Journal of Volcanology and Geothermal Research 84 Ž1998. 239–256
Age and origin of tephras recorded in postglacial lake sediments
to the west of the southern Andes, 448S to 478S
Simon G. Haberle ) , Susie H. Lumley
Department of Plant Sciences, UniÕersity of Cambridge, Downing St., Cambridge CB2 3EA, UK
Received 5 January 1998; accepted 24 January 1998
Abstract
Tephra deposits preserved in lake sediments to the west of the Andes, between 448 and 478S in southern Chile, provide a
record of local postglacial eruption history. A series of 32 tephra layers in the sediments of eight small lakes in the study
area have been investigated by mineral magnetic analysis, electron microprobe analysis and radiocarbon age determinations.
Comparisons with geochemical data from other volcanic sources in southern Chile indicate that Hudson volcano is the most
likely source vent for at least seven of the tephra layers found in Chonos–Taitao lake sediments. The seven tephra eruptions
that have been identified from widespread and identical tephra deposits, date to 14 560, 13 890, 11 060, 7540, 3840, 2740,
and 1560 calendar years ago. The frequency of Hudson volcano eruptions in which tephra is dispersed in both a westerly and
easterly direction, similar to that recorded in 1991 from Hudson volcano, may be around 1 per 3800 calendar years during
the postglacial period. q 1998 Elsevier Science B.V. All rights reserved.
Keywords: tephrochronology; geochemistry; Hudson volcano; radiocarbon age; Chile
1. Introduction
The eruption of Hudson volcano in the austral
winter ŽAugust. of 1991 was the second most violent
volcanic event in Chile this century. This event
produce a large volume of tephra Ž) 4 km3 ., accompanied by SO 2 gas emissions, that had a major
environmental impact over an area of 150 000 km2
across Chile and Argentina ŽNaranjo et al., 1993..
Eruptions of this magnitude have occurred in the
)
Corresponding author. Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Australian National University, Canberra, ACT 0200, Australia.
E-mail: [email protected]
past, but the record of volcanic activity and the
impact of these eruptions on the environment of
southern South America remains incomplete.
We have developed a postglacial record of tephra
falls occurring to the west of Hudson volcano
Ž45854X S, 72858X W., between 448 and 478S latitude
in southwestern Chile, through detailed studies of
tephra layers found in lake sediment cores. Small
lake basins Žgenerally - 200 m diameter. with simple basin morphology and no major stream inputs are
ideal for reducing to a minimum stratigraphic complications of interpretation, such as sediment reworking. Tephra layers recovered from lakes fitting these
criteria were studied to answer the following questions. Firstly, can the volcanic source of each tephra
0377-0273r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 0 2 7 3 Ž 9 8 . 0 0 0 3 7 - 7
240
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
layer be identified using geochemical data? The geochemical results of this study are compared with data
from previous studies in southern South America to
identify potential source volcanoes by means of the
weight percent content of major elements of volcanic
glass from individual centers. Secondly, are single
tephra layers represented in more than one site and
how widespread are these events? Eight lakes ŽFig.
1b. that have been studied as part of a wider
palaeoecological investigation into postglacial vegetation change ŽLumley and Switsur, 1993; Haberle et
al., 1998. contained tephra layers preserved within
the lake sediments. Finally, how frequent are
tephra-producing eruptions during the postglacial period?
Volcanism in the southern Andes occurs in two
separate zones ŽFig. 1a. that have been distinguished
by Stern et al. Ž1984. on the basis of geographical
distribution and geochemistry as the Southern Volcanic Zone ŽSVZ, 338–468S. and the Austral Volcanic Zone ŽAVZ, 498–548S.. Active volcanism in
SVZ results from subduction of the Nazca plate
under the South American plate, with many centers
consisting of basalts and basaltic andesites. In con-
Fig. 1. Ža. Map showing the locations of some of the major volcanic centers in the southern Andes of South America and the extent of the
Southern Volcanic Zones ŽSVZ. and Austral Volcanic Zones ŽAVZ.. NSVZs northern part of SVZ, and SSVZs southern part of SVZ
Žafter Stern et al., 1984; Lopez-Escobar
et al., 1993.. Žb. Location map of lakes studied in this investigation with major volcanic centers in
´
the region. Lakes marked by a star: 1, Laguna Facil; 2, Laguna Oprasa; 3, Laguna Lofel; 4, Laguna Lincoln; 5, Laguna Miranda; 6, Laguna
Stibnite; 7, Laguna Six Minutes; 8, Laguna Marcelo.
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
trast, the AVZ results from convergence of the
Antarctic plate against the southernmost South
American plate and centers there are dominantly
andesitic to dasitic. All these volcanic centers have
been active during the late Quaternary period, with
some resulting in tephra-producing eruptions that
have left buried traces across the landscape ŽStern,
1990; Lopez-Escobar
et al., 1993; Naranjo and Stern,
´
1998..
In 1928, Auer Ž1974. recognised that tephra layers in Tierra del Fuego could be used as effective
isochrons for correlation between postglacial deposits in the region. Auer extended his correlations
farther north in southern South America using geochemical analyses provided by Salmi ŽSalmi, 1941..
Since this pioneering work by Auer and Salmi, little
emphasis has been placed on the use of
tephrochronology as an effective relative dating technique or absolute dating technique with radiocarbon
controls. There is, however, a growing body of data
related to the geochemistry of many SVZ and AVZ
volcanic centers ŽStern et al., 1984; Futa and Stern,
1988; Stern, 1990, 1991; Lopez-Escobar
et al., 1993;
´
Naranjo et al., 1993; Stern and Kilian, 1996., showing distinct geochemical signatures, related to different plate tectonic dynamics, in southern South America.
241
Chaiten
´ volcano. Hudson volcano is characterised by
relatively high TiO 2 and K 2 O contents ŽFuta and
Stern, 1988.. Volcanic centers in the AVZ are characterised by the predominance of andesites and
dacites of variable mineralogy.
The region lies within a zone of high precipitation, produced by the coupled ocean–atmospheric
influence of the Southern Polar Front that migrates
seasonally between 508S Žsummer. and 40–458S
Žwinter.. The climate is strongly oceanic, with mean
annual temperatures around 8–108C and annual precipitation near sea level in the region of 3000 mm
ŽMiller, 1976.. As altitude increases towards the
Andes, precipitation is much higher with estimates
for annual rainfall as much as 10 000 mm ŽFujiyoshi
et al., 1987.. The vegetation is North Patagonian rain
forest dominated by evergreen broadleaf and conifer
taxa ŽVeblen et al., 1983; Gajardo, 1995.. The prevailing winds are northerlyrnorthwesterly ŽMiller,
1976., with only occasional reversals to easterlies
during summer months. Although the Chonos–Taitao
region lies upwind from the volcanic centers of the
Andes, volcanic eruptions of sufficient magnitude
Žwhere tephra must travel between 50 to 120 km
from these centers. could deposit tephra on the
peninsula and islands, depending upon the explosion
size and wind direction at the time of eruption.
