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Meteorites are our only tangible source of information on the earliest history of the Solar System. Over the last ten years the number of meteorites described from Australia has doubled, and this has stimulated many new lines of enquiry. To date, fragments from a total of 474 distinct and authenticated meteorites have been recovered in Australia. The material, including 13 meteorites observed to fall, comprises 389 stones (21 achondrites, 366 chondrites and 2 unclassified stones), 71 irons, 13 stony-irons and one meteorite of unknown class. Two hundred and fifty-seven distinct meteorites are currently known from Western Australia, 123 from South Australia, 48 from New South Wales, 20 from Queensland, 12 from the Northern Territory, 10 from Victoria and 4 from Tasmania. Discoveries include the first lunar meteorite (a fragment of the Moon), Calcalong Creek, found outside of Antarctica. Five meteorites (Veevers [iron], Wolf Creek [iron], Henbury [iron], Boxhole [iron], and Dalgaranga [mesosiderite stony-iron]) are associated with craters. Another eighteen impact structures (lacking meteorites) are known in Australia and the country has one of the world's best preserved impact cratering records stretching back more than 500 million years. Most meteorites in Australia have been found in the Nullarbor Region, which for climatic and geological reasons is one of the most prolific areas of the world for meteorite recoveries outside of Antarctica. Since 1971, several thousand specimens of an as yet unknown total number of distinct meteorites have been recovered from the Nullarbor, including many rare types. 14 C terrestrial ages of Nullarbor meteorites combined with population statistics are providing important information about the number of meteorites falling with time. Moreover, weathering studies of ancient stony meteorite finds, and the stable isotopic composition of carbonate contamination derived from the Nullarbor limestones is yielding palaeoclimatic information for that region of Australia over the last 30,000 years.
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Journal of the Royal Society of Western Australia, 79(1), March 1996
33
© Royal Society of Western Australia, 1996
de Laeter Symposium on Isotope Science
Curtin University of Technology, Perth, 1995
Meteorites recovered from Australia
A W R Bevan
Department of Earth and Planetary Sciences, Western Australian Museum, Francis Street, Perth 6000
Abstract
Meteorites are our only tangible source of information on the earliest history of the Solar System.
Over the last ten years the number of meteorites described from Australia has doubled, and this
has stimulated many new lines of enquiry. To date, fragments from a total of 474 distinct and
authenticated meteorites have been recovered in Australia. The material, including 13 meteorites
observed to fall, comprises 389 stones (21 achondrites, 366 chondrites and 2 unclassified stones), 71
irons, 13 stony-irons and one meteorite of unknown class. Two hundred and fifty-seven distinct
meteorites are currently known from Western Australia, 123 from South Australia, 48 from New
South Wales, 20 from Queensland, 12 from the Northern Territory, 10 from Victoria and 4 from
Tasmania. Discoveries include the first lunar meteorite (a fragment of the Moon), Calcalong Creek,
found outside of Antarctica. Five meteorites (Veevers [iron], Wolf Creek [iron], Henbury [iron],
Boxhole [iron], and Dalgaranga [mesosiderite stony-iron]) are associated with craters. Another
eighteen impact structures (lacking meteorites) are known in Australia and the country has one of
the world’s best preserved impact cratering records stretching back more than 500 million years.
Most meteorites in Australia have been found in the Nullarbor Region, which for climatic and
geological reasons is one of the most prolific areas of the world for meteorite recoveries outside of
Antarctica. Since 1971, several thousand specimens of an as yet unknown total number of distinct
meteorites have been recovered from the Nullarbor, including many rare types. 14C terrestrial ages
of Nullarbor meteorites combined with population statistics are providing important information
about the number of meteorites falling with time. Moreover, weathering studies of ancient stony
meteorite finds, and the stable isotopic composition of carbonate contamination derived from the
Nullarbor limestones is yielding palaeoclimatic information for that region of Australia over the
last 30,000 years.
Introduction
Meteorites are an unique source of information about
the earliest history of the Solar System. Mostly fragments
broken from small planetary bodies, called asteroids, in
solar orbits between Mars and Jupiter, many meteorites
have remained virtually unaltered since their formation
4.55 Ga ago. Some rare types of carbonaceous meteorite
contain water and complex carbon compounds, includ-
ing amino acids. These rocks may be similar to the origi-
nal materials from which the Earth gained the water for
its oceans, the gases for the atmosphere we breathe, and
the building blocks of life. However, aside from the fun-
damental question of the origin of life, basic research on
meteorites is helping us to understand many other as-
pects of our natural environment and history. Research
on Australian meteorites essentially started with the pub-
lication by Haidinger (1861) of a description of two
masses of the Cranbourne iron meteorite found in
Victoria in 1854.
On numerous occasions in the past, meteorites found
in Australia have been reviewed, or listed (e.g. Cooksey
1897; Anderson 1913; Prior 1923; Hodge-Smith 1939; Prior
& Hey 1953; Hey 1966; Mason 1974; Gibbons 1977;
Graham et al. 1985; Bevan 1992a). Most recently, Bevan
(1992a) provided a comprehensive review of meteorite
recovery in Australia. However, since the early 1990’s
there has been a surge in the recovery of meteorites in
Australia that has opened up many new lines of research.
Figure 1 shows the numbers of meteorites known at
various times from Australia during the period 1897-
1996. Mason (1974) documented a total of 184 distinct
meteorites from Australia. During the period 1974-1992,
data were published for 93 new Australian meteorites
(Bevan 1992a). However, since the last review by Bevan
(1992a), data for an additional 197 meteorites from Aus-
tralia have appeared in the literature. This remarkable
recovery rate is largely due to discoveries in the Western
Australian and South Australian Nullarbor Region. For
climatic and geological reasons, the Nullarbor Region is
one of the most prolific desert areas of the world for
meteorite recoveries outside of Antarctica (Bevan & Binns
Figure 1. Cumulative histogram of meteorites known from Aus-
tralia at various times during the period 1897-1996.
Journal of the Royal Society of Western Australia, 79:33-42, 1996
34
Journal of the Royal Society of Western Australia, 79(1), March 1996
1989a,b,c; Bevan 1992a; Bevan & Pring 1993). Recoveries
from the Nullarbor alone account for more than 50% of
all meteorites currently known from Australia, and more
than a thousand recently recovered, and potentially new,
Nullarbor meteorite fragments remain to be described
(Bevan 1992b; Koeberl et al. 1992).
The purpose of this paper is to review Australian me-
teorites, particularly those recovered since the last review
by Bevan (1992a), and with special reference to the
unique environment of the Nullarbor Region, to examine
the climatic and physiographic factors that contribute to
the recovery of meteorites in Australia.
Meteoritic materials and origin
Only a brief resumé of meteorite classification and
genesis is presented here. For more detailed accounts,
the reader is referred to the bibliography and references
therein (e.g. Dodd 1981; McSween 1987).
