (Compare Fig. 1)

Sectipecten, as S. diffluxus, is first recognisable in the Waiauan of North Canterbury, having probably diverged from Mesopeplum stock in immediately pre-Waiauan times. S. diffluxus shows simple sculpture of 24 to 30 subequal, evenly-spaced ribs that are only slightly discrepant on opposite valves. Sectipecten is not known from Lower Tongaporutuan rocks, but reappeared as S. grangei in the Upper Tongaporutuan at several localities in the North and South Islands. Early S. grangei, as at Pohokura Tunnel and one of the three valves from Mount Bruce, Tararua, are not very different from S. diffluxus. They have fewer ribs, which on the right valve show a greater tendency to be grouped and grooved, and on the left valve to be unequal in strength and time of appearance. These tendencies were accentuated in later S. grangei, and forms are found at Te Wera Quarry (uppermost Tongaporutuan) which have as few as 10 compound ribs on the right valve and the same number of primary ribs on the left valve alternating with finer, secondary intercalaries. However, at one horizon shells with a great diversity of sculpture occur together in one fossil population.

Sectipecten grangei is succeeded in the Kapitean by Sectipecten wollastoni, a species which represents the culmination of Sectipecten evolution. Major ribs are reduced in number to as few as 7, and on the right valve are broad, inflated and elaborately grooved towards the ventral shell-margin. Sculpture on opposite valves is highly discrepant.

At the end of Kapitean times Sectipecten wollastoni disappeared from the greater part of New Zealand, but a close relation, S. allani, survived into the Opoitian at Kaawa Creek and the Chatham Islands . S. allani at the Chatham Islands is a development from S. wollastoni, evolved in insular isolation, in which the tendency towards amalgamation of ribs is carried to the extreme: on several specimens the right valve ribs show no signs of grooving at all, but are broad, strong, and inflated from apex to ventral margin. The species is characterised, however, by showing a far greater range of variation, including less advanced shell forms, than the mainland counterpart, S. wollastoni. Only a single right valve is known from Kaawa Creek, so that it is impossible to tell whether the North Auckland population had a range of variation comparable to that of the Chatham Islands . Meanwhile the Kaawa Creek shell, listed as S. cf. allani, is interpreted as being a separate, mainland development from S. wollastoni.

Studies on Australian and New Zealand Diatoms
IV.—Descriptions of Further Sedentary Species

By E. J. Ferguson Wood, Division of Fisheries and Oceanography, C.S.I.R.O., Cronulla, Australia

Distribution. Australia: Port Hacking. New Zealand: Lyall Bay (Petit, 1877).

5. Fragilaria virescens Ralfs (Pl. 50, Fig. 5)

• Ralfs 1843, 12, 110.

• Boyer 1927, 184.

• A. S. 1913, 297, 3–33.

Frustules rectangular, elongate, in ribbon-like chains, valves linear or linear-elliptic, attenuate at apices, obtuse, transversely striate, punctate, pseudoraphe indistinct. Length, 20–70μ.

Distribution. Fresh water. New Zealand: Wellington.

Genus Tabellaria Ehr. 1840

Frustules in filaments or zig-zag chains, sometimes solitary; rectangular in girdle view, septate; valves linear to oblong, inflated at ends and in the middle or panduriform pseudoraphe narrow; striae transverse, punctate; chromatophores numerous, round.

6. Tabellaria flocculosa (Roth) Kütz. (Pl. 50, Figs. 6 a, b)

• Kütz. 1884, 127.

• Boyer 1927, 152. A.S. 1911, 269, 14–19, 22, 23, 27–30.

Conferva flocculosa Roth 1797, 192.

Frustules quadrangular with from 4–8 septa, somewhat incurved at each end, alternating with those at opposite end; valves linear with median inflation larger than terminal; pseudoraphe broad in the middle; transverse striae finely punctate. Length, 30μ.

Distribution. Australia: Lake Dobson, Nepean River, Botany swamps. New Zealand: Wellington water supply.

Genus Rhaphoneis Ehr. 1844

Frustules linear, narrow; valves elliptical to lanceolate; striae transverse, more or less radiating, moniliform; pseudoraphe usually narrow.

7. Rhaphoneis amphiceros Ehr. (Pl. 50, Fig. 7)

• Ehr. 1844, 87.

• Boyer 1927, 190.

• A.S. 1911, 269, 44–55.

Valves broadly lanceolate to semicircular, with produced ends; striae moniliform, radiating, the granules in longitudinal lines. Length, 50–70μ.

Distribution. Australia: Heron Island, Lake Macquarie. Noumea: Bai de Citron. New Guinea: Port Moresby.

var crucifera (Kitt.) (Pl. 50, Fig. 8).

• Amphitetras crucifera Kitt. 1867, 3, 271, 285.

• R. amphiceros var. tetragona Grun in vH 116, 16.

• A. S. 294, 33, 34.

• Boyer 1927, 190.

Boyer points out that var. tetragona in Schmidt's Atlas is the same as Kitton's species, which should therefore become the name of the variety as Kitton's illustration seems clear enough.