1.1. The study area
2. Methods
The study area ŽFig. 1b. lies between the northern
Chonos Archipelago and the southern Taitao Peninsula, a complex island and channel landscape formed
by extensive ice erosion from the Patagonian icefield
that covered this region during the last glaciation
ŽClapperton and Sugden, 1988.. The dominant
bedrock of the region consists of metamorphic rocks
of Paleozoic age and granite of Cretaceous age
ŽNiemeyer et al., 1984., with thirteen Quaternary
large volcanic centers, which form the southern SVZ
Ž41830X –46800X S, Lopez-Escobar
et al., 1993.. Tec´
tonic activity in the region is associated with both
plate subduction and the influence of the Liquine–
˜
Ofqui fault system ŽCembrano et al., 1996.. Geochemically, the volcanic centers of the southern SVZ
are dominantly high-Al basalts, with andesites and
dacites found at Cay, Mentolat, Melimoyu, Yate,
Huequi, Michinmahuida and Hudson and rhyolites at
Fieldwork was conducted in the southern hemisphere summers of 1991, 1992, 1994, 1995 and
1996, with the logistic support of Raleigh International ŽUK. and CONAF ŽCorporacion
´ Nacional
Forestal, Chile.. Sediment sequences were extracted
from eight small closed lake basins ŽFig. 1b. using a
modified 5-cm diameter Livingstone piston corer
ŽWright, 1967.. Six full sequences from basal lateglacial clays to the present were recovered from
Laguna Stibnite Ž46825X S, 74824X W., Laguna Six
Minutes Ž46825X S, 74820X W., Laguna Lofel Ž44853X S,
74824X W., Laguna Lincoln Ž45822X S, 74804X W., Laguna Oprasa Ž44821X S, 73839X W. and Laguna Facil
Ž44819X S, 74817X W., and two partial postglacial sequences from Laguna Marcelo Ž46828X S, 74810X W.
and Laguna Miranda Ž46808X S, 73826X W.. Samples
of the uppermost 10 cm of lake mud sediments were
242
Table 1
Chonos–Taitao tephra glass geochemistry Žtotal dataset normalised EMPA to 100 wt.%, P2 O5 and MnO values, all very low, are not included in table.
SiO 2
TiO 2
Al 2 O 3
FeO a
MgO
CaO
Na 2 O
K 2O
Cl
N
Laguna Oprasa
Opr-8)
Opr-7)
Opr-7))
Opr-6)
Opr-6))
Opr-5)
Opr-4))
Opr-3)
Opr-3))
Opr-1)
54.01"2.75
56.96"0.48
62.22
57.20"1.00
66.33"0.91
54.77"0.03
64.47"1.07
55.83".049
59.77"0.47
56.24"0.30
2.21"0.50
1.97"0.30
1.87
2.06"0.20
1.15"0.18
1.26"0.01
1.54"0.15
2.17".057
1.76"0.45
1.71"0.15
16.38"2.48
14.55"1.22
14.70
15.09"0.42
14.73"0.95
15.57"0.08
14.77"1.27
14.47"1.03
16.51"2.27
15.80"0.79
10.56"3.36
10.51"0.95
8.46
9.94"0.79
6.57"0.14
9.36"0.13
7.30"0.71
10.93"0.77
7.09"2.27
8.46"0.38
3.93"3.57
3.77"0.34
1.76
3.35"1.00
1.04"0.24
5.70"0.06
1.80"0.40
4.08"0.37
1.96"0.73
3.91"0.28
6.78"0.23
6.88"0.06
4.79
6.88"0.14
3.27"0.50
8.81"0.06
4.12"0.46
7.08"1.00
5.95"1.39
7.95"0.31
4.31"0.67
3.48"0.18
3.56
3.59"0.04
3.09"0.16
3.15"0.03
3.83"0.77
3.67"0.06
4.71"0.91
4.12"0.18
1.46"0.36
1.48"0.11
2.33
1.58"0.28
3.55"0.55
1.11"0.06
1.76"0.16
1.48"0.51
1.98"0.56
1.50"0.17
0.15"0.00
0.14"0.01
0.16
0.10"0.02
0.12"0.03
0.08"0.00
0.17"0.02
0.08"0.02
0.09"0.03
0.11"0.01
6
22
1
10
2
28
6
16
2
16
Laguna Facil
Fac-3)
Fac-2)
Fac-2))
Fac-1))
54.75"0.67
55.39"1.11
60.26"1.40
68.52"0.18
1.31"0.03
2.26"0.16
1.75"0.19
1.09"0.01
15.63"0.06
15.55"2.67
15.81"1.48
16.78"0.06
9.45"0.15
9.96"0.92
7.73"1.07
3.47"0.01
5.64"0.13
3.18"1.09
2.69"0.69
0.98"0.02
8.75"0.42
7.75"0.86
5.67"0.68
1.88"0.06
3.28"0.68
3.38"0.30
3.45"0.15
3.83"0.12
0.98"0.06
1.69"0.57
2.30"0.27
3.14"0.10
0.05"0.01
0.08"0.03
0.11"0.01
0.12"0.01
16
10
6
17
Laguna Lincoln
Lin-4)
Lin-3)
Lin-2))
Lin-1)
55.42"0.45
56.24"0.62
64.77"0.06
56.44"0.71
1.80"0.16
2.68"0.14
1.17"0.01
2.24"0.86
15.44"2.08
14.48"0.47
16.99"0.12
15.52"1.57
10.55"1.51
11.65"0.90
5.56"0.31
9.08"0.44
3.57"0.52
3.03"0.66
1.48"0.04
3.34"0.06
8.39"0.25
6.81"0.34
3.56"0.03
7.24"1.43
3.61"0.47
2.90"0.71
3.26"0.09
4.36"0.30
0.95"0.12
1.78"0.35
2.89"0.09
1.47"0.76