Traditionally, meteorites have been divided into three
major categories depending on the relative amounts of
silicate and metallic minerals they contain. Iron meteor-
ites are composed predominantly of iron-nickel metal;
stony meteorites (often called ‘stones’) consist mainly of
silicates, but also contain some metal and other accessory
and minor mineral phases; and stony-irons comprise
metal and silicates in roughly equal amounts. About 95%
of modern observed meteorite falls are stones, around 4%
are irons and only 1% are stony-irons. This simple
classification scheme, however, conceals the diversity of
materials that have fallen to Earth, and modern research
has delineated numerous distinct groups and sub-types
of meteorites.
Stones
Of the two main groups of stony meteorites
recognised, the chondrites are the most numerous, ac-
counting for 87% of all meteorites observed to fall. Chon-
drites contain millimetre-sized beads of stony minerals,
called chondrules, from which the name of the group
originates (Fig 2). Chondrules are unknown in any rocks
from Earth and for more than a century arguments have
continued over how these enigmatic objects might have
formed. While there is still no consensus on the
mechanism by which chondrules were generated, most
researchers agree that chondrules were among the
earliest materials to have formed in the Solar System. An
understanding of the origin of chondrules, and subse-
quent chondrites, is fundamental to our understanding
of how materials (and ultimately planets) formed in the
infant Solar System. Chemical variations between chon-
dritic meteorites define a number of distinct groups.
The largest group, collectively known as the ordinary
chondrites, accounts for more than half of all known mete-
orites (observed falls + chance finds) (e.g. see Fig 3).
Although 75% of their bulk is made up of silicate miner-
als, ordinary chondrites contain substantial amounts of
iron both in the form of silicates and as metal and iron-
sulphide. Two other rarer groups of chondrite, enstatite
and carbonaceous chondrites, represent extremes in compo-
sition. The enstatite chondrites are rich in metal and
sulphide, but the main silicate mineral they contain
(enstatite) is a pure magnesium-silicate containing no
iron. In contrast, carbonaceous chondrites contain little
or no metallic iron, but their silicate minerals are mostly
iron-rich.
Figure 2. Photomicrograph of the Forrest Lakes LL5 ordinary
chondrite showing numerous rounded chondrules.
Figure 3. Mass of the ordinary chondritic (H5) meteorite that fell
on Binningup beach, Western Australia, at 10:10 am on 30 Sep-
tember, 1984.
Carbonaceous chondrites are among the most important
and intriguing classes of meteorites. Sometimes rich in
complex carbon compounds such as amino and fatty
acids, carbonaceous chondrites can also contain appre-
ciable amounts of water (up to 20%), and water-bearing
minerals that formed by the hydrothermal alteration of
other minerals. A rare type of carbonaceous chondrite
[CI], named for the type meteorite Ivuna (that fell in
Tanzania), of which only a few are known, is composed
almost entirely of minerals that formed at low tempera-
tures. Significantly, some of these meteorites have chem-
istries that closely match the Sun’s, and are our best
samples of ‘average’ Solar System material. The majority
of meteorites are believed to be fragmental debris from
the collision of asteroids, but there is astronomical evi-
dence suggesting that some carbonaceous chondrites
may have had a cometary origin.
The achondrites make up around 8% of modern mete-
orite falls. So-called because they lack chondrules, achon-
drites generally have textures showing that they formed
in similar ways to some of the igneous and volcanic
rocks on Earth. Although most achondrites are asteroidal
Journal of the Royal Society of Western Australia, 79(1), March 1996
35
in origin, twelve are fragments of the Moon. These
“lunar” meteorites were probably ejected from the Moon
by large, low-angle impacts. We are able to recognise
lunar meteorites by comparison with the reference
collection of lunar rocks returned by the Apollo space
missions and knowledge of the Moon’s chemistry.
Another twelve achondritic meteorites are planetary in
origin and may be fragments of Mars (e.g. see Gladman
et al. 1996 and references therein). Unlike meteorites of
asteroidal origin, these meteorites crystallized only 200-
1300 million years ago and must have come from a large,
planetary-sized body that remained hot for much longer
than the asteroids.
Irons
The chemical make-up of irons suggests that most
solidified from molten accumulations of metal that could
only have formed deep in the interiors of a number of
small asteroids (Fig 4). Irons often consist of two iron-
nickel minerals arranged in a regular trellis-work
structure of interlocking crystal plates. When cut and
polished surfaces of some irons are treated with acid, this
structure, called a Widmanstätten pattern is revealed (Fig
5). Widmanstätten structures formed as the result of
extremely slow cooling of hot metal in the solid state.
Cooling rate calculations indicate that many irons are
fragments of the cores of small asteroidal bodies ranging
up to a few hundred kilometres in diameter. Like achon-
drites, most iron meteorites tell us that some bodies
smaller than planets in the early Solar System melted
and differentiated, separating metal from silicate to form
‘cores’ and ‘crusts’ like the Earth’s. Other iron meteorites
were never completely melted and some contain inclu-
sions of silicate. The modern classification of irons is
based on chemistry, notably the abundance of Ni, Ga, Ge
and Ir that they contain.
Figure 4. Main mass, weighing 480 kg, of the Haig (group IIIAB)
iron meteorite found on the Nullarbor Plain by Mr A J Carlisle
in 1951 (photograph by D. Elford).
Figure 6. Mass (originally 54 kg) of the Bencubbin meteorite
found in July 1930. Scale bar is 10 cm. (photograph by K
Brimmell).
Figure 5. Cut, polished and acid treated slice of the Haig iron
meteorite showing the Widmanstätten pattern characteristic of
this group of irons (sawn edge measures 8 cm).
Stony-irons
Stony-irons are by far the rarest of the main categories
of meteorites. Two main groups of stony-irons are
recognised. Meteorites of the largest group, the pallasites,
are composed of crystals of olivine set in metallic iron-
nickel. Members of the other major group of stony-irons,
called mesosiderites, are made up of mixtures of fragments
of rock similar to some achondrites in composition, and
nuggets and veins of iron-nickel metal. There are also
several anomalous meteorites (e.g. Bencubbin) that fit
structurally into the stony-iron category, although these
have no relationship to the two major groups. Bencubbin
is a complex mixture of metal and silicate components,
including a variety of chondritic xenoliths an example of
which is seen as a dark area on the cut face of the
meteorite (Fig 6). Bencubbin is not related to any of the
known major groups of meteorites although some
components are chemically and isotopically similar to the
36
Journal of the Royal Society of Western Australia, 79(1), March 1996
CR group of carbonaceous chondrites and an unique
Antarctic chondrite Allan Hills 85085 (Barber &
Hutchison 1991; Weisberg et al. 1995).
