Stratigraphy, geochronology and evolution of the Mt. Melbourne volcanic field (North Victoria Land, Antarctica)

Abstract

Mt. Melbourne (2,732 m a.s.l.) is a large quiescent stratovolcano located in Northern Victoria Land (Antarctica) and is one of a handful of volcanoes on the Antarctic plate with the potential for large-scale explosive eruptions. During the XVIII Italian Expedition in 2002–2003, the Mt. Melbourne volcanic succession was studied in terms of stratigraphy and sampled for 40Ar/39Ar age determinations and geochemistry. The early, Lower Pleistocene, volcanism was largely alkali basaltic to hawaiitic in composition and monogenetic in style, producing tens of small scoria cones and lava flows scattered over a wide area across the Transantarctic Mountains (Random Hills Period). During the Middle Pleistocene, volcanic activity focused to the area of the Mt. Melbourne stratovolcano, where several monogenetic centres show the transition from early sub-glacial/subaqueous conditions to emergent subaerial conditions (Shield Nunatak Period). The oldest exposed deposit associated with the early activity of the Mt. Melbourne stratovolcano (Mt. Melbourne Period) is a trachytic subaerial ignimbrite dated at 123.6 ± 6.0 ka, which reflects the establishment of a crustal magma chamber. Above the ignimbrite a succession of alkali basaltic, hawaiitic, and subordinate benmoreitic lavas and scoria cones is exposed, dated at 90.7 ± 19.0 ka. The Holocene deposits are exposed at the top of Mt. Melbourne, where the crater rim is composed of trachytic to rhyolitic pumice fall deposits, which are also extensively dispersed around the volcano, likely originated from Plinian-scale eruptions. The most recent explosive deposit proved difficult to date accurately because very low quantities of radiogenic 40Ar were released, resulting in imprecise plateau ages of 50 ± 70 and 35 ± 22 ka.

Full text

RESEARCH ARTICLE
Stratigraphy, geochronology and evolution of the Mt.
Melbourne volcanic field (North Victoria Land, Antarctica)
Guido Giordano & Federico Lucci & David Phillips &
Domenico Cozzupoli & Valentina Runci
Received: 24 May 2012 / Accepted: 24 July 2012
#
Springer-Verlag 2012
Abstract Mt. Melbourne (2,732 ma.s.l.) is a large quies-
cent stratovolcano located in Northern Victoria Land
(Antarctica) and is one of a handful of volcanoes on the
Antarctic plate with the potential for large-scale explosive
eruptions. During the XVIII Italian Expedition in 200 2–
2003, the Mt. Melbourne volcanic succession was studied
in terms of stratigraphy and sampled for
40
Ar/
39
Ar age
determinations and geochemistry. The early, Lower Pleisto-
cene, volcanism was largely alkali basaltic to hawaiitic in
composition and monogenetic in style, producing tens of
small scoria cones and lava flows scattered over a wide area
across the Transantarctic Mountains (Random Hills Period).
During the Midd le Pleistocene, volcanic activity focused to
the area of the Mt. Melbourne stratovolcano, where several
monoge netic centres show the transition from early sub-
glacial/subaqueous conditions to emergent subaer ial condi-
tions (Shield Nunatak Period). The oldest exposed deposit
associated with the early activity of the Mt. Melbourne
stratovolcano (Mt. Melbourne Period) is a trachytic subaer-
ial ignimbrite dated at 123.6±6.0 ka, which reflects the
establishment of a crustal magma chamber. Above the ig-
nimbrite a succession of alkali basaltic, hawaiitic, and sub-
ordinate benmoreitic lavas and scoria cones is exposed,
dated at 90.7±19.0 ka. The Holocene deposits are exposed
at the top of Mt. Melbourne, where the crate r rim is com-
posed of trachytic to rhyolitic pumice fall deposits, which
are also extensively dispersed around the volcano, likely
originated from Plinian-scale eruptions. The most recent
explosive deposit proved difficult to date accurately because
very low quantities of radiogenic
40
Ar were released, result-
ing in imprecise plateau ages of 50±70 and 35±22 ka.
Keywords Antarctica
.
Explosive volcan ism
.
Geochronology
.
Mt. Melbourne
.
Geochemistry
Introduction
Ash produced from the 2010 trachyandesitic explosive erup-
tion of Iceland’s Eyjafjallajökull volcan o caused major dis-
ruption to air travel in the northern hemisphere, resulting in
significant economic losses to the global economy. More
recently, ash produced by Chile’s Puyehue-Cordón Caulle
volcano, in 2011, circled the globe at high latitude, disrupt-
ing air traffic in the southern hemisphere, with significant
impact on local economies. These events highlight the im-
portance of scientific assessment of the explosive potential
of volcanoes, globally, which may have the capacity to
produce upper atmospheric ash clouds that can be widely
dispersed by atmospheric circulation. Intra-plate volcanoes
in Antarctic are among the candidates with the potential for
major explosive activity; however, the hazard level of those
volcanoes is yet to be fully determined, largely because
Antarctic volcanoes are extensively ice-covered, and docu-
mentation of their volcanic rock sequences is both challeng-
ing and time-consuming.
Late Cenozoic intra-plate volcanoes in Antarcti ca are
mostly associated with rift zones such as the extensive West
Antarctic Rift System (Behrendt 1999). Antarctic volcanoes
are typically alkaline, ranging from basaltic to phonolitic
and trachytic in composition. Most volcan oes have erupt ed
Editorial responsibility: J.D.L. White
Electronic supplementary material The online version of this article
(doi:10.1007/s00445-012-0643-8) contains supplementary material,
which is available to authorized users.
G. Giordano (*)
:
F. Lucci
:
D. Cozzupoli
:
V. Runci
Dipartimento di Scienze Geologiche,
Università degli Studi Roma Tre,
Largo S. Leonardo Murialdo 1,
00146 Rome, Italy
e-mail: giordano@uniroma3.it
D. Phillips
Department of Geological Sciences, Melbourne University,
Melbourne, Victoria, Australia
Bull Volcanol
DOI 10.1007/s00445-012-0643-8

largely effusively, although explosive eruptions are known
from magma–ice interactions and/or associated with the
most evolved compositions (LeMasurier and Thomson
1990). Holocene felsic pyroclastic deposits dispersed
regionally from Plinian-scale eruptions are known from
Mt. Takahe and Mt. Berlin (Wilch et al. 1999; Dunbar et
al. 2008). Other quiescent potentially explosive volcanoes
include Mt. Melbourne and Mt. Rittman in Northern Victo-
ria Land; this assessment is based on evidence for recent
activity, such as the presenc e of ash layers on ice, age
determinations, and the presence of fumaroli c activity (see
LeMasurier and Thomson 1990 for a complete list; see also
the Smithsonian Institute website).
During the “Austral summer 2002–2003”,theItalian
XVIII Expedition to Northern Victoria Land ( Antarctica)
included a detailed field study of the Mt. Melbourne
Volcanic Province (Kyle 1990a). This field study built
on previous work published by New Zealand, German
and Italian parties, in the 1960s, 1970–1980s and 1980–
1990s, respectively (Nathan and Schulte 1967, 1968;
Kyle and Cole 1974; Lyon and Giggenbach 1974; Lyon
1986;WörnerandViereck1989;Wörneretal.1989; Rocchi
et al. 2003; Armienti et al. 1991; Beccaluva et al. 1991a, b;
Lanzafame and Villari 1991; Salvini et al. 1997; Rossetti et al.
2000;Stortietal.2006).
This paper presents a detailed reconstruction of the lith-
ostratigraphic archi tecture of the volcanic successions of the
Mt. Melbourne stratovolcano and the surro unding volcanic
sequences. A set of stratigraphically controlled samples
have provided new
40
Ar/
39
Ar age determin ations a nd
allowed definition of the magma compositional variation,
which together have allowed us to reconstruct the evolution
of the volcanism in the region and, in particular, the history
of Mt. Melbourne stratovolcano, in terms of eruptive styles
and the potential for future explosive eruptions.
Geological framework and previous studies
The Mt. Melbourne volcanic field belongs to the Tertiary to
Quaternary alkaline volcanoes of Northern Victoria Land
(Fig. 1), which form part of the McMurdo Volcanic Group
(Harrington 1958; Kyle 1990b) and are closely related to the
transtensional tectonic evolution of the Transantarctic
Mountains–Ross Sea b asin system (Sal vini et al. 1997;
Rossetti et al. 2000; Rocchi et al. 2003). This volcanism
forms one of the most extensive alkali volcanic provinces in
the world, with a geographic extent comparable to that of
alkaline rocks in the East African Rift (Kyle 1990b). Mag-
matism in the regio n initiated at about 50 Ma associated
with the extension of the Ross Sea Basin and became more
intense after about 30 Ma when the major NE-trending
faults in the area were re-activated with right-lateral strike–
slip kinematics (Salvini et al. 1997; Rossetti et al. 2000;
Rocchi et al. 2003; Storti et al. 2006). Recently, Lesti et al.
(2008) proposed a relationship between the Cenozoic mag-
matism of southeast Australia and the contemporaneous
activity in Northern Victoria Land. These authors suggested
that transtension associated with the Tasman Zone trans form
may have been responsible for the generation and eruption
of magma across passive margins, in agreement with the
model proposed by Salvini et al. (1997).
The volcanic edifices of the McMurdo Volcanic Group
include both scattered monogenetic scoria cones and lava
flows, and larger shield volcanoes and stratovolcanoes
(LeMasurier and Thomson 1990). Basaltic shield volcanoes
formed close to the coast, i.e. close to the Ross Sea Basin
shoulder. Examples include the 70×20 km Cape Adare
system, Coulman Island and Cape Washington (LeMasurier
and Thomson 1990). Stratovolca noes are charact erised by
more differentiated trachytic to phonolitic compositions,
such as at Mt. Morning (Martin et al. 2010), Mt. Overlord,
Mt. Rittmann, Berlin dome, Mt. Melbourne and Mt. Erebus
(LeMas urier and Thomson 1990). Kyle and Cole (1974)
subdivided the McMurdo Volcanic Group into informal
provinces that include, from north to south, the Hallett,
Melbourne and Erebus volcanic provinces. These volcanic
provinces are based on the spatial distribution, tectonic
setting and petrographic characteristics of volcanoes in the
region. The Mt. Melbourne Volcanic Province (MMVP) is
associated with a series of major NE-trending dextral faults,
which cross-cut the Transantarctic Mountains (Fig. 1), con-
necting with the N–S trending extensional faults of the Ross
Sea basin (Rossetti et al. 2000). The MMVP includes sev-
eral large stratovolcanoes composed of felsic rocks, such as
trachytes and peralkaline trachytes. These rocks exceed in
volume the more basic rocks such as alkali basalts, basanites
and hawaiites (LeMasurier and Thomson 1990). The main
volcanic fields are the Malta Plate au and The Pleiades to the
north, Mount Overlord in the centre and Mount Melbourne
in the south.
Mt. Melbourne
Mt. Melbourne (74.35° S; 164.70° E) is a stratovolcano
located between the Tinker Glacier and the Campbell Gla-
cier (Fig. 1). The volcano is elongate NNE (Fig. 1) along the
main structural fabric of the basement. The total volume of
the volcano’s con e was calculated at 180 km
3
for the summit
cone plus 250 km
3
in the surrounding volcanic field
(Worner and Viereck 1990). The volcano is quiescent, with
fumarolic activity at the summit crater (2,732 m above sea
level), where the temperature of the gas is constant at 59 °C,
just 25 cm below the ice cap (Nathan and Schulte 1967;
Keys et al. 1983; Cremisini et al. 1991). Furthermore, the
undissected cone morphology and widespread pumice fall
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layers, located only a few centimetres below the surface of
the ice cap, have been reported as evidence of recent explo-
sive activity (e.g. Wörner and Viereck 1989). The youngest
age determination obtained for recent deposits is 0.01±
0.02 Ma (Armstrong 1978). However Lyon (1986), based
on the depth withi n the ice cap at which tephra layers from
the most recent explosive activity at Mt. Melb ourne were
found, proposed that the most recent eruption probably
occurred between 1862 and 1922.
Previous detailed work on the Mt. Melbourne volcanic
products includes the results of the German GANOVEX
party (Wörner and Viereck 1989; Wörner et al. 1989), and
Fig. 1 Shaded topography of the Mt. Melbourne volcanic region. The
numbers indicate the location of selected samples (see Appendix 1 for
geographic coordinates) analysed in this study for geochemistry and
age determinations. The main fault systems are from Storti et al 2006.
The red box in the inset locates Mt. Melbourne in the Antarctic
continent
Bull Volcanol

