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The Dalgaranga meteorite crater, 100 km northeast of Yalgoo, Western Australia, was one of the first impact structures identified in Australia, the smallest isolated crater found in Australia, and the only confirmed crater in the world associated with a mesosiderite projectile. 17 years passed before the Dalgaranga meteorites were described in the scientific literature and nearly 40 years passed before a survey of the structure was published. The reasons for the time-gap were never explained and a number of factual errors about the discovery and early history remain uncorrected in the scientific literature. Using historical and archival documents, and discussions with people involved in Dalgaranga research, the reasons for this time gap are explained by a series of minor misidentifications and coincidences. The age of the crater has yet to be determined, but using published data, we estimate the projectile mass to be 500-1000 kg.
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The discovery and history of the Dalgaranga meteorite
crater, Western Australia
D. W. HAMACHER
1
*AND C. O’NEILL
2
1
Nura Gili Centre for Indigenous Programs, University of New South Wales, Sydney, NSW, 2052, Australia.
2
Department of Earth & Planetary Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
The Dalgaranga meteorite crater, 100 km northeast of Yalgoo, Western Australia, was one of the first
impact structures identified in Australia, the smallest isolated crater found in Australia, and the only con-
firmed crater in the world associated with a mesosiderite projectile. Seventeen years passed before the
Dalgaranga meteorites were described in the scientific literature, and nearly 40 years passed before a
survey of the structure was published. The reasons for the time gap were never explained and a number
of factual errors about the discovery and early history remain uncorrected in the scientific literature.
Using historical and archival documents, and discussions with people involved in Dalgaranga research,
the reasons for this time gap are explained by a series of minor misidentifications and coincidences. The
age of the crater has yet to be determined, but using published data, we estimate the projectile mass
to be 500–1000 kg.
KEY WORDS: impact structures, Dalgaranga, mesosiderite, history of meteoritics.
INTRODUCTION
Discovered in 1921, the Dalgaranga meteorite crater
(27!3800500S, 117!1702000 E; Figure 1), 100 km northeast of
Yalgoo, Western Australia, was the one of the first
impact structures recognised in Australia. At 24 m wide
and 4.5 m deep, it is the smallest isolated impact crater
in Australia, and the only confirmed terrestrial meteor-
ite crater formed by a mesosiderite projectile.
The age of the Dalgaranga crater is not known, but
estimates range from 270 000 years using
10
Be/
26
Al
exposure (Shoemaker et al. 1990) to <3000 years based on
its well-preserved condition (Shoemaker & Shoemaker
1988). The lower limit would make it the youngest crater
in Australia and among the 10 youngest craters in the
world (Grieve 1991).
Very little information about the discovery of the cra-
ter or the reasons why nearly 40 years passed before it
was properly surveyed has been reported in the scien-
tific literature. This paper reveals connections between
people and events that have gone unnoticed by the scien-
tific community for nearly 90 years and corrects many
factual errors that are commonly cited in the literature.
This paper uses historical documents collected from
published literature, newspapers, unpublished archival
materials, and personal communication with people
involved in research at Dalgaranga. Documents include
autobiographies and memoirs, biographies, contempo-
rary newspaper articles using the Trove database, and
unpublished letters, manuscripts and other materials
from the archives of the City Library of Carlsbad, the
Western Australian Museum, the State Library of
Western Australia and the Library archives at Arizona
State University. Family trees from Ancestry.com were
used to help identify personnel involved in Dalgaranga
research in cases where only initials were provided in
the literature. Photos of important figures in the history
of Dalgaranga crater research that have passed away are
included where applicable.
DISCOVERY
In the early 1920s, the 260 000-acre Dalgaranga Station
was owned by Alexander Robert Richardson (Figure 2a)
and managed by his nephew, Gerard Eardley Pierce
Wellard (Figure 2b). In 1983, Wellard published a book of
memoirs that included his experiences at Dalgaranga
(Wellard 1983, pp. 9597). This book provides the follow-
ing account of the craters discovery and explains why so
much time passed before the meteorites were reported
in the literature.
An Aboriginal stockman named Billy Seward identi-
fied Dalgaranga crater in 1921. Seward (Figure 2c) was
mustering cattle on horseback when he and the horse
nearly fell into the structure while in full gallop. He told
Wellard and Wellards brother about the big holethat
he stumbled upon. Two days later, Seward took Wellard
to the site. According to Wellard, he immediately recog-
nised it as a probable impact crater. Wellard scanned the
area for evidence of meteorite fragments and collected
about 5060 specimens, enough to fill a gallon can
*Corresponding author: d.hamacher@unsw.edu.au
!2013 Geological Society of Australia
Australian Journal of Earth Sciences (2013)
60, 637–646, http://dx.doi.org/10.1080/08120099.2013.815274
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(Wellard 1983, p. 95). Most of them were collected in the
immediate vicinity of the crater, but some were found up
to 300 m away. He described a majority of the fragments
as being a few centimetres in size. Wellard took the frag-
ments back to his home on the station, and there they
sat for nearly two years.