0.06"0.01
0.14"0.00
0.19"0.05
0.10"0.02
13
17
26
3
Laguna Lofel
Lof-4)
Lof-4))
Lof-3)
Lof-3))
Lof-2)
Lof-2))
Lof-1)
56.60"1.28
67.98"2.74
55.44"0.06
68.62
54.19
66.99"0.44
57.47"0.22
2.04"0.59
0.85"0.26
2.27"0.00
1.05
1.90
0.84"0.42
1.88"0.05
14.90"0.41
15.10"0.11
15.34"0.06
16.85
14.91
15.11"0.88
16.04"0.98
10.06"0.73
4.34"0.04
9.88"0.04
3.43
11.42
4.89"0.88
8.12"0.51
3.42"0.98
1.17"0.79
3.85"0.04
1.02
4.24
1.00"0.76
3.26"0.01
6.57"1.56
3.38"1.45
7.34"0.05
2.04
5.90
3.17"0.54
5.72"1.42
3.84"0.64
3.78"0.71
3.62"0.04
3.51
4.99
5.38"0.96
4.25"0.67
1.80"0.81
2.80"0.79
1.95"0.07
3.07
2.15
2.13"0.90
2.72"1.55
0.08"0.06
0.16"0.04
0.10"0.02
0.19
0.10
0.04"0.03
0.12"0.01
14
3
8
1
1
2
2
Laguna Stibnite
Stb-4)
Stb-4))
Stb-3)
Stb-3))
Stb-2)
Stb-1)
54.89
66.28"4.37
56.17"2.70
61.71
54.59"0.27
51.44"2.13
2.18
1.19"0.57
2.20"0.04
1.85
2.39"0.17
2.12"0.03
14.68
15.12"0.44
14.20"0.23
14.98
15.70"0.36
15.06"2.36
11.36
5.18"2.79
10.44"1.70
7.34
9.90"0.13
11.81"2.95
3.35
1.10"0.78
3.58"1.20
2.27
3.30"0.38
5.25"2.77
6.83
2.68"1.65
6.55"1.48
3.80
7.86"0.18
7.23"1.32
4.24
4.43"1.35
3.74"0.13
4.18
3.75"0.06
4.12"0.00
1.59
3.30"0.42
1.76"0.47
2.68
1.48"0.37
1.38"0.02
–
–
–
–
–
–
1
18
15
1
2
18
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Sample no.
2.38"0.05
1.80
1.78"0.14
1.24"0.04
13.82"0.44
16.71
15.88"0.70
16.60"0.04
10.58"0.42
6.84
8.78"0.57
5.00"0.07
3.38"0.08
2.45
4.34"0.19
1.52"0.01
6.81"0.12
4.79
8.06"0.32
3.52"0.02
3.41"0.01
3.92
3.79"0.28
3.12"0.14
1.91"0.01
2.21
1.34"0.19
2.71"0.05
0.09"0.01
0.14
0.10"0.00
0.10"0.02
6
1
10
22
Laguna Six Minutes
Six-4)
57.03"2.96
Six-4))
65.61"1.17
Six-3)
54.24"3.93
Six-3))
60.98
Six-2)
55.33"4.32
Six-1)
52.85"0.79
1.43"0.05
1.15"0.10
1.90"0.47
1.80
1.99"0.30
2.28"0.46
16.34"0.22
16.10"0.07
13.18"3.08
16.71
15.11"0.36
15.98"1.69
7.76"1.00
4.88"0.40
11.43"4.36
6.84
11.05"2.84
9.69"1.12
3.33"1.35
1.25"0.28
6.65"5.68
2.45
3.54"2.50
3.19"0.40
6.64"1.76
2.77"0.93
5.81"1.53
4.79
6.10"0.51
8.27"0.43
4.75"0.38
4.54"0.23
3.97"0.89
3.92
4.17"0.48
5.16"0.38
1.82"0.65
2.88"0.32
1.54"0.23
2.21
1.45"0.59
1.14"0.35
–
–
–
–
–
13
7
17
1
15
13
Laguna Marcelo
Mar-2)
56.01"1.27
Mar-2))
64.36"1.32
Mar-1)
54.99"3.02
1.47"0.07
1.31"0.30
2.40"0.54
16.85"0.84
15.23"0.87
14.53"0.81
8.03"0.25
5.58"1.51
10.15"2.45
3.54"0.20
1.31"0.10
3.36"0.79
7.43"1.16
3.29"0.20
6.97"0.62
4.26"0.25
5.95"1.08
4.55"0.28
1.48"0.32
2.07"1.20
1.75"0.20
–
–
–
5
16
17
Surface Samples
Surface)
54.09"0.28
Surface))
64.58"0.05
1.52"0.08
1.16"0.01
16.53"0.18
16.11"0.25
8.78"0.52
5.07"0.39
4.59"0.05
1.50"0.10
8.30"0.01
3.24"0.25
4.06"0.08
4.78"0.71
1.31"0.06
2.79"0.27
–
–
4
18
Hudson Õolcano (SSVZ) b
Hudson)
53.15
Hudson))
61.97"2.27
2.40
1.52"0.39
16.31
18.88"2.96
10.68
4.83"0.40
3.77
1.68"0.12
7.01
4.17"0.29
4.85
5.06"1.01
1.31
2.54"0.04
–
–
1
4
SSVZ b
Cay)
Cay))
Maca)
52.84
66.74
52.02
1.02
0.6
1.23
18.5
16.4
18.6
7.63
4.23
8.92
5.14
1.29
4.78
10.3
3.34
9.68
3.52
5.54
3.35
0.76
2.1
0.59
–
–
–
1
1
1
AVZ b
Burney))
Aguilera))
Lautaro))
64.77"0.29
65.00
66.81
0.38"0.06
0.61
0.59
17.86"0.58
16.71
16.62
3.65"0.33
4.05
3.53
2.19"0.01
2.11
2.05
5.47"0.09
4.98
4.32
4.48"0.34
4.24
3.76
1.01"0.11
2.06
2.20
–
–
–
2
1
1
–: not determined; N: number of analyses; major elements are normalised to 100%.
)Basic glass population Ž - 59 wt.% SiO 2 .. ))Silicic glass populations Ž ) 59 wt.% SiO 2 ..
a
Total Fe as FeO.
b
Normalised geochemical data from selected volcanic centres Ždetermined from tephra glass only. in the SSVZ and AVZ ŽFuta and Stern, 1988; Stern, 1990, 1991..
Analysis was performed at the Department of Earth Sciences, University of Cambridge, using a Cameca SX50 spectrometer microprobe, an electron microscope with three wave
dispersive spectrometers and a LINK AN10000 energy dispersive spectrometer running PAP matrix correction software.