those of the II Italian Expedition (Armienti and Tripodo
1991;Armientietal.1991; Beccaluva et al. 1991a, b;
Hornig et al. 1991; Lanzafame and Villari 1991; Müller et
al. 1991). The Mt. Melbourne volcanic products overlie the
Precambrian–Ordovician intrusive and metamorphic base-
ment rocks of the Wilson Terrane. They range from effusive
to explosive and erupted from subaerial to subaqueous/sub-
glacial environments (Wörner and Viereck 1989). The main
compositions range from basanite, alkali basalt and hawaiite
to more evolved comenditic trachyte varieties (Wörner et al.
1989; Beccaluva et al. 1991b; Armienti et al. 1991; Antonini
et al. 1994).
Published age data are all K/Ar determinations (Table 1
and Appendix 5) and suggest that the monogenetic volca-
noes surrounding Mt. Melbourne to the north, across the
Transantarctic Mountains, are Miocene-Pliocene in age
(about 12–3 Ma; Armienti et al. 1991). To the south of
Mt. Melbourne, the remnants of the N-trending Cape Wash-
ington basaltic shield (Fig. 1) yielded younger ages between
2.7 and 1.67 Ma (Kreutzer, 1988, unpublished report, quot-
ed in Wörner and Viereck 1989). All available ages for the
Mt. Melbourne stratovolcano itself are Quaternary (see data
compilation in Kyle 1990a). Unfortunately several pub-
lished ages are either quotations from unpublished reports
(e.g. Kreutzer, 1988) or they are not supported by sample
descriptions, sampling localities, or analytical details (e.g.
Armienti et al. 1991). Furthermore , some published ages
related to the same volcanic units are discordant (e.g. ages
of Shield Nunatak in Table 1). In addition, none of the
reported age determinations indicate the level of uncertainty
in the listed errors (1σ or 2σ). It is clear therefore that new,
stratigraphically controlled
40
Ar/
39
Ar data are essential to
describe the evolution of the Mt. Melbourne volcanic area.
Stratigraphy
The stratigraphy and physical characteristics of the volcanic
products are described for the following areas: the Mt.
Melbourne stratovolcano, the Mt. Melbourne peripheral
centres and the monogenetic volcanic field distributed
across the Transantarctic Mountains. Samples from 33 lo-
calities were collected for geochemical and geochronologi-
cal analyses (Fig. 1 and Appendix 1).
The Mt. Melbourne stratovolcano
Edmonson Point (0 m a.s.l.) to 723 m a.s.l
Edmonson Point is located along the coast to the east of the
summit and reveals the lowest part of the exposed stratigra-
phy of the Mt. Melbourne stratovolcano (Figs. 1 and 2). The
area is characterised by two headlands, a promontory to the
south an d exposed cliffs to the north (Edmonson Point S and
Edmonson Point N respectively), separated by the Edmonson
Point glacier tongue (Baroni and Orombelli 1994). Some of
the localities in the area have been described by Wörner and
Viereck (1989). Despite some ice-covered sections, the area
offers an almost continuous stratigraphic section from sea
level up to the elevation of 723 m a.s.l. (Fig. 2), with excellent
exposures that allow reconstruction of the complete strati-
graphic succession. The succession is subdivided into five
distinctive rock formations, described in stratigraphic order
(Fig. 2).
Edmonson Point trachytic ignimbrite (EPI) The EPI unit is
exposed along the base of the coastal cliffs of Edmonson
Point S (Figs. 2 and 3). The maximum thickness in outcrop
is 30 m, but the base of the EPI is not exposed. There are
two main outcrops, each about 200 m long, displaying very
similar facies over more than 1 km. The ignimbrite com-
prises three main lithostratigraphic sub-units, with deposi-
tional surfaces dipping 35° SW. Several faults produce local
displacements of several decimetres and are associated with
the later intrusion of dykes (Fig. 3a). The lower sub-unit is a
15-m-thick, white-pumice lapilli-rich (30–40 vol%, Ø
max
2–
4 cm), ash-matrix supported (40 vol%), massive and chaotic
deposit, with abundant accessory lithics (10–20 vol%, Ø
max
8 cm). The white pumice (sample G03, Appendixes 6 and 7)
is vesicular, poorly porphyritic and contains phenocrysts of
sanidine (59–61 % Ab), and hedenbergite (48 % Wo, <1 %
En and 51 % Fs). A matrix-supported breccia lens is em-
bedded in the lower sub-unit with gradational contacts
(Fig. 3b). The breccia is composed of angular to subrounded
lithic fragments, up to 60 cm in diameter. Clast types include
(a) pale grey, poorly porphyritic (sanidine and amphibole)
microcrystalline lava of likely trachytic composition (30–
40 % of relative abundance); (b) black, scoriaceous, por-
phyritic lava (plagioclase and pyroxene) of likely basaltic
composition (20–30 %); (c) homog eneous to banded syenite
(5 %); and (d) reddish, hydrothermally altered clasts of
basement gneiss (5–10 %). Above the breccia lens, the
lower ignimbrite sub-unit contains coexisting white-
pumice and black, sanidine-phyric vesicular-pumice lapilli.
The middle sub-unit is a 2-m-thick succession of moderately
sorted, rounded pumice lapilli-rich and plane parallel to
low-angle cross-stratified b eds probably of surge origin.
The upper sub-unit is about 13 m thick, black-pumice-
lapilli-rich (30–40 vol%, Ø
max
10 cm), ash-matrix-
supported (60 – 70 vol%), lithic-poor, massive and chaotic
deposit. The pumice (sample G48, Appendixes 6 and 7)is
black, highly vesicular, porphyritic, spatter-like, and con-
tains Na-sanidine (Ab 55–61 %), andesine (An 46–47 %),
fayalite (Fo 1–2 %) and Fe-hedenbergite (47–48 % Wo, 1–
2 % En and 48–52 % Fs) cryst als. The EPI ignimbrite was
previously interpreted by Wörner and Viereck (1989) and by
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Table 1 Summary of 40Ar/39Ar geochronology results from Mt. Melbourne and surrounding area: all uncertainties are listed at the 95 % confidence level
Area Locality Rock type Sample
number
Sample
type
Plateau
age (ka)
MSWD Mean age
(ka)
MSWD Isochron
age (ka)
MSWD
40
Ar/
36
Ar
ratio
Previous ages
(K/Ar, Ma)
Mt. Melbourne Summit crater
(recent lavas)
Grey porphyritic (snd,
cpx) dense trachiti
spatter
G77 K-Feldspar 50.0±70.0 (2 σ) 0.7 ––– –Armstrong 1978:
Brown porphyritic (snd,
cpx) trachytic pumice
G79 K-Feldspar 35.1±21.9 (2 σ) 1.4 ––61.6±66.4
(95 %)
3.6 297.6±6.4 0.01±0.02;
0.26±0.06;
0.08±0.015;
Kreutzer 1988:
0.015±0.035
Mt. Melbourne Edmonson Point
(ARL Lavas)
Black ropy porphyritic
(pl, ol, amph) basalt
G52 Whole
rock
––111.6±83.8
(2σ)
0.6 37±88 (2σ) 0.3 299.4±4.2
Slope<
1,000 m.a.s.l.
Edmonson Point
(ARL Lavas)
Black porphyritic
(pl, ol) hawaiite
G39 Whole
rock
––297.6± 55.4
(2σ)
1.2
_
32±183 (2σ) 0.5 305.8±5.1 Kreutzer 1988:
Grey porphyritic lava G66 Plagioclase 90.7±19.0 (2σ) 1.0 ––94.4±25.8
(95 %)
1.5 299.4±3.9 0.05±0.02;
0.074±0.11
Edmonson Point
(EPI
Ignimbrite)
Black porphyritic (snd, pl,
ol, cpx) trachiti pumice
G48 K-Feldspar – 118.6±11.6
(95 %)
2.8 103.3±17.3
(95 %)
2.5 301.2±5.0
Grey subaphiric (snd, cpx)
trachytic pumice
G02 K-Feldspar 120.2±12.6
(2σ)
1.4 ––97.4±33.8
(95 %)
2.4 302.1±6.8
G03 K-Feldspar 124.3±6.4 (2 σ) 1.7 ––118.2±16.4
(95 %)
2.3 300.3±10.8
G02+
G03
K-Feldspar 123.6±6.0 (2σ) 1.4 ––115.2±12.8
(95 %)
2.4 301.2±5.2
Mt. Melbourne
surrounding
plain
Shield Nunatak Black lava with
olivine and plagioclase
G46 Whole
rock
––430.5± 82.0
(2σ)
1.1 191±199 (2σ) 0.8 301.2±4.0 Kreutzer 1988:
Lower mugearite
lava 1.55±
0.05,
Upper alkali
basalt
0.07±0.05,
Armienti et al.
1991:
0.48±0.24
Markam Island Black lava with
olivine and plagioclase
G49 Feldspar – Min0 415 ±24
(2σ)
– 263.0±111.7
(95 %)
5.3 349.7±20.8
Random Hills
(Local Suite)
Harrows Peak Black lava with
olivine and plagioclase
G83 Whole
rock
––744.7± 66.2
(95 %)
1.8 669±101
(95 %)
1.7 301.2±4.6
Pinkard Table Bomb of vescicular
black lava with
plagioclase
G26 Whole
rock
––1,368± 90 (2σ) 1.4 1,307±112
(95 %)
1.4 309.6±15.3
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Wörner and Orsi (1990) as a near-vent strombolian to sub-
plinian pumice fall deposit associated with fluvial to debris
flow reworked deposits. We did not observe depositional
features that can be reconciled with a fallout origin for the
EPI ignimbrite nor extensive reworked material; rather, the
unit displays massive, chaotic, polymictic, and poorly sorted
facies that are characteristic of deposits from pyroclastic
density currents. Furthermore, the high proportion of ash
within the ignimbrite (40–70 %), associated with the pres-
ence of a co-ignimbrite breccia containing syenite accessory
lithics, and the gradational up ward compositional zonation
from white to black pumice are all characteristic features of
Plinian-scale, calder a-forming eruptions, rather than small
scale eruptions (e.g. Cas and Wright 1987; Branney and
Kokelaar 2002).
Adelie Penguin Rookery lava field Along the southern head-
land of Edmonson Point, the EPI ignimbrite is intruded by a
series of dykes, which can be mapped into the overlying
Adelie Penguin Rookery lava field (ARL) that they fe d
(Figs. 2 and 3a). At Edmonson Point S, the minimum lava
thickness in outcrop is 300 m. At Edmonson Point N, the
base of the lava field is not exposed , and the thickness in
outcrop reaches 550 m. Feeder dykes general ly trend N010°
to N040° and are 1–10 m thick. Dykes also cross-cut lava
units, indicating that the ARL lavas were emplaced during
several pulses. Dykes are g rey and microcrystalline in the
core and show black glassy margins. The lavas are glassy
and very fragile and generally show radial columnar joint-
ing, which defines megapillows and tubes associated with
breccia domains. These features suggest a sub-aqueous en-
vironment, although unequivocal hyaloclastite was not ob-
served. Individual lava units vary from coherent to vesicular
and show both basal and top aa-type autobreccias, along
with local development of ropy sur faces associated with
small lobes. Flow-banding, where visible, is convolute. At
Edmonson Point S, above 150 m a.s.l., a series of small
scoria cones and spatter agglomerat es transitional to coher-
ent lavas are present, fed by N125°-trending dykes (Fig. 4b,
c). Scoria cones and agglomerates show no evidence of
hyaloclastic fragmentation, suggesting a sub-aerial environ-
ment of emplacement. The lava is hawaiitic (sample G39;
Appendixes 6 and 7), black in colour, porphyritic, and with
phenocrysts of plagioclase (52–77 % An) and olivine (53–
65 % Fo). The groundmass is glassy with micro-
phenocrystals of andes ine (49–50 % An) and an overall
anisotropic texture. At some lo cations, the lava encloses
thermally altered and saccharoidal xenoliths, up to 60 cm
Fig. 2 a Helicopter view of the
Mt. Melbourne stratovolcano;
samples localities (G numbers)
and related elevations a.s.l. are
indicate; note, below the Mt.
Melbourne summit and the
presence of a well preserved
collapse scar (white dashed
line) [legend (see text for
descriptions): EPI Edmonson
Point trachytic ignimbrite
(123.6±6.0 ka); ARL Adelie
Penguin Rookery hawaiitic lava
field (90.7±19.0 ka); ETC
Edmonson Tuff Cone; ROL
600 ma.s.l. ropey basaltic lava
plateau (black dashed lines
indicate the thickness and
exposed extent of the plateau);
SCC 723 ma.s.l. hawaiite scoria
cone]. b schematic stratigraphic
cross-section of the lower
deposits of the Mt. Melbourne
stratovolcano at Edmonson
Point (see text for explanation)
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in diameter. Limited outcrops of benmoreitic (sample G40;
Appendixes 6 and 7) and trachytic lava units (sample G66;
Appendix 6), pale in colour, with a low porphiricity index,
were also sampled (cf. Wörner et al. 1989). The phenocrysts
include plagioclase (33–39 % An), anorthoclase and sani-
dine feldspars (52–75 %) Ab, Fe-olivine (30–32 % Fo)
clinopyroxenes with exsolution lamellae and resorption
sags. The g roundm ass is holocrystalline with a tra chytic
texture and the same mineral assemblage.
Edmonson Point Tuff Cone On the southern promontory
(Edmonson Point S), there is a lapilli tuff cone sequence
covered by the ARL lava and intruded by several about
N010°- and N125°-trending ARL feeder dykes (Fig. 4a).
The Edmonson Po int Tuff Cone (ETC) succession is com-
posed of alternating, moderately sorted, decimetre-thick
beds containing monogenetic black lava lapilli and bombs
with minor palagonitised coarse ash matrix, and yellow to
grey, plane parallel to low-angle cross-stratified, palagoni-
tised, centimetre-thick coarse ash layers (Fig. 4b). The black
lava lapilli and bombs are gen erally equant and glassy, with
polygonal geometries that suggest possible moderate inter-
action with water. Many bombs are bread-crusted and some
are spatter-like, occasionally with cores of thermally altered
granitoid rocks enveloped in a dark red film of scoriaceous,
plagioclase-phyric lava. Such xenoliths are identical to those
described for the ARL lavas. No other types of xenoliths
were observed, suggesting a very shallow level of magma
fragmentation. Rarely, some of the largest bombs form
impact sags on the ash layers, indicating a fall component
to the deposit, although the presence of low-angle c ross-
bedding and moderate sorting suggest lateral flo w. The
ETC, exposed in cliff faces, is cut by normal faults of a
few decimetres to 2 m displacement (Fig. 4b). The ETC
deposits have been previously interpreted as part of a com-
plex, multiple pumice tuff ring (Wörner and Viereck 1989;
Wörner and Orsi 1990). We were unable to loca te any
juvenile clasts that could be described as pumice clasts,
nor any internal unconformity that might indicate multiple
sources. We interpret the ETC as a local tuff cone sequence
and a member of the ARL lava field. The cone likely formed
as a result of local magma–water interaction. It must be
Fig. 3 a The “Edmonson Point trachytic ignimbrite” (EPI), cut by a
feeder dyke to the “Adelie Penguin Roockery l ava fie ld” (ARL);
sample numbers and age determinations are reported in brackets (in
this and successive figures). b detail of the co-ignimbrite breccia lens
embedded within the EPI ignimbrite
Fig. 4 a The upper part of the ARL lava field is composed of
coalescing scoria cones fed by N125°-trending dykes cutting the
“Edmonson Point Tuff Cone” ETC. b The “Edmonson Poi nt Tuff
Cone” (ETC) is composed of stratified lapilli tuff beds; the succession
is cut by several small faults
Bull Volcanol

