Bull Volcanol (2015) 77:80
DOI 10.1007/s00445-015-0968-1
RESEARCH ARTICLE
Tavui Volcano: neighbour of Rabaul and likely source
of the Middle Holocene penultimate major eruption
in the Rabaul area
Chris O. McKee 1
Received: 23 March 2015 / Accepted: 11 August 2015
# Springer-Verlag Berlin Heidelberg 2015
Abstract A major, geologically youthful, submarine caldera
volcano, Tavui, was discovered in the Rabaul area of Papua
New Guinea in 1986. Tavui Volcano has lateral dimensions of
9 to 10 km, slightly smaller than those of Rabaul Volcano, but
Tavui’s caldera is much deeper than the nested caldera complex at Rabaul, and in general, its escarpment walls are very
steep. The two caldera systems are essentially silicic and are
separated by a zone of dominantly basalt-andesite stratovolcanoes. Rock samples dredged from Tavui have low- to
medium-K contents, in contrast to the medium- to high-K
rocks of Rabaul, indicating that the two systems have evolved
separately and that the chemical, and perhaps physical, conditions within these neighbouring systems are different. Tavui is
the likely source of the 6.9 ka BP Raluan Ignimbrite, the
penultimate major eruption deposit in the Rabaul area. The
Raluan Ignimbrite is rhyolitic and has geochemical characteristics incompatible with those of products from Rabaul Volcano. On the other hand, there is a close match between the
geochemistry of the Raluan Ignimbrite and that of rhyolitic
samples dredged from Tavui Caldera. The much older
(≈79 ka) Tokudukudu Ignimbrite, which is also rhyolitic, is
slightly more K-rich than both the Raluan Ignimbrite and rhyolites dredged from Tavui Caldera, but in general, its geochemical characteristics are similar to those of Tavui rhyolites
and, therefore, is considered to be a possible product of Tavui.
The recognition that Tavui was the likely source of the penultimate major eruption and of at least one other significant
Editorial responsibility: M.L. Coombs
* Chris O. McKee
[email protected]
1
Port Moresby Geophysical Observatory, P.O. Box 323, Port
Moresby, NCD, Papua New Guinea
eruption in the Rabaul area markedly changes the perceptions
of local volcanic hazard. In addition, Tavui’s potential for
generation of tsunami is acknowledged, not just in association
with volcanic eruptions but also from earthquake-related and
possibly spontaneous collapse of parts of the steep caldera
walls. The presence of Tavui greatly increases the net geologic
hazard in the Rabaul area.
Keywords Caldera . Rabaul area . Tavui . Papua New Guinea
Introduction
The Rabaul area of New Britain Island, Papua New Guinea, is
known for the fatal and devastating volcanic eruptions of 1937
(Fisher 1939; Johnson and Threlfall 1985) and those of 1994
(GVN 1994; Blong and McKee 1995; Johnson et al. 1996).
Because of these and other local historical eruptions, most
geo-scientific attention at Rabaul has been directed at monitoring the obvious threats from the volcanoes Tavurvur, Vulcan and other centres within the Rabaul Caldera Complex.
However, the discovery in 1986 of a second major potentially
active caldera volcano in the Rabaul area generated a new
focus of interest. The limited information about the products
and eruptive history of Rabaul’s near neighbour, named Tavui
(Fig. 1), is raising new and intriguing questions about volcanism and geologic hazards in the Rabaul area.
Geological mapping in the Rabaul area in 1985–1986
(Nairn et al. 1989, 1995) indicated a long and complicated
eruptive history of the Rabaul Caldera Complex and revealed
the existence of two other Quaternary (but probably extinct)
volcanic systems immediately south of Rabaul. These structures are now known to be part of an approximately linear
array of major volcanic centres extending from the central part
of the Gazelle Peninsula to its northern tip. The same
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Bull Volcanol (2015) 77:80
Page 2 of 21
Fig. 1 Locations of the Tavui and
Rabaul volcanic systems at the
northeastern tip of the Gazelle
Peninsula, New Britain Island,
Papua New Guinea. Other major
volcanoes on New Britain are
shown also
150º
152º
Tavui
4º
Bismarck
Sea
Rabaul
GAZELLE
PENINSULA
Dakataua
Ulawun
Bamus
Langila
Hargy
Witori
NEW BRITAIN
6º
Solomon Sea
PACIFIC
OCEAN
PAPUA
NEW
GUINEA
0
100 km
AUSTRALIA
geological mapping also drew attention to a prominent fault
scarp, the ‘Tavui Fault’ (Nairn et al. 1989, 1995; named from
the local community), forming part of the coast immediately
north of the Rabaul Complex and suggesting large-scale collapse in that area (Fig. 2). Such catastrophic activity was confirmed coincidentally during the 1985–1986 Manus Basin
(Bismarck Sea) cruise of RV Moana Wave (Tiffin et al.
1986) with the discovery of a large, mostly submerged caldera
structure abutting the northeastern flank of Tovanumbatir, the
major stratovolcano immediately north of the Rabaul Complex (Fig. 2). That submerged caldera, the margin of which
includes the Tavui Fault, was given the name Tavui Caldera. It
has been recognised to be part of a large volcanic system now
known as Tavui Volcano.
The discovery of the Tavui centre triggered a search for its
eruptive products. Previously, all known eruption deposits in
the area were assumed to have originated from the Rabaul
Complex. This includes two rhyolitic units, the Raluan Ignimbrite and the Tokudukudu Ignimbrite, despite both having
anomalous geochemical features compared to other rocks in
the Rabaul area, including low-K and high-SiO2 contents.
Later marine surveys in the Manus Basin provided additional details of the Tavui edifice. In 1990, part of the Sonne
68-OLGA II survey targeted Tavui Caldera and included
SeaBeam mapping, multi-level water sampling and dredge
sampling (Tiffin et al. 1990; Tufar 1990; Tufar and Naser
1992; Wallace and Tufar 1998). The main features revealed
by the SeaBeam mapping were the steep, smooth, planar
scarps that make up the caldera wall; a large truncated cone
that constitutes the northern part of the Tavui edifice; and two
apparently youthful post-caldera cones in the northern and
eastern parts of the caldera. Rock samples dredged from the
caldera provided, for the first time, some insights into the
geochemistry of Tavui eruptives. The geochemical characteristics of those samples, notably low-K contents and some
having high SiO2 contents, provided the first clues to the origin of the Raluan Ignimbrite and the Tokudukudu Ignimbrite.
The cruise of RV Melville in 2006 (Tivey et al. 2006), also
using SeaBeam, revealed details of the flanks of Tavui Volcano: the main feature is an extensive apron of deposits including areas showing a series of arcuate terraces.
On-shore fieldwork at various locations including immediately southwest of Tavui Caldera, within Rabaul Caldera, on
the southern and southwestern flanks of the Rabaul shield, at
the Duke of York Islands about 25 km east of Rabaul, and at
Watom Island about 13 km northwest of Rabaul, was conducted intermittently by the author over a period of several years.
The results of that work provided additional details on the
nature of rock units attributed to Tavui and clarified stratigraphic relationships within the tephra sequence in the Rabaul
area.
This paper presents a compilation of all available information on the structure, products, rock chemistry and eruptive
history of Tavui Volcano. All available information on the
Raluan Ignimbrite and Tokudukudu Ignimbrite is provided
also. Relevant background information on Tavui’s nearest
neighbour, the Rabaul Caldera Complex, is presented in order
to demonstrate the chemical differences between rocks of the
Tavui and Rabaul systems, and to show the intertwining of the
eruptive histories of the two systems.
Bull Volcanol (2015) 77:80
Fig. 2 Topography and
bathymetry of the Rabaul-Tavui
area, modified after Figure 13 of
Johnson et al. (2010). Triangles
represent conical volcanic centres
within Rabaul Caldera (solid) and
within the W-T Zone (open).
Solid curves and the ellipse
represent the nesting of caldera
rims of the Rabaul Volcanic
Complex. Parallel northwesttrending lines mark the W-T Zone
of mafic stratovolcanoes. Tavui
Fault is shown marking part of the
southwestern boundary of Tavui
Caldera
Page 3 of 21 80
4°05'
Watom
Watom Island
Island
W
W
Tavui
Tavui
Fault
Fault
TAVUI
TAVUI
-- TT
ZZO
ONN
EE
4°10'
Tovanumbatir
Tovanumbatir
Sulphur Creek
Creek
Sulphur
Palangiangia
Palangiangia
Kabiu
Kabiu
Tavurvur
Tavurvur
Rabalanakaia
Rabalanakaia
4°15'
RABAUL
RABAUL
Vulcan
Vulcan
0
Karavia Bay
Bay
Karavia
5 Km
152°10'
Geological background
Rabaul Caldera Complex
The main topographic features at Rabaul are a largely seafilled caldera which measures 14×9 km and the dominantly
basalt-andesite stratovolcanoes Watom, Tovanumbatir, Kabiu,
Palangiangia and Turagunan, which occupy a broad corridor,
the Watom to Turagunan (W-T) Zone (Johnson et al. 2010),
trending at 310° across the northern to northeastern flank of
the Rabaul Caldera Complex (Fig. 2). The principal intracaldera volcanoes are Vulcan, Tavurvur, Rabalanakaia, Sulphur Creek, Dawapia Rocks and a group of submarine cones,
the Karavia Bay Group, in the southern part of the caldera.
The sequence of major explosive eruptions associated with
episodes of caldera formation at the Rabaul Caldera Complex
is still poorly known, owing mainly to poor exposure, but
extends back in time at least 160 ky (McKee and Duncan,
unpublished data, 2015). The total number of major
ignimbrite-producing eruptions is at least 12, and 4 of these
occurred during the last 18 ky: Kulau Ignimbrite, Namale
Pyroclastics, Vunabugbug Pyroclastics and Rabaul Pyroclastics (Nairn et al. 1989, 1995). The products of these eruptions
Turagunan
Turagunan
152°15'
are mainly dacitic. The most recent of the major eruptions at
Rabaul emplaced the 1.4-ka BP Rabaul Pyroclastics (Heming
1974; Nairn et al. 1989, 1995), which includes the low aspect
ratio Rabaul Ignimbrite (Walker et al. 1980, 1981b). The age
of this eruption has been revised to AD 667–699 using
wiggle-match 14C dating (McKee et al. 2015).
The Raluan Pyroclastics (named by Nairn et al. 1989) are
the deposits of the next youngest, or ‘penultimate’, major
eruptive sequence exposed in the Rabaul area (see below).
These deposits have been regarded as products of the Rabaul
Caldera Complex (Heming 1974; Heming and Carmichael
1973; Walker et al. 1981b; Nairn et al. 1989, 1995; Wood
et al. 1995), but data presented here indicate that at least part
of the Raluan Pyroclastics probably originated from Tavui
Volcano.