The probe operated at 20 kV, using a 10 nA beam current and a 10 mm defocused beam to minimise loss of Na and K Ž50 s count time..
A mixture of minerals, natural oxides and pure metals were employed as standards that were periodically checked in order to verify internal consistency of the results.
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Laguna Miranda
Mir-3)
57.41"0.03
Mir-3))
60.98
Mir-2)
55.77"0.17
Mir-1))
66.09"0.13
243
244
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
taken Žusing a Hongve
sampler; Wright, 1980. from
¨
Lagunas Stibnite, Six Minutes and Marcelo. The
tephra found in these lake mud surface samples from
the Taitao Peninsula is most likely to have been
deposited in 1971, since an explosive eruption of the
Hudson volcano occurred in August of that year
ŽFuenzalida, 1976.. The samples from Laguna Stibnite and Laguna Six Minutes were collected in January 1991, predating the larger more recent eruption
of the Hudson volcano in August 1991 ŽNaranjo et
al., 1993.. The samples from Laguna Marcelo were
collected in January 1992 and these may contain
tephra from this more recent eruption.
Possible tephra layers in the cores were located by
visual inspection, with the aid of the X-ray analyses
and sediment magnetic susceptibility data. Each core
was described in detail and scanned by a magnetic
susceptibility core scanning loop at exactly 2-cm
intervals. This identifies changes in the abundance of
ferrimagnetic minerals, which is used as an indication of changing erosional input to the lake, and can
assist in the location of tephras. Major tephra layers
were located in this way and the glass shards extracted ŽH 2 O 2 digestion., mounted and polished for
electron microprobe analysis ŽEMPA., under the
conditions described in the caption of Table 1 and
following the guidelines set down by Froggatt Ž1992.
and Hunt and Hill Ž1993.. EMPA was chosen over
bulk analytical methods as it is grain specific, avoiding the problems associated with detrital contamination and density fractionation during the sedimentation process ŽFroggatt and Gosson, 1982.. We attempted to obtain more than 10 analysis points for
each sample; in some cases, however, we were able
to obtain less than the recommended sample size in
the thinner tephra layers as only a few shards were
present.
The similarity between geochemical data from
different tephra samples was tested by: Ž1. determining the mean and standard deviation for each measured element; Ž2. constructing plots of the major
elements that have been shown to be useful discriminatory variables, namely SiO 2 , K 2 O and TiO 2 ŽFuta
and Stern, 1988.; and Ž3. numerical analysis Žsimilarity coefficients, Borchardt et al., 1972; Beget
´ et al.,
1991. of the multivariate geochemical data to evaluate and compare the resemblance between selected
samples. The source volcano for each tephra may be
identified by comparing the geochemistry of tephra
glass from each sample with reference geochemical
data sets from previously published tephra glass
geochemistry ŽStern et al., 1984; Futa and Stern,
1988; Stern, 1990, 1991; Lopez-Escobar
et al., 1993;
´
Naranjo et al., 1993.. All major element data have
been normalised to 100% for valid geochemical
comparisons. Chronological control is then provided
by using a combination of AMS and bulk 14 C dating.
The dates are reported throughout this paper as
calibrated ages Žcal yr BP. by using the program
Calib 3.0.3 ŽStuiver and Reimer, 1993., though radiocarbon years before present Žyr BP; present is
1950 AD. are also provided.
3. Tephrochronology of the Chonos–Taitao lake
sediment cores
3.1. Magnetic susceptibility and Õisibility of tephras
High resolution studies of the mineral magnetic
properties of the cores found several narrow layers
that exhibited anomalously high magnetic susceptibility values ŽFig. 2.. Similar patterns of susceptibility variation were identified in all the cores and with
the exception of basal fluvioglacial olive-grey clays,
are considered to be due to tephra deposition in the
lake sediments Žhigh magnetite concentration, Oldfield, 1988.. When located, the tephra layers typically ranged from 0.1 to 0.5 cm in thickness and
from silt to sand grain size in the more distal sites
ŽStibnite, Six Minutes, Marcelo, Lincoln, Lofel,
Oprasa, and Facil., and up to 8 cm thick and coarse
sand grain size in the more proximal site ŽMiranda..
Susceptibility values were also higher in the proximal site than in the other sites, possibly reflecting a
greater concentration of magnetic minerals in the
lake sediments. The sediments lying immediately
above and below the tephra deposits were investigated for evidence of tephra mobilisation, which in
each case suggested that the tephra layers were
discrete and that bioturbation or reworking was not a
significant factor in sedimentation.
3.2. Electron probe analysis of tephras
The geochemical composition of glass shards for
different tephra layers are summarised as means Žand
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
245
Fig. 2. Stratigraphy, magnetic susceptibility variations and radiocarbon dating locations in a series of cores from the Chonos–Taitao region,
Chile. Depth is recorded as meters below water surface.
246
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Fig. 3. Plots of SiO 2 vs. TiO 2 and K 2 O from different volcanic centers in the SSVZ and AVZ. A dashed line marks the limits of the
distribution of wt.% values for the lake mud surface samples and reference tephra samples for Hudson volcano.
standard deviations. of the EMPA results ŽTable 1.. 1
The reported means are averages of analyses collected on multiple discrete shards from each tephra
layer, after normalising to correct for varying degrees of hydration, which ranged from 1 to 5 wt.%
for the tephras analysed during this study. Na 2 O
percentages are low and very similar throughout,
suggesting that Na depletion during analysis was not
significant. We also include the previously published
normalised microprobe analysis of glass from volcanic centers in the SSVZ and AVZ in our analysis.
The reference data from 3 volcanic centers in the
SSVZ ŽCay, Maca and Hudson., 3 volcanic centers
in the AVZ ŽBurney, Aguilera and Lautaro. and
recent tephra from the 1971 and 1991 Hudson eruptions ŽTable 1. show the range in composition from
basalt Ž- 52 wt.% SiO 2 . to rhyolite Ž) 70 wt.%
1
The entire data set Žprior to normalisation. can be accessed
at the WWW page - http:rrwww-palecol.plantsci.cam.ac.ukr
chilertephra.html).
SiO 2 . magmas, though there is a predominance of
basalts and basaltic andesites. Fig. 3 shows that each
volcanic center exhibits a good correlation between
SiO 2 –TiO 2 and SiO 2 –K 2 O, but the relationship between both oxides varies from center to center.