noted that there are no exposures indicative of the strati-
graphic relationship between ETC and the EPI ignimbrite,
both of which are cross-cut and also covered by the ARL
lavas (Fig. 2b). However, the ETC juveniles are identical in
composition to the nearby ARL hawaiitic lavas, and the
inferred monogenetic style is consistent with the emplace-
ment of the severa l small lava flows and scoria cones de-
scribed for the ARL. The stratigraphic position of the ETC
member could therefore be at the base of the ARL Forma-
tion, or alternatively, within it. We interpret the ARL and
ETC unit s as parts of a small volcanic field (Fig. 2b), where
several eruption points were generated along N010°- and
N125°-trending feeder dykes. These orientations are consis-
tent with known regional structural trends (e.g. Rossetti et
al. 2000) and with the local faults, suggesting a tectonic
control over the volcanism in this area. This small volcanic
field was emplaced in several pulses, as indicated by the
different occurrences of mega-pillows, tuff and scoria cones,
produced as a result of different degrees and efficiencies of
interaction with water, most likely a melting ice cover (cf.
Wörner and Orsi 1990). Given the proximity to the sea-
shoreline and known regional uplift rates (see Fitzgerald et
al. 1987), emplacement under sub-aqueous conditions can-
not be entirely ruled out, at least for the lowest outcrops of
Edmonson Point.
600 m a.s.l. “Ropy basaltic lava plateau” The ARL lava
and scoria is covered by a >50-m thick succession of thin,
sub-horizontal, alkali-basaltic lava flow units, with interbed-
ded coarse breccia layers, mostly autobreccias. The top of
these basalts forms a distinct plateau at about 600 m a.s.l. at
Edmonson Point N and at 400 m a.s.l. above Edmonson
Point S (Fig. 2). The topmost flow is characterised by
perfectly preserved ropey structures, which indicate a sub-
aerial environment. The lava (sample G52; Appendixes 6
and 7) is scoriaceous and porphyritic, with phenocrysts of
calcic plagioclase (56–81 % An), Mg-olivine (72 – 75 % Fo),
amphibole (ferro-edenite), ilmenite and magnetite. The
groundmass contains fine-grained labradorite, ferro-
edenitic amphibole (with composition similar to phenoc-
rysts), clinopyroxene and olivine. Rare gabbroic intraclasts
were also observed. The actual contact with the underlying
ARL lavas was not observed. We believe, however, that it is
a low-relief erosional unconformity because the “Ropy ba-
saltic lava plateau” (ROL) shows an almost constant thick-
ness and a widespread flat top, suggesting that the
underlying topography, i.e. the top of ARL, was essentially
flat at the time of ROL emplacement. This is somewhat
counter-intuitive, considering that the ARL was emplaced
from multiple lava sources, scoria cones and spatter agglom-
erates, and should form a hummocky topography. The ROL
plateau shows two distinct elevations, at 400 m a.s.l. above
Edmonson Point S and at 600 m a.s.l. above Edmonson
Point N, with the difference suggesting displacement by a
fault, running NE–SW along the Edmonson glacier tongue
valley (Fig. 2). The ROL plateau was described by Wörner
and Viereck (1989), who interpreted the lava plateau as
having a distal source, although no evidence for this inter-
pretation was provi ded. We have no evidence for either a
local or a distal source for the ROL. The presence of a
vertical dyke, feeder to one of the thin lava flows just above
Edmonson Point S (Fig. 2b), may, however, suggest a local
source to the lava field.
723 m a.s.l. hawaiite scoria cone Above the ROL plateau,
an undissected scoria cone rises to an elevation of 723 m
a.s.l. (Fig. 2). The cone is composed of quaquaversally
dipping, small lava flows (20–30 m thick and lensoidal)
interlayered with scoria lapilli and bomb beds. The summit
of the cone comprises spatter rags and splinters, and scoria
bombs and lapilli (sample G58; Appendixes 6 and 7). Clasts
in this unit are moderately porphyritic (5 %), with phenoc-
rysts of Mg-olivine (59–66 % Fo), plagioclase (58–65 %
An), clinopyroxene (10 % Wo, 81 % En and 9 % Fs) and
amphibole ( ferro-edenite–kaersutite). The clasts’ ground-
mass includes fine-grained andesine, amphibole and ol-
ivine, with same composition as the phenocrysts.
Intraclasts of olivine-gabbro have been identified with
plagioclase and Mg-olivine. Many bombs have cores of
thermally altered granitoid clasts from the underlying
basement.
Summit area
The summit cone of the Mt. Melbourne volcano was sur-
veyed, from the summit crater (2,732 m a.s.l., Fig. 5a) down
to 2,253 m a.s.l. (Fig. 2). The area was described previously
in Wörner and Viereck (1989, 1990). The crater rim is
uniformly covered by a blanket (10–70-cm thick) of dark
grey juvenile lapilli and bombs up to 50 cm in diametre
(Fig. 5c, d) and a variety of xenolith blocks, which include
variably porphyritic, massive to flow-banded, pale grey to
dark lava and clasts of older pyroclastic material, as well as
pre-volcanic rocks. The blanket is a fall deposit and proba-
bly from the most recent eruption. The juvenile products
(samples G56, G57 and G75; Appendixes 6 and 7)are
mainly trachytic to rhyolitic, grey, porphyritic, vesicular to
dense clast s, with some showing spatter morphology and
internal rheomorphic textures produced by post-
fragmentation ductile deformation (Fig. 5c). Phenocrysts
include plagioclase (20–38 % An), and clinopyroxene (44–
46 % Wo, 18–23 % En and 30–36 % Fs) and Fe-olivine (13–
16 % Fo), whereas the groundmass contains Na-sanidine,
clinopyroxene, plagioclase, opaques and F-apatite crystals.
The deposit also contains dense clasts of trachyte and rhy-
olite, which may be either dense juvenile clasts or xenoliths
Bull Volcanol