Tavui Volcano
The mostly submarine Tavui Volcano appears to be somewhat
smaller and less complex than its southern neighbour, yet it
possesses a number of impressive features including a welldefined caldera and an extensive apron of deposits on its
flanks (Fig. 3).
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Page 4 of 21
Bull Volcanol (2015) 77:80
Fig. 3 SeaBeam map of the Tavui area (Tivey et al. 2006), showing an
extensive area of seafloor interpreted as an apron of tephra deposits on the
northern and western flanks of Tavui Volcano. Bold broken red lines mark
the boundaries of three units, A, B and C, interpreted to be tephra
deposits. The lobate unit A is closely linked to Tavui, whereas units B
and C may have contributions from both Rabaul and Tavui centres.
Arcuate terraces, thought to be products of flowage, are best developed
along the north-trending axis of unit A. A prominent conical feature (V)
about 40 km north of Tavui Caldera is interpreted to be an active volcanic
cone. North of the interpreted tephra field is the northeast-trending fabric
of back-arc volcanism near and at the margin of the South Bismarck plate.
The SeaBeam data is from the RV Melville cruise (MGLN06MV) of
2006 which used a SeaBeam 2000 system with a 120° swath and 121
beams (Tivey et al. 2006). Vertical resolution of the SeaBeam data is
about 5 m, while lateral resolution, which is a function of the grid cell
size, is 100 m (Tivey, personal communication, 2015). The contour
interval is 20 m
Caldera
southwestern part of the floor of Tavui Caldera lies about
1100 m below sea level. This compares with a maximum
water depth in Rabaul Caldera of about 300 m. The greater
depth of Tavui Caldera in its southwestern sector, bordered on
three sides by steep, smooth, planar scarps, the most extensive
of which is the southwestern scarp, may be a result of trapdoor collapse opening in the southwest.
The floor of Tavui Caldera is dominated by a large cone,
4.5 km wide and 750 m high, which occupies the northern
sector, and a smaller cone, 1.5 km wide and 200 m high, in the
eastern corner of the caldera (Fig. 4). The larger intra-caldera
Tavui Caldera is approximately square or rhombic in plan
view, having sides about 9–10 km long oriented approximately northwest and northeast (Fig. 4). The rectilinear outline of
Tavui Caldera may indicate a tectonic influence on caldera
development as the orientations of the caldera walls parallel
the common northwest and northeast regional structural trends
(Lindley 1988; Nairn et al. 1989, 1995). While Tavui Caldera
is only slightly smaller in area than Rabaul Caldera, it is much
deeper (Figs. 2, 3 and 4). The featureless central and
Bull Volcanol (2015) 77:80
Page 5 of 21 80
Fig. 4 Detailed bathymetry of Tavui Caldera (from SeaBeam data) and
topography of the northern flank of Tovanumbatir Volcano, modified
after Tufar (1990) by Brian Taylor. Note the mostly steep, smooth,
planar caldera walls. Two intra-caldera cones occupy the northern and
eastern parts of the caldera. The highest part of the caldera rim (about
20 m below sea level) is the summit of a large cone which forms the
northern upper flank of the Tavui edifice. Solid bars mark sites of dredge
sampling during the Sonne 68-OLGA II research cruise in 1990 (Tufar
1990). The SeaBeam data (from the same cruise in 1990) was generated
from a system having 90° swath and using 16 beams per ping (Tivey,
personal communication, 2015). Estimated vertical resolution of the
SeaBeam data is about 10 m. The contour interval is generally 50 m,
but in places, the interval is 25 m
cone is grossly asymmetrical, having an extensive southwestern flank, while development of its northern to eastern flank
has been severely restricted by the proximity of the northeastern wall of the caldera. The arcuate ridge that forms the cone’s
summit opens to the southwest into a shallow, smooth-
surfaced depression on the upper southwestern flank of the
cone. These features indicate collapse of this part of the cone.
The apparent smoothness of the upper southwestern flank of
the cone may reflect post-collapse mantling with tephra. The
lower western to southern flank of the cone also has smooth
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Bull Volcanol (2015) 77:80
Page 6 of 21
slopes. The smaller intra-caldera cone is also asymmetrical,
having a more extensive southwestern flank. The unmodified
slopes and the preservation of a broad (300×400 m) slightly
eccentric summit crater indicate that this cone is youthful.
cone has been truncated by an east-northeast-trending channel
about 1 km wide. The upper part of this channel has breached
the northeastern rim of Tavui Caldera and appears to be incising the northeastern flank of the large intra-caldera cone.
Deposit apron and flanks
Tavui Fault
SeaBeam mapping in the vicinity of Tavui (Tivey et al. 2006)
is incomplete but appears to show a coherent, 18-km-long
lobate deposit on the northern and western flanks of the Tavui
edifice (marked by boundary A in Fig. 3). The generally
smooth surface of the northern part of this deposit is punctuated by a series of discontinuous, irregularly arcuate, northfacing escarpments as much as 100 m high. This topography
has the appearance of a set of large-scale ripples or terraces.
The deposit extends for only 6 km on the western flank of
Tavui where topography is quite rugged, including steep-sided
radial ridges and channels and several depressions 1–2 km
across, with suggestions of the same large-scale ripples or
terraces that are present on the northern flank. Emplacement
of this deposit appears to be by flowage processes, probably in
relation to a large-scale eruption.
The lower northwestern flank of the Tavui edifice has rugged terrain which is also terraced or rippled but, in addition,
displays hummocks and depressions (marked by boundary B
in Fig. 3). Elsewhere in this region, a broad field of cover
deposits (marked by boundary C in Fig. 3), probably originating mainly from Rabaul Volcano, extends over the sea floor to
about 40–50 km north of the Gazelle Peninsula. Near the
northern margin of this cover deposit field, about 40 km north
of Tavui, is a steep conical feature having basal dimensions of
about 5×3.5 km and standing about 540 m above the sea floor
(marked by V in Fig. 3). This feature appears to be a youthful
volcano. Seismic activity about 50 km north of Rabaul in
October 1994 (Stewart and Itikarai, unpublished data, 1996)
may have originated from this cone. Further north and northwest, the topographic fabric has a strong northeast trend, controlled by processes related to rifting near the local margin of
the South Bismarck Plate.
A large part of the upper western to northwestern flank of
the Tavui edifice shows rough topography which includes a
broad (3–4 km wide) channel extending to the northwest
(Fig. 4). In contrast, the upper southeastern flank of the edifice
has relatively smooth slopes. Several prominences along the
northwestern and southeastern parts of the caldera rim have a
common elevation about 800 m above the floor of the caldera
(and about 300 m below sea level).
The upper northern flank of Tavui Volcano is dominated by
a large cone about 6 km in diameter and about 1000 m high
(Fig. 4). The summit of this cone reaches to within about 20 m
of the sea surface. The southern to southwestern flank of this
cone is missing, presumably engulfed during one or more
caldera-forming events. The lower southeastern flank of this
The only subaerial part of Tavui Volcano is the upper southwestern wall of its caldera, mapped as the Tavui Fault (Fig. 2).
The somewhat irregular face of the on-shore part of the fault,
indented towards the southwest in contrast to the smooth planar surface of the submarine part of the fault, probably is a
function of slumping and erosional retreat. Exposures in the
Tavui Fault scarp include Rabaul-sourced rocks, two rhyolitic
units believed to be from Tavui, other units which could be
from Tavui but which currently are of unknown origin and the
Tavui Limestones.
The presence of the Late Pleistocene Tavui Limestones
formation in the escarpment of the Tavui Fault and in a
slumped block adjacent to the fault (Nairn et al. 1989, 1995)
has important implications for ground movements in the local
area. According to Nairn et al. (1989, 1995) the 10–25-mthick Tavui Limestones were formed in the time interval
268–85 ka (based on nanofossil data), possibly during the last
interglacial high sea level stand at 125 ka, although the top of
the formation at one locality near Tavui Point has a 14C date of
46.3±1.2 ka (University of Waikato, WK-28956). Of critical
importance is the observation that the limestones directly
overlie subaerially deposited tephra with only slight unconformity at the contact. This relationship implies very rapid submergence to water depths of at least 25 m, sufficient to allow
growth of 10–25 m of clean coral. The present position of the
top of the limestone formation, 30–40 m above sea level,
indicates subsequent relative uplift of about 40 m.
These large-scale ground movements may be related to
caldera developments and to resurgence driven by magma intrusion.
Rhyolitic rocks in the Rabaul area
Rhyolitic rocks are rare in the stratigraphic sequence of the Rabaul area. Only two subaerially outcropping rhyolitic rock units
are known: the Raluan Ignimbrite and the Tokudukudu
Ignimbrite.
Raluan Ignimbrite
Stratigraphic context and characteristics
Raluan Ignimbrite is a low aspect ratio, large-volume pyroclastic flow deposit (at least 4 km3, see discussion in the “Volcanic hazard” section), having widespread but patchy
Bull Volcanol (2015) 77:80
distribution in the Rabaul area (Walker et al. 1981b; Nairn
et al. 1989). This ignimbrite is one of two components of the
Raluan Pyroclastics (Nairn et al. 1989, 1995). The other
(underlying) component is a basaltic scoria fall deposit, the
Raluan Scoria, the volume of which has been estimated to be
as much as 0.5 km3 (Walker et al. 1981b). Initial investigations
(Walker et al. 1981b) and the results of the geological mapping programme of 1985–1986 (Nairn et al. 1989, 1995) suggested that there was no appreciable time interval between the
sequential eruptions of the scoria followed by the ignimbrite
as no weathering break or palaeosol was seen in conformable
contacts. The stratigraphic contact between the two components is indeed mostly conformable, except where the passage
of the ignimbrite has eroded the underlying scoria. This erosional process may account for localised incorporation of scoria fragments into the ignimbrite. The stratigraphic position of
this pair of deposits, below the sequence formed by the large
volume 1.4-ka Rabaul Pyroclastics deposits and the smaller
scale Rabaul-sourced 4.2–1.4-ka Talili Pyroclastics Subgroup
deposits (Nairn et al. 1989, 1995; McKee unpublished data,
2015), and the apparently close temporal relationship between the basaltic scoria and the rhyolitic ignimbrite led
to the concept that together, as the Raluan Pyroclastics,
they represent deposits of the penultimate major eruption of Rabaul Volcano (Walker et al. 1981b). However,
it is now believed that the scoria and the ignimbrite had
separate sources (see below), signifying that the Raluan
Scoria would not qualify as a plinian accompaniment to
the Raluan Ignimbrite.