It was not until 1923 that Wellard made an effort to
have the specimens examined scientifically, although no
reason is given for the delay. That July, Richardson vis-
ited his nephew at Dalgaranga Station (Anonymous
1923). Wellard told his uncle about the crater and asked
him to take the meteorites to the Western Australian
Museum in Perth to be studied. Richardson agreed and
took them back to his farm, Lowlands, on the Serpentine
River near Perth (Anonymous 1931). He placed the bag of
specimens in his office but soon forgot about them. For
six months they sat unnoticed, until one day the
75-year-old Richardson stubbed his toe on the bag, which
jogged his memory enoughto remember that they
needed to go to the museum but had forgotten they were
from Dalgaranga Station (Wellard 1983, p. 96).
Richardson took the bag of meteorites to the
Department of Mines in Perth, which shared the same
building as the Western Australian Museum. At the time
Richardson dropped off the specimens, the Department
of Mines was in the process of relocating to a new facility.
During the moving process, according to Wellard, the
bag of meteorites was misplaced. Eager to learn more
about the meteorites his uncle took in for study, Wellard
claims that he sent a number of inquiries about the col-
lection to the museum but never received an answer. In
May 1924, Wellard travelled to Perth so his wife could
give birth to their daughter, Rosemary (Anonymous
1924; Wellard 1983, p. 163). While in Perth, he visited the
museum and enquired about the meteorites. No one
seemed to know anything about the stones or where
they were located. Wellard tells us that he was eventually
able to find a man from the Department of Mines who
remembered receiving the bag of stones but did not
know what they were or where they were from. The man
reportedly said that the bag had been misplaced during
the relocation, and its whereabouts were unknown. This
was apparently the last correspondence between Wellard
and the museum regarding the meteorites. It is uncer-
tain if Wellards specimens were ever located (A. Bevan
pers. comm. 2012).
The Simpson Study
The eventual study of meteorites from Dalgaranga was
instigated by a chain of events, sparked by the
occurrence of a rare phenomenon some six years after
Wellards visit to the museum. At 14:00 on 7 April 1930, a
fireball streaked across the sky in the vicinity of
Gundaring, WA (Simpson 1938). The fireball burst into
two halves above the village of Cuballing, travelling in
parallel paths and appearing to strike the Earth in the
distance (Simpson 1938). The Government Astronomer,
Harold Burnham Curlewis, used descriptions from
observers to calculate the fireballs trajectory and esti-
mate where it landed (Curlewis 1930). The incident gen-
erated substantial public interest and numerous articles
about the fireball appeared in newspapers across
Australia (Simpson 1938). Unfortunately, several
searches of the fall-area estimated by Curlewis were
unfruitful (Anonymous 1937).
In February 1937, W. G. Armstrong found a 53.5 kg IIC
iron meteorite in the Kumarina copper field, approxi-
mately 430 km northeast of Dalgaranga (Grady 2000,
p. 285). Three months later, F. Quinn found a 112.5 kg
IIIAB iron meteorite in Gundaringwithin the fall-area
predicted by Curlewis (Grady 2000, p. 227). This was
hailed in the press as the meteorite that formed the
fireball in 1930
1
(Simpson 1938). The discovery of the
Kumerina and Gundaring meteorites once again stirred
up significant public interest in meteorites (Simpson
1938). Edward Sydney Simpson (Figure 2d), the
Government Mineralogist and Analyst for WA and one
of the founders of the Western Australian School of
Mines, displayed specimens of both finds at a meeting of
the Royal Society of Western Australia in June 1937
(Anonymous 1937). Simpson studied these and a dozen
other meteorites from across WA, publishing his results
in June 1938 (Simpson 1938).
One of the meteorites studied by Simpson was from
Dalgaranga. According to Simpson (1938), Wellard con-
tacted him about the meteorites he had found on his
sheep station. Simpson explained that the original
Figure 1 Panoramic image of Dalgaranga crater. Image courtesy of Megan Argo, taken November 2009.
1
Years later, analysis of the Gundaring meteorite revealed
that it had been exposed to the elements for quite some
time, thus negating it as the remnant of the 1930 fireball
(Buchwald 1975; McCall et al. 2006, p. 310).
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collection of specimens had been lost, but Wellard was
able to secure a 40 g fragment (Figure 3) from the current
station manager and gave it to Simpson (by this time,
Wellard no longer managed or resided at Dalgaranga).