from older lavas (samples G73, G77, G78 and G80). One
sample (G71; Appendixes 6 and 7) from the crater rim is a
black, porphyritic, vesicular lava bomb containing phenoc-
rysts of calcic-plagioclase (59–66 % An), Mg-olivine (65–
75 % Fo ) and clinopyroxene (47 % Wo, 37 % En and 16 %
Fs), and rare ferro-richterite amphibole set in a groundmass
of calcic plagioclase and olivine. Accessory lithics of gab-
broic–dioritic composition are also present.
The upper coarse fall deposit covers gradationally a low-
er pumice lapilli unit, more than 15-m thick and exposed
inside the northern crater wall (Fi g. 5d). This deposit is
clast-supported, ash-matrix-free, sorted and composed
largely of angular pumice clasts (average of 4–5cmin
diametre, with blocks up to 20 cm large), locally broken
in-place into smaller, jigsaw-fit pieces. These characteristics
are consistent with pyroclastic fall origin. The pumice (sam-
ple G79; Appendixes 6 and 7) is pale grey, highly vesicular,
porphyritic with phenocrysts of anorthoclase (63–68 % Ab)
and clino pyroxene (32–52 % Wo, 6–8 % En and 41–60 %
Fs); anorthoclase glomerocrysts (63–64 % Ab) are also
present.
At 2,253 m a.s.l. (N74°21′10.9″ ; E164°44′47.6″)isa
subvertical cliff about 50–100 m high (Figs. 2 and 5b),
which exposed hydrotherma lly altered (yellow to red in
colour) pyroclastic deposits, cut by several N–S oriented
open fractures. This cliff can be traced across the entire
eastern flank of the volcano, with a N–S orientation,
forming a clear arcuate, down-slope concave structure
(Fig. 2). We infer that the cliff corresponds to a previously
unidentified incipient collapse scar and also represents a
zone of recent, focussed hydrothermal activity that is not
evident elsewhere along the volcano slopes.
Dispersal of the most recent fall deposits
Where seracs cut through the ice cover of the Mt. Mel-
bourne stratocone, continuous layers of tephra are seen
(Fig. 6a), as previously described by Lyon (1986). We
sampled the topmost tephra layer, 16 km NE of the summit
(Figs. 1 and 6c; sample G62). The tephra occurs just 10 cm
below the ice top and is consistently 3-cm thick, and is
composed of well sorted , pale grey, highly vesicular
(>60 %) and poorly porphyritic angular trachytic pumice
1.5 cm lapilli, with maximum size of 2 cm (Fig. 6d). The
deposit contains 1 % of 0.5 cm lava lithic clasts (Fig. 6d).
There are phenocrysts of plagioc lase (21 % An), Fe-olivine
(15 % Fo) and clinopyroxene (46 % Wo, 21 % En and 33 %
Fs). The depositional characteristics are typical of a primary
fall deposit. Characteristics such as the texture of the pum-
ice, the composition of mineral phases and the bulk trachytic
composition (Appendixes 6 and 7 ; Appendix 8 also reports
trace elements data) are all consistent with those of the most
recent deposit at the summit crater (sample G56), which we
infer correlative. Other apparently correlative deposits
Fig. 5 a The summit crater
floor (ca. 600 m in diametre). b
the eastern flank of the volcano
is cut by an arcuate vertical
scarp (see also Fig. 2), several
tens of metres high, which
shows hydrothermally altered
pyroclastic rocks (note the pale
colour); this scar is interpreted
as an incipient sector collapse. c
The uppermost tephra which
blanket the summit crater rim
are trachytic scoria and spatter
bombs, which cover
conformably (d) grey, trachytic
pumice lapilli and bomb bed up
to 15 m thick. Note the
coarsening upward grain size
Bull Volcanol

exposed along vertical cliffs (Fig. 6a) east and west of the
summit are inaccessible, so we could not produce an isopach
map of this fall deposit.
Mt. Melbourne peripheral centres
Approximately 10– 25 km from the Mt. Melbourne summit
are several monogenetic volcan ic centres. The most promi-
nent are Baker Rocks in the northern area (Fig. 7a), and
Shield Nunatak (Fig. 7b), Oscar Point and Markham Island
in the southern area (Fig. 7c). North of Baker Rocks, a series
of similar but smaller monogenetic volcanoes, outcrop along
the coastal cliffs (N74°12′34.7″ ; E164°48′22.0″ and N74°
09′02.9″; E164°47′26.2 ″) up to 400 m a.s.l. (N74°19′031″;
E165°03′002″). Shield Nunatak has been described in detail
by Wörner and Viereck (1989). The main characteristic
common to Baker Rocks, Shield Nunatak and the cliffs
immediately to the west of Oscar Point is a yellow to
orange, lower succession 50– 300-m thick of palagonitised
lapilli tuffs, cut through by wavy dikes and apophyses that
are feeders to scoria cones and lava flows (Fig. 7c ). The
Fig. 6 a Helicopte r view of ice-seracs (ap proxim ate cliff’sheight
100 m), which show continuous layers of ash of likely fallout origin.
b Sample G62 is composed of a 3-cm-thick pumice lapilli layer
embedded in ice near Baker Rocks, 16 km to the NNE of the Mt.
Melbourne summit. c The outcrop area for sample G62. d Grainsize of
pumice and lithic clasts of G62; clasts in the lower white inset are the
largest
Fig. 7 Helic opter views of monogenetic centres peripheral to Mt.
Melbourne: a Baker Rocks, b Shield Nunatak, c Oscar Point: a
>200 m thick succession of thinly bedded palagonitised lapilli tuffs is
cut by several wavy dikes and apophyses, which are feeders to a
summit scoria cone deposit
Bull Volcanol