Raluan Ignimbrite is unusual in the context of other major
eruption deposits in the Rabaul area in that it appears to lack
an underlying plinian fall phase. However, it is possible that a
fall phase was generated but that deposition took place over
the sea (mainly to the north) and so is not represented in any
on-shore areas. The total absence of rhyolitic fall components
would indicate fundamental differences between the mode of
eruption of Raluan Ignimbrite and that of the deposits of other
major eruptions in the Rabaul area. The aspect ratio of Raluan
Ignimbrite appears to be even lower than that of Rabaul Ignimbrite which is regarded as a type example (Walker et al.
1980), and the absence of any part of the flow deposit thicker
than 6 m is reminiscent of the thinly deposited flow phase of
the 6-ka BP Koya eruption (Ui 1973) believed to be from
Kikai Volcano, Japan (Ui et al. 1984; Walker et al. 1984).
Other distinguishing characteristics of Raluan Ignimbrite are
that it contains accretionary lapilli, as much as 3 cm in size,
and fragments of coral, while charcoal appears to be absent.
Wavy and contorted colour bands, which are more common in
distal exposures, appear to be the effects of water staining and
may be evidence that the deposit was wet at the time of emplacement. These characteristics, particularly the apparent absence of an underlying plinian deposit and the incorporation
of coral fragments, are interpreted as being consistent with a
Page 7 of 21 80
submarine source for the Raluan Ignimbrite (see BVolcanic
hazard^ section for further discussion).
Wallace et al. (2002) reported the discovery of low-K rhyolitic glass fragments in part of the Raluan Scoria at one location in the northeastern part of Rabaul Caldera. The glass was
reported to be identical in all respects to Raluan Ignimbrite
glass and led Wallace et al. (2002) to conclude that the basaltic
and rhyolitic magmas had interacted. This finding was used by
Johnson et al. (2010) to support the proposal that the rhyolite
of the Raluan Pyroclastics was erupted from the same vent as
that of the scoria (Walker et al. 1981b). However, there are
concerns now that part of this scoria sampling site may have
been contaminated by rhyolitic material falling from the overlying body of Raluan Ignimbrite. Interaction between the rhyolitic and basaltic magmas would be confirmed if mingled
clasts, showing juxtaposition of basaltic and rhyolitic material,
could be found in either the ignimbrite or the scoria, or in both
units.
Source
Determination of the source of Raluan Ignimbrite based on
thickness and textural characteristics is complicated by a number of factors. As Raluan Ignimbrite is regarded as being of
low aspect ratio (Walker et al. 1981b), some near-vent, ridgetop deposits of the rhyolite could well be thin and fine grained
because of emplacement as ignimbrite veneer deposits (Walker et al. 1981a), while thick exposures at some distance from
the source may be lee-side lenses, or valley-fill ignimbrite.
Prior to this study, the thickest known exposure of the rhyolite
was 6 m in the northeastern part of Rabaul Caldera (Nairn
et al. 1989). This information plus grain size data led to the
belief that the Raluan Ignimbrite was sourced in the northcentral part of Rabaul Caldera (Walker et al. 1981b). However,
new exposures on the lower northern flank of Tovanumbatir
(upper southwestern flank of Tavui) have revealed the coarsest
known deposits of Raluan Ignimbrite containing pumice
clasts to 0.8 m. These observations favour a nearby vent such
as Tavui as the source of the Raluan Ignimbrite, rather than a
vent within the Rabaul Complex, as clasts approaching 1 m
size would not be transported far from the source.
The ignimbrite and the scoria of the Raluan Pyroclastics
appear to have been erupted from different vents. Thickness
and grain size data for the scoria initially indicated
strombolian to sub-plinian dispersal from a source on the
north-south axis of Rabaul Caldera, somewhat north of the
centre of the caldera (Walker et al. 1981b). Additional thickness and grain size data (Nairn et al. 1989, 1995) suggested
sub-plinian dispersal from a source in the southeastern part of
the W-T Zone, possibly Kabiu or Palangiangia (Fig. 5). The
presence of another scoria deposit, of different character,
which overlies the rhyolite in exposures in the northeastern
part of Rabaul Caldera indicates that the coarse-grained,
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Page 8 of 21
Bull Volcanol (2015) 77:80
Fig. 5 Raluan Scoria fall
isopachs (in cm), modified after
Figure 5 of Nairn et al. (1995) to
show Tavui Caldera. The source
of the scoria fall deposit appears
to be Kabiu or Palangiangia, vents
within the W-T Zone
poorly sorted overlying scoria is a product of the nearby
Palangiangia, while the finer grained, better sorted Raluan
Scoria could more likely have originated from the more distal
Kabiu (Nairn et al. 1989, 1995).
Age
The age of the Raluan Pyroclastics (see Table 1) is probably
about 6.9 ka BP, although initial dating suggested that these
deposits could be as young as 3.5 ka BP (Macnab 1970; Nairn
et al. 1989). The results of radiocarbon dating of soils beneath
the Raluan Pyroclastics at six locations around Rabaul Caldera
range between 5120±120 and 7410±72 BP (Nairn et al. 1995,
reporting results from Beta Analytic Inc.) and have a weighted
mean age of 6896±40 BP (using the method of Long and
Rippeteau 1974). The younger age was obtained from peat
beneath the ignimbrite at Arumbum, 40 km south of Rabaul
(Fig. 8). Four thermoluminescence dates on crushed samples
(coarse-grained quartz separates and fine-grained polymineral
aggregates) from the Raluan rhyolite range between 5400±
600 and 8000±1100 BP (D. Price, University of Wollongong,
personal communication). The weighted mean of the four
thermoluminescence dates is 6385 ±423 BP (using the
method of Long and Rippeteau 1974). One radiocarbon
date on coral contained within the ignimbrite is about
8 ka. A radiocarbon date of 470±40 BP for material at
the interface separating the scoria and the ignimbrite is
clearly inconsistent with all of the other dating results for
the Raluan Pyroclastics and is not accepted here. This
young age may be a function of some form of postdepositional hydrological contamination (D. Hood, Beta
Analytic Inc., personal communication).
Tokudukudu Ignimbrite
Apart from the Raluan Ignimbrite, the only other subaerially
exposed rhyolitic rock unit in the Rabaul-Tavui area is a thin
deposit in the lower part of the stratigraphic sequence exposed
in the Tavui Fault scarp. The discovery of this unit and the
recognition of its rhyolitic nature came about through the Rabaul area geological mapping campaign of 1985–1986 (Nairn
et al. 1989, 1995; Wood et al. 1995). The unit is here named
the Tokudukudu Ignimbrite, from the nearby village.
The Tavui Fault scarp exposure of the Tokudukudu Ignimbrite is the only one known. The Tokudukudu Ignimbrite exposure at this location is only about 0.7 m thick. The yellow-
Bull Volcanol (2015) 77:80
Table 1
Page 9 of 21 80
Radiometric ages for rhyolitic rocks of the Rabaul area
Deposit dated
Material
Sample no.
Locationa
14
Raluan Ignimbrite
Soil—underlying
RP98412M3
470±40
Peat—underlying
PNGf07
Peat—underlying
P1345
Soil—underlying
RP91001MI
Soil—underlying
RP92004MI
Soil—underlying
RP92002MI
Adelaide Gully
4° 12.91′ S
152° 11.45′ E
Arumbum
4° 38.26′ S
152° 06.74′ E
Arumbum
4° 38.26′ S
152° 06.74′ E
Kulaun Pltn
4° 22.98′ S
152° 21.65′ E
Rakunai Rd
04° 16.23′ S
152° 06.64′ E
Talwat
4° 14.95′ S
Soil—underlying
RP92005MI
Soil—underlying
RP92003MI
Soil—underlying
RP94010
Pumice
W2702
Pumice
W824
Pumice
W743
Pumice
W1059
Pumice
W2701
Tokudukudu Ignimbrite
152° 13.84′ E
Vuvu Rd
4° 14.45′ S
152° 07.61′ E
Burma Rd
4° 14.31′ S
152° 08.13′ E
Kuraip
4° 14.28′ E
152° 07.55′ E
Adelaide Gully
4° 12.91′ S
152° 11.45′ E
Arumbum
4° 38.26′ S
152° 06.74′ E
Adelaide Street
4° 12.84′ S
152° 11.39′ E
C date (years BP)b
TL date (years BP)c
3340±100
3500±65
5120±120
6530±140
6630±120
6950±90
7250±90
7410±72
Adelaide Street
4° 12.84′ S
152° 11.39′ E
Tavui Ref. section
4° 09.31′ S
152° 10.62′ E
5400±600
6200±1600
7100±800
8000±1100
78,700±12,500
a
Horizontal datum for location co-ordinates is Australian Geodetic Datum 1966. This applies to Tables 2 and 3 also
b
All 14 C dates from Beta Analytic Inc., USA, except those for PNGf07 and P1345 which are from N.Z.D.S.I.R., Lower Hutt, New Zealand
c
TL dates from TL Dating Laboratory, University of Wollongong, Australia
white pumice and ash deposit is fine grained, the largest pumice clasts being 1–2 cm. As with the Raluan Ignimbrite, the
Tokudukudu Ignimbrite has no associated plinian fall phase.
The age of the Tokudukudu Ignimbrite is not well
established. The only reliable age dating result is a
thermoluminescence date of 78.7±12.5 ka BP (D. Price,
University of Wolongong, personal communication), obtained as part of this study (Table 1). While not precise,
this result seems reasonable for the stratigraphic position
of the Tokudukudu rhyolite.
80
Bull Volcanol (2015) 77:80
Page 10 of 21
Rabaul and Tavui rock series
Geochemical data sources
Geochemical data from Rabaul and Tavui considered here are
derived from Heming and Carmichael (1973), Heming
(1974), Nairn et al. (1989), Wallace and Tufar (1998), unpublished data and new data. The analytical methods used were
classical wet chemical for major element data reported by
Heming and Carmichael (1973) and Heming (1974), and standard XRF for all other published data. Four new analyses
supplied by Dr S. Eggins (personal communication) were obtained by ICPMS. The largest aggregate data set is that of
Nairn et al. (1989) which comprises 95 analyses, 56 of which
are analyses of samples collected in 1985–1986 and 39 are
from the earlier work of Heming and Carmichael (1973) and
Heming (1974) and from unpublished data. Wallace and Tufar
(1998) reported 10 analyses of dredge samples from Tavui
Caldera.
Uncertainties of the data were not discussed by Heming
and Carmichael (1973), Heming (1974) and Wallace and
Tufar (1998), but Nairn et al. (1989) reported that their major
and trace element analyses of international laboratory standards (conducted at the University of Canterbury, New
Zealand) compared with published results. For major elements, the discrepancies are typically better than 4 %, while
for trace elements, the discrepancies have a wide range of
variability, up to 25 %, but are typically better than 10 %.