Simpson stated that Wellards description of the crater
confirmed rumours he had heard when he visited Yalgoo
Figure 2 (a) A. R. Richardson (Wellard 1983, p. 20), (b) G. E. P. Wellard (Wellard 1983, p. 35), (c) B. Seward (Wellard 1983, p. 36),
(d) E. S. Simpson (Geological Survey of Western Australia), (e) H. H. Nininger (Nininger 1972, p. 96), (f) A. Nininger (Carlsbad
City Library), (g) G. I. Huss (Doris Banks), (h) R. M. Pearl (Wilson 2012), (i) E. M. Shoemaker (Wikimedia Commons).
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in 1932, although he had not visited the structure him-
self. In the paper, Simpson unintentionally misspelled
Wellards name as Willard,which would lead to a series
of events many years later that were resolved by an
incredible coincidence. Simpson misunderstood Wellard
and quoted the craters diameter as 75 yards acrossat
the top, 50 yards at the bottom,and 15 feet deep.
Wellard (1983, p. 96) says the only measurement he made
was by counting the number of steps he took to walk
around the rim, which was about 225 feet. Therefore, it
was actually "22 m (77 ft) in width as opposed to "70 m
(230 ft). This is close to the accepted estimate of 24 m
(Haines 2005, p. 483). From Wellards description that the
northwestern side of the crater appeared to be thrust
upward more than any other part of the rim, Simpson
concluded that the impactor had travelled from the
southeast. He classified the Dalgaranga meteorite as a
medium octahedrite and hoped for a chance to visit the
site to collect and analyse more specimens. Unfortu-
nately, Simpson passed away from heart complications
on 30 August 1939 before he was able to return to the site
(Prider 1988).
The Nininger Expeditions
For many years, Simpsons paper was the only original
source of information regarding the crater and associ-
ated meteorites. At the time, no proper survey of the
crater had ever been conducted or published. Therefore,
the only record of the crater itself was the anecdotal
account from Wellard reported by Simpsonand one of
the important facts (the crater dimensions) was incor-
rect. Over the next several years, numerous researchers
cited the Simpson paper without the crater or meteorites
undergoing any further investigation (Nininger & Huss
1960, p. 620).
Simpsons description of Dalgaranga eventually
caught the attention of Harvey Harlow Nininger
(Figure 2e), an American entomologist and self-taught
meteoriticist, commonly dubbed the Father of American
Meteoritics (Palmer 1999). Nininger had assembled the
largest personal meteorite collection in the world, num-
bering over 6000 specimens (Nininger 1972, p. 146, 206).
One subject of interest to Nininger was the explosive
formation of meteorite craters. According to Nininger, no
crater less than 28 m in diameter exhibited evidence of
formation under explosive vapourisation of the projectile.
One diagnostic piece of evidence that could be used to test
whether this occurred was the presence of metallic
spheroids, which formed when the meteorite melted on
impact and solidified as it cooled. Spheroids were found at
Barringer (Meteor) crater in Arizona (D¼1.2 km) and
Odessa crater in Texas (177 m), but none were found at
Haviland crater in Kansas (16.8 m) or the Sikhote-Alin cra-
ters in eastern Siberia (<25 m) (Nininger & Huss 1960,
pp. 621622). Many questions about the formation of these
spheroids remained unanswered, and Nininger believed a
crater the size of Dalgaranga as reported by Simpson
(70 m) could help shed light on the issue (Nininger &
Huss 1960;Huss1962a).
A trip to Australia was necessary, but by the late 1950s
Nininger had reached a state of financial crisis. In 1958,
he sold 20% of his extensive meteorite collection to the
British Museum for $140 000 U.S.over $1.1 million U.S.
in 2013 currency (Nininger 1972, pp. 204206). This pro-
vided him with the funds to lead a 72-day expedition to
Australia, New Zealand, Fiji and Hawaii with his wife,
Addie (Figure 2f), and amateur geologist, Allan O. Kelly,
to study craters and search for meteorites and tektites.
The Australian leg of the expedition took place over
17 days. The team flew to Perth in February 1959 and
drove to Dalgaranga to survey the impact structure
(Kelly 1961, pp. 145148). This would be the first scientific
investigation of the Dalgaranga meteorite craternearly
38 years after its discovery. With directions from a local
shop-keeper named John L. S. JackNevill and the assis-
tance of the current station manager, Cyril H. Ross (who
purchased the lease in 1942; Anonymous 1998, p. 6), his
wife and an Aboriginal employee, Niningers team
reached the crater on 9 February and set up camp near
the crater rim (Nininger & Huss 1960, pp. 620621; Kelly
1961, p. 148). Upon first investigating the structure, they
realised that the measurements reported by Simpson
were in error (Nininger 1959a). To compound their frus-
tration, the metal detector they brought would not func-
tion properly, and they were reduced to looking for
meteorites visually and searching for spheroids using
magnets (Nininger & Huss 1960). During the survey,
Niningers team noticed a striking lack of meteorites in
the area. They were only able to collect 23 specimens (e.g.