palagonitised lapilli tuffs are also cut by unconformities, and
syn-eruptive faults and fractures, and show extensive soft-
sediment deformation. The lapilli tuffs are ubiquitously bedded,
alternating poorly sorted, centimetre-thick ash layers and mod-
erately sorted, decimetre-thick lapilli beds. Beds locally show
both normal and inverse grading. Armored lapilli are common.
Lapilli-sized clasts are dense to vesicular dark and glassy lava,
generally polygonal in shape. This suggests that the clasts are
juvenile fragments from hyaloclastic/phreatomagmatic pro-
cesses of fragmentation (Cas 1992;McPhieetal.1993). Bed-
ding varies from parallel- to low-angle cross-stratified, which
suggests emplacement by variably concentrated density cur-
rents. Generally, no lithics from the underlying basement were
found. These features together are interpreted to indicate mono-
genetic eruptions in a sub-glacial (or sub-aqueous) environ-
ment. Once the ice cover melted completely (or the thickness
of the deposit exceeded the water depth), phreatomagmatic and
hyaloclastic fragmentation ceased, giving way to strombolian
to effusive eruptions (e.g. Wörner and Viereck 1989; Smellie
and Chapman 2002 and references therein).
The scoria and lava that form the sub-aerial scoria cone at
the top of Shield Nunatak are porphyritic alkali basalt (sam-
ples G45 and G46; Appendix 6), with phenocrysts of augitic
clinopyroxene, olivine (70 –80 % Fo) and plagioclase (56–
64 % An), set in a groundmass of labradoritic plagioclase
(52–56 % An), clinopyroxene and olivine similar in com-
position to phenocrysts. Alkali-basaltic rocks erupted from
Shield Nunatak have textures, phenocrysts assemblages and
groundmass associations very similar to those of Markham
Island (sample G49), Oscar Point (sample G50) and Baker
Rocks (sam ples G23 and G61)( Appendixes 6 and 7).
The monogenetic volcanic field distributed across
the Transantarctic Mountains
The Random Hills area is located north of Mt. Melbourne
(Fig. 1) and comprises a series of monogenetic scoria and
lava centres, directly overlying the Ordovician granitic base-
ment. In the Random Hills area, Pinkard Table is a NNE–
SSW ridge, topped by a series of small, perfectly preserved,
scoria cones (Fig. 8a), not previously described. The scoria
cones are at ∼1,600 m a.s.l. and are composed of lapilli and
bombs, with the latter including highly vesicular scoria and
subordinate lava fragments and xenoliths derived from the
underlying granite basement. Scoria clasts are red, with
some plastically deformed. The scori a is a highly porphy-
ritic alkali ba salt (sample G26; Appendix 6) with calcic-
plagioclase (labradoritic), relics of altered forsteritic olivine,
diopsidic clinopyroxene, microphenocrysts of edenitic am-
phibole and ilmenite as the dominant phenocrysts phases.
The groundmass is microcrystalline labradoritic plagioclase.
The geometry and structure of the scoria cones, as well as
the absence of any indication of magma–water interaction,
suggests that the style of activity was strombolian and the
environment sub-aerial. A few kilometres to the east of
Pinkard Table, four well-preserved small scoria cones, are
perfectly aligned along the N–S crest (Fig. 1). The scoria
products of these cones are hawaiitic in composition (sam-
ple G38; Appendix 6) with similar petrographic character-
istics to that of the Pinkar d Table centre.
Further to the east, the Harrow Peaks outcrop is located
on a saddle at 800 m a.s.l. (Wörner and Viereck 1989) and
characterised by an eroded centre composed of a prominent
black porphyritic lava plug, with megapillow structures up
to 40 m across (Fig. 8c).TheplugisfedbyaN008°-
oriented dyke, which intrudes one of the many parallel
fractures that pervasively cut the Ordovician granite base-
ment. The lava plug is in transitional to intrusive contact
with palagonitised yellow to brown lapilli tuffs (Fig. 8d),
which generally dip (20°) almost parallel to the present day
steep slopes of the saddle, down to 300 m a.s.l. The lower
beds of the palagonitised tuff include many blocks of the
underlying granite, some of which are rounded. The lava is a
hawaiite (sam ple G83; Appendix 6), with sparse phenoc-
rysts of clinopyroxene (augite–Fe–augite) and plagioclase
(40–44 % An) and accessory magnetite in a microcrystalline
groundmass. Previously undescribed monogenetic centres,
showing petrographic, stratigraphic and morphologic char-
acterstics very similar to Harrow Peaks, occur to the south
(N74°06′44.3″; E164°45 ′32.9″; 449 m a.s.l.), and further
north, along the Tinker Glacier valley (N74°56′40.5″;
E164°25′49.7″; 353 m a.s.l.).
To the southwest of Mt. Melbourne, small monogenetic
centres are scattered on the Deep Freeze Range, Browning Pass
and the Northern Foothills, including the small, previously
undescribed scoria cone of Mt. Abbott (Fig. 8b), just west of
the Italian Base (Fig. 1). Mt. Abbott scoria cone is well pre-
served and is composed of loose, reddish to brown scoria bombs
and lapilli, and spatter bombs. Sample G25 (Appendix 6)from
this locality is an alkali basaltic with andesinic plagioclase.
Geochronology
Twenty-six sites from the Mt. Melbourne area were initially
sampled for
40
Ar/
39
Ar age determinations (Appendix 1). Un-
fortunately, due to younger than expected ages and low po-
tassium concentrations, insufficient feldspar was recovered
from a number of samples. Consequently,
40
Ar/
39
Ar results
are reported for only seven feldspar separates (Table 1). Based
on initial feldspar age results, five additional, holocrystalline
lava samples were selected for whole-rock
40
Ar/
39
Ar step-
heating analyses (Table 1). Analytical metods are detailed in
Appendix 2.
40
Ar/
39
Ar results obtained from seven feldspar separates
and five whole-rock samples are summarised in Table 1 and
Bull Volcanol

Fig. 9. Detailed analytical data are listed in Appendixes 3
and 4. All uncertainties are reported at the 95 % confidence
level. The volcanic successions at Edmonson Point yielded
age results of variable uncertainty. The lowermost EPI ignim-
brite (Figs. 2 and 3) produced the most consistent ages, from
three different samples (G02, G03 and G48). Samples G02
and G03 yielded plateau ages of 120.2±12.6 and 124.3±
6.4 ka, respectively. Isochron ages are within error of these
ages, with (
40
Ar/
36
Ar)
i
ratios indistinguishable from the atmo-
spheric value of 295.5 (Table 1). The weighted mean age for
all plateau segments from G02 and G03 is 123.6±6.0 ka.
Although sample G48 did not produce a statistical plateau
age, all steps have broadly similar ages, averaging 118.6±
11.6 ka (Table 1). The consistency of the above results pro-
vides confidence in the about 120 ka age for this unit. The
overlying ARL lavas produced more discordant ages. Three
whole-rock aliquots of sample G39 yielded statistical plateau
ages, but with large uncertainties. The weighted mean age for
the three aliquots is 298±55 ka. However, isochron plots for
this sample produced a negative age result and an elevated
(
40
Ar/
36
Ar)
i
ratio, possibly indicating some excess argon con-
tamination (Table 1). In contrast, K-feldspar from sample G66
gave a plateau age of 90.7±19.0 ka, with a similar isochron
age and atmospheric (
40
Ar/
36
Ar)
i
ratio (Table 1). Supported by
stratigraphic relationships, we suggest that the latter age of
about 90 ka provides the best estimate for the age of ARL lava
field. Only one sample (G52) was dated from the ROL alkali-
basaltic ropy lavas, which overlie the ARL lavas. Three
whole-rock aliquots from sample G52 again produced plateau
ages, but with large uncertainties, giving an imprecise weight-
ed mean age of 112±84 ka (Table 1). This age is within error
of results from the underlying lavas and, within the uncertain-
ties, is also consistent with stratigraphic relationships. G77
and G79 represent samples of the youngest volcanic deposits
on Mt. Melbourne. Feldspar separates from both samples
released very low quantities of radiogenic
40
Ar , resulting in
very imprecise plateau ages of 50±70 and 35±22 ka, respec-
tively (Table 1). These data suggest an Upper Pleistocene to
Holocene age for these deposits. In addition, a grey pumice
lapilli fall deposit, very similar in chemistry to G56 and G77
(see Appendix 6), occurs in the upper ice cap in the area
(sample G62; Fig. 6c), supporting a very young age. In addi-
tion to the Mt. Melbourne volcanic samples,
40
Ar/
39
Ar results
were also obtained from volcanic deposits in the area surround-
ing Mt. Melbourne. Three whole-rock lava aliquots of sample
G26, from Pinkard T able, yielded plateau ages, with a mean
age of 1,368±90 ka (Table 1). Similar whole-rock aliquots
from a Harrow Peaks (Random Hills) lava sample (G83) are
characterised by a mean age of 745±66 ka (Table 1). Whole-
rock aliquots from a Shield Nunatak lava sample (G46) pro-
duced more discordant results, with an imprecise average age
of 431±82 ka (Table 1). A final plagioclase feldspar sample
from Markham Island (G49) yielded a discordant age spec-
trum, with a maximum apparent age of 415±24 ka, an impre-
cise isochron age of 263±112 ka and an (
40
Ar/
36
Ar) ratio of
350±21 (Table 1). These results only constrain these Markham
Island volcanic deposits to be less than ∼400 ka.
Whole-rock geochemistry
A total of 31 sites from the Mt. Melbourne area were
sampled for g eochemical analysis (Appendix 1). Analytical
methods are detailed in Appendix 2.
The major elements for the analysed samples are presented
in Appendix 6 and used to classify the volcanic rocks
Fig. 8 a One of the preserved
scoria cones at the top of the
Pinkard Table crest (1,600 m
a.s.l.). b Helicopter view of Mt.
Abbott (529 m a.s.l.). c
Helicopter view of the Harrow
Peak centre; the main outcrop is
a 30-m high lava plug, with ra-
dial jointing. d The main lava
plug laterally feeds small lava
intrusions cutting the associated
palagonitised hyaloclastitic
debris
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Fig. 9 Plateau ages (box heights are 1σ) and
36
Ar/
40
Ar vs
40
Ar/
39
Ar plots for the dated samples (data-point error ellipses are 68.3 % confidence)
Bull Volcanol