Geochemistry and mineralogy
Rhyolitic rocks such as the Raluan Ignimbrite and the
Tokudukudu Ignimbrite are dissimilar to the ‘main series’ of
compositions at Rabaul (Wood et al. 1995) that is dominated
by high-K dacite and high-K, high-silica andesite but which
also includes medium-K basaltic andesite and medium-K basalt (Fig. 6). The phenocryst assemblage of the rhyolites includes all of the minerals present in the basalt-to-dacite main
series, namely plagioclase, two pyroxenes, Fe-Ti oxides and
apatite, but also includes quartz and hornblende (Wood et al.
1995). The Raluan and Tokudukudu rhyolites, for which nine
analyses are presented in Table 2, have lower K2O and other
incompatible element contents than would be expected for
Rabaul main series rhyolite of the same SiO2 contents (Fig. 6).
Rock samples from dredging at three sites in Tavui Caldera
(see Fig. 4 for locations) consist predominantly of diverse
pumices and subordinate lavas (Tufar 1990; Tufar and Naser
1992; Wallace and Tufar 1998). A common mineralogical
feature of the pumice samples, which include both rhyolitic
and dacitic varieties, is phenocrystic quartz. Rare hornblende
also is present. A suite of nine rock samples selected for analysis has a broad range of SiO2 contents from about 54 to 75 %
(normalised to 100 % volatile free). The normalised
compositions have been used to chemically classify the samples, which range from basaltic andesite to rhyolite (Table 3).
An apparent compositional gap between 58 and 67 % SiO2
could be a function of the small sampling base. Tavui samples
straddle the boundary between the low- and medium-K fields
in the K2O-SiO2 co-variation plot (Fig. 6). They also define a
low-angle trend that is in marked contrast to the more steeply
sloping, higher K, main series trend of Rabaul-sourced rocks.
Raluan Ignimbrite and Tokudukudu Ignimbrite rhyolite
samples plot at the high SiO2 end of the trend of Tavui compositions (Fig. 6). A single sample from the Tokudukudu Ignimbrite is slightly more K-rich than Raluan Ignimbrite and
rhyolitic rocks from Tavui, but chemically quite distinct from
the Rabaul ‘main series’ trend (Fig. 6). Also, one dacite analysis, from a grey pumice clast hosted by the Raluan Ignimbrite
(RP98413, Table 2), lies on the Tavui K2O-SiO2 trend (Fig. 6).
More generally, the averages of normalised values of major
element contents of the Raluan and Tokudukudu rhyolites are
similar to those of Tavui rhyolites, as shown in Table 4.
Interpretation
On the basis of these relationships, it is proposed that the
Raluan Ignimbrite and Tokudukudu Ignimbrite originated
from Tavui Volcano rather than from the Rabaul Caldera
Complex, as previously supposed. Previously, a Rabaul
source was assumed for the Raluan rhyolite based on perceptions of ‘remarkable’ similarity between the mineralogies of
the rhyolite and of Rabaul dacites, and on crystal fractionation
modelling which supported the concept of a liquid line of
descent from basalt to rhyolite (Heming 1974). However, as
stated above, there are significant mineralogical differences
between the Raluan rhyolite and dacites from Rabaul, and
although crystal fractionation would account for the Rabaul
main series progression from basalt to rhyodacite (see the least
squares results in Heming 1974), it fails to generate a rhyolitic
composition that matches that of Raluan rhyolite. The similarity of the K2O-SiO2 relationship for the compositions of Tavui
rocks and those of Raluan and Tokudukudu eruptives suggests
that together they constitute a separate fractionation series.
The mineralogy of Tavui rhyolites, which includes quartz
and hornblende, is consistent with the mineralogy of Raluan
and Tokudukudu rhyolites and also supports the concept of a
Tavui-Tokudukudu-Raluan fractionation series.
Partial melting of crustal material was previously proposed
as a mechanism for the generation of the Raluan rhyolitic
magma (Smith and Johnson 1981) as an alternative to the
process of crystal fractionation. Also, Wood et al. (1995), in
reference to the experimental work by Drummond and Defant
(1990), pointed out that a sodic, low-K, low-alumina rhyolite
(like the Raluan rhyolite) could be generated by low-volume
partial melting of high-alumina basalt. The main reason for
suggesting this alternative process was the poor least squares
Bull Volcanol (2015) 77:80
Page 11 of 21 80
Fig. 6 K2O-SiO2 co-variation for
Rabaul and Tavui rocks shown in
relation to the classification grid
of Gill (1981). Raluan
Pyroclastics compositions occupy
the same field as compositions of
dredge samples from Tavui
Caldera
High - K
lm
ai n
Medium - K
au
3
Ra
b
K 2 O wt percent
se
rie
s
4
2
1
Scoria
Low - K
Basaltic
Andesite
Basalt
50
Andesite
Rhyolite
Dacite
60
70
SiO2 wt percent
Raluan Pyroclastics
fit in deriving Raluan rhyolite from a Rabaul dacite in the
crystal fractionation modelling exercise. The need to invoke
partial melting of crustal material at Rabaul to explain the
presence of the Raluan Ignimbrite rhyolite may be unnecessary in view of the recognition of a Tavui-TokudukuduRaluan rock series containing intermediate compositions that
could be explained by crystal fractionation within the Tavui
system. However, partial melting cannot be ruled out as a
possible mechanism for the generation of the Raluan rhyolite.
Tavui rocks have many chemical characteristics similar to
those of rocks from the trench-parallel eastern New Britain arc
zones F and Gs of Johnson (1977), as shown in Fig. 7, corresponding to Wadati-Benioff Zone (WBZ) depths of 95–
185 km (Table 5). Also, Tavui rocks are similar to some arclike seafloor rocks dredged from the eastern extremity (RD14)
of the Eastern Manus Rifts (Fig. 7) to the northwest of Rabaul
(Sinton et al. 2003), as shown in Table 5. On the other hand,
rocks from the Rabaul system seem somewhat out of place,
having some similarities to the rocks of Johnson’s zone Hs
(Table 5, Fig. 7), which corresponds to much greater depths to
the Wadati-Benioff Zone (295–415 km).
Discussion
While the Raluan rhyolite was arguably sourced at Tavui,
there seems little doubt that the basaltic scoria of the Raluan
Pyroclastics came from a W-T Zone vent, probably Kabiu.
Tavui
Tokudukudu Rhyolite
Similarly, consecutive eruptions of dacite from sources within
Rabaul Caldera and basalt from vents in the W-T Zone mark
the early stages of the Mid-Late Holocene Talili Pyroclastics
Subgroup eruptions (Nairn et al. 1995; McKee, unpublished
data, 2015). A modern analogue for chemically contrasting
products from consecutive or contemporaneous eruptions
from neighbouring source vents is the simultaneous eruptions
of andesite at Karymsky Volcano and of basalt at the nearby
(6-km distant) Academy Nauk vent on Kamchatka Peninsula
in 1996 (Izbekov et al. 2004). The indicated consecutive eruptions of the basalt and the rhyolite of the Raluan Pyroclastics
from separate but adjacent chemically distinct magma systems
lead to intriguing questions about (1) the relationship between
the Rabaul and Tavui caldera systems and (2) the relationship
that both of these systems have to the major basalt-andesite
corridor that separates them and which was responsible for the
creation of the W-T stratovolcanoes.
Rabaul and Tavui magma systems
The distinctly different petrological trends shown by Rabaul
and Tavui could result from a number of factors. These include marked lateral variations in mantle source compositions
over small distances, differences in the depth and shape of the
sub-caldera magma reservoirs and differences in the chemical
conditions in these adjacent systems.
80
Table 2
Bull Volcanol (2015) 77:80
Page 12 of 21
Major and trace element data for samples from Raluan Ignimbrite and Tokudukudu Ignimbrite
Stratigraphy Raluan Ignimbrite
Tokudukudu Ignimbrite
Sample no.