Outline quadrate; pseudoraphe double, cruciform. Length, 40μ.

Distribution. Australia: Heron Island. Noumea. Bai de Citron.

8. Rhaphoneis cocconeiformis (A.S.) Hanna & Grant (Pl. 50, Fig. 9)

• Hanna & Grant 1926, 165, 20, 9.

• Coscinodiscus cocconeiformis. A. S. 1876, 58, 25, 26, 28.

Valve circular, much resembling. Coscinodiscus nitidus; pseudoraphe narrow, indistinct; surface punctate, puncta arranged radially to ends of pseudoraphe. Diameter 40μ. The bilateral symmetry of this species precludes its inclusion in the genus Coscinodiscus.

Distribution. Australia: Bate Bay in sand at 200 m.

9. Rhaphoneis surirella (Ehr.) Grun. (Pl. 50, Fig. 10)

• Grun. in vH. 1880, 36, 26, 27a.

• Zygoceros surirella Ehr. 1840, 4, 12.

var. australis Petit 1877.

• R. fasciola var. australis Petit 1877.

• Dimerogramma australe Boyer 1928.

Valves elliptical, ends acute; pseudoraphe broad, slightly constricted in the middle; striae radiate at ends, coarsely punctate. Length, 50μ.

Distribution. Australia: Port Hacking. New Zealand: Otago, Lyall B. (Petit, 1877).

Genus Cymatosira Grun. 1862

Frustules tumid in the middle in girdle view, arranged in ribbons; valves fusiform; pseudoraphe absent.

10. Cymatosira lorenziana Grun. (Pl. 50, Fig. 11)

• Grun. 1862, 378.

• Boyer 1927, 192.

Valves fusiform, ends produced; puncta in transverse and diagonal rows. Length, 25μ.

Distribution. Australia: Heron Island. Indonesia.

Genus Trachysphenia Petit, 1877

Frustules rectangular; valves cuneiform or elliptic-lanceolate, with rounded ends; striae transverse, puncta in longitudinal rows; pseudoraphe narrow, linear.

11. Trachysphenia australis Petit (Pl. 50, Fig. 12, a and b)

• Petit 1877, 3, 190.

• Boyer 1927, 191.

Has characters of genus, of which it is the type species.

Distribution. Australia: Hawkesbury River. New Zealand: Dunedin, Campbell I. (type loc., P. Petit).

Genus Omphalopsis Grev. 1863c

Frustules united into a filament, lateral view cruciform, with central and terminal nodules and interrupted transverse striae.

12. Omphalopsis australis Grev. (Pl. 50, Fig. 13)

• Grev. 1863c, 37, 1, 10, 11.

• A.S. 1899, 209, 54.

Cells in chains, valves cruciform, sides biconcave with convex central portion and rounded apices; terminal and central areas clear, with rows of radiating puncta. Length, 40μ.

Distribution. Australia: Heron I. (Type loc. Woodlark I. Grev. 1863). Indonesia.

Genus Entopyla Ehr. 1848

Frustules free or in very short chains, arcuate in girdle view, divided by longitudinal septa with a row of septa along each border; valves linear-elliptic, sometimes constricted, dissimilar, lower being concave, hyaline at apices, upper not hyaline, convex, surface costate. costae alternating on each side of pseudoraphe; chromatophores numerous.

13 Entopyla australis Ehr. (Pl. 50, Fig. 14)

• Ehr. 1846, 6.

• A. S. 1902, 230, 1–16.

• Boyer 1927, 162.

Frustules free or in very short chains, valves linear to linear-elliptic or constricted, with rounded or cuneate ends, costae with fine puncta between them; foramina correspond to intercostal spaces, close to border, appearing as large cells in girdle view; in concave lower valve apices are hyaline, in upper valve costae radiate at apices; lower valve also depressed along longitudinal axis. Length, 200μ.

Distribution. Australia: Cairns Harbour. New Zealand: Dunedin.

Genus Asterionella Hassall, 1850

14. Asterionella bleakleyi W. Sm. (Pl. 50, Fig. 15)

• W. Sm., 1956, 2, 82.

• Boyer, 1927, 213.

A large species found in stellate formation; cells attached to each other by the larger ends; frustules with one swollen pole and a slight constriction just above the spatulate end;

the other pole slightly inflated in valve—and straight in girdle view; chromatophores about 12, not at ends of cell. Resembles A. kariana but is larger and chromatophores are more numerous. Length, 115–120μ.

Distribution. Australia: Heron Island. New Zealand. Cook Strait. Fiji.

15. Asterionella formosa Haas (Pl. 50, Fig. 16)

• Haas in W. Sm. 1856, 81

• A. S. 1911, 269, 20–21, 36–37.

Cells arranged in a spiral, attached to each other by the sides of their swollen bases; frustules also enlarged apically in valve view, at times slightly inflated near middle of valve; apex truncate. Length, 60μ.

Distribution. Fresh water. New Zealand: Wellington (Wainui-o-mata).

16. Asterionella notata Grun (Pl. 50, Fig. 17)

• Grun. in vH. 1885.

• Gran. 1905, 119.

• Ostenfeld 1915, 9, 2.