Fig. 9 (continued)
Bull Volcanol

according to LeMaitre (2002). A complete discussion of the
geochemistry data, including trace elements, is beyond the
scope of this paper, which is centered on the stratigraphy and
geochronology of Mt. Melbourne. Analyses were recalculated
to 100 % on a volatile-free basis and plotted on a total alkali-
silica (TAS) diagram (Fig. 10a). CIPW norms and Alkali
Index were calculated for all samples to evaluate (1) the
normative content of quartz (Q), nepheline (Ne) and leucite
(Lc) and hence the variations in silica saturation and (2) the
evolution of the [K
2
O/(K
2
O+Na
2
O)]×100 index and the al-
kali signatures of the magmatism in the area. All the studied
samples belong to the alkaline series (Fig. 10a), according to
classifications proposed by Kuno (1966), Irvine and Baragar
(1971) and Bellieni et al. (1983). The least evolved rocks are
alkali basalts. Differentiated products include intermediate
hawaiites, benmoreites (based on their sodic signature;
Na
2
O–2.0>K
2
O; LeMaitre 2002) and trachytes (normative
equation [100×Q/(Q+An+Ab+Or)] always<20 %; Le Bas
and Streckeisen 1991). Remarkably, benmoreites are rare and
mugearitic rocks absent, suggesting the occurrence of a com-
positional gap, termed the Daly gap (e.g. Bonnefoi et al. 1995)
also recognised for other Cenozoic volcanic complexes of
Northern Victoria Land (Wörner and Viereck 1989; Armienti
and Tripodo 1991; Armienti et al. 1991; Beccaluva et al.
1991a, b;Mülleretal.1991). The most explosive eruptions
have been trachytic, such as the one that produced the Edmon-
son Point Ignimbrite (samples G03 and G48; Appendix 6).
Two samples plot in the rhyolite field, close to the boundary
with trachytes (Fig. 10), and are from the pyroclastic deposits
at the top of Mt. Melbourne (samples G75 and G78; Appen-
dix 6). The rhyolites at Mt. Melbourne had not been reported
previously. The presence of normative corundum (0.8 %) in
G75 and normative acmite (2.7 %) in G78, together with the
Agpaitic Index [(Na
2
O+K
2
O)/Al
2
O
3
molar ratio] in the range
of 0.94–1.04, do not permit a clear definition of the peralka-
line character of these rocks. All analysed samples belong to
the Na-Alkaline series, showing a strong Na signature (AI<
35 %; AI0 Alkali Index [K
2
O/(K
2
O+Na
2
O)]×100; Stewart
and Thornton 1975;D’Amico et al. 1989) for the least evolved
rocks, and a low-K signature (40 %<AI<50.7 %) for the
benmoreiitic, trachytic and rhyolitic rocks. The progressive
K
2
O enrichment in evolved rocks (Fig. 10b) reflects the
kaersutite–kataphorite amphibole in less evolved products
versus Na-sanidine+a northoclase feldspars in the most
evolved samples (Appendix 7a, e). CIPW normative compo-
sitions are characterised by the presence of nepheline (Na-
foid, 0–4.6 %), with leucite always absent (K-foid, 0 %) and
normative quartz <15 % (Q,0–14.6 %) (Appendix 6), high-
lighting the evolutionary trend from silica-undersaturated
(normative nepheline content of 1.4 % at Random Hills,
1.1 % at Markham Island, and 4.6 % at Edmonson Point), to
slightly silica-oversaturated conditions (maximum normative
quartz content of 14.6 % at Mt. Melbourne summit crater
trachytes). The Harker diagrams shown in Fig. 11 illustrate
the linear correlation of major oxides vs. SiO
2
(wt%) [see also
Appendix 8 for selected LILE and HFSE elements abundan-
ces and relative bivariate diagrams vs. SiO
2
(wt%)].
Discussion
This study has generated a new set of stratigraphically linked
geochronology and geochemistry data, which were used to
develop an improved temporal reconstruction of the Mt. Mel-
bourne volcanic field. However, the presence of extensive ice
cover on the volcanic field limits evaluation to scattered out-
crops (Figs. 1 and 2), which places limitations on any com-
prehensive interpretation of the volcano’s evolution. Our data
Fig. 10 a Total alkali-silica diagram (Le Bas et al 1986; Le Bas and
Streckeise n 1991) for samples analysed in this study. RH Random
Hills, HP Harrow Peaks, BR Baker Rock, EP Edmonson Point, MM
Mt. Melbourne, BR pumice layer G62, SN Shield Nunatak, MI OP
Oscar Point/Markham Island, CW Cape Washington, MA Mt. Abbott. b
Classification of the alkali signature of the analysed samples in a K
2
O
vs. Na
2
O wt% diagram
Bull Volcanol

cover most of the existing outcrops, however, and provide the
best available basis for reconstructing the main events in the
evolution of the Mt. Melbourne volcanic field.
Evolution in time and space of the volcanic activity
The only work that has previously attempted to summarise
the volcanological evolution of the Mt. Melbourne volcanic
field is that of Wörner and Viereck (1989). Lacking a
reliable age data set, those authors used the erosional char-
acter, inferences of magma–ice interaction, the available
ages, and the geographic distribution of magma types, to
reconstruct five phases of volcanism: (1) the oldest phase
involved the emplacement of the Washington Ridge (2.6 –
1.7 Ma Kreutzer, 1988, unpublished data) and the Random
Hills monogenetic volcanoes, with magm as belonging to a
basanite-tephrite trend; (2) trachytic xenoliths found in the
Mt. Melbourne pyroclastics were interpreted as belonging to
Fig. 11 Harker diagrams for major oxides vs. SiO
2
wt% and total ferromagnesian vs. alkali ratio diagram
Bull Volcanol

a pre-Older Drift volcanic phase, possibly as old as 2.5 Ma;
(3) the mugearitic lavas at the base of Shield Nunatak
(unconstrained age of 1.55 Ma; Kreutzer, 1988, unpublished
data), along with volcanic centres of Baker Rocks, Edmonson
Point and Oscar Ridge, were interpreted as an “older series”,
also pre-Older Drift; (4) the emergent sub-glacial to sub-aerial
alkali basalts and hawaiites of Shield Nunatak and Oscar
Ridge were attributed to a “younger series” of pre-, syn-
Younger Drift age; (5) finally, the alkali basalt to trachyte
products of Mt. Melbourne were emplaced from an uncon-
strained age up to recent times. Later K-Ar age determinations
by Armienti et al. (1991)indicateda12–3 Ma age range for
the Random Hills monogenetic volcanism, and 0.7–0.4 Ma
for Oscar Point and Shield Nunatak, respectively, the latter
contrasting with the pre-, syn-Younger Drift age suggested by
Wörner and Viereck (1989).
Based on our data, we present a substantially different
reconstruction of Mt. Melbourne volcanic field’s evolution
and suggest that neither the erosional aspect nor the extent
of magma-water(ice) interaction can be used successfully in
this area to constrain the succession of volcanic phases. This
conclusion is based on the following considerations. The
first is that Antarctic glaciers have had very different types
of erosional behaviours over time and location (e.g. Di
Nicola et al. 2009), due to climate changes and local extent
of the ice cover; it is therefore difficult in the Mt. Melbourne
area to use such an approach. Fo r example, the 1,368 ka
scoria cone at Pinkard Table appears almost pristine despite
being much older than the 745 ka lava edifice at Harrow
Peaks (Fig. 8a, b). It is therefore very difficult to use mor-
phology as an indicator of age. Indication of magma–water
(ice) interaction is also not a particula rly reliable procedure
to establish periods when the ice cover was present. Mag-
ma–ice interaction depends on many factors, of which the
ice thickness is only one. Furthermore, in Antarctica, gla-
ciers behave very differently depending on whether they are
from the continental ice sheet, or represent small local
glaciers, as is the case for the Mt. Melbourne area, where
the net accu mulation and mass balance with time varies
locally (Orombelli et al. 1991; Jacobs 1992). Our approach,
therefore, is to use only the observed stratigraphic relation-
ships and the associated age determinations, together with
chemical compo sitions to reconstruct the volcanic evolution
of the region. The evolution of the Mount Melbourne vol-
canic field can be described in three main periods, charac-
terised by distinct volcanic systems and different volcanic
styles (Fig. 12).
Random Hills Period The new
40
Ar/
39
Ar age determina-
tions presented in this paper indicate that the monogenetic
centres belonging to the Local Suite (Random Hills and Mt.
Abbott) are Lower–Middle Pleistocene, and postdate the
emplacement of the Pliocene Cape Washington shield
volcano (Fig. 12a, b). Ages obtained at Pinkard Table and
at Harrows Peaks are 1,368±90 and 745±66 ka, respective-
ly, but distinctly younger than previous K–Ar determina-
tions (Armienti et al. 1991; Appendix 5). It is well known
that the K–Ar dating method has a number of limitations,
particularly an inability to reveal argon loss or gain, and
various analytical issues. The
40
Ar/
39
Ar method largely
overcomes these limitations and usually produces more
precise and accurate age results. In this case, the older K/
Ar dates could be due to the presence of excess argon,
analytical issues or even analysis of different volcanic units.
As Armienti et al. (1991) provide little description of their
samples, sampling localities and analytical methods, it is not
possible to further evaluate the reasons for the discrepanci es.
The small lava volumes and the poorly evolved, mafic
compositions suggest that this dominantly effusive volca-
nism was associated with lithospheric fractures able to tap
small batches of magma from the mantle, as also indicated
by the xenoliths in these rocks (cf. Hornig et al. 1991;
Beccaluva et al. 1991a, b; Wysoczanski an d Gamble
1992). In the Mt. Melbourne area, projection of the main
dextral transcu rrent Priest ly and Campb ell fault syste ms
(Fig. 1), which controlled Cenozoic magmatism across this
part of the Transantarctic belt (Rossetti et al. 2000; Storti et
al. 2006), indicates that active intraplate tectonics may con-
trol local extension, the degree of partial melting, and the
passage of mantle-derived magma throu gh the crust (Rocchi
et al. 2003).
Wörner and Vierec k (1989) document a mugearitic lava
flow at the base of Shield Nunatak, and report an age of
1.55 Ma (Kreutzer, 1988, unpublished report; Table 1). If
the age of this lava flow is correct , then differentiated
magma also erupted during the Random Hills Period.
Shield Nunatak Period Closer to Mt. Melbourne, w e
obtained two imprecise, though consistent, ages for the
monogenetic centre of Shield Nunatak (431±82 ka) and
Markham Island (<400 ka) (Fig. 12c). Previous published
ages for Shield Nunatak are quite disco rdant, ranging from
0.07±0.05 Ma (Kreutzer, 1988, unpublished report quoted
in Wörner and Vierec k 1989) to 0.48±0.24 Ma (Armienti et
al. 1991). The latter result is consistent with our
40
Ar/
39
Ar
ages, whereas the younger age of 0.07±0.05 Ma appears
anomalous. Possible explanatio ns for the young K-Ar age
include analytical issues such as incomplete degassing of
argon, a common problem associated with retentive
feldspar-rich melts. If our older result is correct, it suggests
that, durin g the Middle Pleistocene, the volcanic activity,
whichalsoproducedOscarPoint(0.71±0.18Main
Armienti et al. 1991; Appendix 5) and Baker Rocks (0.74
±0.1;0.2±0.04MainArmstrong19 78; App endix 5),
moved progressively toward the younger centre of volcanic
activity associated with Mt. Melbourne. The magma
Bull Volcanol

chemistry is alkali basaltic for all these centres, indicating
continuity with the previous Random Hill Period.
Mt. Melbourne Period (Fig. 12d) The oldest exposed de-
posit associated with the Mt. Melbourne stratovolcano is the
Fig. 12 Evolution of Mt. Melbourne volcanic field (see text for explanation)
Bull Volcanol