The stony-irons may have formed by the mixing of
both solid and liquid metal and silicates at various
depths within their parent asteroids. A close relationship
between some pallasites and one of the groups of irons
suggests that they may have formed in the semi-molten
regions between the metallic cores and rocky outer skins
of small planet-like asteroids, whereas mesosiderites
originated as mixtures of solid and liquid metal and
achondritic rocks of diverse origins.
Recovery of meteorites in Australia
Currently, fragments from a total of 474 distinct and
authenticated meteorites have been described from Aus-
tralia. The material comprises 389 stones (21 achondrites,
366 chondrites and 2 unclassified stones), 71 irons, 13
stony-irons and one meteorite of unknown class. One
meteorite, Murchison Downs, previously thought to be
distinct has been shown by Bevan & Griffin (1994) to be a
transported fragment of the Dalgaranga mesosiderite and
is not included in the total. Two hundred and fifty-seven
distinct meteorites are currently known from Western
Australia, 123 from South Australia, 48 from New South
Wales, 20 from Queensland, 12 from the Northern
Territory, 10 from Victoria and 4 from Tasmania.
Discoveries include the first lunar meteorite, Calcalong
Creek, found outside of Antarctica (Hill et al. 1991).
Only thirteen well-documented observed meteorite
falls have been recorded from Australia (Bevan 1992a).
The most recently recovered fall (Fig 3) is a single stone
of an ordinary chondrite weighing 488.1 grams, that fell
on Binningup beach in Western Australia on 30 Septem-
ber, 1984 (Bevan et al. 1988). Several large fireballs, some
associated with sonic phenomena, from which meteorites
may have been deposited, have been recorded in
Australia over the last few years (e.g. see McNaught
1993). However, no known material that can be linked to
these events has been recovered. A list of the authenti-
cated observed meteorite falls from Australia is given in
Table 1. One of the most recent discoveries is a 34 kg
mass of ordinary chondrite found near Broken Hill in
December 1994 (Grossman 1996)
In Australia, most chance meteorite recoveries, or
finds, have resulted from the clearing of land for agricul-
ture and pastoralism, and also mining and prospecting
activity. The distribution of meteorite falls and finds in
Australia is shown in Fig 7. The general lack of discover-
ies in tropical Australia (north of latitude 23° S) probably
reflects a climate and physiography that are not
conducive to the preservation and recognition of meteor-
ites, respectively. As noted by Mason (1974) and Bevan
(1992a), there remain surprisingly few documented
discoveries from central Australia and Queensland.
To date, the largest single mass of meteorite found in
Australia is an 11.5 tonne fragment of the Mundrabilla
iron found in 1966 on the Nullarbor Plain in Western
Australia (Wilson & Cooney 1967). Since the discovery of
this mass, more than twelve additional masses of the
same meteorite totalling more than 22 tonnes have been
recovered from a large area of the central Nullarbor in
Western Australia (e.g. see De Laeter 1972; De Laeter &
Cleverly 1983; De Laeter & Bevan 1992 and references
therein).
Five meteorites (4 irons and 1 stony-iron) are associ-
ated with meteorite impact craters (Bevan 1992a, 1996).
Figure 7 shows the locations of the Dalgaranga, Veevers,
Wolfe Creek, Boxhole and Henbury impact craters.
Mount Darwin crater in Tasmania (Fig 7) is undoubtedly
of impact origin but no meteorites have been collected
(Fudali & Ford 1979). An additional small crater, the
Snelling crater, has recently been discovered in Western
Australia (E S Shoemaker, pers. comm.). However, no
meteorites are reported to have been collected from the
locality. Throughout Australia another eighteen larger
structures are known to varying degrees of certainty to
be the deeply eroded remains of giant meteorite or aster-
oidal impact craters (Shoemaker & Shoemaker 1988,
1996). No meteoritic material is known from these sites
although there is, in many cases, abundant evidence of
meteorite impact that may include characteristic macro-
scopic shatter-cones, microscopic shock-metamorphic ef-
fects in the target rocks, and noble metal geochemical
anomalies.
Table 1.
Australian observed meteorite falls (in chronological order)
Name Date of fall class State co-ordinates
Tenham (spring) 1879 L6 Qld 25° 44'S 142° 57'E
Rockhampton* (spring) 1895 stone Qld 23° 23'S 150° 31'E
Emmaville 1900 Eucrite NSW 29° 28'S 151° 37'E
Mount Browne 17.7.1902 H6 NSW 29° 48'S 141° 42'E
Narellan 8.4. 1928 L6 NSW 34° 3'S 150° 41' 20"E
Moorleah Oct. 1930 L6 Tas 40° 58.5'S 145° 36'E
Karoonda 25.11.1930 CK4 SA 35° 5'S 139° 55'E
Forest Vale 7.8.1942 H4 NSW 33° 21'S 146° 51' 30"E
Millbillillie Oct. 1960 Eucrite WA 26° 27'S 120° 22'E
Woolgorong 20.12.1960 L6 WA 27° 45'S 115° 50'E
Wiluna 2.9.1967 H5 WA 26° 35' 34"S 120° 19' 42"E
Murchison 28.9.1969 CM2 Vic 36° 37'S 145° 12'E
Binningup 30.9.1984 H5 WA 33° 09' 23"S 115° 40' 35"E
*specimen lost
Journal of the Royal Society of Western Australia, 79(1), March 1996
37
Figure 7. Geographical distribution of meteorite finds and observed falls in Australia and sites of five meteorite
impact craters associated with meteorites, Wolfe Creek (W), Dalgaranga (D), Veevers (V), Henbury (H), Boxhole
(B), and one crater, Mount Darwin (M), at which meteorites are lacking.
The Nullarbor Region
The anomalously large number of meteorites found in
the Nullarbor Region (Fig 7) does not mean that more
meteorites have fallen there than anywhere else in Aus-
tralia, but reflects an unique physiographic environment
and a sustained research effort to recover meteorites from
the region. The Nullarbor Region is coincident with a
geological structure, the Eucla Basin, that straddles the
border between South Australia and Western Australia.
The sedimentary basin comprises essentially flat-lying
limestones of Lower-Middle Miocene Age (ca. 15 Ma)
outcropping over an area of ca. 240,000 km2. (Lowry
1970). The arid to semi-arid climate of the Nullarbor that
has persisted for tens of thousands of years or more,
combined with a lack of vegetation and pale country
rock, has made the Nullarbor ideal for the prolonged
preservation and easy recognition of meteorites. Essen-
tially, meteorites have been accumulating in the
Nullarbor since climatic conditions allowed for their
preservation. Moreover, in the Nullarbor there is good
evidence to suggest that meteorites are lying on, or near,
the surfaces on which they fell and that,
physiographically, the region has remained essentially
undisturbed for at least the last 30,000 years (Benbow &
Hayball 1992).