Cells in chains, usually in a shallow spiral with chain axis through spatulate ends of each cell; frustules arranged almost at random about chain axis; frustules swollen at one pole, otherwise almost straight, tapering slightly; chromatophores numerous throughout cell. Length, 35–50μ.

Distribution. Australia: Heron Island, Tasman Sea, east of Port Hacking.

Genus Plagiogramma Grev. 1859

17. Plagiogramma atomus Grev. (Pl. 50, Fig. 18)

• Greville 1863c, 36, 1–9.

• A. S. 1892, 211, 24, 25.

Frustule nearly rectangular in girdle view; in valve view constricted in the middle with rostrate ends, puncta fine. Length, 30–40μ.

Distribution. Australia: Heron Island. (Type loc. Woodlark I.)

18. Plagiogramma constrictum Grev. (Pl. 50, Fig. 19)

• Grev. 1863c, 36, 1, 8.

• A. S. 1893, 210, 28–30.

Frustules quadrangular, with central and apical hyaline spaces abruptly raised; valves lanceolate with sinuate margins, pseudoraphe evident. Length, 60μ.

Distribution. Australia: Sahul Bank. (Timor Sea). New Zealand: Oamaru (Gr. & St. 1887, 73).

19. Plagiogramma interruptum (Greg.) Ralfs (Pl. 50, Fig. 20)

• Ralfs in Pritch, 1861, 774.

• A. S. 1899, 209, 38.

• Denticella interrupta Greg. 1857, 494, 10, 30.

Frustule in girdle view nearly rectangular, middle part slightly convex, ends expanded; in valve view lanceolate with very fine sculpture and a large round punctum in the middle of the central hyaline area. Length, 25μ.

Distribution. Fresh water. Australia: Lake Conjola.

20. Plagiogramma labuense Cl. (Pl. 50, Fig. 21)

• Cl. 1883, 498.

• A. S. 1893, 211, 9.

Valves constricted in the middle, rostrate at ends; central nodule large, circular, reaching margin; costae transverse, punctate, puncta in longitudinal rows; pseudoraphe linear, distinct. Length, 40μ.

Distribution. Australia: Lake Macquarie.

21. Plagiogramma rutilarioides Cl. (Pl. 50, Fig. 22)

• Cl. 1881, 18, 5.

• A. S., 1893, 209, 2.

Frustules in valve view fusiform, with rounded ends; hyaline median space extending to margin, pseudoraphe variable; striae transverse, punctate, puncta in longitudinal rows. Length, 40–60μ.

Distribution. Australia: Port Hacking. (Identified by N. I. Hendey.)

22. Plagiogramma schmidtii (sp. nov.) (Pl. 50, Fig. 23)

A. S. 1893, 209, 9.

Valvae bicuneatae, cum striae transversis et longitudinalibus.

Valves bicuneate, widest in the middle, ends rounded; central and terminal hyaline spaces marked, striae marked, forming squares. This species is shown as Plagiogramma sp.from the Aegean by Schmidt, and has apparently not been named. Length, 30–50μ.

Distribution. Australia: Heron I.

23. Plagiogramma wallichianum Grev. (Pl. 50, Fig. 24)

• Grev. 1865, 13, 1.

• Boyer 1927, 179.

Valves linear with rounded ends, pseudoraphe absent; central space rectangular, terminal spaces large; striae at right angles, evident also in central and terminal spaces. Length, 30μ.

Distribution. Australia: Heron I.

Genus Synedra Ehr. 1830.

24. Synedra acus Kütz. (Pl. 50, Fig. 25)

• Kutz. 1844, 68.

• A. S. 1914, 303, 7.

• Boyer 1916, 18, 11, 9; 1927, 201.

Frustules elongate, slender, valves lanceolate, acicular, ends elongate, sub-capitate or obtuse; striae transverse, central space usually evident. Length, 120μ.

Distribution. Australia: Botany swamps.

25. Synedra hennedyana Greg. (Pl. 50, Fig. 26 a, b)

• Greg. 1857, 21, 532.

• Boyer 1927, 211.

Frustules elongate, slender; valves elongate, swollen in the middle, apices subcapitate; pseudoraphe indistinct, striae transverse, irregular in the middle. Length, to 1 mm.

Distribution. Australia: Port Hacking, Lake Macquarie as an epiphyte and in fish stomachs.

26. Synedra goulardii (Breb.) Grun. (Pl. 50, Fig. 27)

• Grun. 1880 in Cl. & Grun. 107, 6, 119. Breb in litt.

• A. S. 1913, 300, 10–18.

Valves strongly constricted, ends acute to capitate, striae strongly punctate, transverse, somewhat radial at ends; large quadrate central area. Length, 60–80. Width, 10μ.

Distribution. Fresh water. New Zealand: Wellington (Wainui-o-mata).

27. Synedra tabulata (Ag.) Kutz. (Pl. 50, Fig. 28)

• Kütz., 1844, 68.

• Diatoma tabulatum Ag. 1832, 50.

• S. affinis Kg. 1844, 68. A.S. 1914; 304, 10–48.