trachytic EPI ignimbrite at Edmonson Point, dated at 123.6±
6.0 ka. Although the restricted exposure of the EPI ignimbrite
limits support for interpretations of the eruption, some can be
made. The first is that the EPI is associated with establishment
of the first crustal magma chamber in this area, where magma
resided for sufficient time to differentiate trachytic composi-
tions. Evidence for this magma chamber is also provided by
the syenitic clasts found as accessory lithics within the ignim-
brite. The second implication of the EPI ignimbrite is that the
trachytic magma was able to produce a large-scale eruption.
All subsequent volcanic activity has been limited to the area
presently occupied by the main stratovolcano, indicating that
the 180 km
3
of products w hich form th e stratovolcano
(Worner and Viereck 1990), were erupted since 123 ka, with
an average output rate of 1.5 km
3
/kyear. The most recent,
Holocene deposits are exposed at the top of Mt. Melbourne,
where the crater rim is composed of trachytic-rhyolitic pumice
fall deposits. Although a precise age was not obtained from
these younger summit samples, our data suggest that these
deposits are very young (50±70 and 35±22 ka), further sug-
gesting growth of the Mt Melbourne stratocone in Upper
Pleistocene–Holocene time (cf. Armstrong 1978).
Magmatic activity of the Mt. Melbourne stratovolcano is
bi-modal (Fig. 10), with dominantly explosive products
from evolved magmas such as trachytes and rhyolites (EPI
ignimbrite and the recent deposits), along with the domi-
nantly effusive eruption of poorly evolved alkali basalts and
hawaiites [ARL, ROL and hawaiite scoria cone (SCC)
Fms.]. The overlapping compositions of the Edmonson
Point trachytes and the Mt.Melbourne summit trachytes
suggest a cyclicity of the basalt-trachyte trend. The Harker
diagrams variations (Fig. 11; Appendix 8), the observed
mineral assemblages and the mineral chemistries (Appendix 7)
suggest that the differentiation trend reflects crystal fraction-
ation from alkali basalts to trachytes/rhyolites.
Size of the most recent explosive eruption at Mt Melbourne
Based on composition, texture and depositional characteris-
tics, we have inferred as correlative the most recent pumice
fall deposit that drapes the Mt. Melbourne summit crater rim
(samples G56 and G79) and the pumice lapilli layer exposed
within the ice cap some 16 km to the NNE (sample G62). With
just two points, we could not produce an isopach map of this
fall deposit. Nevertheless, in view of the extreme limitations
offered by the Antarctic environment and the importance of
making the most out of available data to constrain the size of
the most recent e xplosive eruption at Mt Melbourne, we
propose a line of reasoning, which enables qualitative classi-
fication of this eruption as at least as sub-plinian and probably
Plinian, based on the tentative reconstruction of the column
height able to generate the pumice and lithic grain sizes of
sample G62, at 16 km NNE from crater rim.
Prevailing winds in this part of Northern Victoria Land
are catabatic winds dominantly from the W and subordinate-
ly NW, i.e. from the main Reeves (270°) and Priestly valleys
(330°) (Brom wich et al. 1990; Argentini et al. 1995).
Pumice clasts of G62 do float and density is therefore lower
than 1,000 kg/m
3
. A minimum isopleth area of 100 km
2
can
be approximated by if it is assumed that G62 is along a NNE
axis of maximum dispersal (which is very unlikely consider-
ing the known prevailing wind directions) with a highly
eccentric isopleth (0.9 ratio; nine times longer than wide;
e.g. Carey and Sigurdsson 1987; Pfeiffer et al 2005). Accord-
ing to calculations given in Carey and Sparks 1986, the 1.5-
cm average pumice clast size of G62 can be dispersed by a
column 14 km high. This is also consistent with average lithic
size of 0.5 cm. By taking into account also the 2 cm maximum
pumice clast size and 0.6 cm maximum lithic clast size of
G62, it is possible to infer also a wind velocity of up to 20–
30 m/s. This is a minimum scenario and allows classification
of this eruption as sub-plinian in scale. In a more realistic
scenario, taking into consideration prevailing wind directions
of the region, the G62 deposit would represent the thickness
and grain size of deposits well off-axis within a much larger
isopleth with maximum dispersal toward the east or southeast.
In this case, a much higher eruption column would be inferred
andtheeruptionclassifiedasPlinianinintensityandof
significantly larger magnitude.
Conclusions
We have reconstructed the evolution of the Mt. Melbourne
volcanic area using stratigraphy, petrography and geochemistry,
and age determinations. In summary:
1. Volcanism in the Mt. Melbourne area started during the
Upper Pliocene with formation of the Cape Washington
shield volcano; during the Lower and Middle Pleistocene
(Random Hills Period and Shield Nunatak Period, respec-
tively), volcanism migrated towards the Transantarctic
Mountains, where tens of small, monogenetic scoria cones
and lava flows were emplaced over a wide area likely in
response to active intra-plate tectonics; in this period, the
erupted magmas were predominantly alkali basaltic to
hawaiitic;
2. The Upper Pleistocene–Holocene Mt. Melbourne stra-
tovolcano (<123 ka, Mt. Melbourne Period) is associat-
ed with the establishment of a crustal magma chamber.
Effusive to strombolian eruption styles produced alkali-
basaltic and hawaiitic fissure centres, whereas Plinian
explosive volcanism is associated with trachytic–rhyolitic
compositions, which have also characterised the most
recent activity of the volcano; the average eruption rate
is 1.5 km
3
/ka.
Bull Volcanol

3. Mt. Melbourne must be considered a potentially active
volcano (Nathan and Schulte 1968;LeMasurierand
Thomson 1990). The outlined evolution of the Mt.
Melbourne stratovolcano suggests that intense, poten-
tially Plinian explosive activity is cyclically associated
with the evolution of the magma to volatile-rich trachyt-
ic–rhyolitic compositions. We suggest that the potential
for a renewal of intense explosive activity in the near
future must be considered, given that the last eruptions
were explosive and associated with the most evolved
magma compositions. Although such an eruption may
not directly threaten human populations, it could have
important effects on the local environment, on global
climate (e.g. Sadler and Grattan 1999; Oppenheimer
2003), and on economies in the southern emisphere.
Acknowledgements This work was funded by PNRA 2002–2003
Project 4.4 (coordinator R. Funiciello). The work benefited of com-
ments by J. Gamble and L. Viereck-Gotte on an earlier version and of
anonymous reviewers. We also acknowledge J. White and E. Calder
for the editorial responsibility. GG thanks P. Pertusati, the alpine guides
Palla and Igor and the helicopter pilots Nigel and Steve for the unvalu-
able and precious help in the field.
References
Antonini P, Civetta L, Orsi G, Piccirillo EM, Bellieni G (1994) The
Mount Melbourne and Mount Overlord subprovinces of the
McMurdo Volcanic Group (Northern Victoria Land–Antarctica):
new geochemical and Sr-isotope data. Terra Antarct 1(1):115–119
Argentini S, Del Buono P, Della Vedova AM, Mastrantonio G (1995)
A statistical analysis of wind in TerraNovaBay, Antarctica, for the
austral summers 1988 and 1989. Atmos Res 39(1–3):145–156
Armienti P, Tripodo A (1991) Petrologicaphy and chemistry of lavas
and comagmatic xenoliths of Mt. Rittmann, a volcano discovered
during the IV Italian Expedition in Northern Victoria Land
(Antarctica). Mem Soc Geol Ital 46:427–452
Armienti P, Civetta L, Innocenti F, Manetti P, Tripodo A, Villari L, De
Vita G (1991) New petrological and geochemical data on Mt.
Melbourne volcanic Field, Northern Victoria Land Antarctica (II
Italian Antarctic Expedition). Mem Soc Geol Ital 46:397–424
Armstrong RL (1978) K-Ar dating: Late Cenozoic McMurdo Volcanic
Group and dry valley glacial history, Victoria Land, Antarctica:
New Zealand. J Geol Geophys 21:685–698
Baroni C, Orombelli G (1994) Abandoned penguin rookeries as Ho-
locene paleoclimatic indicators in Antarctica. Geology 22(1):23–
26
Beccaluva L, Coltorti M, Orsi G, Saccani A, Siena F (1991a) Nature
and evolution of the sub-continental litospheric mantle of Antarc-
tica: evidence from ultramafic xenoliths of the Melbourne Volca-
nic Province (Northern Victoria Land, Antarctica). Mem Soc Geol
Ital 46:353–370
Beccaluva L, Civetta L, Coltorti M, Orsi G, Saccani E, Siena F (1991b)
Basanite to tephrite lavas from Melbourne Volcanic Provin ce,
Victoria Land, Antarctica. Mem Soc Geol Ital 46:383–395
Behrendt JC (1999) Crustal and lithospheric structure of the West
Antarctic Rift System from geophysical investigations—a review.
Glob Planet Chang 23:25–44
Bellieni G, Justin Visentin E, Le Maitre RW, Piccirillo EM and Zanettin B
(1983) Proposal for a division of the basaltic (B) field of the TAS
diagram. IUGS subcommission on the Syste matics of Igneous
Rocks. Circular no.38, Contribution no.102
Bonnefoi CC, Provost A, Albarède F (1995) The “Daly gap” as a
magmatic catastrophe. Nature 378:270–272
Brandelik A (2009) CALCMIN—an EXCEL™ Visual Basic applica-
tion for calculating mineral st ructural formulae from electron
microprobe analyses. Comput Geosci 35:1540–1551
Branney MJ and Kokelaar P (2002) Pyroclastic density currents and
the sedimentation of ignimbrites. In: Branney M.J. & Kokelaar:
(eds) Pyroclastic density currents and the sedimentation of ignim-
brite Geol Soc Mem 27: 1–138
Bromwich DH, Parish TR, Zorman CA (1990) The confluence zone of
intense catabatic winds at Terra Nova Bay, Antarctica, as derived
from airborne Sastrugi surveys and mesoscale numerical model-
ing. J Geophys Res 95:5495–5509
Carey S, Sigurdsson H (1987) The eruption of Vesuvius in A.D. 79: II.
Variation in column height and discharge rate. Geol Soc Am Bull
99(2):303–314
Carey S, Sparks RSJ (1986) Quantitative models of the fallout and
dispersal of tephra from volcanic eruption columns. Bull Volcanol
48:109–125
Cas RAF (1992) Submarine volcanism: eruption styles, products, and
relevance to understanding the host rock successions to volcanic-
hosted massive sulfide deposits. Econ Geol 87(511):541
Cas RAF, Wright JV (1987) Volcanic successions: modern and ancient.
Chapman & Hall, London, p 528
Cremisini C, Gianelli G, Mussi M, Torcini S (1991) Geochemistry and isotope
chemistry of surface waters and geothermal manifestations at T erra Nova
Bay (V ictoria Land, antartica). Mem Soc Geol Ital 46:463–475
D’Amico C, Innocenti F and Sassi FP (1989) Magmatismo e
Metamorfismo, Utet, 536p
Di Nicola L, Strasky S, Schlüchter C, Salvatore MC, Akçar N, Kubik
PW, Christl M, Kasper HU, Wieler R, Baroni C (2009) Multiple
cosmogenic nuclides document complex Pleistocene exposure
histo ry of glacial drifts in Ter ra Nova Bay (northern Victoria
Land, Antarctica). Quat Res 71:83–92
Dunbar NW, McIntosh WC, Esser RP (2008) Physical setting and
tephrochronology of the summit caldera ice record at Mount
Moulton, West Antarctica. Geo l Soc Am Bull 120:796–812.
doi:10.1130/B26140.1
Fitzgerald PG, Sandford M, Barrett PJ, Gleadow AJW (1987) Asym-
metric extension assoc iated with uplift and subsidence in the
Transantarctic Mo untains and Ross Embayment. Earth Planet
Sci Lett 81:67–78
Harrington HJ (1958) Nomenclature of rock units in the Ross Sea
Region, Antarctica. Nature 182(4631):290
Hornig I, Wörner G, Zipfel J (1991) Lower crustal and mantle xen-
oliths from the Mt. Melbourne Volcanic Field, Northern Victoria
Land, Antarctica. Mem Soc Geol Ital 46:337–352
Irvine TN, Baragar WRA (1971) A guide to the chemical classification
of the common volcanic rocks. Can J Earth Sci 8:523–548
Jacobs SS (1992) Is the Antarctic sheet growing? Nature 360:29–33
Keys JR, McIntosh WC, Kyle PR (1983) Volcanic activity of Mount
Melbourne, Northern Victoria Land. Antarct J US 18:10–11
Kuno H (1966) Lateral variation of basalt magma types across conti-
nental margins and island arcs. Bull Volcanol 29:195–222
Kyle PR (1990a) Melbourne Volcanic Province. In: LeMasurier WE
and Thmson JW (eds), 1990. Volcanoes of the Antarctic plate and
southern oceans. Am Geophys Union, Antarct Res Series 48: 48–
52
Kyle PR (1990b) McMurdo Volcanic Group, Western Ross Embay-
ment. In: LeMasurier WE and Thmson JW (eds), 1990. Volcanoes
of the Antarctic Plate and Southern Oceans. Am Geophys Union,
Antarct Res Series 48: 19–145
Bull Volcanol