Figure 3) with a total mass of 149 g. The largest single
fragment weighed only 30 g. This stands in contrast to an
account given by Peter Lancaster Brown, who claimed
that metallic fragments were not difficult to findwhen
he visited the crater in the early 1950s (Brown 1975,
p. 191). This suggests that prospectors may have removed
most of the larger fragments as word of the crater spread.
The crater appeared to be an explosion impact,
caused not by vaporisation but by violent fragmentation
of the projectile (Nininger & Huss 1960). Since Simpson
reported that the meteorite was nickeliron in composi-
tion, the low number of fragments collected seemed to
contradict the fragmentation hypothesis. The team
reconsidered that the projectile was stony iron in compo-
sition and concluded that the main mass of the impactor
must be buried within the crater (Nininger & Huss 1960,
Figure 3 Meteorite fragment from Dalgaranga bent by the
impact. Collected by Nininger and Kelly, pictured with a U.S.
5 cent coin for scale (Alan O. Kelly Collection, Carlsbad City
Library, photo 00010196).
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p. 622). Attempts to find this mass failed. They decided to
focus their efforts, given the short amount of time they
had left, on collecting the material for future analysis.
The team mapped the crater and the distribution of
meteorites before leaving early the next afternoon
(Figure 4). They never published their maps, with the
first published maps of the crater compiled from a sur-
vey conducted in 1986 (Shoemaker et al. 2005). The teams
maps are included in Kellys unpublished book manu-
script in the Carlsbad City Library, California (Kelly
1961, p. 152). Kelly provides two maps of the crater: a
cross-section and an aerial view, which are published
here for the first time (Figure 5).
During the survey, Kelly found numerous Aboriginal
flint flakes around the crater, which he thought might
have marked places where Aboriginal people collected
meteorites (Kelly 1961, pp. 153154). Kelly noted that flint
is not native to the area, so the flakes must have been
brought in by human agency. He estimated that the
impact would have occurred within the last few hundred
years based on the degree of weathering and erosion on
the crater walls and in the ejecta. In his mind, there was
little doubtthat Aboriginal people witnessed the fall,
since it would have been visible from some distance,
even in daylight, had it occurred during human habita-
tion of Australia. He speculated that Aboriginal people
had taken the meteorite fragments and left behind the
flint flakes as an exchange gift for the fiery god that
came out of the sky(Kelly 1961, p. 153). No Aboriginal
oral traditions of the Dalgaranga crater or meteorites
are reported in the literature, but Bevan & Griffin (1994)
believe that a meteorite fragment reportedly recovered
near Murchison Downs, WA in 1925 was transported by
human agency from Dalgaranga crater, some 200 km
away. They suggest it may have been transported by
Aboriginal people, but nothing more is known about
how or why it was found so far from the impact site. It
Figure 4 Previously unpublished images of Dalgaranga cra-
ter from the 1959 Nininger and Kelly Expedition. (a) The rim
of the crater as seen from the focus with a shovel for scale.
(b) A large mulga bush growing in the craters focus before
it was cut down in 1959 (Alan O. Kelly Collection, Carlsbad
City Library, photos 00010235 and 00010124, respectively).
Figure 5 Maps of Dalgaranga crater produced by Nininger
and Kelly in 1959 (Kelly 1961, p. 166167), courtesy of the
Carlsbad City Library. (a) A birds eye view of the crater and
ejecta blanket. The arrow indicates the proposed trajectory
of the impactor. (b) Cross-section of crater and breccia fill
across points C and D. The arrow indicates the proposed
impact angle of the meteorite (Top: southwest to northeast.
Bottom: northwest to southeast).
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should be noted that the label on the Murchison Downs
fragment gave the donors name as Richardson,
although it is uncertain if this is a reference to Wellards
uncle, A. R. Richardson (A. Bevan pers. comm. 2012).
On 13 February, the team came upon an Aboriginal
camp near Leonora, WA, where many of the locals had
collected tektites, which they colloquially called meteor-
ites(Kelly 1961, p. 162). Nearly everyone at the camp
knew about them, and Nininger was able to purchase
two samples. Apparently, Aboriginal people had been
collecting them for years to sell to museums or white col-
lectors. Kelly explains that as the demand for tektites
waned, many of the Aboriginal people simply lost or dis-
carded their collections (Nininger 1972, p. 213).
