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Foraminifera are single-celled, amoeba-like, protozoans which
form a shell, or test, either from calcium carbonate (calcite)
or from cemented grains of sand or other material (e.g., sponge
spicules). The largest foraminifers reach sizes up to a few
centimetres, but most adult tests are pinhead-sized, about
1/5 to 1 millimetre. They live exclusively in the sea, but
are found from the highest tide line to the greatest depths
of the Earth's oceans. In favourable environments, their abundance
can reach many thousands of tests per cubic centimetre of
sediment.
The test is generally formed by a succession of chambers,
with variation in chamber size, shape, and arrangement (growth
plan) resulting in an incredible variety of final shapes and
forms
Examples of the variety of shape and form in Oligocene
benthic foraminifera
Two main types of foraminifera are recognised on the basis
of the material forming their tests.
1. Calcareous foraminifers, with calcite tests, are
the more numerous and diverse, and include both bottom-dwelling
(benthic) and floating (planktic) species. In some instances
calcareous foraminifers become so abundant as to become sediment-formers.
Globigerina ooze, formed beneath tropical and subtropical
waters of the world's oceans, is an example of such a sediment.
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Cibicides sp., a calcareous
benthic foraminifera |
Globigerina sp., calcareous
planktic foraminifera |
2. Agglutinated foraminifers, with tests of cemented
grains, are also widespread in the marine environment, but tend
to be most abundant under restricted conditions such as low
salinity. They probably are ancestral to the calcareous forms.
The fossil record of foraminifera extends back at least to Early
Cambrian times (c. 550 Ma). Peaks of foraminiferal diversity
and abundance occurred during the latest Paleozoic (c. 320-250
Ma), the Late Cretaceous (c. 80-65 Ma) and the Cenozoic (65
Ma to present day).
Clavulina sp., an agglutinated benthic foraminifera
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HOW ARE FORAMINIFERA USED?
Petroleum exploration. The petroleum exploration
industry has for a long time been a major stimulus for foraminiferal
research. During the 1930's foraminifera became the first
microfossil group to be used extensively for age assessment
of strata encountered during drilling, and still today are
the major "workhorse" microfossil for subsurface
exploration. This is because foraminiferal tests survive inside
the millimetre-sized rock chips produced by rotary drilling,
whereas larger fossils, such as molluscs, are obliterated.
Age and correlation of sedimentary rocks. Like
other fossil groups, foraminiferal species evolve over time,
and stages in their evolution provide a basis for subdividing
the rock column. Once the ranges of various species in the
rocks have been established, the age of an unknown bed can
be determined from the assemblage of foraminifers present.
First and last occurrences of species are especially important
"bioevents", marking unique moments in geological
time. Where these can be identified and their absolute age
determined, perhaps by magnetostratigraphy, these bioevents
can become proxies for absolute age determinations.
Because planktic foraminifera are able to spread quickly
throughout large areas of the Earth's oceans, their bioevents
are especially valuable for age determinations and for correlation
over intercontinental distances. Benthic foraminiferal distribution
is strongly controlled by local conditions, but many species
nonetheless can be used for local or even regional correlations.
Foraminiferal bioevents and assemblages provide the primary
criteria for recognising New Zealand's Cenozoic
Series and Stages.
Ancient environments.
Many foraminiferal species live within a limited range of
environmental conditions, and (unless transported from another
environment) occur only where these conditions are found.
Major factors influencing foraminiferal distribution include
temperature, water depth, type and abundance of food, salinity,
and oxygen availability. Thus, it is possible to recognise,
for example, assemblages indicating deep or shallow water,
nearshore or offshore or oceanic, brackish or normal marine,
and cold or intermediate or warm-water environments.
Reconstruction of the distribution of ancient environments,
and especially of changes in water depth, provides important
information for studies of sedimentary basin evolution used
in scientific research and petroleum exploration.
Evolutionary studies. Foraminifera are ideal
subjects for testing various aspects of evolutionary theory,
because large populations of individuals, whose characteristics
can be measured and treated statistically, can be obtained
from closely spaced rock samples at carefully selected localities
to provide an evolutionary time series. It is then possible
to show how distribution of a particular characteristic changes
over time within successive populations.