Lithology
Location
RP98413
Dacite
4 12.01 S
152 11.45 E
RP98410
Rhyolite
4 12.91 S
152 11.45 E
RAB59
Rhyolite
4 12.84 S
152 11.33 E
RAB159
Rhyolite
4 11.68 S
152 09.17 E
RP98411
Rhyolite
4 12.91 S
152 11.45 E
RP98415
Rhyolite
4 08.61 S
152 09.53 E
RAB182a
6830
Rhyolite
Rhyolite
4 09.31 S
152 10.62 E –
RAB182g
Rhyolite
4 09.31 S
152 10.62 E
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
S
62.31
0.46
14.79
5.92
0.13
3.34
6.62
3.24
0.98
0.07
0.01
70.91
0.31
13.19
2.63
0.10
0.80
2.58
4.34
1.66
0.07
0.01
73.11
0.31
13.04
2.34
0.08
1.18
2.62
4.36
1.58
0.06
–
72.25
0.31
12.87
2.31
0.07
0.85
2.33
4.26
1.65
0.06
–
74.17
0.34
13.16
2.11
0.08
0.46
2.09
4.92
1.58
0.06
0.01
72.19
0.30
12.63
2.16
0.08
0.57
2.08
4.27
1.83
0.05
0.01
73.28
0.31
13.03
2.06
0.08
0.47
1.96
4.44
1.66
0.05
–
72.26
0.32
12.04
1.88
0.08
0.41
1.58
3.95
1.94
0.04
–
70.13
0.32
13.22
2.33
0.08
0.72
2.53
3.39
2.19
0.04
–
LO1
Total
SiO2*
K2O*
Sc
V
Cr
Ni
Cu
Zn
Ga
Rb
Sr
Y
Zr
Nb
Ba
La
–
98.50
63.26
0.99
24
128
12
12
28
59
14
12
257
24
78
1
180
6
–
96.66
73.36
1.72
12
26
6
<2
12
52
13
20
219
34
127
1
270
8
1.41
100.09
74.09
1.60
–
23
<5
<5
–
43
12
21
174
29
135
<5
329
9
2.97
99.93
74.52
1.70
–
19
21
7
–
42
11
20
175
29
131
<5
340
11
–
98.98
74.93
1.60
12
12
<1
<2
6
51
13
20
202
36
138
2
305
10
–
96.17
75.06
1.90
10
18
4
<2
10
44
12
23
179
32
135
1
275
10
2.91
100.25
75.28
1.71
–
13
<5
<5
–
42
12
21
174
32
139
<5
335
12
4.89
99.39
76.47
2.05
–
–
–
–
–
–
–
–
–
–
–
–
–
–
5.05
100.00
73.86
2.31
Ce
Pr
Nd
Hf
Ta
Tl
Pb
13
2
7
3
2
0.6
5
17
<2
8
4
1
0.5
5
22
–
16
–
–
–
8
26
–
18
–
–
–
8
18
1
9
4
1
<0.3
6
17
<2
7
5
1
<0.3
5
22
–
18
–
–
–
9
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
SiO2* and K2O* are the values after the analysis has been re-calculated to 100 % on LOI-free and water-free basis. Analyses prefixed RAB are from
Nairn et al. (1989). Analysis 6830 is from Heming (1974). Analyses prefixed RP are new and were supplied by Dr Stephen Eggins, Australian National
University, Canberra, ACT, Australia
Mantle source heterogeneity, related to variations in mantle
partial melting, prior depletion and addition of subductionrelated components, was concluded to be responsible for the
diversity of magma types in the Manus back-arc basin (Sinton
et al. 2003). However, the 87Sr/86Sr value (0.7036) for one
sample of the Raluan rhyolite (no. 6830 in Table 2) falls within
the Rabaul main series basalt-dacite range of 0.7035–0.7040
(Peterman and Heming 1974), which suggests that there are
no marked lateral variations in mantle source compositions
beneath the Rabaul and Tavui systems. Lavas from the Eastern
Bull Volcanol (2015) 77:80
Table 3
Page 13 of 21 80
Major and trace element data for samples dredged from Tavui Caldera
Sample no. WT9004
Lithology Basaltic andesite
Location
4 5.85 S
152 11.43 E
9002
Basaltic andesite
4 5.85 S
152 11.43 E
WT9001
Andesite
4 5.85 S
152 11.43 E
9008
Dacite
4 5.70 S
152 14.04 E
9006
Dacite
4 5.85 S
152 11.43 E
WT9010
Dacite
4 5.60 S
152 2.71 E
9007
Dacite
4 5.70 S
152 14.04 E
WT9009
Rhyolite
4 5.60 S
152 12.71 E
9005
Rhyolite
4 5.85 S
152 11.43 E
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
LOI
Rest
Total
SiO2*
53.43
0.81
18.23
9.81
0.18
3.71
9.36
2.99
0.64
0.20
–
0.19
99.55
53.77
53.59
0.79
18.15
9.57
0.17
3.56
9.04
3.30
0.64
0.20
0.63
0.17
99.81
54.13
57.47
0.81
16.91
9.54
0.19
2.85
7.58
3.47
0.96
0.19
1.09
0.20
101.27
57.48
66.00
0.57
14.45
4.93
0.14
1.53
4.53
3.99
1.08
0.15
2.57
0.13
100.07
67.78
66.64
0.56
14.49
4.84
0.14
1.52
4.35
4.16
1.09
0.15
1.81
0.14
99.89
68.04
66.93
0.58
14.08
4.78
0.13
1.68
3.99
4.37
1.11
0.14
–
0.15
97.94
68.44
68.18
0.56
14.43
4.36
0.14
1.27
3.94
4.34
1.12
0.14
1.04
0.13
99.65
69.23
71.36
0.45
13.22
3.15
0.11
0.89
2.83
4.59
1.36
0.08
2.57
0.14
100.75
72.79
72.72
0.36
12.57
2.41
0.11
0.50
2.24
4.49
1.49
0.05
2.63
0.15
99.72
75.02
K2O*
Sc
V
Cr
Co
Ni
Cu
Zn
Ga
Rb
Sr
Y
Zr
Nb
Ba
La
Ce
Sm
0.64
32
285
113
25
27
99
97
18
7
506
23
49
–
136
6
11
3
0.65
32
298
93
25
<7
79
93
15
5
508
13
51
<5
139
–
–
–
0.96
27
250
257
23
9
49
115
18
11
502
25
65
1
196
7
15
3
1.11
19
88
139
11
<7
<10
70
13
13
328
26
99
<5
241
–
–
–
1.11
17
76
168
11
9
54
81
12
17
328
22
99
<5
241
–
–
–
1.14
18
79
243
12
13
25
76
16
13
296
32
109
1
241
8
17
4
1.14
16
68
76
<7
8
37
69
12
12
318
28
106
<5
259
–
–
–
1.39
14
40
138
4
6
24
67
15
19
249
36
130
2
292
9
21
4
1.54
10
19
148
<7
30
180
54
9
20
231
32
134
<5
310
–
–
–
Eu
Tb
Yb
Lu
Hf
Pb
Th
1
<1
2
<1
1
–
–
–
–
–
–
–
<10
<10
1
<1
3
<1
1
1
–
–
–
–
–
–
<10
<10
–
–
–
–
–
<10
<10
1
<1
3
<1
3
5
–
–
–
–
–
–
<10
<10
1
<1
4
<1
4
7
–
–
–
–
–
–
12
<10
SiO2* and K2O* are the values after the analysis has been re-calculated to 100 % on LOI-free and water-free basis. Analyses prefixed WT were supplied
by Prof. Werner Tufar, Philipps University, Marburg, Germany, and were reported by Wallace and Tufar (1998). All other analyses were supplied by the
Australian Geological Survey Organization and were reported by Wallace and Tufar (1998)
Manus Rifts have 87Sr/86Sr values >0.70355 (Sinton et al.
2003), consistent with those for both Tavui and Rabaul.
The similarity of the areal extents of the Rabaul and Tavui
calderas and the similarity of individual volumes for the larger
80
Bull Volcanol (2015) 77:80
Page 14 of 21
Table 4 Averages of normalised
values of major element contents
of Raluan and Tokudukudu
rhyolites and rhyolitic samples
dredged from Tavui Caldera
Source/unit
SiO2
TiO2
Al2O3
Fe2O3
MnO
MgO
CaO
Na2O
K2O
P2O5
Raluan
Tokudukudu
Tavui
74.82
73.86
73.91
0.33
0.34
0.42
13.24
13.92
13.23
2.28
2.45
2.85
0.08
0.08
0.11
0.70
0.76
0.72
2.24
2.66
2.60
4.49
3.57
4.66
1.75
2.31
1.47
0.06
0.04
0.07
Values after the analysis have been re-calculated to 100 % on LOI-free and water-free basis
eruptions from the two systems (4–10 km3, according to Nairn
et al. 1989 and Walker et al. 1981b) suggest that the respective
sub-caldera magma systems would be of similar size. A seismic tomographic experiment carried out in the Rabaul area in
1997 (Finlayson et al. 2003) confirmed earlier indications of a
shallow magma body beneath Rabaul Caldera (McKee et al.
1984, 1989; Mori and McKee 1987). The seismic tomographic imaging and detailed analysis depicted a shallow lowvelocity zone, interpreted to be a magma body, about 6 km
wide at a depth of 3–6 km in the central part of Rabaul Caldera
(Finlayson et al. 2003; Itikarai 2008). At Tavui, the seismic
tomographic imaging did not reveal a similar low-velocity
zone within the depth limits of the experiment (≈12 km).
Re-processing of the tomographic data revealed a subsidiary
shallow (2–4 km) low-velocity region to the northeast of Rabaul which was interpreted to be associated with Tavui (Bai
and Greenhalgh 2005). However, further analysis of the tomographic data indicates that the subsidiary low-velocity region
is not associated with Tavui but is related to the W-T system
(Itikarai 2008). Assuming that the latest eruption at Tavui was
of moderate-large volume, such as that of the Raluan Ignimbrite, and that it occurred about 7 ky ago, there would be a
reasonable expectation of residual magma within the subcaldera magma system. As thermal models of a cooling and
Fig. 7 New Britain arc zones of
Johnson (1977) in relation to
Tavui and Rabaul and areas of
back-arc basin volcanism (shaded
grey) in the eastern Bismarck Sea
(Sinton et al. 2003). RD14 is the
site of sample collection from the
Eastern Manus Rifts (Sinton et al.
2003). Transform segments of the
northern boundary of the South
Bismarck plate are represented by
bold broken lines with relative
movement indicated by opposing
arrows. The axis of the New
Britain Trench is shown by the
continuous line with teeth
crystallising magma body suggest times of the order of 103–
104 years for 10–20 % of the magma to crystallise (Tait et al.
1989; Huppert and Sparks 1988; Jarvis and Woods 1994), it
seems likely that residual magma would still be hot enough
about 7 ky after the eruption to cause a seismic velocity anomaly. The failure to detect a (magmatic) seismic velocity anomaly within 12 km of ground surface raises the question: Could
a sub-caldera magma reservoir at Tavui be at somewhat greater depth, say 12–15 km?
Greater depth of the magma reservoir at Tavui could have a
significant impact on Tavui’s behaviour and eruptive products.
As shown by Woods and Pyle (1997), the depth and vertical
extent of a magma body and the volatile contents of the magma affect the pressure in a cooling and crystallising body of
magma stored in the crust. For shallow sill-like bodies or
reservoirs containing magma having high volatile contents,
the magma becomes vapour saturated on emplacement. The
pressure in the reservoir increases as the melt cools and crystallises due to the exsolution of volatiles. This process may
lead to the eruption of relatively unevolved crystal-poor magma. For deep magma bodies or reservoirs with low volatile
contents, the magma remains undersaturated until a significant
fraction of the melt has crystallised. These results suggest that
inter-eruption time scales are greater for deeper magma bodies
New
Ireland
RD 14
Bismarck
4°
T
R
Sea
Hn
Hs
Gn
Gs
New Britain
F
E
6°
Solomon
150°
152°
Sea
Bull Volcanol (2015) 77:80
Page 15 of 21 80
Table 5 Selected compositional characteristics of rocks from the New Britain arc zones and from samples from the Eastern Manus Rifts (RD14), Tavui
and Rabaul
Zone
Depth to WBZ (km)
E
∼70–95
F
∼95–130
Gs
∼130–185
Gn
∼185–295
Hs
∼295–415
Hn
∼415–540
RD14
∼150–200
Tavui
∼170
Rabaul
∼150
Na2O
K2O
Sc
Rb
Zr
Ba
La
Yb
Hf
2.51
0.43
31
5.9
31
92
1.41
1.23
0.9
2.49
0.50
31
6.2
34
110
2.85
1.53
1.1
2.35
1.01
31
11.1
45
179
5.82
1.44
1.2
2.90
0.91
31
10.7
50
185
5.02
2.11
1.3
3.21
1.29
28
19.5
94
143
10.25
2.31
1.9
3.45
0.67
28
9.6
138
90
7.53
3.84
3.3
∼3.2
∼0.6
∼33
∼7
∼39
∼150
∼4.5
∼1.3
∼0.7
3.2
0.65
32
6
50
138
5.6
2.0
1.1
3.4
1.5
nd
23
77
245
7
nd
nd
206
18.72
18.75
18.72
18.69
18.65
18.50
18.80
nd
18.82
Pb/204Pb
Chemical characteristics are normalised to SiO2 =55: New Britain arc zones from Woodhead and Johnson (1993), RD14 from Sinton et al. (2003) and
Tavui and Rabaul from Nairn et al. (1989, 1995), Tufar and Naser (1992) and Wallace and Tufar (1998)
owing to the greater amount of crystallisation required before
the pressure is high enough to trigger an eruption. The apparently lower frequency of eruptions and the generation of more
evolved rock compositions at Tavui compared with Rabaul
would be consistent with the pressure evolution in a deeper
magma storage system beneath Tavui.