Because the expedition covered such a large area, sev-
eral months passed before Nininger was able to properly
study the specimens from Dalgaranga. When he did, he
realised these were not octahedrite (NiFe) meteorites as
classified by Simpson, but rare mesosiderite (stony-iron)
meteorites (Nininger & Huss 1960). This was significant
as no other impact crater in the world was associated
with this type of meteorite. Upon discovering this,
Nininger realised that they had relied too heavily on
Simpsons paper (Nininger & Huss 1960, p. 623). The com-
bination of their tight schedule, the intense heat and the
various technical issues meant that they had missed an
opportunity to investigate the site in detail. This would
have aided in answering pertinent questions about the
impact cratering process, so Nininger was eager to return
to Dalgaranga to conduct a more in-depth survey.
Nininger organised the second expedition to Australia,
and on 18 October 1959 Nininger arrived at Dalgaranga
with his son-in-law, Glenn I. Huss (Figure 2g), a geologist
and director of the American Meteorite Laboratory in
Denver, Colorado (Nininger 1972, p. 213). They remained
at the site for nearly two weeks, making detailed measure-
ments and maps of the crater, collecting 207 additional
specimens, clearing the trees within the crater and exca-
vating the crater floor to search for the main projectile
they thought lay within (Nininger & Huss 1960, pp. 627
628; Cleverly 1962; Huss 1962a,b; McCall & de Laeter 1965,
p. 28). The results of both surveys were published in 1960
(Nininger & Huss 1960). Huss (1962b) described the crater
as square in shape, similar to the Barringer Meteorcra-
ter in Arizona.
According to Huss (1962b), he and Nininger noted that
the crater displayed a bilateral symmetry. At an azimuth
of 289!(northwest), the rim lay flat and revealed almost
no rim rubble. The rim tilted increasingly until at points
90!on either side, the rim was 40!to the horizontal
before levelling out again to almost flat at a point just
south of due east. The highest concentration of ejecta
corresponded with the areas where the rim displayed
the greatest tilt. The ground some 1520 m from the
southwest rim showed a fairly heavy layer of coarse, dis-
integrated granite. The northeast rim revealed a large
quantity of large blocks of laterite. A thick layer of
ejected laterite extended 4560 m to the north-northeast
and east side of the crater (Huss 1962b). Based on their
geological mapping, it seems the impactor struck the
edge of a small mound or hillock of laterite.
Among their findings was the realisation that the pro-
jectile consisted of mainly stone (90%) with nests of
mesosideritic (stony-iron) and sideritic (iron) materials.
Nininger also concluded that the impactor, which he and
Huss estimate had a mass of 1020 tonnes, had not under-
gone vaporisation but instead impacted at a relatively
low speed, completely shattering the meteorite and cre-
ating the shallow crater (Nininger & Huss 1960, p. 639;
Nininger 1972, p. 215). Nininger & Huss (1960) claimed
that the reason so few meteorite fragments remained is
that much of the stony components had eroded away,
leaving behind iron components.
Huss cut down the largest mulga bush in the centre of
the crater and counted the growth rings, which num-
bered 54 (Huss 1962b, p. 14). This means the tree germi-
nated around 1905roughly consistent with Simpsons
estimate based on the bushs height of 4.5 m as cited by
Wellard. The tree had germinated on top of a 1.6 m layer
of breccia fill, and no fill had accumulated around the
roots, showing conclusively that the age of the crater far
exceeded the age of the tree. Examining the rocks on the
crater wall and the fill exposed from the excavation of
the crater floor, Nininger & Huss (1960) estimated that
the crater formed some 25 000 years ago.
There was no communication between Wellard and
Niningers team during the expedition. Wellard had long
since sold the lease for Dalgaranga Station and moved
700 km away to Yladgee station near Gnowangerup,
about 300 km southeast of Perth (Barunha 1934; Kelly
1961, p. 149). In fact, Nininger & Huss (1960) and Huss
(1962b) cite Wellards name as Willardand include the
same historical inaccuracies that were recorded in the
Simpson paper, simply because they did not know this
information was in error.
Nearly 40 years after the craters discovery, it was
finally surveyed, and the true nature of the Dalgaranga
impactor was reported in the scientific literature.
Further studies of the meteorites and crater would be
undertaken (e.g. McCall 1977; Shoemaker et al. 1990,
2005; Consolmagno & Britt 1995; Smith & Hodge 1996;
Hidaka & Yoneda 2011). But a year after Nininger &
Husss paper was published, an extraordinary coinci-
dence occurred that linked everyone involved.
An Extraordinary Coincidence
In August 1961, Wellard and his wife, Katherine (n!
ee
Clifton), decided to take a trip to England on the Royal
Dutch Mail Line ship Johan van Oldenbarnevelt (Wellard
1983, p. 97). After three days at sea, Wellards wife became
engaged in a conversation with a Mrs Pearl.The woman
mentioned that her husband was a professor of geology
in the United States with a special interest in meteorites.
