14C
TIMING OF VOLCANIC AND PALEOSEISMIC EVENTS IN KAMCHATKA
N.E. Zaretskaya
Geological Institute of RAS, Moscow, Russia. E-mail: zaretsk@ginras.ru
Radiocarbon dating is widely used to date volcanic events in Kamchatka [1, 2, 3, 5]. A
high frequency of explosive eruptions, wide area of tephra deposition and high rate of organic
accumulation on the peninsula due to moderate and wet climate result in accumulation of so
called «soil-pyroclastic» or «peat-pyroclastic» sequences and provide a great opportunity to
reconstruct a detailed radiocarbon and calendar chronology of volcanic Holocene events in
Kamchatka, and to date paleoseismic events (paleotsunamies) buried in the peat bogs [6].
Samples originated from many sites all over the peninsula. Thus, many catastrophic and
moderate eruptions were dated and their ages estimated and then calibrated (transferred to
calendar ages) [4].
Nevertheless, there are some ambiguities and peculiarities of radiocarbon dating of such
geologic events.
First of all, samples often contain material of different ages (heterochronous sample):
1. Wood samples (logs) could have an inbuilt age, which we can hardly estimate due to high
compression by pyroclastic deposits;
2. Peat is often composed of variety of Carex (and other) species, some of which could pass
their roots through layers of tephra or tsunami deposits and thus yield younger ages than
expected age of peat horizon underlying tephra layer.
Calibration of the 14C ages of «instantaneous» geological events is also a problem,
because calibrating a single date or a number of combined individual dates gives a time range,
and not a certain age of the individual event.
All this details should be taken into account when reconstructing a continuous
radiocarbon and calendar chronology of volcanic and related events and paleotsunamies.
However, several strong volcanic events (such as the Kurile Lake caldera catastrophic
eruption) and moderate eruptions have been dated and radiocarbon and calendar chronology built
in the southernmost part of the Kamchatka Peninsula.
Also, volcanic and paleotsunami events were dated on the northeastern part of
Kamchatka, and some paleoenvironmental data was obtained.
The procedure of radiocarbon dating, age estimation and calibration is proposed in the
presentation.
This work became possible thanks to RFBR grant # 02-05-64991.
Refernces
1. Braitseva O.A., Melekestsev I.V. Litasova S.N., Sulerzhitsky L.D., Ponomareva V.V.
Radiocarbon dating and teprochronology in Kamchatka Radiocarbon, v. 35, No. 3, 1993,
p.463-477.
2. Braitseva O.A. Melekestsev I.V. Ponomareva V.V., Sulerzhitsky L.D. Ages of calderas
large explosive craters and active volcanoes in the Kuril-Kamchatka region Russia. Bulletin
of Volcanology No.57 1995, p.383-402.
3. Braitseva O.A. Ponomareva V.V., Sulerzhitsky L.D., Melekestsev I.V. Bailey J. Holocene
key-marker tephra layers in Kamchatka, Russia // Quaternary research, v. 47, 1997, p. 125139.
4. Braitseva O.A. Melekestsev I.V. Ponomareva V.V., Sulerzhitsky L.D. Geochronology of
the largest Holocene explosive eruptions in Kamchatka and their reflex in the Greenland Ice
Sheet // DAN, v. 352, #4, 1997b, p. 516-518.
5. Zaretskaia N.E., Ponomareva V.V., Sulerzhitsky L.D., Zhilin M.G. Radiocarbon studies of
peat bogs: an investigation of South Kamchatka volcanoes and Upper Volga archeological
sites // Radiocarbon, v.43, n.2, 2001, p.535-543.
6. Zaretskaya N.E., Ponomareva V.V., Uspenskaia O.N., Bliakharchuk T.A., Gunova V.S.
Paleoenvironmental history of the Northeastern Kamchatka coastal area in the second half of
the Holocene // PAGES meeting on «High Lattitude Paleoenvironment», Moscow, 2002.