Hudson volcano basalts and basaltic andesites show
variable Al 2 O 3 concentrations between 15 and 19
wt.%, intermediate K 2 O, and high TiO 2 and FeO
wt.% values, distinguishing Hudson from other volcanic centers. The plots of SiO 2 vs. TiO 2 and K 2 O
ŽFig. 3. illustrate this bimodal distribution of the
glass geochemistry from the recent eruptions. In this
case, it is likely that two geochemical populations
have originated from more than one magma source
within the same volcanic center, as was reported
during the 1991 eruption of Hudson volcano ŽNaranjo
et al., 1993.. However, it must be stressed that some
eruptions may be completely basaltic and others
andesiticrdacitic.
The microprobe analysis of glass from 32 tephra
samples show that the tephras range from basalt to
basaltic andesites and andesites Ž52–63 wt.% SiO 2 .,
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
and more rarely dacitic type magma. All show a high
TiO 2 Ž) 1 wt.%. and FeO Ž) 5 wt.%. content. A
mixed assemblage of glass is identified in some
samples on the basis of high standard deviations in
the initial averaging analysis ŽFroggatt and Gosson,
1982.. These samples were then divided into basic
ŽSiO 2 - 59 wt.%. and silicic ŽSiO 2 ) 59 wt.%. glass
populations. A bimodal distribution of grains within
tephra layers is unlikely to suggest a multiple source,
since two eruptions would have to occur simultaneously, distributing tephra to the same areas in similar
proportions.
Plots of SiO 2 vs. TiO 2 and K 2 O ŽFig. 4. illustrate
the similarity between the distribution of Hudson
volcano reference data and the Chonos–Taitao lake
tephra samples. Many samples fall in the field of
Hudson composition, indicating that some tephras
are chemically similar and may be derived from the
same volcanic center. There is a good correlation
between the geochemical composition of tephras
found to the southwest of Hudson volcano, in the
Taitao region, and the Hudson volcano reference
data. Tephra recovered from lakes in the Chonos
region, northwest of Hudson volcano, do not all fall
in the field of Hudson composition as well as those
from lakes in the Taitao region. Outliers within each
tephra sample may reflect a wider geochemical range
for Hudson glass element composition than is illustrated by the limited number of reference samples
available to this analysis. Outliers may also be explained by analytical variations, though the low variability in Na 2 O and continued checks against standards during analysis suggests that this is unlikely to
be a significant contributing factor. Alternatively,
some tephras found in the Chonos region may be
derived from other volcanic centers in the southern
SVZ.
Similarity coefficients ŽSC. are used to evaluate
the similarity between the multivariate geochemical
data from the Chonos–Taitao tephra layers Žwhere
sample size ) 1. and the Hudson volcano reference
data. A matrix of SC values is presented in Table 2,
where values G 0.92 are generally taken as indicative of correlations between tephra samples and those
between 0.6–0.90 are typically obtained for noncorrelative, unrelated tephras ŽFroggatt, 1992.. Significant SC values are found between a number of
tephras containing the basic glass population Žboxed
247
values in Table 2a., suggesting that many of these
tephras are identical and may be correlated to the
same eruption event. The silicic glass population
from Hudson volcano and the recent surface samples
are shown to be identical ŽTable 2b..
3.3.
14
C r calibrated age and correlation of tephras
If tephras recovered from the Chonos–Taitao lakes
are derived from Hudson eruptions, then there should
be at least some with the same age. A series of
radiocarbon dates have been obtained from all lakes
Žexcept Laguna Marcelo, Table 3. in order to either
directly date the tephra deposition events ŽAMS dating analysis., or to closely bracket the age of the
tephra layers by interpolating bulk-sediment radiocarbon ages, assuming linear age model for sedimentation rates in these lake basins.
A total of 7 tephra groups were recognised as
being correlated on the basis of age determination
andror geochemical content ŽFig. 5.. These tephras
are assigned the codes HW1 to HW7 ŽTable 4.,
denoting a tephra layer that has been correlated and
traced in more than one site, at a distance of more
than 50 km from its source at Hudson volcano.
Where more than one age is associated with geochemically similar tephra layers, the ages have been
pooled to provide a more precise date for the tephra
eruption event. The calibrated ages for correlated
tephra layers found within the Chonos–Taitao lakes
are 14 560, 13 890, 11 060, 7540, 3840, 2740, and
1560 cal yr BP.
With the exception of the two recently documented eruptions of the Hudson volcano in 1971 and
1991 ŽFuenzalida, 1976; Naranjo et al., 1993., only
two postglacial tephras identified in southern South
American sediments have been previously assigned
to this volcano and dated ŽStern, 1991; Naranjo and
Stern, 1998.. The first, an eruption of significant
magnitude which is dated to around 7530 cal yr BP
ŽH 1 ., and a second which is dated at 3885 cal yr BP
ŽH 2 .. Isopleth and isopach maps for these two eruptions shows the tephra dispersal in a predominantly
southeastern direction ŽNaranjo and Stern, 1998..
Nevertheless, two tephra layers in this study, Opr-5
and Mir-1, that are to the west of Hudson volcano
are possibly correlated with these two eruptions on
the basis of their similar ages. The pooled mean of
248
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Fig. 4. Plots of SiO 2 vs. TiO 2 and K 2 O for the 32 tephra samples from lakes in the Chonos–Taitao region. The dashed line marks the limits
of the distribution of wt.% values for the lake mud surface samples and reference tephra samples for Hudson volcano Žsee Fig. 3..
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Fig. 4 Žcontinued..
249
250
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Table 2
Similarity coefficient ŽSC. calculations Žafter Borchardt et al., 1972. comparing major element analysis of tephras from the Chonos–Taitao
region, including the reference samples for Hudson volcano and other SSVZ and AVZ centers Žcoefficients calculated using SiO 2 , Al 2 O 3 ,
TiO 2 , FeO, CaO, Na 2 O and K 2 O.
SC values for basic and silicic glass population Žsignificant values are boxed..
Basic glass population Ž- 59 wt.% SiO 2 ..
b
Silicic glass population Ž) 59 wt.% SiO 2 ..
a
ages for these tephras gives eruption dates at 7540
cal yr BP and 3840 cal yr BP for HW4 Žs H 1 . and
HW5 Žs H 2 ., respectively. The inability to correlate
at least four tephra layers from the Chonos region,
namely, Opr-6, Opr-4, Opr-2, and Fac-3 Žcorrelations
for Lof-1, Lof-2 and Lof-3 are uncertain. with any
other tephra layer may be due to incomplete recovery of all tephras in our cores. It cannot be discounted that these eruptions deposited tephra in the
other Chonos–Taitao lakes, though these deposits
may remain undetected without fine-resolution mi-
croscopic analyses ŽRose et al., 1996.. Alternatively,
these uncorrelated tephras may be derived from minor postglacial eruptions of other southern SVZ volcanic centers.