Influence of the W-T basalt-andesite system
Xenolithic and xenocrystic basaltic material has been involved
in the eruption of many intermediate and felsic magmas at
Rabaul. Heming (1974) was the first to draw attention to this,
noting the presence of crystals and fragments of basaltic material in the andesites and dacites of the intra-caldera centres
Rabalanakaia, Sulphur Creek and Tavurvur. Walker et al.
(1981b) noted the presence of mafic pumice clasts in several
Rabaul-sourced dacitic ignimbrites and stressed the role that
mafic magmas at Rabaul may play in mobilising the more
silicic magmas, so producing major, caldera-forming eruptions.
Also, basalt has had a significant influence on the trend of
chemical compositions of material erupted at Tavurvur since
1994 (Johnson et al. 1996; Roggensack et al. 1996; Patia
et al. 1997 and Davies et al., unpublished data, 1997). In the
eruption that started at Rabaul in 1994, hybridised andesitic
magmas, showing strongly bimodal phenocryst assemblages
and linear compositional arrays that extend from end-member
dacite towards basalt compositions, have been erupted mainly
from Tavurvur and, to a much lesser extent, from Vulcan: these
more mafic compositions are interspersed with dacites (Patia
2003). The moderately large SO2 flux observed in Tavurvur’s
1994 eruption column and the very low SO2 flux at Vulcan
(Roggensack et al. 1996), together with high dissolved S contents (≈1800 ppm, S.M. Eggins, unpublished data) in basaltic
melt inclusions trapped in olivine phenocrysts in Tavurvur
eruptives, are consistent with degassing of basaltic magma
through the Tavurvur vent at the commencement of the 1994
eruption. These results indicate that basalt magma was injected
into and largely confined within the eastern to northeastern
sector (Tavurvur-side) of the caldera dacite magma body (Patia
2003). The pattern of basaltic magma influence on the products
and on the activity of intra-caldera vents in the eastern to northeastern part of Rabaul Caldera may support the suggestion of
Johnson et al. (2010) that there is a connection between this part
of the Rabaul system and the immediately adjacent basaltandesite W-T system.
It appears that the Raluan Ignimbrite and Tokudukudu Ignimbrite lack the mafic pumice clasts seen in several Rabaulsourced ‘mixed-magma’ ignimbrites, seemingly precluding
actual contact and mixing of basaltic and felsic magmas in
these eruptions. Yet the indications of only a short time interval between the eruptions of the basaltic Raluan Scoria, from a
W-T Zone vent, probably Kabiu, and the Raluan rhyolitic
ignimbrite, probably from Tavui, could suggest a connection
between the two systems. It is possible that processes associated with the moderate-scale basaltic Raluan Scoria eruption
may have de-stabilised a primed Tavui system triggering the
rhyolitic Raluan Ignimbrite eruption.
Volcanic hazard
Submarine eruptions and associated hazards at Tavui
The global distribution of active volcanoes suggests that submarine settings are the most common environment for eruptions. However, many submarine eruptions, particularly those
that take place at great depth, are poorly understood because
of the paucity of observations. It is likely that many deep
80
Page 16 of 21
submarine eruptions go un-noticed because of the suppression
of explosivity by great hydrostatic pressure. Generally, poor
access to the deposits of deep submarine eruptions places
additional severe limitations on improving the understanding
of submarine eruption processes. However, observations and
studies of some recent submarine eruptions and their effects
have been enlightening and challenge the prevailing intuitive
idea that deep submarine explosive eruptions cannot generate
subaerial emission plumes. A large magnitude (VEI 5,
1.5 km3) explosive silicic submarine eruption in 2012 from
Havre Volcano, in the Kermadec Arc region of the southwest
Pacific, generated a subaerial emission plume from vents at
water depths of about 700–1400 m (Carey et al. 2014). In
2010, South Sarigan Volcano, Mariana Islands, erupted from
vents about 200–350 m below the sea surface and generated a
subaerial plume, reportedly to an altitude of about 12 km
(Green et al. 2010). Further studies of these and other similar
eruptions will provide guidelines to the various relationships
and thresholds (e.g. depth, eruption magnitude) associated
with subaerial plume generation from submarine eruptions
and other aspects of submarine eruption dynamics.
It seems likely that Tavui has been a mostly submarine
feature throughout its existence. A deep submarine environment for Tavui could have severely restricted the generation of
subaerial eruption columns as there is an apparent absence of
Tavui-sourced airfall tephra in the pyroclastic sequence in the
Rabaul area. In addition, plinian layers are absent beneath the
only known deposits having suggested links to Tavui, the
Raluan and Tokudukudu ignimbrites.
Any vents that developed or were re-activated within the current Tavui Caldera would lie at great water depth, about 400–
1100 m (Figs. 2, 3 and 4), which could mean that only the larger
eruptions from these vents would break through the sea surface
and leave deposits outside of the caldera. Lesser intra-caldera
activity at Tavui would be confined beneath the thick canopy
of seawater and so could go un-noticed. Re-activation of the large
cone that constitutes the northern upper flank of the Tavui edifice
would likely not be restricted significantly by overlying seawater
as the summit of this cone is within 20 m of the sea surface.
A major eruption from a submarine system such as Tavui
might be expected to be accompanied by the generation of
tsunami. Powerful expulsion of large volumes of tephra and
accompanying edifice collapse would likely be the main
mechanisms of tsunami formation. However, collapse of parts
of the steep caldera wall, de-stabilised by earthquake shaking
or during smaller scale eruptions, or even spontaneously, also
could generate tsunami. Exposures in coastal environments
have not revealed the presence of any tsunami deposits that
might be associated with activity at Tavui. However, the poor
exposure of Tavui eruptives in general renders the question of
associated tsunami deposits unresolved.
Pumice rafts are a likely product of silicic eruptions at
Tavui. The integrity of pumice rafts in open waters can be
Bull Volcanol (2015) 77:80
fleeting, but initially, at least the rafts would represent a hazard
to shipping by obstruction of water ways. Tavui is located
within a major shipping corridor and Rabaul hosts one of the
busiest ports in the region. Rafts of dacitic pumice were generated in all three historical eruptions from initially submerged
vents at the Vulcan centre at Rabaul—the 1878, 1937 and
1994 eruptions, each of which was of VEI 4 scale. The largest
of these rafts was formed during the mostly submarine eruption that created Vulcan Island in 1878 (Brown 1878; Johnson
et al. 1981). The 1878 pumice raft spread far across St
Georges Channel, the body of water separating New Britain
and New Ireland, and became a significant hazard for shipping
(Brown 1878). Pumice rafts may play a role in assisting the
passage of pyroclastic flows over water as at Krakatau in 1883
(Carey et al. 1996) and as suggested at Myojin Knoll in the
Izu-Bonin arc (Fiske et al. 2001).
Current activity status of Tavui and net local volcanic
hazard
The current activity status of Tavui has been difficult to discern. Some indications of Tavui’s condition have come from
seismic surveillance and from physical and chemical analysis
of water in its caldera. Until recently, Tavui was outside the
Rabaul seismic network, making location of any earthquakes
from Tavui unreliable. Nevertheless, there have been indications since 1992 of seismicity immediately northeast of Rabaul, in an area between the Rabaul and Tavui systems
(Itikarai 1995). Analysis of this ‘northeast’ seismicity
(Itikarai 2008) may indicate activity within the W-T Zone
and possible association with a localised seismic lowvelocity zone at a depth of ≈2–4 km (Bai and Greenhalgh
2005; Itikarai 2008). Any relationship between this seismicity
and Tavui is unresolved at present, although the apparently
post-caldera cone in the eastern corner of Tavui Caldera lies
near the northern part of the ‘northeast’ zone of seismicity.
Several investigations were carried out at Tavui in 1993
during the cruise of RV Franklin to test for hydrothermal
venting (Binns 1993). A hydrocast was conducted in the eastern part of the caldera. No transmissivity anomaly was detected. Three water samples were collected during this traverse at
depths of 1090 m (very close to the caldera floor), 795 m and
600 m. Subsequent methane analyses indicated only background values. These results suggest that there was no hydrothermal venting at that time in the portion of Tavui Caldera
that was studied.
Despite the apparent quiescence at Tavui currently, the indications that it was the source of the 6.9-ka BP penultimate
major eruption in the Rabaul area suggest that it is potentially
active. Other geological evidence of potential for activity is
the presence and youthful appearance of at least one of the
intra-caldera cones at Tavui. These considerations markedly
change the perceptions of local volcanic hazard. Tavui would
Bull Volcanol (2015) 77:80
have to be acknowledged as a separate, major, potentially
active and therefore hazardous centre. This would increase
the net volcanic hazard in the Rabaul-Tavui area.
Scale and implications of the 6.9-ka BP Raluan Ignimbrite
eruption
The Raluan Ignimbrite, if sourced at Tavui, would provide
useful insight to the hazard implications of a large-scale eruption at Tavui. However, it is necessary to first review the scale
of the Raluan Ignimbrite eruption. The bulk tephra volume of
the Raluan Ignimbrite has been estimated to be between
≈4 km3 (Walker et al. 1981b) and ≈5 km3 (Nairn et al. 1989,
1995) implying VEI 5 scale of activity. These tephra volume
estimates were based largely on limited comparison with the
1.4-ka BP Rabaul Ignimbrite, the bulk tephra volume of which
was calculated to be at least 8 km3 (Walker et al. 1981b), and
on the assumption that the source of the Raluan Ignimbrite
was within Rabaul Caldera.