Kyle PR, Cole JW (1974) Strucutral controls of volcanism in the
McMurdo volcanic Group, McMurdo Sou nd, Antarctica. Bull
Volcanol 38:16–35
Lanzafame G, Villari L (1991) Structural evolution and volcanism in
Northern Victoria Land (Antarctica): data from Mt. Melbourne–Mt.
Overlord–Malta Plateau Region. Mem Soc Geol Ital 46:371–381
Le Bas MJ, Streckeisen A (1991) The IUGS systematics of igneous
rocks. J Geol Soc Lond 148:825–833
Le Bas MJ, LeMaitre RW, Streckeisen A, Zanettin B (1986) A chem-
ical classification of volcanic rocks based on the total alkali-silica
diagram. J Petrol 27:745–750
LeMaitre RW (ed) (2002) Igneous rocks: a classification and glossary
of terms: recommendations of the International Union of Geolog-
ical Sciences. Subcommission on the Systematics of Igneous
Rocks. Cambridge University Press, Cambridge
LeMasurier WE and Thomson JW (eds) (1990) Volcanoes of the
Antarctic plate and southern oceans. Am Geophys Union, Antarct
Res Series 48:512
Lesti C, Giordano G, Salvini F, Cas R (2008) Volcano tectonic setting
of the intraplate, Pliocene–Holocene, Newer Volcanic Province
(southeast Australia): role of crustal fracture zones. J Geophys
Res 113:B07407. doi:10.1029/2007JB005110
Lyon GL (1986) Stable isotope stratigraphy of ice cores and the age of
the last eruption at Mt.Melbourne, Antarctica. NZJ Geol Geophys
29(1):135–138
Ly on GL, Giggenbach WF (1974) Geothermal activity in Victoria
Land, Antarctica. NZ J Geol Geophys 17:511–521
Martin A, Cooper A, Dunlap W (2010) Geochronology of Mount Morning,
Antarctica: two-phase evolution of a long-lived trachyte–basanite–
phonolite eruptive center. Bull Volcanol 72(3):357–371
Matchan E, Phillips D (2011) New 40Ar/39Ar ages for selected young
(<1 Ma) basalt flows of the Newer Volcanic Province, southeast-
ern Australia. Quat Geochronol 6:356–358
McPhie J, Doyle M and Allen R (1993) Volcanic textures: a g uide
to the interpretation of textures in volcanic rocks. Cent re for
Ore Deposit and Exploration Studies, University o f Ta smania,
198 p
Min K, Mundil R, Renne PR, Ludwig KR (2000) A test for systematic
errors in 40Ar/39Ar geochronology through comparison with U–
Pb analysis of a 1.1 Ga rhyolite. Geochim Cosmochim Acta
64:73–98
Müller P, Schmidt-Thome M, Kreuzer H, Tessensohn F, Vetter U
(1991) Cenozoic Peralkaline magmatism at the western margin
of the Ross Sea, Antarctica. Mem Soc Geol Ital 46:315–336
Nathan S, Schulte FJ (1967) Recent thermal and volcanic activity on
the Mt. Melbourne, Northern Victoria Land, Antarct ica. NZ J
Geol Geophys 10:422–430
Nathan S, Schulte FJ (1968) Geology and petrology of the Campbell–
Aviator Divide, Northern Victoria Land, Antarctica. Part I: Post
Paleozoic rocks. NZ J Geol Geophys 11:940–975
Oppenheimer C (2003) Climatic, environmental and human conse-
quences of the largest known historic eruption: Tambora volcano
(Indonesia) 1815. Prog Phys Geogr 27:230–259
Orombelli G, Baroni C, Denton GH (1991) Late Cenozoic galcial
history of the Terra Nova Bay region, Northern Victoria Land,
Antarctica. Geogr Fis Dinamica Quaternaria 13:139–163
Pfeiffer T, Costa A, Macedonio G (2005) A model for the numerical
simulation of tephra fall deposits. J Volcanol Geotherm Res
140:273–294
Phillips G, Wilson CJL, Phillips D, Szczepanski S (2007) Thermo-
chronological (40Ar/39Ar) evidence for Early Palaeozoic basin
inversion within the southern Prin ce Charles Mountains, East
Antarctica: implications for East Gondwana. J Geol Soc
164:771–784
Renne PR, Swisher CC, Deino AL, Karner DB, Owens TL, DePaolo
DJ (1998) Intercalibration of standards, absolute ages and uncer-
tainties in 40Ar/39Ar dating. Chem Geol 145:117–152
Renne PR, Mundil R, Balco G and Min K (2009) Simultaneous
determination of 40 K decay constants and age of the Fish Canyon
sanidine 40Ar/39Ar standard. GSA Annual Meeting, Portland,
abstract 160–3
Rocchi S, Storti F, Di Vincenzo G, and Rossetti F (2003) Intraplate
strike-slip tectonics as an alternative to mantle plume activity for
the Cenozoic rift magmatism in the Ross Sea region, Antarctica:
in Storti, F, Holdsworth, R.E. and Salvini, F. (eds), Intraplate
Strike-Slip Deformation Belts, Geol Soc London, Special Publi-
cation 210: 145–158
Rossetti F, Storti F, Salvini F (2000) Cenozoic non-coaxial transtension
along the western shoulder of the Ross Sea, Antarctica, and the
emplacement of McMurdo dyke arrays. Terra Nova 12:60–66
Sadler J, Grattan JP (1999) Volcanoes as agents of past environmental
change. Glob Planet Chang 21:181–196
Salvini F, Brancolini G, Busetti M, Storti F, Mazzarini F, Coren F
(1997) Cenozoic geodynamics of the Ross Sea Region, Antarc-
tica: crustal extension, intraplate strike-slip faulting and tectonic
inheritance. J Geophys Res 102:24669–24696
Smellie JL, Chapman MG (2002) Volcano–ice interaction on Earth and
Mars. Geol Soc Lond 202:437, Special Publication
Steiger RH, Jager E (1977) Subcommission on geochronology: con-
vention on the use of decay constants in geo- and cosmochronol-
ogy. Earth Planet Sci Lett 36:359–362
Stewart DC, Thornton CP (1975) Andesites in oceanic regions. Geology
3:565–568
Storti F, Rossetti F, Laufer AL, Salvini F (2006) Consistent kinematic
architecture in the damage zones of intraplate strike–slip fault
systems in North Victoria Land, Antarctica and implications for
fault zone evolution. J Struct Geol 28:50–63
Wilch TI, McIntosh WC, Dunbar NW (1999) Late Quaternary volcanic
activity in Marie Byrd Land:Poten tial 40 Ar/39Ar-dated time
horizons in West Antarctic ice and marine cores. Geol Soc Am
Bull 111(10):1563–1580
Wörner G, Orsi G (1990) Volcanic geology of Edmonson Point, Mt.
Melbourne Volcanic Field, North Victoria Land, Antarctica.
Polarforschung 60(2):84–86
Wörner G, Viereck L (1989) The Mt. Melbourne volcanic field
(Victoria Land, Antarctica). I Fie ld observations. Geol Jahrb
E38:369–393
Worner G and Viereck L (1990) Mount Melbourne. In: LeMasurier
WE and Thmson JW (eds), 1990, Volcanoes of the Antarctic Plate
and Southern Oceans. Am Geophys Union, Antarct Res Series 48:
72–78
Wörner G, Viereck L, Hertogen J, Niephaus H (1989) The Mt. Mel-
bourne Field (Victoria Land, Antarctica) II. Geochemistry and
magma genesis. Geol Jahrb E38:395–433
Wysoczanski RJ, Gamble JA (1992) Xenoliths from the Volcanic
Province o f West Antarctica and implications for lithospheric
structure and processes. In: Yoshida Y, Kaminuma K, Shiraishi
K (eds) Recent progress in Antarctic Earth Science. Terra Science
Publication, Tokyo, pp 273–277
Yavuz F (2007) WinAmphcal: a Windows program for the IMA-04
amphibole classification. Geochem Geophys Geosyst 8:Q01004.
doi:10.1029/2006GC001391
Bull Volcanol