Valves lanceolate, narrow; tapering to the obtuse, somewhat capitate ends; pseudoraphe broad, lanceolate; striae marginal. Length, up to 130μ.

Distribution. Australia: South coast estuaries of New South Wales. New Zealand: Lake Ellesmere.

Genus Grammatophora Ehr. 1839

28. Grammatophora angulosa Ehr. (Pl. 50, Fig. 29)

• Ehr. 1840, 73.

• Cupp. 1943, 174, 124.

Frustules with irregularly bent, undulate septa, inner ends of which are hooked away from valve; valve surface punctate-striate, puncta extending on valve mantles at poles; pseudoraphe narrow Length, 15–30μ.

Distribution. Australia: Bate Bay, at 200 m. New Zealand: Wellington Harbour.

Genus Terpsinoe Ehr. 1843

29. Terpsinoe americana (Bailey) Ralfs (Pl. 50, Fig. 30)

• Ralfs in Pritch. 1861, 859.

• Boyer 1927, 145.

• Tetragramma americana Bail. 1853, 7.

Sub-Order Raphidioidineae
Family Eunotiaceae

Sub-Order Monoraphidineae
Family Achnanthaceae

transverse striae; lower valve with narrow axial area and a stauros reaching margin; striae coarse. Length, 25μ.

Distribution. New Zealand: Lake Ellesmere.

42. Achnanthes inflata (Kütz) Grun. (Pl. 51, Fig. 44 a, b, c)

• Grun. 1868, 98.

• Hust. 1933–37, 421, 873.

• Stauroneis inflata Kutz. 1844, 105, 30, 22.

Valves swollen in the middle, with capitate ends; lower valve with broad, somewhat asymmetric stauros and punctate striae arranged transversely, raphe slightly excentric, axial area narrow, linear; upper valve with transverse, punctate striae and excentric pseudoraphe.

Distribution. New Zealand: Lake Ellesmere.

43. Achnanthes lanceolata (Breb.) Grun. (Pl. 51, Fig. 45)

• Grun. in Cl. & Grun, 1880, 23.

• A. S. 1927, 411, 20–44.

• Hust. 1933, 408, 863.

Frustules chevron-shaped in girdle view; valves elliptic to elliptic-lanceolate, ends broad, upper valve with narrow pseudoraphe and horse-shoe shaped hyaline space on one side extending to margin; lower valve with central raphe and dilated central area; striae thick, radiate. Length, 60μ.

Distribution. New Zealand: Lake Ellesmere.

44. Achnanthes laterostriata (Hust.) (Pl. 51, Fig. 46)

Hust. 1933, 392, 840.

Valves with middle part broadly elliptic with broadly rostrate to slightly capitate blunt ends; pseudoraphe narrowly lanceolate, without central area, striae punctate; lower valve with straight raphe, narrow axial area and no central area, striae marked, radial with several short, marginal striae near centre of valve. Length, 20μ.

Distribution. Australia: Botany swamps.

45. Achnanthes pulchella Heiden and Kolbe. (Pl. 51, Fig. 47 a, b)

Heiden & Kolbe 1928, 579, 5, 104, 104a.

Frustule chevron-shaped in girdle view; valves slightly constricted in the middle, then bluntly hastate with slightly concave margins and sharply rounded apices, upper valve with linear axial area, and transverse rows of coarse rectangular puncta; lower valve with straight raphe, narrow; axial area, stauros reaching margins and transverse striae, rather finely punctate. Length, 35μ.

Distribution. Australia: Heron Island.

46. Achnanthes taeniata Grun. (Pl. 51, Fig. 48)

• Grun. in Cl. & Grun. 1880, 20.

• Hust. 1933, 382, 828.

Cells in long, more or less fragilaria-like chains; valves linear with slightly convex sides and broadly rounded ends; thin walled, marked transapical striae on both valves, pseudoraphe narrow; raphe straight, axial area very narrow, chromatophore H-shaped. Length, 10–40μ.

Distribution. Australia: off Maria Island in winter. Ross Sea.

47. Achnanthes sp. (Pl. 51, Fig. 49)

Frustule in valve view elliptic-lanceolate, with rostrate ends; upper valve with slightly excentric pseudoraphe and central area; striae radial, coarsely punctate, median striae shorter than the rest.

Distribution. Australia: Bate Bay, at 200 m.

Genus Campyloneis Grun. 1862

Valves elliptical, dissimilar; upper valve with radiate rows of coarse puncta and pseudoraphe, lower valve with central nodule, raphe; and radiate, punctate striae; interior stratum of reticuli between the valves.

48. Campyloneis grevillei (W. Sm.) Grun. (Pl. 51, Fig. 50)

• Grun. 1868, 1, 10.

• Hust. 1933, 321.

• Cocconeis grevillei W. Sm. 1853, 22.

Valves elliptical to circular; upper valve with narrow median line and rows of puncta or quadrate alveoli; lower valve with radiate; punctate striae; axial area narrow; raphe not reaching ends; between valves is coarse axial rib from which radiate strong costae, forming a variable network. Length, to 60μ.

