NATIONAL MUSEUM

OF

VICTORIA

MELBOURNE :: AUSTRALIA

MEMOIRS

(World List abbrev. Mem. nat. Mus. Vict.)
C. W. BRAZENOR, Acting Director

No. 22 14th JUNE, 1957 Part 5

The “Devonian Foraminifera”
from Tamworth, New South Wales

by

ALAN WOOD

PUBLISHED BY ORDER
OF THE TRUSTEES

The Devonian Foraminifera from Tamworth,
New South Wales

by
ALAN WOOD,
UNIVERSITY COLLEGE OF WALES,
ABERYSTWYTH.

(Received for publication May 10, 1956.)

In view of the general rarity of well authenticated calcareous Foraminifera in
rocks of Devonian and earlier age, the fossils described by Chapman) from
Devonian limestones have some importance. Three genera, Psammosphaera,
Valvulina and Pulvinulina were recorded, with five species in all, of which three
were considered new to science.

During a visit to Australia, supported by a grant from the Royal Society
and Nuffield Foundation, I was able, by courtesy of Mr. E. D. Gill, Curator of
Fossils, to examine the type specimens preserved in the National Museum of
Victoria, Melbourne. It was clear that these supposed foraminifera are oolite
grains, more or less affected by dolomitization and by mechanical distortion.)

The rock is a fine grained, partially dolomitized, oolite. with limonite often
present in the interior of the ooids, and forming a delicate tracery around the
dolomite crystals. The matrix is clear, well crystallized, and free from limonite,
except along later shear cracks. Considerable variation is seen in the
dolomitization of the ooids, some being affected around their periphery, others
in their centre (Fig. 3). The undolomitized portion is either a fine grained
mineral, dusky in transmitted light, probably calcite, or light brown limonite.
Radial structure is rarely seen. Some ooids are distorted, and may be drawn
out into fantastic shapes along movement planes, the planes themselves being
sometimes invisible as they traverse the matrix. The rock has a complex
history, the matrix probably being re-crystallized before the dolomitization of
the ooids, but precise evaluation of the conditions of deposition and diagenesis is
not necessary for the present purpose. No fragments of organic origin were
seen in the slides.

(ı)F. Chapman, 1918. “Devonian Foraminifera: Tamworth District, New South
Wales,” Proc. Linn. Soc. N.S.W. 43 (2): 385-394,

(2)When, at a later time, I visited the Bureau of Mineral Resources, Canberra, I
found that Miss Irene Crespin had long been of the opinion that these bodies were
not Foraminifera, though she had not examined the types.

2652/57.

2

The following comments on Chapman’s figures will make the position clear:-—

PLATE XXXIX

,

Fig. 1. “ Psammosphaera neminghensis.” An ooid with a rim of dolomite,
penetrating to the centre in the lower half of the specimen. The distinct wall
shown in the lower right hand side of Chapman's figure is not visible in the
specimen, though an increase of crystal size does give the impression of a wall
in the upper half. The aperture is relatively smaller than figured, and not so
deep. It appears to be accidental. Slide P 13048.

Fig. 2. “ P. neminghensis.” An ooid dolomitized around the periphery, the
interior filled with a fine grained deposit. Slide P 13048, specimen marked “b ”.

Fig. 3. “ Valvulina plicata.” The apparent infolding of the wall is an
accident of dolomitization, and is nowhere so clear as delineated, while the wall
itself is the result of re-crystallization, and is not so uniform in thickness as
would appear from the figure. Slide P 13052, specimen labelled “h ”.

Fig. 4. “V. plicata.” A double ooid, dolomitized on the outside and also
near the centre. A shear line lies nearby, and it is probable that this is a case
of mechanical juxtaposition of two ooids. Slide P 13048, specimen marked “a mA

Fig. 5. “ V. bulloides.” An ooid without any distinct structure, irregularly
re-crystallized, and probably fractured. Slide P 13053.

Fig. 6. “ V. bulloides.” Either a compound ooid, or one affected by a minute
shear, The interior is filled partly by dolomite crystals, partly by limonite. On
the lower left hand side the infilling crystals reach the outer boundary, and at
this point there is no possibility that a wall is present. The apparent wall seen
elsewhere is due to more finely crystalline calcite or dolomite. Slide P 13054,
specimen marked “g”.

Fig. 7. “ V. bulloides.” An ooid with one side more re-crystallized than the
other. The indentation shown at the base does occur, though it is relatively
smaller, and the faint dark band extending towards the interior is present also.
The tube leading towards it from the interior cannot be distinguished. Slide
213092:

PLATE XL

Fig. 8. “Valvulina oblonga.” A compound ooid, the centre of the larger
component being filled with limonite. The remainder is irregularly dolomitized.
The dark band shown on the right hand side of Chapman’s figure is present,
though it does not appear to separate a wall from an infilling. It cannot be

”

traced round the curved base. Slide P 13048, specimen marked “c”.
The original of “ Pulvinulina bensoni” has not been seen.

Two further points are worthy of mention. First, the dolomite crystals
stand out boldly against the less highly refractive matrix, partly because of their
!imonitic coating. This led Chapman to imagine he could see the objects in

3

three dimensions, and, as it were, look inside the curved wall of a Psammosphaera.
This appearance is clearly an optical illusion, since the specimens are large
compared with the thickness of the section. Secondly, comparison of the three
photographs illustrating Chapman’s paper will show that he interpreted two
different things as the wall of Psammosphaera. In figure 10 the larger crystals
are inside the “ wall”, and are interpreted as infilling, while in figure 11 it is
the large crystals that make the wall, as they do in figure 12.

Finally, the fact that the crystals making the wall are secondary, and are
not the primary quartz crystals of an agglutinated test, is sufficient in itself to
show that these objects are not Foraminifera.

DESCRIPTION OF PLATE 1.

Figure 1.—Original of Chapman’s figure 2 on his plate XXXIX. To show coarse
dolomite crystals around a fine grained interior.

Figure 2.—Original of Chapman’s figure 8 on his plate XL. Showing irregular
dolomitization, and fine grained exterior.

Figure 3.— General view to show varied character of ooids.

By Authority: W. M. Houston, Government Printer, Melbourne.

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