Mr Wellard, who had joined the conversation, mentioned
that he also had an interest in meteorites. The woman
was sure her husband would like to meet him. A few
days later, Wellard met up with the womans husband, a
Professor Pearl.Pearl explained that he and his wife
had flown to Perth from America for the sole purpose of
studying a special meteorite and visiting a unique
impact crater called Dalgaranga to meet the man who
found the meteorite, a Mr Willard.He conceded that
while he had studied the meteorite, he was very disap-
pointed that he was unable to locate Willard. Somewhat
taken aback, Wellard told Pearl that he was now talking
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to the very person he was unable to find! Pearl promised
to send Wellard a copy of the report on the Dalgaranga
meteorite he had studied, which he honoured to the joy
of Wellard.
The identity of Professor Pearlwas not given in
Wellards memoirs. Further investigation reveals that
this was in fact Professor Richard Maxwell Pearl
(Figure 2h) from Colorado College in Colorado Springs
(Wilson 2012). Professor Pearl was well known for his
studies of minerals, gems and meteorites, and was a
member, and later Fellow, of the Society of Research on
Meteorites, which later became the Meteoritical Society
(Bostick 2002). Richard and his wife, Mignon, were
friends and colleagues of Harvey Nininger. Pearl and
Nininger had collaborated on various projects, and it is
now evident how Pearl came to learn of Dalgaranga.
Glenn Huss published a two-part account of the second
survey in which he participated (Huss 1962a,b). He con-
firmed that in early 1962, Wellard had met Richard and
Mignon Pearl on the ocean liner to Amsterdam.
Information from Wellards book is included on a
tourist sign at the crater, although many pieces of the
story we have provided here are not included, and some
of the details on the sign are inaccurate. It is noteworthy
that Dalgaranga was not Wellards final encounter with
newly discovered meteorites. Around 1976, a 33.6 kg
meteorite was discovered near Gnowangerup, WA by a
road worker and given to Wellard. He donated it to the
Western Australian Museum in October 1979 (de Laeter
1982, p. 137).
After Nininger and Huss published their survey of
Dalgaranga crater, a Mr Lathamconducted a follow-up
excavation on the southern side of the crater floor.
Latham sent two small specimens to Jack Nevill, who
sent the fragments to F. William G. Power, a mine inspec-
tor and WWII POW from Geraldton, who forwarded
them to geochemist William H. Cleverly, also at the
School of Mines and an honorary associate at the
Western Australian Museum (Bevan 1997). It is apparent
from correspondence that Jack Nevill obtained some
20 kg of meteorites from Dalgaranga, which he shipped
to Nininger in Sedona, Arizona in 1959 (Nininger 1959b).
Samples of the material collected by Latham and Nevill
are currently located in the Western Australian Museum
(catalogue number WAM 12365) and the Western
Australia School of Mines in Kalgoorlie, WA.
The McCall Expedition
In September 1963, University of Western Australia geol-
ogist Gerard J. H. JoeMcCall led a two-day expedition
to Dalgaranga, accompanied by Edward P. Henderson,
curator at the U.S. National Museum, and E. Car, a biolo-
gist at the Western Australian Museum (McCall 1963).
McCall notes that Niningers measurements were accu-
rate, citing a rim-to-rim diameter of 21.3 m, and a maxi-
mum depth of 3.2 m from the rim to the top of the
breccia fill. McCall (1963) noted that the granite and lat-
erite separated by a layer of thin shaly ironshowed a
regular outward pit of "30!from the crater centre. He
then described the sediment within the crater, which
had not previously been published. Using the pit dug by
Nininger, McCall explains that the crater is infilled by a
twofold unconsolidated deposit composed of soil and
granite and laterite boulders at the top and a metre of
course stratified grits of granite detritus at the base (pos-
sibly of eolian origin). McCall did not reach the bottom of
these sediments using the second pit dug by Nininger,
which had a depth of 1.37 m. Based on the depth and
nature of the sediment, McCall reports that the crater is
of considerable age, although he does not provide an esti-
mate. He cites the slope of the wall of granite rock at
5060!and notes that the rim is higher to the east with
no marginal raised mound above the level of the sur-
rounding plain to the north. McCalls favourite experi-
ence (McCall pers. comm. 2012) was the 1969 Australian
Institute for Mining & Metallurgy (AusIMM) meeting in
Cue, WA. As part of the meeting, a session was held at
the crater in which the attendees sat along the rim while
McCall spoke from the craters focus.
The primary goal of the expedition was to collect
meteorite fragments, but pickings were slim, and the
McCall team was only able to collect a handful of small
chips of iron.Henderson was allowed to take all of the
recovered material on the condition that a specimen of
mesosiderite material be given to McCall for analysis. In
1965, McCall published the first thin-section analysis of a
Dalgaranga mesosiderite, using specimens collected dur-
ing the survey (McCall 1965). Given the mineralogical
composition of the fragment, McCall estimated that the
projectile was only 12 tonnes (for reasonable higher-
impact velocities, and assuming no atmospheric frag-
mentation), not 1020 tonnes as quoted by Nininger &
Huss (1960).