Distribution. Australia: Cairns, Bate Bay, at 200 m. New Zealand: Lyall B. (Petit, 1877).

Genus Cocconeis Ehr. 1838 em. Grun. 1868.

49. Cocconeis apiculata A. S. (Pl. 51, Fig. 51)

• A. S. 1894, 198.

• Boyer 1927, 251.

Cells elliptical with apiculate ends, upper valve with narrow axial area, striae punctate, radiate. Length, 60–70μ.

Distribution. Australia: Lake Macquarie, in fish stomachs.

50. Cocconeis debesi Hust. (Pl. 51, Fig. 52 a, b)

Valves elliptic-lanceolate, ends rounded; upper valve with radial, to transverse interrupted striae, and longitudinal hyaline lines, pseudoraphe, linear, narrow; lower valve with short, radial striae at margin, and scattered puncta between margin and narrow axial area. Length, 35μ.

Distribution. Australia: Heron Island.

51. Cocconeis distans A. S. (Pl. 51, Fig. 53)

• A. S. 1875, 3, 22, 1894, 193, 29.

• Cl. 1895, 27, 172.

• Boyer 1927, 246.

• Hust. 1933, 343, 797.

Valves elliptic to elliptic-lanceolate; upper valve with lanceolate axial area; striae with 3–4 puncta in longitudinal, distant rows; lower valve regularly punctate in radiate, transapical rows, with a narrow hyaline area at margin; raphe straight, axial area and central nodule very narrow. Length, 30–50μ.

Distribution. Australia: Lake Macquarie, in fish stomachs.

52. Cocconeis maxima (Grun.) Perag. (Pl. 51, Fig. 54)

• Perag. 1897, 18, 3, 1–4.

• Hust. 1933, 335, 789.

• Mastogloia maxima Grun. 1863, 156, 4, 1.

• C. lorenziana A. S. 1894, 191, 28–34.

Cells elliptical; upper valve with irregular central area, strongly marked marginal striae interrupted by a hyaline zone parallel to margin; internal striae punctate, and interrupted by a second hyaline zone; lower valve finely punctate, with straight raphe. Length, 40μ.

Distribution. Australia: Heron I.

53. Cocconeis pellucida Hantzsch (Pl. 51, Fig. 55)

• Hantzsch in Rab. 1863, 21.

• Boyer 1927, 247. A.S. 1894, 194, 2, 195, 1–9.

• Hust. 1933, 357, 812.

Valves elliptical, upper with median area straight, linear-lanceolate with 4–6 longitudinal blank lines crossing striae which are very fine; lower valve with straight raphe and small, opposed terminal nodules; longitudinal rows more numerous than in upper valve. Length, 50–70μ.

Distribution. Australia: Sussex Inlet.

54. Cocconeis placentula Ehr. (Pl. 51, Fig. 56)

• Ehr. 1838, 194.

• Boyer 1927, 244.

• Hust. 1933, 347, 802.

Valves elliptical; lower valve with clearly punctate, radial striae and narrow, linear pseudoraphe; upper valve with nariow raphe and lateral areas; striae radial, fine, punctate; loculi rudimentary. Length, 20–60μ.

Distribution. New Zealand: Wellington water supply, L. Ellesmere, New Zealand (Ehr. 1869). Australia (Østrup, 1910).

Sub-Order Biraphidineae
Family Naviculaceae

69. Navicula weissflogii (Grun.) Cl. (Pl. 52, Fig. 72)

• Cl. 1894, 152.

• Boyer 1927, 375.

Brebissonia weissflogii Grun. in Cl. 1878, 7, 1–9.

Valves rhomboid with obtuse ends; raphe with distinct median and terminal pores; axial area indistinct, central area elongate; striae transverse in middle, radiate at ends, punctate, puncta forming undulating longitudinal rows. Length, 60–80μ.

Distribution. Australia: Botany Bay.

70. Navicula semen (Ehr.) Donk. (Pl. 52, Fig. 73)

• Donk. 1871, 21.

• Boyer 1927, 373.

• A. S. 1886, 72, 1; 1913, 299, 18–20

• Pinnularia semen Ehr. 1843. A.

Valves oblong-elliptic with broad, sub-rostrate ends; axial area well defined, somewhat irregular, dilated in middle; raphe oblique, sinuous; striae radiate, distant in the middle, closer at ends and slightly convergent; puncta indistinct. Length, 50–100μ.

Distribution. Australia: Lake Macquarie, in fish stomachs.

71. Navicula sulcifera Hust. (Pl. 52, Fig. 74)

• Hust. 1955, 24, 8, 1.

Valves elliptic, with sub-acute ends; axial area narrow, linear, slightly dilated centrally; central area large, dilated towards lateral areas which are narrow, lanceolate, and separated from axial areas by a band of punctate striae, with a strong linear furrow in each half; striae transverse, punctate. Length, 50–70μ.

Distribution. Australia: Port Hacking, Bate Bay at 200 m. (Identified by N. I. Hendey).

72. Navicula torneensis Cl. (Pl. 52, Fig. 75)

• Cl. 1891, 33, 2, 6

• Cl.-Eul. 1953b, 120, 101a.