It could be expected that tephra deposited in the
Chonos–Taitao region from an eruption of the Hudson volcano would be of similar composition.
Tephras HW1 to HW7 are all bimodal in composition, with the exception of HW5 , though there is
intersite variation between geochemically identical
tephras. The observed discrepancies could be ex-
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Table 3
Radiocarbon age determinations for tephras and associated lake
sediments from five lakes in the Chonos–Taitao region ŽQ series
are bulk radiometric dates and the AA and Beta series are AMS
dates.
Sample depth
Žm.
Radiocarbon age
Žyears BP.
Laboratory reference
number
Laguna Stibnite
2.91–3.01
2.96
3.25
3.75–3.85
4.32–4.42
4.80
5.04–5.12
5.25
5.53–5.73
6.58–6.78
1635"40
1830"75
2600"60
4590"55
6290"60
9995"85
11 005"75
11 965"100
13 920"80
14 335"145
Q-2835
AA-10296
AA-10295
Q-2836
Q-2837
AA-10294
Q-2838
AA-10293
Q-2839
Q-2840
Laguna Six Minutes
3.63
1605"55
3.96
2560"55
5.05
9930"85
5.34
11 855"120
AA-10300
AA-10299
AA-10298
AA-10297
Laguna Lincoln
2.06–2.16
2.82–2.92
3.60–3.70
4.30–4.40
4.94–5.08
2470"40
4905"30
8380"80
11 145"105
13 320"120
Q-2962
Q-2961
Q-2960
Q-2959
Q-2958
Laguna Miranda
5.05–5.15
6.89–6.99
8.36–8.46
1160"30
2710"35
4250"35
Q-2977
Q-2976
Q-2975
Laguna Lofel
3.90–4.00
5.90–6.00
7.90–8.00
9.90–10.00
11.80–11.90
2350"40
4580"45
7275"65
10 720"90
13 480"110
Q-2967
Q-2966
Q-2965
Q-2964
Q-2963
Laguna Oprasa
3.60–3.70
5.52–5.60
7.60–7.68
8.20
8.82-8.90
930
9.60–9.70
10.04–10.12
10.30–10.40
120"30
3875"35
7750"55
9830"90
10 255"75
12 390"120
12 165"100
12 970"120
13 560"125
Q-2974
Q-2973
Q-2972
Beta-107815
Q-2971
Beta-107816
Q-2970
Q-2969
Q-2968
251
Table 3 Žcontinued.
Sample depth
Žm.
Radiocarbon age
Žyears BP.
Laguna Facil
2.80–2.90
4.80–4.90
210"30
2690"30
Laguna Facil
6.80–6.90
752
7.90–8.00
830
10.12–10.22
6245"45
10 080"100
9050"60
12 480"100
13 230"140
Laboratory reference
number
Q-2982
Q-2981
Q-2980
Beta-107812
Q-2979
Beta-107813
Q-2978
Depths are given as meters below water surface at time of coring.
plained by within lake processes such as, differential
settling of grains within the lake system, due to
sediment focusing andror differing densities of the
basalticrdacitic grains, relative to other components
of the sediment. Alternatively, increased distance
from the source volcano may cause sorting of the
basic and silicic glass shard populations.
3.4. Frequency and distribution of tephra falls from
Hudson Õolcano
The sequence of tephra layers recognised in the
Chonos–Taitao study region constitutes a partial
record of the actual sequence of tephra eruptions
from Hudson volcano during the postglacial period.
It is likely that there were many more eruptions from
Hudson volcano, and possibly other SSVZ and AVZ
volcanic centers, which are not recorded in the lakes
due to small eruption size, a wind direction not
favourable to tephra dispersal in a westerly direction,
or methodological procedures that are not sensitive
enough to recognise all tephras in this study. Naranjo
and Stern Ž1998. show a series of 9 tephras deposited in peat over the last 9350 calendar years
ŽJunco Alto, 92 km southeast of Hudson volcano.,
that they suggest could also have been derived from
the Hudson volcano. A detailed sedimentological
analysis of the Laguna Miranda sequence, the most
proximal lake to Hudson volcano in this study, revealed at least 22 presumed tephras deposited over
the last 5 millennia ŽHaberle et al., in press of which
252
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Fig. 5. Stratigraphy and tephra correlations in a series of cores from 8 lakes in a latitudinal transect from south ŽTaitao region. to north ŽChonos region.. Correlations between
cores based on electron lake mud–water interface.
Tephra
name
Sample
Chronological control yr BP
Žcal yr BP.
Pooled mean of 14 C dates,
yr BP Žcal yr BP.
Dating T
test ŽXi 2 .
Geochem
SC mean
Other possible
tephra correlates
HW1
Opr-1
Fac-1
Stb-1
Six-1
Opr-3
Fac-2
Stb-2
Six-2
Opr-5
H1
Mir-1
H2
Stb-3
Six-3
Stb-4
Six-4
12 390"120 Ž14 730–14 280.
12 480"100 Ž14 830–14 420.
11 965"100 Ž14 120–13 790.
11 855"120 Ž14 000–13 650.
9830"90 Ž11 010–10 960.
10 080"100 Ž11 960–11 190.
9995"85 Ž11 670–11 000.
9930"85 Ž11 330–11 000.
;6750 a Ž7540.
;6700 b Ž7530.
; 3535a Ž3820.
; 3600 b Ž3885.
2600"60 Ž2760–2720.
2560"55 Ž2750–2520.
1830"75 Ž1830–1630.
1605"55 Ž1540–1410.
12 440 Ž14 560.
0.17
Ž3.84.
0.29
Ž3.84.
3.14
Ž7.81.
–
Lin-1
ŽLof-1, Lof-2?.
Lin-2
ŽLof-2, Lof-3?.
Lin-3, Lof-4
HW2
HW3
HW4
HW5
HW6
HW7
11 920 Ž13 890.
9950 Ž11 060.
–
0.935
6725 Ž7540.
–
–
3570 Ž3840.
–
–
2580 Ž2740.
0.23
Ž3.84.
–
0.920
1690 Ž1560.
0.950
Opr-7, Mar-1
Lin-4, Mir-2
Mar-2, Mir-3
Opr-8
The significant correlations between each sample are show on the basis of a T test of similarity Žscores given for samples shown to be the same at 95% confidence level. for the
AMS dates and mean Similarity coefficients for the geochemical data.