William Cleverly and Maitland Keith Quartermaine
visited the crater in 1962 (Cleverly 1962). According to
Cleverly, Simpsons claim that the impactor came
from the southeast was unsupported by the apparent
excavations conducted by Nininger, since they seemed to
be in the opposite direction in the crater. Nothing about
this trip or survey was published in the literature except
a photo of the crater, which was published in Bevan
(1996, p. 426).
SITE PROTECTION
On 25 July 1962, Cleverly (1962) wrote a letter to William
D. L. DavidRide, then Director of the Western Austra-
lian Museum and President of the Royal Society of West-
ern Australia, encouraging him to lodge an application
to establish the crater and the surrounding area as a pro-
tected reserve. In the letter, Cleverly pointed out several
areas of concern regarding the preservation of the crater
and of the material within. These included fire hazards
by the mulga scrub, damage caused by prospectors and
researchers, and litter from visitors. Much of this is com-
pounded by the fact that the crater is very small and that
further excavations could erase important evidence
regarding the history of the fill-material.
The application was successful, and the crater was
declared a Ministerial Temporary Reserve (3232H)
through the Western Australia Department of Mines on
9 June 1965 (Cleverly 1962; A. Bevan pers. comm. 2012).
Dalgaranga is registered as a protected site under the
Mines Department and permission to collect must be
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gained from the Minister for Mines. Meteoritic material
is registered in the collection at the Western Australian
Museum in accordance with the Museum Act 1969.
The Dalgaranga crater is now classified as a State
Geoheritage Reserve (Grey et al. 2010).
THE SHOEMAKER STUDY
In 1986, Eugene Shoemaker (Figure 2i) and his astrono-
mer-wife, Carolyn, visited Dalgaranga crater and
conducted an in-depth study of the structure and associ-
ated meteorites (Shoemaker et al. 1990, 2005). The
Shoemakers mapped the site and excavated the interior,
using the original pit dug by Nininger near the eastern
edge of the crater floor. The bilateral symmetry of the
ejecta is consistent with laboratory experiments of low-
angle impacts (Gault & Wedekind 1978), suggesting the
projectile impacted at a low incidence angle of 1015!
from the horizontal (Shoemaker et al. 2005, p. 542).
The age of the Dalgaranga impact remains a conun-
drum, with estimates varying by three orders of magni-
tude. Nininger and Huss collected charcoal from the
crater rim and within the excavated pit for dating but
never published the results. McCall (1963) claimed the
structure was of considerable agebased on sedimenta-
tion within the crater. Shoemaker et al. (1990) conducted
a
10
Be/
26
Al exposure age test on samples collected from
the top of the granite bedrock near the crater rim, giving
an age of 270 000 years. This fits a low model erosion rate
comparable to other parts of the Australian landscape.
However, breccia block samples taken from the lower
part of the crater walls have relatively high
10
Be and
26
Al
abundances. This indicates the samples were exposed on
the surface prior to the impact, thus complicating the
use of this technique. Shoemaker et al.(1990) proposed to
use the silicate phase of a sample meteorite for
14
C test-
ing, which they believed would give a more accurate esti-
mate. The results were never published. Upon surveying
the crater in the late 1980s, the Shoemakers believed the
preservation of subtle morphology in the ejecta
suggested an age of less than 3000 years (Shoemaker
et al. 2005, p. 542). Despite these efforts, the age of the
Dalgaranga impact is still unknown.
SIZE AND MASS ESTIMATES
The mass of the Dalgaranga impactor is also not well
known, with early estimates varying by an order of mag-
nitude. Estimates of 10 00020 000 kg (D¼1.72.1 m) by
Nininger & Huss (1960) were based on a lack of speci-
mens expected for a fragmentation crater of this size
leading them to believe is was mostly stone in composi-
tion. McCall (1965) noted the poor recovery of meteoritic
material from the site, and on comparison with other
fragmentation craters, suggested a mass of around 1000
2000 kg, or 0.71.0 m in diameter. Brown (1975) claimed
that meteorite fragments were not hard to find in the
early 1950s, indicating that prospectors may be partially
responsible for the lack of recoverable material by the
time McCall reached the site in the 1960s. In 1996, Toby
R. Smith, Paul W. Hodge, Alex W. R. Bevan and Jenny
Bevan surveyed the crater. Smith & Hodge (1996)
analysed soil samples from Dalgaranga to study the
small meteoritic particles that are formed as the projec-
tile passes through the atmosphere and strikes the
Earth. The high abundance of these particles in the soil
at Dalgaranga, their size (0.40.1 mm) and the fact that
they are heavily weathered and unmelted are consistent
with fragmentation as opposed to vapourisation. Based
on the mass of the fragments, Smith & Hodge (1996) esti-
mate the impactor mass was on the order of 4000 kg
double the upper estimate of McCall (1965).