Valves small, rhombic-elliptic with bluntly rounded ends; axial area narrow, slightly lanceolate, central area circular; striae radial, strongly punctate. Length, 20–25μ.

Distribution. Australia: Port Hacking.

73. Navicula virihensis Cl.-Eul. (Pl. 52, Fig. 76)

• Cl.-Eul. 1953b, 141, 790a.

Valves linear-lanceolate with rounded, rostrate to sub-capitate ends; central and axial areas asymmetric; striae radial, distant near central area, parallel and closer together towards ends. Length, 30μ.

Distribution. Fresh water. New Zealand: Wellington.

74. Navicula vulpina Kütz. (Pl. 52, Fig. 77)

• Kutz. 1844, 92.

• Boyer 1927, 388.

• A. S. 1934, 395, 7–9.

Valves lanceolate with obtuse ends; axial area narrow; central area large, circular; striae coarse, linear, radiate, convergent at ends. Length, 70μ.

Distribution. Fresh water. Australia: Lake Dobson, Georges Basin.

75. Navicula digitoradiata (Greg.) Ralfs (Pl. 52, Fig. 78)

• Ralfs 1861, 904.

• Cl. -Eul. 1953b, 160, 822.

• Pinnularia digitoradiata Greg. 1859, 9, 1, 32.

Valves sub-linear to elliptic-lanceolate with rounded ends; axial area linear, narrow; central area irregular; striae coarse, radial in centre, transverse and convergent at ends. Length, 35–45μ.

Distribution. Australia: Port Hacking.

76. Navicula lyra var. (Pl. 52, Fig. 79)

A large form with rhomboid valves, a narrow axial area and narrowly lyrate extensions of the central area, reaching the margins near the rounded ends; striae fine, transverse, punctate. Length, 100–120μ.

Distribution. Australia: Lake Macquarie. Rare.

Genus Diploneis Ehr. 1840

77. Diploneis advena (A. S.) Cl. (Pl. 52, Fig. 80)

• Cl. 1894, 81.

• Navicula advena A. S. 1875, 8, 29, 12, 41.

Valves linear-elliptic with parallel to slightly concave sides, and blunt, semicircular ends; central area small, quadrate, horns narrow, parallel; longitudinal canal linear, slightly convergent at poles; transapical ribs radial, transverse in the middle; loculi unpaired, with a small pore near valve margin. Length, 50μ.

Distribution. Australia: Bate Bay at 200 m.

78. Diploneis campylodiscus (Grun.) Cl. (Pl. 52, Fig. 81)

• Cleve 1894, 99.

• Hust. 1933–37, 600, 1017.

• Navicula campylodiscus Grun. in A. S. 1875, 8, 9, 10, 12.

Valves broadly elliptic; central area moderately large, quadrate; horns separated therefrom, slightly divergent at base; longitudinal canal broad, semi-lanceolate; transapical striae strongly radial, loculi unpaired. Length, 40–55μ.

Distribution. Australia: Bate Bay at 200 m.

79. Diploneis finnica (Ehr.) Cl. (Pl. 52, Fig. 82)

• Cl. 1891, 43, 2, 11.

• Hust. 1933–37, 669, 1064.

• Cocconeis finnica Ehr. 1838, 194.

Valves elliptic; central area elongated; horns strong, parallel; longitudinal canal rather broad, semilanceolate; transapical striae strong, radial, with a double row of pores between each; loculi unpaired. Length, 70–80μ.

Distribution. Australia: Bate Bay at 200 m.

80. Diploneis gemmata (Grev.) Cl.

• Cl. 1894, 98.

• Hust. 1933–37, 644, 1050.

• Navicula gemmata Grev. 1859, 249, 5, 7.

Valves linear, with parallel or slightly concave sides and broadly rounded ends; central area large, quadrate; horns strong, parallel; longitudinal canal broad, linear with a series of teeth between it and the horns, these teeth opposite the transverse striae. Loculi unpaired.

var. pristiophora (Jan.) Cl. (Pl. 52, Fig. 83)

• Cl. 1894, 99.

• Hust. 1933–37, 646, 1050c.

• Navicula pristiophora Jan. in A.S. 1881, 70. 72.

Differs from type in more constricted middle.

Distribution. Australia: Sahul Bank.

81 Diploneis interrupta (Kütz) Cl. (Pl. 52, Fig. 84)

• Cl. 1894, 84.

• Hust. 1933–37, 602, 1019.

• Navicula interrupta Kütz 1844, 100, 29, 93.

Valves linear-elliptic with deeply constricted middle and semicircular ends; central area large; horns strong, separated, parallel; longitudinal canal narrow, linear; transapical ribs, well marked, radial; loculi in the middle missing or rudimentary. Length, 30–50μ.

Distribution. Australia: Bate Bay, at 200 m.

82. Diploneis notabilis (Grev.) Cl. (Pl. 52, Fig. 85)

• Cl. 1894, 93.

• Hust. 1933–37, 682, 1074.