Many of the early meteorite recoveries from the
Nullarbor resulted from a programme of search and re-
covery by personnel from the Kalgoorlie School of Mines
(see Cleverly 1993 and references therein), although
numerous recoveries have been made by rabbit trappers,
notably the Carlisle family from Kalgoorlie (Bevan
1992a). Until recently, there were few meteorites known
from the area of the Nullarbor in South Australia.
However, collecting by rabbiters and prospectors has
resulted in a great number of new recoveries from the
area that account for most of the large increase from the
50 meteorites reported by Bevan (1992a) to the current
123 known from South Australia. Unfortunately, most of
this South Australian material now resides in collections
outside of Australia.
Nomenclature
The described meteorites from the Nullarbor Region
now account for more than 50 % of all meteorites known
from Australia. As meteorites are named after the geo-
graphical localities where they are found, the general
lack of geographical names in the Nullarbor, and the
great number of new recoveries has caused difficulties
for meteorite nomenclature. The problem has been over-
come by the introduction of a system of meteorite no-
menclature based on geographically named areas. Sev-
enty-four named areas have been delineated (47 in West-
ern Australia; 27 in South Australia) in the Nullarbor
Region and new and distinct meteorites take the name of
the area in which they are found and a three digit
number (e.g. Cook 005), usually in chronological order of
discovery (Bevan & Binns 1989a; Bevan & Pring 1993).
Some nomenclatural anomalies have occurred and these
include the Haig, Rawlinna (stone), Cook 003 and
Maralinga meteorites, the localities of which lie outside
the newly designated areas with the same names.
38
Journal of the Royal Society of Western Australia, 79(1), March 1996
Palaeoclimatic information from meteorites
in the Nullarbor Region
As soon as meteorites enter the Earth’s atmosphere
they are subject to contamination from, and alteration by,
the terrestrial environment. Prolonged weathering
transforms many of the minerals in meteorites, masks
their original textures, redistributes elements, and even-
tually destroys them. However, the processes of weather-
ing leave a terrestrial ‘fingerprint’ in meteorite finds that
may be used in climatic research. Meteorites that survive
prolonged weathering are potential recorders of
environmental conditions during their period of terres-
trial residence. Although in its infancy, the use of ancient
Nullarbor meteorite finds as indicators of palaeoclimate
is yielding promising results.
Recent research on meteorites from the Nullarbor and
other hot desert regions of the world for which terrestrial
age data are available (Jull et al. 1990; Jull et al. 1995) has
suggested that the weathering characteristics of ancient
meteorite finds may reflect the climatic conditions within
a millennium or so of their fall (Bland et al. 1995a,b). This
discovery has stimulated a completely new area of
palaeoclimatic research, and the Nullarbor region is
proving to be one of the most significant areas of the
world for the use of meteorites as palaeoclimatic indica-
tors.
Within the limits of the data currently available (Jull et
al. 1995), the distribution of 14C terrestrial ages of ordi-
nary chondritic meteorites from the Nullarbor Region
show an apparently uninterrupted exponential decrease
from the present day to around 30 ka BP (Fig 8). The
oldest terrestrial age of a stony meteorite yet published
from the Nullarbor (27±1.4 ka) is in good agreement with
the estimated age (<30 ka) of the present calcareous clay
cover of the Nullarbor (Benbow & Hayball, 1992).
biological studies of the region. For example, a number
of workers, notably Thorne (1971), have suggested on the
basis of faunal remains from caves that the climate of the
Nullarbor has not changed significantly during the last
20 ka (e.g. see Wyrwoll 1979; Davey et al. 1992 and
references therein). However, pollen from three caves in
the Nullarbor examined by Martin (1973) indicated that
the period 20 ka to ca. 10-8 ka BP was slightly more arid
than that of today, with annual rainfall averaging ca. 180
mm. The palynological evidence suggests that from
around 10-8 ka BP to 5-4 ka BP the rainfall increased on
the Nullarbor, and has since maintained an annual
average of about 250 mm. Further evidence from pollen
from the dessicated guts of some dated mummified
mammalian carcasses (Ingram 1969), supports the
conclusion that the annual rainfall in the Nullarbor Plain
area has remained roughly constant since about the
middle Holocene (ca. 5 ka BP).
Currently, the Nullarbor has no active surface drain-
age. However, higher lake levels and relict stream
courses traversing the region testify to a period of greater
effective precipitation (Jennings 1967a,b, 1983; Lowry
1970; Lowry & Jennings 1974; Graaff et al. 1977; Street-
Perrott & Harrison 1984). When these channels were last
active is unknown, although U-series dating of calcite
speleothems from Nullarbor caves (Goede et al. 1990)
suggests that no significant calcium carbonate deposition
has taken place during the last 300-400 ka. Presently,
active deposition of speleothems in Nullarbor caves is
almost exclusively gypsum and halite (Goede et al. 1990;
Goede et al. 1992). As a mechanism for halite deposition,
Goede et al. (1992) suggest that periodic changes to
slightly higher effective precipitation in the Nullarbor re-
initiated percolation and, provided that the seepage was
subject to strong evaporation in the cave atmosphere, led
to the deposition of halite speleothems.
U-series ages of halite speleothems from the
Nullarbor have been reported by Goede et al. (1990,
1992). One large (2.78 metres long) broken salt stalag-
mite from Webbs Cave gave a ‘bulk’ age indicating pro-
longed deposition during the Late Pleistocene between
ca. 37 ka and 20 ka BP (Goede et al., 1992). Previous
dating (Goede et al., 1990) of a small (0.16 m) halite
stalagmite from the same cave yielded an age of 2.5±1.2
ka indicating that there have been at least two phases of
halite speliothem formation in Webbs Cave within the
last 37 ka.
The work of Goede et al. (1990, 1992) shows that dur-
ing the Late Pleistocene (ca. 30-20 ka BP) and again in
the Holocene (ca. 2.5 ka BP) there were minor changes
to more humid conditions in the Nullarbor following
periods of prolonged aridity, and support the conclu-
sions of Martin (1973) and Lowry & Jennings (1974).
Significantly, the age range of the oldest salt stalagmite
(37-20 ka) from Webbs Cave overlaps with the apparent
onset of accumulation of stony meteorites from around
30 ka BP on the Nullarbor surface. If any stony meteor-
ites significantly older than 30 ka exist in the Nullarbor,
it is possible that they are buried in the calcareous clay
cover. However, it should be noted that 26Al/53Mn dat-
ing of the Mundrabilla iron meteorite by Aylmer et al.
(1988) gave a terrestrial age >1 Ma, indicating that it is
the oldest meteorite fall yet recovered from the
Nullarbor.
The preservation and accumulation of meteorites as
the result of prolonged aridity in the Nullarbor from ca.
30 ka BP is consistent with palaeoclimatic evidence from
a wide variety of geomorphological, palaeontological and
Figure 8. Distribution of 14C terrestrial ages of chondritic meteor-
ite finds from the Nullarbor Region of Australia (after Jull et al.