In the Raluan Ignimbrite volume considerations of Walker
et al. (1981b), reference was made to the absence of Raluan
Ignimbrite to the north and east of Rabaul Caldera (areas
mostly covered by sea water) and southwest of Kerevat
(Fig. 8). However, the geological mapping of Heming
(1974) and Nairn et al. (1989, 1995), archaeological work at
the Duke of York Islands (P. White, personal communication)
and geological reconnaissance at various locations (McKee,
unpublished data) have established that Raluan Ignimbrite
emplacement covers an area that extends more than 45 km
east-west, from the Duke of York Islands to beyond Kerevat,
and more than 57 km north-south, from Watom Island to beyond Arumbum (Fig. 8). At all of these distal parts of the
distribution of the Raluan Ignimbrite, the Rabaul Ignimbrite
is present also. A new appreciation of the volume of the
Raluan Ignimbrite can be gained by comparison of the thicknesses of the two ignimbrites at all of these and other distal
locations. At most of these locations, the thickness of the
Raluan Ignimbrite is between about 50 and 80 % that of the
Rabaul Ignimbrite, as indicated in Fig. 8, suggesting that the
volume of the Raluan Ignimbrite may be between about 4 and
6.5 km3. However, at several locations on Watom Island, the
Raluan Ignimbrite thickness is much greater than the thickness
of Rabaul Ignimbrite (ratio>4:1). This observation indicates
that the volume of the Raluan Ignimbrite may exceed the
earlier volume estimates of Walker et al. (1981b) and Nairn
et al. (1989, 1995) because, firstly, it confirms dispersal of this
deposit northwest of Rabaul, and secondly, it suggests that the
Raluan Ignimbrite is more voluminous than the Rabaul Ignimbrite off-shore to the northwest of Rabaul. In addition, a
Raluan Ignimbrite source within Tavui Caldera could imply
that a considerably greater volume of the ignimbrite was deposited on the sea floor, on and beyond the flanks of Tavui
Volcano, than would have occurred if the source was within
Page 17 of 21 80
Rabaul Caldera. There would likely be a substantial increase
in the estimated volume of the Raluan rhyolite eruption if the
lobate deposit on the northern and western flanks of the Tavui
edifice (marked by boundary A in Fig. 3) could be identified
as being a product of that eruption. Also, a significant volume
of Raluan Ignimbrite may have been trapped within (a preexisting) Tavui Caldera (see below). Therefore, it is likely that
the volume of the Raluan Ignimbrite exceeds previous estimates. It would follow that a Tavui source for the Raluan
Ignimbrite would indicate that Tavui has experienced eruptions approaching the scale of VEI 6.
The large magnitude of the Raluan Ignimbrite eruption
(VEI 5–6) would normally be associated with large-scale edifice modification. The steep and relatively smooth scarps that
form the northwestern, southwestern and southeastern walls
of Tavui Caldera could be evidence of ‘recent’ collapse. However, the volume of the current basin at Tavui appears to be
much greater than the bulk volume of the Raluan Ignimbrite—
possibly a further example of the ‘volume problem’ noted at
many calderas (Williams 1941). The volume of Tavui Caldera,
conservatively calculated below the elevation of the lowest
parts of the caldera rim, commonly about 300 m below sea
level, is about 35 km3. This volume estimate is significantly
greater than the dense rock equivalent of the estimated volume
of the Raluan Ignimbrite. This discrepancy could be explained
if collapse associated with the Raluan eruption merely deepened (and perhaps widened) a pre-existing caldera. The
growth of the Tavui Limestones formation in the Late Pleistocene appears to follow a rapid submergence event which
may be related to an earlier caldera-forming episode.
Modelling a submarine source at Tavui for the Raluan Ignimbrite is problematic. It would seem to be very difficult to
generate high energy pyroclastic flows if the submarine source
is at great depth. The model developed by Fiske (1963) and
Fiske and Matsuda (1964) for the generation of subaqueous
pyroclastic flows involves rapid accumulation of pyroclastic
debris around the vent and subsequent lateral transport, largely
by slumping. Such pyroclastic flows would not be particularly
energetic. A mechanism that imparts great lateral force on
erupted pyroclastic debris would be required to generate pyroclastic flows that have sufficient energy to escape the vent
area in a (possibly) deep subaqueous environment and that are
subsequently emplaced over a broad area of land and seafloor.
The problems of generating energetic subaerial pyroclastic
flows from subaqueous vents could be overcome if the vents
are not too deep. For a certain (unknown) range of depths, not
too deep and not too shallow, it may be possible to generate
subaerial pyroclastic flows with no significant accompanying
fall deposits. This could be achieved if a tall subaerial plinian
emission column was not formed. Instead, the rapid upwelling of large quantities of tephra from source vents at some
intermediate depth could form a wet tephra emission column
above the sea surface. Collapse of parts of this column could
80
Bull Volcanol (2015) 77:80
Page 18 of 21
Fig. 8 Locations of distal
exposures of Raluan Ignimbrite
(solid circles), comparison of
thicknesses (m) of Rabaul
Ignimbrite (top measurement) and
Raluan Ignimbrite (bottom
measurement) and location of the
only known exposure of the
Tokudukudu Ignimbrite (open
circle). Most of the ignimbrite
thickness measurements are new
(i.e. this study), but measurements
at Arumbum are from Nairn et al.
(1989). Topography is expressed
as form lines
impart sufficient energy for the formation of fast-moving, possibly wet pyroclastic flows that were able to travel across the
sea surface and onto land masses, as in the case of the pyroclastic flows of the 6-ka BP Kikai eruption (Ui et al. 1984;
Walker et al. 1984), perhaps assisted across the sea by the prior
generation of pumice rafts (e.g. Carey et al. 1996; Fiske et al.
2001). At the same time, rapid accumulation of pyroclastic
debris around submarine vents could lead to the generation
of submarine pyroclastic flows as per the model of Fiske
(1963) and Fiske and Matsuda (1964). It is possible that during earlier times, source vent areas at Tavui were less deep
than at present, creating conditions favourable for the generation of subaerial pyroclastic flows as outlined here. In
recognition of historical observations of subaerial emission
plumes associated with submarine eruption source vents several hundreds of metres deep (Green et al. 2010; Carey et al.
2014), a tall emission column may have been established at an
early stage of the Raluan Ignimbrite eruption but fall-out may
have taken place over the sea, perhaps in a generally northerly
direction, and so is not represented in any on-shore areas.
Concluding remarks
1. The adjacent Tavui and Rabaul caldera volcanoes have
evolved separately and have produced distinctly different
Bull Volcanol (2015) 77:80
2.
3.
4.
5.
rock series. The Tavui rock series is characterised by a
weak trend of K2O enrichment over the range of compositions from low-SiO2 andesite to rhyolite. This lowmedium-K trend is appropriate for Tavui’s position with
respect to the Wadati-Benioff Zone. In contrast, the
Rabaul-sourced rock series which is continuous between
basalt and dacite shows strong K2O enrichment. This
medium-high-K trend would be appropriate for locations
over much deeper parts of the Wadati-Benioff Zone.
Tavui Volcano is the likely source of the large volume
(>4 km3) 6.9-ka BP Raluan Ignimbrite and the 79-ka BP
Tokudukudu Ignimbrite, both of which have low-K contents and are the only known rhyolitic deposits in the
tephra sequence of the Rabaul-Tavui area. Other rhyolitic
rocks having similar geochemical characteristics have
been dredged from Tavui Caldera.
The Raluan Ignimbrite is closely associated with a preceding basaltic scoria but the mafic magma evidently
originated from the W-T Zone, a chain of basalt-andesite
volcanoes separating the Tavui and Rabaul systems.
There is no confirmed evidence of direct contact between
the basaltic and rhyolitic magmas.
It is thought that Tavui was a submarine centre at the time
of the Raluan Ignimbrite eruption. Recent evidence of the
formation of subaerial emission columns from submarine
vents at considerable depth indicates that a process similar
to the standard mechanism for the generation of pyroclastic flows, i.e. eruption column collapse, could operate for
some submarine eruptions and may have occurred at
Tavui in the generation of the Raluan Ignimbrite. Critical
factors in this process are the depth of the vent(s) and the
discharge rate of the eruption. It is possible that the Tavui
edifice was previously at a shallower depth, which would
have created conditions more favourable for the generation of subaerial pyroclastic flows from eruption column
collapse. A too shallow depth would have allowed the
establishment of a tall eruption column from which significant fall deposits would be expected, but there appear
to be no fall deposits associated with the Raluan Ignimbrite. However, it remains possible that a tall subaerial
emission column was formed during the early stages of
the Raluan Ignimbrite eruption, but that fall-out occurred
over sea-covered areas generally to the north, thus
preventing the deposition of an on-shore plinian fall
phase.
The likely Middle Holocene activity and the youthful appearance of post-caldera cones at Tavui mean that it
should be regarded as potentially active. This volcanic
potential taken together with the steep walls of its caldera
indicates that Tavui represents a significant tsunami threat
also. This markedly changes the perceptions of volcanic
and tsunami hazard in the Rabaul area, increasing the net
local geologic hazard.
Page 19 of 21 80
Acknowledgments The Tavui study was initiated by exchanges with
David Wallace (deceased), formerly of Geoscience Australia, who participated in the Sonne 68-OLGA II research cruise that visited the Tavui area
in 1990 and made the first collection of dredge rock samples from Tavui.
Prof. Hugh Davies of the Earth Sciences Department, University Papua
New Guinea is gratefully acknowledged for thoughtful reviews of several
versions of the manuscript and for mineralogical assistance. Dr R. Wally
Johnson formerly of Geoscience Australia helped to shape an early version of the manuscript. Chemical analyses of some of the dredge samples
from Tavui were kindly supplied by Prof. Werner Tufar of Philipps University, Marburg, Germany. Chemical analyses of four samples from the
Raluan Ignimbrite were kindly supplied by Dr Stephen Eggins of the
Australian National University Canberra, Australia. The manuscript was
improved significantly following reviews by Prof. John Sinton, University of Hawaii, and Prof. James Mori, Kyoto University. Marissa Sari of
Port Moresby Geophysical Observatory helped with word processing of
the manuscript. Sonick Taguse of Papua New Guinea’s Mineral Resources Authority prepared the line diagrams. COM publishes with the
permission of the Secretary, Department of Mineral Policy and
Geohazards Management, Papua New Guinea.
References
Bai C, Greenhalgh S (2005) 3-D multi-step travel time tomography: imaging the local, deep velocity structure at Rabaul Volcano, Papua
New Guinea. Phys Earth Planet Inter 151:259–275
Binns RA (1993) Cruise report—eastern Manus basin—RV Franklin
Blong R, McKee CO (1995) The Rabaul eruption 1994: destruction of a
town. Natural Hazards Research Centre, Macquarie University
Brown G (1878) Journal of the Rev. G. Brown 1860–1902 (11 volumes).
Mitchell Library, Sydney, Australia
Carey S, Sigurdsson H, Mandeville C, Bronto S (1996) Pyroclastic flows
and surges over water: an example from the 1883 Krakatau eruption.