Valves elliptic to circular, central nodule quadrate, horns strong, parallel, longitudinal canal rather narrow, linear to lanceolate: transverse striae marked, radial, crossed by undulating longitudinal ribs rather more widely spaced than the transverse striae. Length, 50–70μ.

Distribution. Australia: Bate Bay, at 200 m.

83. Diploneis bombus Ehr.

• Ehr. 1844, 84.

• Hust. 1933–37, 704, 1086.

Valves constricted in the middle with elliptical to semicircular ends; central nodule large, rectangular; horns divergent at base, strongly convergent at apices; longitudinal canal broad, linear, transapical striae strong, radial crossed by 2 to 5 longitudinal ribs.

var. bombiformis (Cl.) Hust. (Pl. 52, Fig. 86)

• Hust. 1933, 706, 1086f.

• D. bombiformis Cl. 1894, 87, 1, 26.

Smaller than type with fewer longitudinal ribs. Length, 40–50μ.

Distribution. Australia: Bate Bay, at 200 m.

84. Diploneis beyrichiana A. S. (Pl. 52, Fig. 87)

A. S. 1881, 69, 16, 17.

Valves slightly constricted in the middle, with rather abruptly obtuse ends; central nodule quadrate; horns strong, slightly divergent at base, longitudinal canal lanceolate; striae transverse, crossed by longitudinal ridges. Length, 50–70°

Distribution. Australia. Bate Bay, at 200 m.

85 Diploneis rostrata sp. nov. (Pl. 52, Fig. 88)

Valves oblong-elliptic with rounded corners and narrowly rostrate ends, raphe fine, straight, horns with smooth interior and serrate outer margins; longitudinal canal narrow; valve surface with widely spaced striae, not so evident in inner portion of valve. Length, 30–40μ.

Distribution. Australia Bate Bay, at 200 m.

86. Diploneis suborbicularis (Greg.) Cl. (Pl. 52, Fig. 89)

Valves broadly elliptical; central nodule quadrate; horns divergent; longitudinal canals linear, narrow, with a row of puncta or faint continuation of the costae; costae transverse, radial at ends. Length, 40–60μ.

Distribution. Australia: Bate Bay, at 200 m.

Genus Dictyoneis Cl. 1890

Valves lanceolate or panduriform; terminal fissures usually in opposite directions; surface with outer and inner striation, outer finely punctate, inner coarsely cellular or reticulate; marginal cells usually larger than the rest, forming apparent marginal loculi, but are not detached from the valve as in Mastogloia.

87. Dictyoneis marginata (Lewis) Cl. (Pl. 52. Fig. 90)

• Cl. 1890, 16.

• Naurcula marginata Lewis 1862, 161.

Valves strongly constricted in the middle, tapering to the rounded ends; raphe straight, but curved at ends, axial area small almost linear; surface areolate with irregular arrangement; marginal areolae usually twice the size of the rest; outer surface punctate. Length, 100–120μ.

Distribution. Australia. Botany Bay, in mud; Bate Bay, in sand, at 200 m.

Genus Frustulia, A G. 1824

88. Frustulia rhomboides v. saxonica f, undulata Hust. (Pl. 52, Fig. 91)

Hust. 1930, 369.

Valves with slightly undulating rhombic form and slightly constricted ends. Length, 100μ.

Distribution. Fresh water: Australia: Lake Dobson.

Genus Pinnularia Ehr. 1843

89. Pinnularia acrosphaeria (Breb.) Rab. (Pl. 52, Fig. 92)

• Rab. 1853, 45, 6, 36.

• A. S. 1875, 43, 14–19, 21. 22.

• Cl. 1895, 27, 86.

• Boyer 1927, 441.

• Frustulia acrosphaeria Breb. 1838, 19.

Valves linear, slightly swollen in middle and at ends; axial area about half valve width; median area punctate; striae nearly parallel, radiate at ends. Length. 80μ.

Distribution. Fresh water. New Zealand: Wellington.

90. Pinnularia cardinalis Ehr. (Pl. 53, Fig. 93)

Ehr. in W. Sm. 1853, 19. 166.

Valves linear with rounded ends, axial area wide, expanded in the middle; costae radiate. Length, 100–120μ.

Distribution. Fresh water. New Zealand: Wellington.

91. Pinnularia legumen Ehr. (Pl. 52, Fig. 94)

• Ehr. 1854, 2

• Boyer 1927, 435

• A. S. 1875, 44, 44–47.

Valves linear-lanceolate, with more or less triundulate margins and broad, subcapitate ends, axial area less than ¼ valve width, widened in the middle to give a circular central area; striae strongly divergent in middle, convergent at ends. Length, 65–90μ.

Distribution. Australia: Lake Dobson.

92. Pinnularia nobilis Ehr. (Pl. 53, Fig. 95)

• Ehr. 1840, 20,

• Boyer 1927, 445.

Valves slightly swollen in the middle and at ends, which are rounded; raphe complex; axial area linear slightly widened in the middle; striae slightly divergent in the middle, then parallel, slightly convergent at ends, crossed by a broad band. Length, 70–80μ.

Distribution. Australia: Port Hacking in brackish upper reaches.

93. Pinnularia notata Heiden & Kolbe (Pl. 52, Fig. 96)

Heiden & Kolbe 1928.