An impactor of the order of 1 m in diameter is likely
to have lost over half of its kinetic energy during its pas-
sage through the atmosphere, making final estimates of
its size uncertain (Melosh 1989). However, we can apply a
Pi-Group scaling approach for sensible estimates on the
impactor and target rock to obtain some quantitative
assessment of the robustness of the previous estimates.
Using this approach, the final diameter of the impactor
Lis derived using Collins et al. (2005, their equations 21
and 22), given by:
L$Df
1:451%ri
rt
!"
1=3
%y0:44
i%g&0:22
E%sin1=3u
2
6
6
6
4
3
7
7
7
5
1:282
ð1Þ
Here D
f
is the final crater diameter (24 m), r
i
is the
impactor density, assumed to be 4250 kg m
&3
for a meso-
siderite (Britt & Consolmagno 2003), r
t
is the target rock
density (2650 kg m
&3
for Archean granite of the Pilbara
craton; McCall 1965), v
i
is the impactor velocity (4000
22 000 m s
&1
; Melosh 1989), g
E
is Earths gravitational
acceleration, and uis the angle of incidence (assumed to
be low angle for Dalgaranga based on crater morphol-
ogywe explore a range from 5!to 20!).
The effect of these parameters is shown in Figure 6for
(a) varying impact velocity, and (b) impact angle. Assum-
ing this scaling is valid for a small fragmentation crater
like Dalgaranga, estimates for the impactors size range
from 0.4 to 1.1 m in diameter. The mass of the impactor, if
a mesosideritic density is assumed, is between 200 and
3000 kg at the extreme, with the most probable bounds
between 500 and 1000 kg, roughly consistent with the esti-
mates given by McCall (1965) and Smith & Hodge (1996).
SUMMARY
An Aboriginal stockman, named Billy Seward, discov-
ered Dalgaranga crater in 1921, and meteorite fragments
were recovered by the station manager, Gerard Wellard.
Wellard sent specimens to Perth to be investigated, but
they were lost. Seventeen years passed before a proper
study of Dalgaranga meteorite was published, but some
of the information about the crater itself was in error. A
further 19 years passed before a survey of the crater was
published, and we have pieced together the reasons for
this. We provide early maps of the crater and numerous
historical details about its study that have not been pre-
viously published. We explain how early mistranslations
in data about the crater led to many errors in estimates
about its size. To date, the mineralogy of the Dalgaranga
impactor is well understood, but estimates of its mass
644 D. W. Hamacher and C. O’Neill
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TAJE_A_815274.3d (TAJE) 09-08-2013 11:22
have varied widely. Using pi-scaling equations, we esti-
mate it is on the order of 5001000 kg. Estimates of the
craters age vary by two orders of magnitude, from a few
hundred years to a few hundred thousand years. Its age
remains a mystery, and we encourage future work to
help solve this piece of the puzzle. Historical photos from
the Nininger & Kelly expedition, a detailed account of
this trip by Allan Kelly, and correspondence between
William Cleverly and David Ride are provided in a
supplementary paper.
ACKNOWLEDGEMENTS
We thank Amy Davis, Gary Huss, Peggy Schaller, Alex
Bevan, Joe McCall, John Goldsmith and Peter Downes
for their assistance, advice and comments. We are
indebted to the Carlsbad City Library (California),
Arizona State University Library, the State Library of
Western Australia, the Geological Survey of Western
Australia, and the Western Australian Museum for
archival materials. This research made use of the
National Library of Australias Trove archival database
(trove.nla.gov.au), the NASA Astrophysics Data System
(adsabs.harvard.edu), and Ancestry.com. We would also
like to acknowledge the referees for their helpful and
useful comments. ONeill acknowledges DP110104145,
FT100100717, and Centre of Excellence for Core to Crust
Fluid Systems (CCFS) support from the Australian
Research Council.
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SUPPLEMENTARY PAPERS
Photos from the Allan O. Kelly Collection. Carlsbad
History Collection, Carlsbad City Library, California
Allan O. Kelly Geology Papers, 19171993. MS 014. Series
I: Correspondence, 19331993. Folder 194.
Chapter 8 of Kelly (1961): The Dalgaranga Meteorite
Crater(22 pp.). Carlsbad City Library, California.
Cleverly W. H. 1962. Letter to David Ridedated
25 July 1962. Western Australian Museum Archives.
Reproduced with permission, Royal Society of Western
Australia.
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