Other possible tephra correlates based on high SC scores andror similar ages are also given when shown to be significant.
a
Inferred ages determined by a linear age model for Laguna Oprasa and Laguna Miranda sedimentation rates.
b
Dates of tephra layers H 1 and H 2 found in Patagonia and Tierra del Fuego and attributed to past Hudson eruptions by Naranjo and Stern Ž1998..
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
Table 4
Ages Žstandard and calibrated. of Hudson volcano tephra deposits, determined from direct AMS dating of organics associated with tephras and geochemical analysis of glass
shards
253
254
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
only the three thickest tephras are studied here.
Improved dating control, combined with geochemical analysis, may allow these tephras to be correlated
with those from the Chonos–Taitao lakes and further
afield.
This study has identified seven eruption events
occurring throughout the postglacial period, distributing tephra from the north to the south of the
Chonos–Taitao region, and in at least two cases
ŽHW4 and HW5 . the tephras are found as far south as
Patagonia and Tierra del Fuego ŽNaranjo and Stern,
1998.. The recurrence interval between explosive
eruptions of Hudson volcano is highly irregular and
it is difficult to establish a clear frequency for eruptions from this data. Tephras HW4 and HW5 represent the most widespread tephra deposits in this
sequence, suggesting that major eruptions of Hudson
volcano that distributed tephra in both a westerly and
easterly direction from the Andes, similar to that
which occurred in 1991, have occurred in the past at
a frequency of between once every 3800 calender
years Ž3350 " 250 14 C years, Naranjo and Stern,
1998.. The most proximal site to Hudson volcano is
Laguna Miranda, around 50 km to the southwest of
the volcano, that records minor eruptions at an average of 1 every 225 calendar years, though this
estimate should be considered a minimum since
tephra preservation at any one site will depend on
wind direction at the time of the eruption.
Few studies in southern South America have
utilised tephras as relative dating horizons ŽHeusser,
1964, 1990; Heusser et al., 1989.. The Hudson volcano tephrochronology provides the opportunity to
strengthen the chronological interpretations of
palaeoecological and archaeological records in this
region. For example, there is currently considerable
debate concerning the evidence in southern South
America for the cold climate Younger Dryas phase
between 12 900 and 11 100 cal yr BP ŽHeusser and
Rabassa, 1987; Ashworth and Markgraf, 1989; Ashworth and Hoganson, 1993., due primarily to conflicting interpretations of the chronology of events
recorded in the available palaeoecological records.
Hudson tephras HW2 Ž13 890 cal yr BP. and HW3
Ž11 060 cal yr BP. span this period of climatic
change at the transition to the postglacial warm
period and could be used to strengthen site chronological interpretations and examine environmental
conditions across a number of sites in the region just
prior to, and at the end of, the Younger Dryas chron
ŽHaberle et al., 1998..
4. Summary and conclusions
Many studies have shown that tephra layers can
be used as important stratigraphic marker horizons
where more than one site is being investigated in a
region. With a tight chronological framework these
tephras can now be utilised as time stratigraphic
horizons, reducing the necessity for excessive numbers of radiocarbon age determinations. A
tephrochronology is superior to a radiocarbon
chronology in that individual layers are often deposited in less than one week, enabling one to correlate cores with precision. In many cases, sediments
from lakes with no inlet streams provide an ideal
environment for the preservation of discrete tephra
layers due to their continuous, often undisturbed
sediments. The glaciated regions of southern South
America provide an ideal source for suitable lakes.
The answers given for the three questions posed
at the beginning of this study have enabled us to
construct a preliminary tephrochronology for the
Chonos–Taitao region. Comparisons with geochemical data from other volcanic sources in southern
Chile indicate that Hudson volcano is the most likely
source vent for at least seven of the tephra layers
found in Chonos–Taitao lake sediments. The dates
for correlated eruption events are 14 560, 13 890,
11 060, 7540, 3840, 2740, and 1560 cal yr BP. The
frequency of Hudson volcano eruptions in which
tephra is dispersed in both a westerly and easterly
direction, similar to that recorded in 1991 from
Hudson volcano, is around 1 per 3800 years during
the postglacial period.
Acknowledgements
We would like to thank Raleigh International and
CONAF for logistic support and permission to carry
out this work in Region XI, Chile. Many international venturers, including some 25 Chilean venturers, contributed outstandingly to the success of this
work in difficult and remote terrain. Keith Bennett
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
and Julie Fossitt assisted during fieldwork. Stephen
Read, Thomas Bleser, Steve Boreham, Jane Bunting
and Ray Fella provided assistance with microprobe
analyses. Keith Bennett, Charles Stern and one
anonymous reviewer provided valuable comments on
the results and interpretations of the tephra data set.
This project is funded by a Natural Environment
Research Council Studentship and the Leverhulme
Trust Fund.
References
Ashworth, A.C., Hoganson, J.W., 1993. The magnitude and rapidity of the climate change marking the end of the pleistocene in
the mid-latitudes of South America. Palaeogeogr., Palaeoclimatol., Palaeoecol. 101, 263–270.
Ashworth, A.C., Markgraf, V., 1989. Climate of the Chilean
Channels between 11,000 to 10,000 yr BP based on fossil
beetle and pollen analyses. Rev. Chil. Hist. Natural 62, 61–74.
Auer, V., 1974. The isorhythmicity subsequent to the Fuego–
Patagonian and Fennoscandian ocean transgressions of the
latest glaciation. Ann. Acad. Scien. Fennicae III, Geol. Geograph. 115, 1–188.
Beget,
´ J.E., Reger, R.D., Pinney, D., Gillispie, T., Campbell, K.,
1991. Correlation of the holocene Jarvis Creek, Tangle Lakes,
Cantwell, and Hayes tephras in South-Central and Central
Alaska. Quat. Res. 35, 174–189.
Borchardt, G.A., Aruscavage, P.J., Millard, H.T. Jr., 1972. Correlation of the Bishop ash, a pleistocene marker bed, using
instrumental neutron activation analysis. J. Sediment. Petrol.
42, 301–306.
Cembrano, J., Herve,
´ F., Lavenu, A., 1996. The Liquine–Ofqui
˜
fault zone: long-lived intra-arc fault system in Southern Chile.
Tectonophysics 259, 55–66.
Clapperton, C.M., Sugden, D.E., 1988. Holocene glacier fluctuations in South America and Antarctica. Quat. Sci. Rev. 7,
185–198.