Valves linear-lanceolate, sides parallel then tapering to rounded apex; raphe curved at both ends and in middle, axial area narrow on one side of raphe, central area excentric, striae strongly divergent in the middle, convergent at ends. Length, 50–70μ.

Distribution. New Zealand: Lake Ellesmere.

94. Pinnularia viridis (Nitzsch) Ehr. (Pl. 52, Fig. 97)

• Ehr. 1838, 182.

• Boyer 1927, 446.

• Bacillaria viridis Nitzsch 1817, 97.

• Navicula viridis (Nitzsch) Kütz 1844, 97.

• A. S. 1875, 44, 42, 45.

Valves linear-elliptic with rounded ends; raphe complex; axial area narrow, widened in the middle, costae coarse, slightly divergent in the middle, convergent at ends, crossed by a broad band. Length, 150μ.

Distribution. Fresh water. Australia: L. Dobson. New Zealand: Lake Ellesmere. (Australia, Østrup 1910; A. S. 1875.)

var. rupestris (Hantzsch) Cl. (Pl. 53, Fig. 98)

• Cl. 1895, 2, 92.

• P. rupestris Hantz in Rab. 1864, 1023.

• Nav. rupestris A. S. 1876, 45, 38–44.

Striae finer than in type. Length, 75μ.

Distribution. Australia: Lake Macquarie, fish stomachs.

Genus Trachyneis Cl. 1894

95 Trachyneis aspera v. pulchella (W.Sm.) Cl. (Pl. 53, Fig. 99)

• Cl. 1894, 26, 191

• Boyer 1927, 428

• Stauroneis pulchella W. Sm. 1853, 61, 19, 194.

• Illustrated in A. S. 1885, 48, 12, 13.

Valves elliptic-lanceolate; axial area narrow, slightly sinuate; alveoli elongate; central area widened symmetrically.

Distribution. Fresh and brackish water. Australia: Port Hacking, Nepean River, Lake Macquarie. Noumea (Bai de Citron).

Genus Pleurosigma W. Sm. 1853

96. Pleurosigma directum Grun. (Pl. 53, Fig. 100)

• Grun. in Cl. & Grun. 1880, 53.

• Hendey 1937, 34, 348.

Cells solitary; valves flat or nearly so, rhombic-lanceolate to elliptic-lanceolate; raphe distinct, median, only very slightly sigmoid; central nodule small, striations faint. Length, 70μ.

Distribution. New Zealand: Hauraki Gulf.

97. Pleurosigma obscurum W. Sm. (Pl. 53, Fig. 101)

• W. Sm. 1853, 65.

• Boyer 1927, 468.

Valves linear, scarcely if at all sigmoid, with obliquely rounded, obtuse ends; raphe sigmoid, very excentric, near margin at ends; striae oblique, very fine. Length, 70–150μ.

Distribution. Australia: L. Coila.

98. Pleurosigma speciosum W. Sm. (Pl. 53, Fig. 102)

• W. Sm. 1853, 63, 197.

• Boyer 1927, 469.

Valves linear-lanceolate, obtuse, slightly sigmoid; raphe sigmoid, slightly excentric at ends; striae fine, diagonal. Length, 100μ.

Distribution. Australia: Hawkesbury River.

Genus Stauroneis Ehr. 1843

99. Stauroneis acuta W. Sm. (Pl. 53, Fig. 103)

• W. Sm. 1853, 59.

• Boyer 1927, 425.

• A. S. 1903, 241, 4.

Valves rhombic-lanceolate, obtuse with a diaphragm at each end; axial area broad; stauros broad, widened towards margin; striac fine, punctate. Length, 100μ.

Distribution. Fresh water. Australia: Lake Dobson. (Australia, Østrup 1910). New Zealand: Foveaux Strait (Petit 1877).

var. inflata (Held.) Freng. (Pl. 53, Fig. 104).

• Freng. 1926, 30.

• S. inflata Heid. in A. S. 1903, 241, 1, 8, 11.

Central portion of valve inflated.

Distribution. Tasman Sea phytoplankton.

100. Stauroneis fulmen Brightw.

• Brightw. 1859, 180, 9, 6.

• A.S. 1903, 241, 1.

Valves elongate, margin convex in the middle, and midway towards end tapering to rounded ends; stauros dilated to margin; axial area broad, striae fine, finely punctate.

Distribution. Australia: Bass Strait in plankton. (Type loc. Yarra Fossil.)

• v. capitata Heid. (Pl. 53, Fig. 105)

• Heid. in A. S. 1903, 241, 6, 7.

Ends capitate.

Distribution. Fresh water. New Zealand: Wellington. This specimen also came from Lake Dobson.

Note.—The example of Stauroneis phoenicenteron used for illustration in Part II approximates S. anceps, and a more typical illustration of S. phoenicenteron is given in Pl. 53, Fig. 106 in this paper. This variety also came from Lake Dobson.

Genus Anomoeoneis Pfitz. 1871

101. Anomoeoneis serians (Breb.) Cl. var. brachysira (Breb.) Hust.