1995).
Journal of the Royal Society of Western Australia, 79(1), March 1996
39
Bland et al. (1995a, b) have attempted to quantify the
state of weathering of a number of ordinary chondrite
finds from the Nullarbor using 57Fe Mössbauer spectros-
copy. By comparing the abundance of ferric iron oxide/
oxyhydroxide species in individual meteorites against
terrestrial age, Bland et al. (1995b) suggest that meteorite
weathering is sensitive to climate at the time of fall.
Moreover, meteorites appear to obtain their weathering
characteristics within ca. 1000 years of fall. Gradual
weathering rates, like those that have persisted in the
Nullarbor, allow the formation of stable surface oxide
layers, and a reduction in the porosity of the meteorites
that provides protection against further significant
weathering during periods of more effective precipita-
tion. Moreover, carbonates derived by the meteorite from
the Nullarbor limestone also fill pore space in some
stones (Bevan & Binns 1989b). It appears that once a
stony meteorite reaches a state of temporary equilibrium
after initial weathering, the energy of the surrounding
environment needs to be raised significantly to alter the
remains further, or destroy them.
Figure 9 shows a plot of total ferric oxidation (%) in
Nullarbor H-group ordinary chondrites against terrestrial
age (after Bland et al. 1995b). Periods of climatic change
derived from biological and geomorphological studies
outlined above are marked for comparison. Even within
the limits of the small data set currently available there is
a remarkable co-incidence between the ‘rustiness’ of
chondritic meteorites as measured by Mössbauer (Bland
et al. 1995b), and periods of alternately higher and lower
effective precipitation in the Nullarbor during the Late
Pleistocene and Holocene.
Recent recoveries of rare meteorites in
Australia
Bevan (1992a) listed a number of rare meteorites re-
covered from Australia. The most significant of the ob-
served falls (Table 1) are the two carbonaceous chon-
drites Murchison [CM2] (CM= Mighei type carbon-
aceous chondrite) and Karoonda [CK4] (CK= Karoonda
type carbonaceous chondrite; see Bevan 1992a and ref-
erences therein). Carlisle Lakes, a previously anomalous
and ungrouped chondritic meteorite find from the
Nullarbor (Binns & Pooley 1979) has recently been
shown to belong to an entirely new group of chondrites
including an observed fall, Rumuruti, from Kenya
(Schulze et al. 1994). The new group of chondrites,
known as the ‘R’ group (after Rumuruti), includes sev-
eral other meteorites from Antarctica and one from the
Reg El Acfer in North Africa (Bischoff et al. 1994; Rubin
& Kallemeyn 1989, 1993, 1994; Schulze et al. 1994). A
new group of carbonaceous chondrites, the CR group
(named after the type meteorite Renazzo), has been de-
scribed (e.g. see Weisberg et al. 1993). Spettel et al. (1992)
have suggested that Loongana 001, an unusual chon-
drite found in 1990 in the Western Australian Nullarbor
is related to the CR group. However, Kallemeyn &
Rubin (1995) have shown that the meteorite does not
belong to any of the established carbonaceous chondrite
groups and along with the Coolidge chondrite found in
the USA, forms a distinct grouplet of carbonaceous
chondrites related to the CV group (named after the
type meteorite Vigarano).
Bevan (1992a) noted that out of the main groups or
sub-types of meteorites then known, only ten were not
represented in collections from Australia. In the last
three years, however, several ordinary chondrites of
petrologic type 7 have been described providing
examples previously missing (Wlotzka 1994), along with
a possibly new petrologic type 2 (?) member of the CV
group of carbonaceous chondrites, Mundrabilla 012
(Ulff-Møller et al. 1993). One enstatite chondrite of type
7, Forrest 033, has been recorded (Wlotzka 1994). A new
CV3 chondrite, Denman 002, has been described from
the South Australian Nullarbor (Dominik & Bussy 1994).
Jull et al. (1995) have made a preliminary study of the
carbonates from some weathered ordinary chondrites
from the Nullarbor. The results show that there are some
variations in d13C, and there is a weak correlation of d13C
and carbonate content with terrestrial age that may be
linked to palaeoclimatic events.
Figure 9. Plot of total ferric oxidation (%) of weathered H-group
ordinary chondrites from the Nullarbor Region of Australia as
determined by Mössbauer against their 14C terrestrial ages.
Marked above are significant palaeoclimatic events in SW Aus-
tralia for the same period; see text for references (after Bland et
al. 1995b)
Figure 10. Mass (1.536 kg) of the Cook 003 CK4 chondrite found
in the South Australian Nullarbor. The knobbly surface is due to
large protruding chondrules (photograph by K Brimmell).
40
Journal of the Royal Society of Western Australia, 79(1), March 1996
Sleeper Camp 006 and Cook 003 (Fig 10), two stones
found in the Western Australian and South Australian
Nullarbor respectively, are additional CK4 chondrite
finds. Cook 003 may be paired with an earlier reported
discovery, Maralinga (Geiger et al. 1992). Two other re-
coveries from the Nullarbor, Camel Donga 003 and
Watson 002 are the first known examples of CK3 chon-
drites from Australia and their reported find-sites are
sufficiently far apart to discount pairing (Wlotzka
1993a,b).
In terms of achondrites, Calcalong Creek (Hill et al.
1991; Wlotzka 1991), reportedly discovered within the
strewn field of the previously known Millbillillie achon-
drite (eucrite) in Western Australia, is the first lunar
meteorite found outside of Antarctica. Calcalong Creek
is a polymict lunar breccia with the highest KREEP com-
ponent of any known lunar meteorite (Hill et al. 1991).
New achondrites from the Nullarbor include several
howardites; Camel Donga 004, Hughes 004, Hughes 005,
Old Homestead 001, Mundrabilla 018 (Wlotzka 1995)
and Muckera 002. Old Homestead 001 and Mundrabilla
018 were found close together, as were Hughes 004 and
005 and these may be fragments of the same fall. The
fragments constituting Muckera 002 were found near
the site of discovery of the Muckera meteorite (now
Muckera 001) which is also a howardite. Eagles Nest
found in central Australia and Reid 013 from the
Nullarbor, two new examples of brachinaites (olivine-
rich achondrites named after the type meteorite found
at Brachina in South Australia) have been found
(Wlotzka 1992b,1993b). Reid 013 is remarkably similar
to Nova 003, a meteorite the locality of which is
uncertain (Wlotzka 1993b). Three new ureilites, Hughes
007, Hughes 009 and Nullarbor 010, have been found in
the Nullarbor and the latter meteorite is similar to Nova
001, an ureilite originally reported as found in Mexico
although now considered to be of uncertain location
(Wlotzka 1993a).