Froggatt, P.C., 1992. Standardisation of the chemical analysis of
tephra deposits. Report on the ICCT working group. Quat. Int.
13–14, 93–96.
Froggatt, P.C., Gosson, G.J., 1982. Techniques for the Preparation
of Tephra Samples for Mineral and Chemical Analysis and
Radiometric Dating, Vol. 23. Victoria Univ. of Wellington
Publication.
Fuenzalida, R., 1976. The Hudson volcano. Proceedings of the
IAVCEI symposium on Andean and Antarctic volcanology
problems, 1974, Santiago, Chile, pp. 78–87.
Fujiyoshi, Y., Kondo, H., Inoue, J., Yamada, T., 1987. Characteristics of precipitation and vertical structure of air temperature
in northern Patagonia. Bull. Glacial Res. 4, 15–24.
Futa, K., Stern, C.R., 1988. Sr and Nd isotopic and trace element
compositions of Quaternary volcanic centers of the southern
Andes. Earth Planet. Sci. Lett. 88, 253–262.
255
Gajardo, R., 1995. La Vegetation
´ Natural de Chile: Clasificacion
´
y Distribucion
Editorial Universitaria, Santiago de
´ Geografica.
´
Chile.
Haberle, S.G., Lumley, S.H., Bennett, K.D., 1998. Late Quaternary vegetation dynamics in the Taitao Peninsula–Chonos
Archipelago, Region XI, Chile. Prog. Abstr. PEP I: Pole–
Equator–Pole Paleoclimate of the Americas. Merida,
´
Venezuela. Mar. 16–20, 1998.
Haberle, S.G., Szeicz, J.M. Bennett, K.D., in press. Late holocene
vegetation dynamics and lake geochemistry at Laguna Miranda, Region XI, Chile. Rev. Chil. Hist. Natural.
Heusser, C.J., 1964. Some pollen profiles from Laguna de San
Rafael area, Chile. In: Cranwell, L.M. ŽEd.., Ancient Pacific
Floras. Univ. of Hawaii Press, Honolulu, pp. 95–114.
Heusser, C.J., 1990. Late-glacial and holocene vegetation and
climate of subantarctic South America. Rev. Palaeobot. Palynol. 65, 9–15.
Heusser, C.J., Rabassa, J., 1987. Cold climate episode of Younger
Dryas age in Tierra del Fuego. Nature 328, 609–611.
Heusser, C.J., Heusser, L.E., Hauser, A., 1989. A 12 000 yr BP
tephra layer at Bahia Inutil ŽTierra del Fuego, Chile.. Anales
de Instituto de la Patagonia Serie Ciencias Naturales 19,
39–49.
Hunt, J.B., Hill, P.G., 1993. Tephra geochemistry: a discussion of
some persistent analytical problems. The Holocene 3, 271–278.
Lopez-Escobar,
L., Kilian, R., Kempton, P.D., Tagiri, M., 1993.
´
Petrography and geochemistry of Quaternary rocks from the
X
Southern Volcanic Zone of the Andes between 41830 and
X
46800 S, Chile. Rev. Geol. Chile 20, 33–55.
Lumley, S.H., Switsur, R., 1993. Late Quaternary chronology of
the Taitao Peninsula, southern Chile. J. Quat. Sci. 82, 161–165.
Miller, A., 1976. The climate of Chile. In: Schwerdtferger, W.
ŽEd.., Climates of Central and South America: World Survey
of Climatology, Vol. 12. Elsevier, Amsterdam.
Naranjo, J.A., Stern, C.R., 1998. Holocene explosive activity of
Hudson Volcano, southern Andes. Bull. Volcanol. 59, 291–
306.
Naranjo, J.A., Moreno, H., Bamks, N.G., 1993. La erupcion
´ del
volcan Hudson en 1991 Ž468S., Region
´ XI, Aisen,
´ Chile. Serv.
Nac. Geol. Min. Bol. 44, 1–50.
Niemeyer, H.R., Skarmeta, J.M., Fuenzalida, R.P., Espinosa,
W.N., 1984. Hojas Peninsula de Taitao y Puerto Aisen, Region Aisen del General Carlos Ibanez
˜ del Campo. Servicio
National de Geologia y Mineria, Carta Geologica de Chile,
No. 60–61, 80 pp.
Oldfield, F., 1988. Magnetic and element analysis of recent lake
sediments from the Highlands of Papua New Guinea. J. Biogeog. 15, 529–553.
Rose, N.L., Golding, P.N.E., Battarbee, R.W., 1996. Selective
concentration and enumeration of tephra shards from lake
sediment cores. The Holocene 6, 243–246.
Salmi, M., 1941. Die postglazialen eruptions schichten Patagoniens und Feuerlands. Ann. Acad. Scien. Fennicae, series A III
2, 1–115.
Stern, C.R., 1990. Tephrochronology of southernmost Patagonia.
Nat. Geograp. Res. 6, 110–126.
Stern, C.R., 1991. Mid-holocene tephra on Tierra del Fuego 548S.
256
S.G. Haberle, S.H. Lumleyr Journal of Volcanology and Geothermal Research 84 (1998) 239–256
derived from the Hudson volcano 468S.: evidence for a large
explosive eruption. Rev. Geol. Chile 182, 139–146.
Stern, C.R., Kilian, R., 1996. Role of the subducted slab, mantle
wedge and continental crust in the generation of adakites from
the Andean autral volcanic zone. Contrib. Miner. Petrol. 123,
268–281.
Stern, C.R., Futa, K., Muehlenbachs, K., 1984. Isotope and trace
element data for orogenic andesites from the Austral Andes.
In: Harmon, R.S., Barreiro, B.A. ŽEds.., Andean Magmatism:
Chemical and Isotopic Constraints. Shiva, pp. 31–46.
Stuiver, M., Reimer, P.J., 1993. Extended 14 C database and
revised CALIB radiocarbon calibration program. Radiocarbon
35, 215–230.
Veblen, T.T., Schlegel, F.M., Oltremari, J.V., 1983. Temperate
broad-leaved evergreen forests of South America. In: Ovington, J.D. ŽEd.., Ecosystems of the World 10: Temperate
Broad-leaved Evergreen Forests. Elsevier, Amsterdam.
Wright, H.E. Jr., 1967. A square-rod piston sampler for lake
sediments. J. Sediment. Petrol. 37, 975–976.
Wright, H.E. Jr., 1980. Cores of soft lake sediments. Boreas 9,
107–114.