Stable isotope studies. Foraminiferal tests
often provide the calcium carbonate used for oxygen and carbon
stable isotope analyses. The isotope analyses frequently will
use a particular planktic or benthic species, and a foraminiferal
specialist will be required to select sufficient specimens
to provide the few tens of milligrams of material required.
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NEW ZEALAND STUDIES
Historical. Formal study of New Zealand foraminifera
began in the late 1850s when the Austrian research vessel
Novara collected samples from Cenozoic
rocks in the Auckland area. Fossil foraminifera from these
samples were subsequently described in 1864 in scientific
reports by F. Karrer and G. Stache.
The first relatively comprehensive descriptions of living
foraminifers from New Zealand waters were provided by H.B.
Brady in 1884 (Challenger Expedition) and E. Heron-Allen and
A. Earland in 1922 (Terra Nova Expedition).
The modern era of foraminiferal research, with New Zealand
scientists studying New Zealand foraminifera, began in 1933
when H. J. Finlay took on the position of micropaleontologist
with the Vacuum Oil Company. Vacuum Oil were exploring for
petroleum in the Gisborne district, and needed foraminiferal
age determinations for their samples. Later, in 1938, the
New Zealand Geological Survey employed Finlay as its first
micropaleontologist. During the late 1930s and early 1940s
Finlay and J. Marwick, a macropaleontologist, collaborated
to produce the scheme of fossil zones comprising New Zealand's
Cenozoic Series and Stages. Their scheme is still used today,
albeit with considerable refinement, for the biostratigraphic
classification of New Zealand strata.
N. deB. Hornibrook became Chief Micropaleontologist of the
NZ Geological Survey with Finlay's sudden death in 1951, and
foraminiferal study flourished under his guidance to gain
world recognition. Especially notable amongst his multitude
of significant contributions were Handbook of New Zealand
Microfossils (1968) and Manual of New Zealand
Permian to Pleistocene Foraminiferal Biostratigraphy (1989),
which made the main aspects of New Zealand foraminiferal faunas
and zonation scheme available to students and to the wider
public. Hornibrook also established the National Foraminiferal
Collection and fostered many workers who made their careers
in foraminiferal studies. When he retired and became an Emeritus
Research Associate in 1981, the Micropaleontology Section
of the New Zealand Geological Survey employed 5 full time
foraminiferal specialists, and several technical staff. Within
a decade, with changes in government policy and decreases
in science funding, redundancies and attrition had reduced
the number to 3, with disproportionately reduced technical
support.
New Zealand Geological Survey was succeeded in the late 1980s
by DSIR Geology and Geophysics, and when the latter organisation
was dis-established in 1993, micropaleontology became part
of the Institute of Geological and Nuclear Sciences.
Current. Today, there are five micropaleontologists
involved in foraminiferal studies at Geological and Nuclear
Sciences. There is also considerable informal and formal collaboration
with Dr Bruce Hayward
(Research Associate,
University of Auckland), in his work on modern foraminifera.
Research at GNS is focused mainly on Late Cretaceous (c. 80
Ma) through Quaternary (pre-modern) foraminiferal taxonomy,
biostratigraphy and paleoenvironmental significance. High
resolution biostratigraphy, which involves identification
of closely spaced bioevents, often in conjunction with various
quantitative techniques, is a major research direction, and
there is also an increasing emphasis on Quaternary faunas.
Results from this research often have immediate application
in other geological studies.
Commercial work, mainly for petroleum exploration companies,
occupies c. 30% of staff time. This work is valued not only
for its financial contribution, but also because it is an
important data source and an opportunity for testing biostratigraphic
concepts and research results.
Present GNS staff, and their main research interests are
listed below. For more details, please consult staff profiles.
These workers are:
Links to other sites about foraminifera
SELECTED LITERATURE ON NEW ZEALAND FORAMINIFERA
New Zealand Geological Survey Paleontological Bulletins.
#28. Vella, P. 1957: Studies in New Zealand Foraminifera
64 p.