A new lodranite (an anomalous stony-iron meteorite
of rare type possibly related to the ureilite achondrites),
named Gibson, has been found in north-western Austra-
lia and is the first meteorite of its kind found in Australia
(Wlotzka 1992b). Since 1992, two important new masses
of iron meteorites have been reported. Two distinct
group IIE irons, Watson (93 kg) (Olsen et al. 1994) and
Miles (265 kg), have been reported from the South
Australian Nullarbor and Queensland, respectively
(Wlotzka 1992a, 1994). A new iron, Hidden Valley weigh-
ing 7 kilograms, belonging to chemical group IIIAB was
also found in Queensland in 1991 (Wlotzka 1994). These
discoveries bring the total number of distinct irons
reported from Australia to 71.
Meteorite groups and types remaining to be reported
from Australia include chondrites belonging to EH3-4,
EL5, CI, CK5, CO3, and a possibly new ‘CH’ group of
carbonaceous chondrites (Bischoff et al. 1993), and achon-
drites belonging to the calcium-poor groups, aubrites and
diogenites.
Summary
Over the last ten years, the number of meteorites
known from Australia has doubled. Even so, the large
number of recent recoveries probably represents a small
fraction of the meteorites that are available for collection
in the country’s arid and semi-arid zones. Together with
meteorites from other hot and cold deserts of the world,
the concentration of meteorites in the Nullarbor (Fig 11)
is already providing a valuable research resource. New
groups of meteorites are being recovered that are ex-
tending our knowledge of the early Solar System; statis-
tical studies are providing information on the flux of
meteorites with time; and terrestrial age dating com-
bined with weathering studies are yielding
palaeoclimatic information about the areas of meteorite
accumulation.
Figure 11. Crusted fragment of the Camel Donga eucrite achon-
drite shower at the site of discovery on the Nullarbor Plain (lens
cap for scale is 5 cm diameter).
Although various dating techniques have been applied
to a wide variety of terrestrial materials (e.g. see Lamb
1977), one of the major problems of Quaternary
palaeoclimatic research is the paucity of dateable materi-
als that can provide an absolute chronology for events.
Concentrations of meteorites, such as in the Nullarbor
Region, provide dateable materials of a variety of terres-
trial exposure times spanning the accumulation period,
and may allow changes in weathering rates through time
to be estimated. The pioneering work of Bland et al. (1995
a,b), Jull et al. (1995) and others is demonstrating that
weathered stony meteorites have the potential to provide
useful palaeoclimatic information over the period of their
accumulation.
The surfaces of ancient stony meteorites from the
Nullarbor frequently possess variably thick carbonate
coatings (caliches) that have been derived via the calcare-
ous clay from the limestone country rock (Bevan & Binns
1989 a,b). Additionally, extensively weathered Nullarbor
stony meteorites contain veins and pockets of carbonate
that have penetrated the fabric of the meteorite along
cracks and pores. Detailed mineralogical and isotopic
studies of carbonates from Nullarbor meteorites have yet
to be performed. However, measurements of the stable
isotopic compositions of these evaporitic deposits may
aid in determining the source materials and the
mechanisms of calichification, related to temperatures of
deposition. Since these carbonates are likely to have
grown much more rapidly than marine carbonates they
could be used to derive high resolution temperature
profiles, and offer possibilities of palaeotemperature
Journal of the Royal Society of Western Australia, 79(1), March 1996
41
assessment over the time span of meteorite accumulation
in the Nullarbor.
Meteorites found in Australia are playing an increas-
ingly important role in fundamental research across a
wide spectrum of disciplines both within the country and
overseas. There is every reason to believe that dense
accumulations of meteorites, as in the Nullarbor, exist
throughout the arid zone of Australia. Eventually, Aus-
tralia may outstrip Antarctica and the USA as a source of
meteorite recoveries. This seemingly unlikely source of
Quaternary palaeoclimatic information provides yet
another aspect to meteorite research in Australia. What
studies of ancient meteorite finds from Australia are
likely to reveal in detail about past climates is unknown.
Like all fundamental scientific research, one never knows
how useful it will be until it is done!
Acknowledgements: The author thanks an anonymous reviewer for
many helpful comments that improved the manuscript. Danielle
Hendricks, Peter Downes, Jennifer Bevan and Kris Brimmell are thanked
for their assistance in the preparation of the manuscript. John de Laeter is
thanked for constant encouragement and help over many years of
research into Australian meteorites.
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... This is notably lower than the values observed in other hot deserts, where meteorites are collected. For instance, the average annual rainfall in the Dar al Gani collection area (Libya) is 10-20 mm (Schlu¨ter et al. 2002), 20-40 mm in the Dhofar collection area in Oman (data from the National Center for Atmospheric Research, Boulder, Colorado, USA), and it is about 250 mm in the Australian Nullarbor Plain (Bevan 1996). In addition to the very low pluviometry, the San Juan area is also characterized by low relative humidity. ...
Article
We describe the geological, morphological, and climatic setting of the San Juan meteorite collection area in the Central Depression of the Atacama Desert (Chile). Our recovery activities yielded 48 meteorites corresponding to a minimum of 36 different falls within a 3.88 km 2 area. The recovery density is in the range 9-12 falls km ) 2 depending on pairing, making it the densest among meteorite collection areas in hot deserts. This high meteorite concentration is linked to the long-standing hyperaridity of the area, the stability of the surface pebbles (> Ma), and very low erosion rates of surface pebbles (approximately 30 cm Ma ) 1 maximum). The San Juan meteorite population is characterized by old terrestrial ages that range from zero to beyond 40 ka, and limited weathering compared with other dense collection areas in hot desert. Chemical weathering in San Juan is slow and mainly controlled by the initial porosity of meteorites. As in the Antarctic and other hot deserts, there is an overabundance of H chondrites and a shortage of LL chondrites compared with the modern falls population, suggesting a recent (< few ka) change in the composition of the meteorite flux to Earth.
... P. A. Bland et al. For the NR, there is good evidence to suggest that most meteorites are lying on, or near, the surfaces on which they fell (Bevan, 1992(Bevan, , 1996. Relict stream courses traversing the Nullarbor testify to a period of greater effective precipitation (Lowry and Jennings, 1974;van de Graaff et al., 1977). ...
Article
Ordinary chondrites (OC) recovered from the desert areas of Roosevelt County, New Mexico, the Nullarbor Region of Western Australia, and the Algerian and Libyan Sahara, for which ¹⁴C terrestrial ages have been determined, were examined by ⁵⁷Fe Mössbauer spectroscopy. OC were chosen as a standard sample to investigate weathering processes as their well constrained trace and bulk element chemistry, normative mineralogy and isotopic composition define a known, pre-weathering, starting composition. Given that terrestrial ages are known, it is possible to compare (initially very similar) samples that have been subsequently weathered in a range of climatic regimes from the present day to > 44 ka BP. In addition, recently fallen equilibrated OC contain iron only as Fe⁰ and Fe²⁺, thus the abundance of ferric iron is directly related to the level of terrestrial weathering.
