HOLOCENE FORAMINIFERIDA FROM THE FITZROY RIVER ESTUARY,
NORTH WEST AUSTRALIA
By a. C. Collins
Honorary Associate in Palaeontology, National Museum of Victoria.
Abstract
Six species are recorded or described. One of these Sipholrochammina aff. lobaia docs not appear to
have been previously recorded from Australian waters, another Nubeculopsis queenslandica is discussed
in terms of its validity as a species and genus, and the remaining four are described as new. Of these, three
have morphological features which appear to justity the erection of new genera. They are Munkiella {M.
lingula(a), Bisaccoides [B. cuspidatus) and De/oslne/la (D. planispiralis). Specimens were obtained from a
shallow borehole in a mangrove flat, and there is no evidence of their existence in the local living fauna,
though this appears probable.
Material
The foraminiferida described herein derive
from a shallow core (maximum depth 280 cm)
taken in the course of geomorphological in-
vestigations by Dr J. N. Jennings of the
Research School of Pacific Studies, Australian
National University. The samples listed were,
amongst others, entrusted to the author some
years ago for examination of their fossil con-
tent for any light it might throw on the matter
of marine transgression in the area. However,
apart from this core (site distinguished as
Munkayarra H. 12), only very sparse as-
semblages of foraminiferids were found, up to
a maximum of 17 specimens per sample, and in
most cases less or nil.
The location of the core was at grid reference
189003 on 1:50000 R.A.S.C. sheet 3663-III,
Derby, Lat. 17°28' S., Long. 123^35' E. It was
drilled in low mangrove scrub (Avicennia
marina), but the area is one of extremely fast
lateral erosion by the main estuarine currents,
and it is probable that the sediments concerned
have long since been removed in this manner
(Jennings, pers, comnh)
Four samples were taken from the core, as
described hereunder:
275-280 cm. SiU with a few small clay lumps.
Residue after washing through a 180-mesh
sieve was almost entirely marine skeletal
material, including pteropod and other
moiluscan shells, ostracods, sponge spicules
in profusion, alcyonarian spicules and
foraminiferids, with mica flakes and a few
small angular sand-grains. Approximately
Memoirs oi" the National Museum Victoria, 1
No. 42, 1981.
150 species of foraminiferids were found,
mostly smaller benthic species with a few
pelagic forms and the juvenile tests or small
fragments of the commoner larger species.
The general even size of specimens suggests
that the assemblage is a current-sorted
thanatocoenosis having little relation to the
living local population at the time of
deposition.
195-200 cm. Generally similar to the above, but
with a more diverse foraminiferid assemblage
of ca. 200 species.
85-90 cm. Similar to the foregoing samples but
containing a proportion of woody fibre and
having a smaller assemblage of ca. 110
species.
0-5 cm. Quite different to the deeper samples,
containing much fibrous material and a small
assemblage (ca. 20 species) of foraminiferids,
dominated by the agglutinated genera
Trochammina and Sipholrochammina.
Small hollow agglutinated tests with a pink
shining chitinoid lining were also present,
and in the lack of expert opinion were pro-
visionally considered to be Thecamoebidae.
Very little can be deduced from these widely-
spaced samples, other than an increasing
freshwater influence in the later stages of
deposition. The Fitzroy estuary ahernates be-
tween a short phase when fresh water
dominates and a long phase when salinities are
very high and marine influence dominates.
(Jennings, pers. comm.). Reworking is prob-
ably common, as noted earlier. The assem-
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