#34. Hornibrook, N. deB. 1961: Tertiary foraminifera from
Oamaru district, New Zealand 1: Systematics and distribution,
194 p.
#38. Scott, G.H. 1965: The utility of Haeuslerella
Parr (foraminifera) in New Zealand middle Tertiary biostratigraphy,
47 p.
#42. Jenkins, D.G. 1971. New Zealand Cenozoic planktonic
foraminifera, 277 p.
#43. Hornibrook, N. deB. 1971.
A revision of the Oligocene and Miocene foraminifera from
New Zealand described by Karrer and Stache in the reports
of the Novara Expedition (1864), 85 p.
#52. Strong, C.P. 1984: Triassic foraminifera from Southland
Syncline, New Zealand, 63 p.
#56. Hornibrook, N. deB., Brazier, R.C.,
Strong, C.P. 1989: Manual of New Zealand Permian to Pleistocene
foraminiferal biostratigraphy, 175 p.
#61. Scott, G.H. 1990: Guide to some Neogene Globorotalids
(Foraminiferida) from New Zealand, 135 p.
#63. Hayward, B.W. 1990: Taxonomy, paleobiogeography and
evolutionary history of the Bolivinellidae (foraminifera),
132 p.
Institute
of Geological and Nuclear Sciences Monographs.
#12. Hornibrook, N. deB. 1996: New Zealand Eocene and Oligocene
benthic foraminifera of the Family Notorotaliidae, 52 p.
#16. Hayward, B.W., Hollis C.J., Grenfell, H.R.1997: Recent
Elphidiidae (Foraminiferida) of the south-west Pacific and
fossil Elphididae of New Zealand, 170 p.
#21. Hayward, B.W., Grenfell, H.R., Reid, C.M., Hayward,
K.A. 1999: Recent New Zealand shallow-water benthic foraminifera:
taxonomy, ecologic distribution, biogeography, and use in
paleoenvironmental assessment, 264 p.
Other:
Crundwell, M.P., Scott, G.H., Thrasher, G.P. 1994: Calibration
of paleobathymetry indicators by integrated seismic and
paleontological analysis of foreset sequences, Taranaki
Basin, New Zealand. 1994 New Zealand Petroleum Conference
Proceedings: p. 169-178.
Hayward, B.W. 1986: A guide to paleoenvironmental assessment
using New Zealand Cenozoic foraminiferal faunas. New
Zealand Geological Survey Report PAL 109: 73 p.
Kaiho, K., Morgans, H.E.G., Okada, H. 1993: Faunal turnover
of intermediate-water benthic foraminifera during the Paleogene
in New Zealand. Marine Micropaleontology 23: p.51-86.
Morgans, H.E.G., Scott, G.H., Beu, A.G., Graham, I.J.,
Mumme, T.C., St George, W., Strong, C.P. 1996: New Zealand
Cenozoic Timescale (Version 11/96). Institute of Geological
& Nuclear Sciences science report 96/38: 12 p.
Morgans, H.E.G., Edwards, A.R., Scott, G.H., Graham, I.J.,
Kamp, P.J.J., Mumme, T.C., Wilson, G.J., Wilson, G.S. 1999:
Integrated stratigraphy of the Waitaikian-Otaian Stage boundary
stratotype, Early Miocene, New Zealand. New Zealand Journal
of Geology & Geophysics 42: p. 581-614.
Scott, G.H. 1995: Coiling excursions in Globorotalia miotumida:
high-resolution bioevents at the Middle-Upper Miocene boundary
in southern temperate water masses? Journal of Foraminiferal
Research 25: p. 299-308.
Strong, C.P. 2000: Cretaceous-Tertiary foraminiferal succession
at Flaxbourne River, Marlborough, New Zealand. New Zealand
Journal of Geology and Geophysics 43: p. 1-20.
Strong, C.P., Hollis, C.J., Wilson, G.J. 1995: Foraminiferal,
radiolarian and dinoflagellate biostratigraphy of Late Cretaceous
to Middle Eocene pelagic sediments (Muzzle Group), Mead
Stream, Marlborough, New Zealand. New Zealand Journal
of Geology and Geophysics 38: p. 65-206.
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