... Over this period, the monthly averages of minimum daily temperatures are in the )3 to 12 °C range (average 4 °C), and the monthly averages of daily maximum temperatures are in the 18–31 °C range (average 25 °C). For the Hi gh An de s (Ea ste rn An de an ran ge ) (P re an deBevan 1996). In addition to the very low pluviometry, the San Juan area is also characterized by low relative humidity. ...
Article
Abstract– We describe the geological, morphological, and climatic setting of the San Juan meteorite collection area in the Central Depression of the Atacama Desert (Chile). Our recovery activities yielded 48 meteorites corresponding to a minimum of 36 different falls within a 3.88 km2 area. The recovery density is in the range 9–12 falls km−2 depending on pairing, making it the densest among meteorite collection areas in hot deserts. This high meteorite concentration is linked to the long-standing hyperaridity of the area, the stability of the surface pebbles (> Ma), and very low erosion rates of surface pebbles (approximately 30 cm Ma−1 maximum). The San Juan meteorite population is characterized by old terrestrial ages that range from zero to beyond 40 ka, and limited weathering compared with other dense collection areas in hot desert. Chemical weathering in San Juan is slow and mainly controlled by the initial porosity of meteorites. As in the Antarctic and other hot deserts, there is an overabundance of H chondrites and a shortage of LL chondrites compared with the modern falls population, suggesting a recent (< few ka) change in the composition of the meteorite flux to Earth.
Chapter
The geological antiquity of Australian land surfaces and the sedimentary and volcanic cover of Precambrian cratons in the central and western parts of the continent, allow preservation of a range of circular features, including morphological and drainage rings, circular lakes, volcanic craters, tectonic domes, oval granite bodies, mafic igneous plugs, salt diapirs, and magnetic, gravity and seismic anomalies of unknown origin. These include 38 confirmed asteroid and meteorite impact structures and craters and more than 40 ring, dome and crater features of unknown origin. Many of these structures display structural and geophysical elements consistent with impacts. Exposed features include circular crater-like morphological patterns which may intersect pre-existing linear structural features, central morphological highs and unique thrust and fault patterns. Buried circular features include single or multi-ring magnetic patterns, circular magnetic quiet zones, corresponding gravity patterns and low velocity and non-reflective seismic zones. Discrimination between impact structures and igneous plugs, volcanic caldera and salt domes requires field work possibly drilling. Large circular structures such as Mount Ashmore and Gnargoo are considered to have convincing structural deformation features to warrant classification as likely impact structures. Examples of crater-form features containing elements consistent with, but unproven to be of, impact origin include Auvergne, Delamere, Fiery Creek, Monte Christo, Mount Moffatt, Tanami East, Youngerina, Tingha. Examples of buried multi-ring features of possible to probable impact origin include Augathella, Balfour Downs, Calvert Hills, Camooweal, Green Swamp Well, Herbert, Ikybon River, Ilkurka, Lennis, McLarty Hills, Mount Davies, Mulkara, Neale, Sheridan Creek, Oodjuongari and Renehan. The origin of the very large circular magnetic and gravity pattern of the Diamantina River drainage feature and the multiple TMI ring pattern of the Deniliquin-Booligal region remains unresolved. Compared with frequency distribution patterns of extra-terrestrial impact structures worldwide, the Australian record displays a relatively a common occurrence of large impact structures and relative depletion in small impact structures and craters, explained by the better preservation of large structures at deep crustal zones as compared to the erosion of small craters, and a good geophysical coverage of large parts of the continent.
Chapter
Circular drainage patterns, round lakes and oval depressions may provide hints of possible underlying ring or dome structures, requiring field tests or drilling where no outcrop occurs (Grieve RAF, Pilkington M, Aust Geol Surv J Aust Geol Geophys 16:399–420, 1996; Glikson AY, Uysal IT, Earth-Sci Rev 125:114–122, 2013). Structural domes and near-circular fold structures may initially be mistaken for impact structures, as are basins of approximately circular or slightly elongate pattern and plutonic domes such as oval granite intrusions, laccoliths and gabbro plugs. In orogenic belts, domes may be produced by compression and associated folding, including folding fold sets with different trends producing domes at the culminations of crossing anticlines. Diapirs are cored by relatively low-density rocks or magma, an example being granite domes rising in response to the gravity instability of the granitic magma relative to the denser country rocks. Circular drainage patterns, round lakes and oval depressions may provide hints of possible underlying ring or dome structures, requiring field tests or drilling where no outcrop occurs (Grieve RAF, Pilkington M, Aust Geol Surv J Aust Geol Geophys 16:399–420, 1996; Glikson AY, Uysal IT, Earth-Sci Rev 125:114–122, 2013). Structural domes and near-circular fold structures may initially be mistaken for impact structures, as are basins of approximately circular or slightly elongate pattern and plutonic domes such as oval granite intrusions, laccoliths and gabbro plugs. In orogenic belts domes may be produced by compression and associated folding, including folding fold sets with different trends producing domes at the culminations of crossing anticlines. Diapirs are cored by relatively low-density rocks or magma, an example being granite domes rising in response to the gravity instability of the granitic magma relative to the denser country rocks.
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A broken, orientated, stony meteorite mass weighing 38.75 kg was found in 1971 at a locality (29° 37′ 45″S, 116° 28′ 56″E) near Bunjil in the northern wheatbelt of Western Australia. The presence of relict chondrules and the mean compositions of the ferro-magnesian silicates (olivine Fa25.1; orthopyroxene Fs21.4) show that the meteorite belongs to the L-group of ordinary chondrites. The strongly recrystallized chondritic texture and the presence of large (> 50 μm) crystals of plagioclase feldspar (now partially converted to maskelynite) show that the meteorite belongs to petrologic type 6. Olivine containing abundant planar fractures and displaying incipient mosaicism, together with plagioclase partially altered (< 75%) to isotropic glass with variable compositions, and the presence of shock-veins, indicate that the meteorite has been subjected to shock-loading appropriate to stage 4 (approximately 30 kb shock pressure). Bunjil is very similar to the previously described Latham (L6) ordinary chondrite reportedly found nearby, and the two meteorites may belong to the same fall.