Bull Volcanol 57:493–511
Carey RJ, Wyzokzanski R, Wunderman R, Jutzeler M (2014) Discovery
of the largest historic silicic submarine eruption. EOS Trans Am
Geophys Union 95(19):157–159
Drummond MS, Defant MJ (1990) A model for trondhjemite-tonalitedacite genesis and crustal growth via slab melting: archaean to modern comparisons. J Geophys Res 95:21503–21521
Finlayson DM, Gudmundsson O, Itikarai I, Nishimura Y, Shimamura H
(2003) Rabaul volcano, Papua New Guinea: seismic tomographic
imaging of an active caldera. J Volcanol Geotherm Res 124:153–
171
Fisher NH (1939) Geology and vulcanology of Blanche Bay, and surrounding area, New Britain. Territory of New Guinea Geological
Bulletin 1
Fiske RS (1963) Subaqueous pyroclastic flows in the Ohanapecosh
Formation, Washington. Geol Surv Am Bull 74:391–406
Fiske RS, Matsuda T (1964) Submarine equivalents of ash flows in the
Tokiwa Formation, Japan. Am J Sci 262:76–106
Fiske RS, Naka J, Iizasa K, Yuasa M, Klaus A (2001) Submarine silicic
caldera at the front of the Izu-Bonin arc, Japan: voluminous seafloor
eruptions of rhyolite pumice. Geol Soc Am Bull 113(7):813–824
Gill JB (1981) Orogenic andesites and plate tectonics. Springer, Berlin
Green DN, Evers LG, Fee D, Matoza RS, Snellen M, Smets P, Simons D
(2010) Hydroacoustic, infrasonic and seismic monitoring of the submarine eruptive activity of subaerial plume generation at South
Sarigan, May 2010. J Volcanol Geotherm Res 257:31–43
GVN (1994) Rabaul. Bulletin of the Global Volcanism Network 19(8) 2–
6, and 19(9) 4–7
Heming RF (1974) Geology and petrology of Rabaul Caldera, Papua
New Guinea. Geol Soc Am Bull 85:1253–1264
80
Page 20 of 21
Heming RF, Carmichael ISE (1973) High temperature pumice flows from
Rabaul Caldera, Papua New Guinea. Contrib Mineral Petrol 38:1–
20
Huppert HE, Sparks RSJ (1988) The generation of granitic magmas by
intrusion of basaltic melts into the continental crust. J Petrol 29:599–
624
Itikarai I (1995) Rabaul 1992. Bull Volcanic Eruptions 32:130–131
Itikarai I (2008) The 3-D structure and earthquake locations at Rabaul
Caldera, Papua New Guinea. Unpublished Master of Philosophy
thesis, Australian National University, Canberra
Izbekov PE, Eichelberger JC, Ivanov BV (2004) The 1996 eruption of
Karymsky Volcano, Kamchatka: historical record of basaltic replenishment of an andesitic reservoir. J Petrol 45(11):2325–2345
Jarvis RA, Woods AW (1994) The nucleation, growth and settling of
crystals in a turbulently convecting melt. J Fluid Mech 273:83–108
Johnson RW (1977) Distribution and major element chemistry of late
Cainozoic volcanoes at the southern margin of the Bismarck Sea,
Papua New Guinea. Australian Bureau of Mineral Resources Report
188
Johnson RW, Threlfall NA (1985) Volcano town—the 1937–43 Rabaul
eruptions. Robert Brown and Associates, Bathurst
Johnson RW, Everingham IB, Cooke RJS (1981) Submarine volcanic
eruptions in Papua New Guinea: 1878 activity of Vulcan (Rabaul)
and other examples. In: Johnson RW (ed) Cooke-Ravian volume of
volcanological papers. Geological Survey of Papua New Guinea
Memoir 10:167–179
Johnson RW, McKee CO, Eggins S, Woodhead J, Arculus RJ, Chappell
BW, Sheraton J (1996) The 1994 eruptions at Rabaul Volcano,
Papua New Guinea: taking petrologic pathways towards understanding a restless caldera. Eos 76:171
Johnson RW, Itikarai I, Patia H, McKee CO (2010) Volcanic systems of
the Northeastern Gazelle Peninsula, Papua New Guinea: synopsis,
evaluation, and a model for Rabaul volcano. Geoscience Australia,
Canberra
Lindley ID (1988) Early Cainozoic stratigraphy and structure of the
Gazelle Peninsula, East New Britain: an example of extensional
tectonics in the New Britain arc-trench complex. Aust J Earth Sci
35:231–244
Long A, Rippeteau B (1974) Testing contemporaneity and averaging
radiocarbon dates. Am Antiq 39:205–215
Macnab RP (1970) Geology of the Gazelle Peninsula, T.P.N.G. Bureau of
Mineral Resources Australia Record 1970/63
McKee CO, Lowenstein PL, de Saint OP, Talai B, Itikarai I, Mori J (1984)
Seismic and ground deformation crises at Rabaul Caldera: prelude to
an eruption? Bull Volcanol 47:397–411
McKee CO, Mori J, Talai B (1989) Microgravity changes and ground
deformation at Rabaul Caldera, 1973–1985. In: Latter JH (ed)
Volcanic hazards, assessment and monitoring. Springer, New
York, pp 399–428
McKee CO, Baillie MG, Reimer PJ (2015) A revised age of AD 667–699
for the latest major eruption at Rabaul. Bull Volcanol 77:65
Mori J, McKee CO (1987) Outward-dipping ring fault structure at Rabaul
Caldera as shown by earthquake locations. Science 235:193–195
Nairn IA, Talai B, Wood CP, McKee CO (1989) Rabaul Caldera, Papua
New Guinea—1:25,000 reconnaissance geological map and eruption history. New Zealand Geological Survey, Department of
Scientific and Industrial Research
Nairn IA, McKee CO, Talai B, Wood CP (1995) Geology and eruptive
history of Rabaul Caldera, Papua New Guinea. J Volcanol Geotherm
Res 69:259–288
Patia H (2003) Petrology and geochemistry of the recent eruption history
at Rabaul Caldera, Papua New Guinea: implications for magmatic
processes and recurring volcanic activity. Master of Philosophy thesis, Australian National University, Canberra
Patia H, Eggins S, McKee CO, Johnson RW (1997) The 1994 to present
eruption at Rabaul, Papua New Guinea: evidence of repeated
Bull Volcanol (2015) 77:80
basaltic magma influx into a sub-caldera dacite magma reservoir.
Volcanological Society of Japan (abstract)
Peterman ZE, Heming RF (1974) 87Sr/86Sr ratios of calc-alkaline lavas
from the Rabaul Caldera, Papua New Guinea. Geol Soc Am Bull 85:
1265–1268
Roggensack K, Williams SN, Schaefer SJ, Parnell RA (1996) Volatiles
from the 1994 eruptions at Rabaul: understanding large caldera systems. Science 273:490–493
Sinton J, Ford LL, Chappell B, McCulloch MT (2003) Magma genesis
and mantle heterogeneity in the Manus back-arc basin, Papua New
Guinea. J Petrol 44:159–185
Smith IEM, Johnson RW (1981) Contrasting rhyolite suites in the late
Cenozoic of Papua New Guinea. J Geophys Res 86:10257–10272
Tait SR, Jaupart C, Vergniolle S (1989) Pressure, gas content and eruption
periodicity of shallow crystallizing magma chambers. Earth Planet
Sci Lett 92:107–123
Tiffin DL, Taylor B, Crook KAW, Sinton J, Frankel E (1986) Surveys in
the Solomon Islands and Papua New Guinea using SeaMARC II—
report of the RV MOANA WAVE, 29 November 1985–9 January
1986. CCOP-SOPAC Cruise Report 117, South Pacific Applied
Geoscience Commission, Suva
Tiffin DL, Taylor BD, Tufar W, Itikarai I (1990) A SeaBeam and sampling survey of newly discovered Tavui Caldera near Rabaul, Papua
New Guinea. SOPAC Cruise Report 132, South Pacific Applied
Geoscience Commission, Suva
Tivey MA, Bach W, Seewald J, Tivey MK, Vanko DA, Party SS (2006)
Cruise report for RV Melville Cruise MGLN06MV—hydrothermal
systems in the Eastern Manus Basin: fluid chemistry and magnetic
structure as guides to subseafloor processes
Tufar W (1990) Sonne 68-OLGA II Research Cruise, April 29 to June 5,
1990, preliminary cruise report. SOPAC Cruise Report 136, South
Pacific Applied Geoscience Commission, Suva
Tufar W, Naser G (1992) Lagerstattenkundliche Detailuntersuchungen
rezenter Erzvokommen im Bereich einer Platten-Kollisionzone,
speziell in der Back-Arc Spreizungszone am Beispiel des ManusBeckens (Papua-Neuguinea). ForschungsfahrtSonne 68 - OLGA II,
Philipps Universitat, Marburg/Lahn, Bundesrepublik Deutschland
Ui T (1973) Exceptionally far-reaching, thin pyroclastic flows in southern
Kyushu, Japan. Bull Volcanol Soc Jpn 18:153–168
Ui T, Metsugi H, Suzuki K, Walker GPL, McBroome LA, Caress ME
(1984) Flow lineation of Koya low aspect ratio ignimbrite, South
Kyushu, Japan. A progress report of the U.S.-Japan Cooperative
Science Program 9–12
Walker GPL, Heming RF, Wilson CJN (1980) Low aspect ratio ignimbrites. Nature 283:286–287
Walker GPL, Wilson CJN, Foggatt PC (1981a) An ignimbrite veneer
deposit: the trail-marker of a pyroclastic flow. J Volcanol
Geotherm Res 9:409–421
Walker GPL, Heming RF, Sprod TJ, Walker HR (1981b) Latest major
eruptions of Rabaul Volcano. In: Johnson RW (ed) Cooke-Ravian
volume of volcanological papers, Geological Survey of Papua New
Guinea Memoir 10:181–193
Walker GPL, McBroome LA, Caress ME (1984) Products of the Koya
eruption from the Kikai Caldera, Japan. A progress report of the
U.S.-Japan Cooperative Science Program 4–8
Wallace DA, Tufar W (1998) OLGA II oceanographic survey of Tavui
Caldera, Rabaul. Australian Geological Survey Organisation,
Canberra
Wallace P, Eggins S, Arculus RJ (2002) Pre-1400 BP magmatic history of
Rabaul, PNG. Abstracts of the 16th Australian Geological
Convention (Adelaide) 67:253
Williams H (1941) Calderas and their origin. University of California,
Department of Geological Sciences Bulletin 25:239–346
Wood CP, Nairn IA, McKee CO, Talai B (1995) Petrology of Rabaul
Caldera, Papua New Guinea. J Volcanol Geotherm Res 69:285–302
Bull Volcanol (2015) 77:80
Woodhead JD, Johnson RW (1993) Isotopic and trace-element profiles
across the New Britain island arc, Papua New Guinea. Contrib
Mineral Petrol 113:479–491
Page 21 of 21 80
Woods AW, Pyle DM (1997) The control of chamber geometry on
triggering volcanic eruptions. Earth Planet Sci Lett 151:155–
166