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The first meteorites recovered from Western Australia were a number of irons, the earliest of which was found in 1884 east of the settlement of York. These were named the 'Youndegin' meteorites after a police outpost. Some of the larger specimens were taken to London to be sold as scrap metal, but were recognized as meteorites and eventually acquired by museums. The main mass of Youndegin (2626 kg) was recovered in 1954 and is retained in the collection of the Western Australian Museum. Despite a sparse population and relatively recent settlement by Europeans (1829), a number of factors have contributed to the excellent record of meteorite recovery in Western Australia. Primarily, large regions of arid land have allowed meteorites to be preserved for millennia, and these are generally easily distinguished from the country rocks. A less obvious, but significant, factor is that, in antiquity, Australian Aborigines do not appear to have utilized meteorites extensively. Finally, systematic collecting from the Nullarbor Region, has contributed to the large numbers of recoveries since 1969. The 'Father' of the State's meteorite collection was the chemist and mineralogist Edward Sydney Simpson (1875-1939) who, from 1897 to 1939, recorded and analysed many of the meteorites that formed the foundation of the collection. The first Catalogue of Western Australian Meteorites was published by McCall & de Laeter in 1965 (Western Australian Museum, Special Publications, 3). Forty-eight meteorites were listed, 29 of which were irons (some of which have since been paired). Interest in meteorites increased in the 1960s, so that when the second supplement to the catalogue was published in 1972, 92 meteorites were listed with stones accounting for most of the additional recoveries. Today, the collection contains thousands of specimens of 248 distinct meteorites from Western Australia (218 stones, 26 irons and four stony-irons), and around 500 samples of potentially new meteorites (mostly chondrites from the Nullarbor) that remain to be examined. There are also specimens of 160 meteorites from other parts of Australia and the rest of the world. While numerically the collection is small compared to other major collections in the world, it contains a high percentage of main masses from Western Australia (around 85%), including many rarities, and has an aggregate weight in excess of 20 tonnes. The small proportion of falls to finds (4 : 244) reflects the sparse population of the State. This may change significantly when a network of all-sky fireball cameras is established in the Nullarbor Region.
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The Geology of Australia provides a vivid and informative account of the evolution of the Australian continent over the past 4400 million years. Starting with the Precambrian rocks which hold clues to the origins of life and the development of an oxygenated atmosphere, it then covers the warms seas, volcanism and multiple orogenies of the Palaeozoic, which built the eastern third of the Australian continent. This illuminating history then details the breakup of Gondwana and the development of the continental shelves and coastlines. Separate chapters cover the origin of the Great Barrier Reef, the basalts in Eastern Australia and the geology of the Solar System. From Uluru to the Great Dividing Range, from sapphires to the stars, The Geology of Australia is a comprehensive exploration of the timeless forces that have shaped this continent and that continue to do so.
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During the last 35 years, the number of meteorites available for study has increased by an order of magnitude (from around 2000 to nearly 30 000). The largest contribution has come from meteorites recovered from the Antarctic ice (more than 20 000); however, since the late 1980s a significant number (more than 8000-9000) have come from so called 'hot' deserts. The most notable arid areas of the world for meteorite recoveries are the wider Sahara (Algeria, Libya, Niger and other unspecified localities in NW Africa), Roosevelt County in New Mexico, USA, the Nullarbor Region of Australia, and, more recently, the deserts of the Arabian Peninsula in Saudi Arabia and Oman. Other areas in which meteorites have been found in numbers include the Namibian Desert in SW Africa and the Atacama Desert in Chile. This wealth of material has greatly extended our knowledge of early solar system materials by providing occasional samples of meteorites hitherto unknown to science, and allowing the construction of new groups of related meteorites. In addition, these accumulated collections have also allowed estimates to be made of the flux of meteorites to Earth with time, studies of their mass/type distribution on Earth and palaeoclimatic studies of the areas from which meteorites have been recovered. This paper documents the history of meteorite recovery from the 'hot' deserts of the world, and notes the effects that this abundance of material has had on the science of meteoritics.
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This paper is part of the special publication Meteorites: flux with time and impact effects (eds M.M. Grady, R. Hutchinson, G.J.H. McCall and D.A. Rothery). The Nullarbor Region of Australia is one of the most prolific sites for meteorite recoveries outside of Antarctica. Reported 14C terrestrial ages for chondritic meteorites from the Nullarbor indicate an age range from present day to c.35 ka. There is good evidence to suggest that meteorites are lying on, or close to the surfaces on which they fell and that, physiographically, the region has remained essentially undisturbed for at least the last 30 ka. The Nullarbor can thus provide important data on the flux of meteorites over the period of accumulation. One significant factor influencing flux calculations based on meteorite accumulation sites is the determination of the number of falls represented in the recovered population. In the case of the Nullarbor, a general lack of transportation processes in the region and careful documentation of the distribution of finds allows confident 'pairing' of meteorites. For example, strewn fields of showers that have remained undisturbed for thousands of years are easily recognized and mapped today. Mass distribution statistics confirm that there are few undetected pairs in the population of meteorites so far described from the Nullarbor, and there is no evidence of selection of meteorites of a specific terrestrial age. The Nullarbor is the largest accumulation of meteorites nearest to Antarctica with a terrestrial age range (0-35 ka) that overlaps the Antarctic population (0 to >1 Ma). Analysis of the well-documented population of meteorites from the Nullarbor compared with Antarctica suggests that there are many unrecognized paired meteorites in the Antarctic population and the abundance of small meteorites at that site can be accounted for, at least in part, by the presence of large shower falls of common chondrites. The data suggest that there may also be many unrecognized paired meteorites in collections from the Sahara.
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In arid Western Australia external paleodrainge systems are marked by playas. These systems have been reconstructed using contour maps of the present land surface, combined with geological and other maps. The paleodrainages are well preserved in an extensive, relict duricrusted landscape, and most patterns formed during the Late Cretaceous to Early Tertiary. Significant flow in the central-desert paleodrainages stopped before the mid-Miocene. The paleodrainage patterns are preserved because of the tectonic stability of the area, and because a change from a humid to an arid climate during the Tertiary, which slowed down erosion and sedimentation
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The Murchison Downs mesosiderite was reportedly recovered in 1925 from a locality ca. 200 km to the NE of the crater-forming Dalgaranga mesosiderite in Western Australia. A comparison of data from the literature on the chemistry and mineralogy of Murchison Downs and Dalgaranga, and a re-investigation of the metallography and mineralogy of Murchison Downs and Dalgaranga, suggests strongly that the two meteorites belong to the same fall. Murchison Downs may be one of the few examples of a meteorite transported by Aborigines and, pending further work, should be paired with the Dalgaranga meteorite. -Authors
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Meteorites are associated with five impact structures in Australia. Three of them are group IIIAB irons (Wolf Creek, Henbury, and Boxhole). Veevers is a group IIAB iron, and material recovered from the crater at Dalgaranga is a mesosiderite stony-iron. The impacts range in age from a few thousand years (Dalgaranga, Henbury, Veevers, and Boxhole) to 300 000 yr (Wolfe Creek Crater). Metallographic studies of the surviving fragments at some of the craters show that impact damage ranges from simple fracturing, through shock-hardening of metal, to plastic and shear deformation, reheating and attendant recrystallisation, and, ultimately, melting.
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