International Journal of Coal Geology 132 (2014) 6–12
Contents lists available at ScienceDirect
International Journal of Coal Geology
journal homepage: www.elsevier.com/locate/ijcoalgeo
Blue-fluorescing amber from Cenozoic lignite, eastern Sikhote-Alin, Far
East Russia: Preliminary results
Igor Yu. Chekryzhov ⁎, Victor P. Nechaev, Valery V. Kononov
Far East Geological Institute, 159 Pr 100-let Vladivostoku, Vladivostok, Russia
a r t i c l e
i n f o
Article history:
Received 3 April 2014
Received in revised form 11 July 2014
Accepted 13 July 2014
Available online 1 August 2014
Keywords:
Blue amber
Paleogene lignite
FTIR
Volatiles
Wildfire
Perylene
a b s t r a c t
Blue and greenish-yellow, in addition to ordinary yellow-orange amber, has recently been found in a lignite seam
in the Zerkal'nenskaya depression, Primorsky Krai, Russia. The amber is associated with abundant charcoal and
fusain fragments in the host rocks. Its FTIR spectra indicate the presence of significant quantities of volatile matter, including free hydroxyl groups and carbon dioxide. Both CO2 and OH− contents are greater in the greenishyellow and blue hard varieties, suggesting rapid heating, possibly from a wildfire, followed by rapid cooling in
water as a causative agent of amber hardening and extreme polymerization. This process and the following
amber deposition in the reduced environment might produce the fluorescent aromatics that have been previously suggested and confirmed by this study as the blue glow main cause.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Amber, a gem that originates from fossilized plant resin, is widely
distributed throughout the world, mostly in Cenozoic and Cretaceous
sediments, and less commonly in older marine deposits. However, concentrations of commercially-valuable amber are quite rare. The largest
amber deposits are located in the southeastern Baltic regions. Amber
is characterized by a wide spectrum of colors, mainly yellow, red,
brown, and orange. A blue variety is one of the most uncommon and
valuable on the market. This variety is unusually luminous under normal sunlight, more brightly blue fluorescent under ultraviolet light,
and appears yellow or brown under artificial light. Famous deposits of
blue amber are located along the Atlantic coast of Central America, the
largest of which is exploited at the El Cacao Mine, Dominican Republic
(Iturralde-Vincent, 2001). The Dominican amber originated from angiospermous (Hymenaea) resin (Iturralde-Vincent, 2001; Langenheim and
Beck, 1965). Its blue glow was determined to have been caused by the
presence of perylene, as suggested by optical absorption, fluorescence,
and time-resolved fluorescence measurements (Bellani et al., 2005).
Another well-studied deposit containing both common and blue
amber varieties of Albian age was described at the El Soplao site, northern Spain (Menor-Salván et al., 2010; Najarro et al., 2009). This amber is
Cupressaceae in origin. Causes of its blue color were not determined.
⁎ Corresponding author. Tel.: +7 908 4485166.
E-mail addresses: chekr2004@mail.ru (I.Y. Chekryzhov), vnechaev@hotmail.com
(V.P. Nechaev), kononov46@mail.ru (V.V. Kononov).
http://dx.doi.org/10.1016/j.coal.2014.07.013
0166-5162/© 2014 Elsevier B.V. All rights reserved.
Small pieces of blue amber have recently been found in a lignite bed
from the Voznovo Formation, which is situated in the Zerkal'nenskaya
depression, eastern Sikhote-Alin, Far East Russia (Figs. 1 and 2). This
paper presents the first description of these pieces, including results of
our field observations, Scanning Electron Microscopy, Fourier Transform
Infrared Spectroscopy, as well as fluorescence and fluorescence excitation measurements. Some paleontological data that have been already
published (Pavlyutkin et al., 2011) are also discussed.
2. Geological outline
The Voznovo Formation consists of volcano-sedimentary deposits
(primarily mudstone, sandstone, tuffaceous mud- and sandstones, and
tuff) and includes a lignite bed that is up to 2 m thick. The section
studied at an active open-pit mine and from cores of coal exploration
boreholes is shown in Fig. 1.
The age of the upper part of the formation that overlies the lignite
bed is Early Oligocene, according to the most recent paleobotanical
data (Pavlyutkin et al., 2011), while K–Ar dating of the underlying
Suvorovo Formation basalt was determined to be Eocene (45.8 ±
1.1 Ma, Otofuji et al., 1995; 47.3 ± 1.21 Ma, Okamura et al., 1998). All
of the deposits of the Voznovo Formation are considered to be continental in origin. Nevertheless, recent work suggests that some of them
might be accumulated in the brackish-water environment. Significant
Na2O/Al2O3 elevations determined by XRF analyses below and above
the lignite bed confirm this suggestion (Fig. 1), while low Na2O/Al2O3
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
7
Fig. 1. Location of the Voznovo lignite deposit, its lithological column with Na2O/Al2O3 variations in the rocks along the section, and photograph showing the occurrence of blue amber with
charcoal in the lignite. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
values suggest that the amber-bearing sediments themselves were
deposited in the fresh-water environment.
been found in highly carbonaceous mudstone and lignite only, while
sandstone contains only friable yellow amber inclusions.
3. Methods
4.2. Paleobotanical data
The Voznovo amber was studied under reflected and transmitted
white and UV light using a Zeiss Stemi DV4® optical microscope
equipped with a Nikon Coolpix 4500® camera and Multispec® UV
lamp. Surface features and inorganic geochemistry were examined
using a JSM-6490LV scanning electron microscope equipped with EDS
INCA Energy, X-max and VDS INCA Wave applications. In addition,
Fourier Transform Infrared Spectroscopy was used with the help of a
Nicolet 6700 spectrometer (Thermo Scientific, USA) using potassium
bromide (KBr) disks prepared from powdered samples (3 mg) mixed
with dry KBr. All these works were undertaken at the Far East Geological
Institute (FEGI), Vladivostok, Russia. Fluorescence and fluorescence
excitation experiments were performed at room temperature using a
RF 5301 (Shimadzu) spectrofluorimeter at the Institute of Chemistry,
Vladivostok, Russia.
The plant fossil assemblage of the Voznovo Formation is dominated
by gymnosperms (Pavlyutkin et al., 2011). Among them, 45 species
belonging to three orders, namely Ginkgoales, Pinales, and Cupressales
including five families were identified. The Pinaceae family, which is a
well-known source of resin and amber (Tappert et al., 2011, 2013), is
represented by 31 species. The Cupressaceae family plants, also wellknown sources of resin and amber (Menor-Salván et al., 2010; Tappert
et al., 2011, 2013), are represented by Thuja nipponica Tanai et Onoe
and Cupressaceae sp. Araucariaceae is represented by a single pollen
grain. Fossil angiosperms of the Hymenaea family, which is the source
of Dominican amber (Iturralde-Vincent, 2001; Langenheim and Beck,
1965), have not been found at all.
4. Results
Fourier Transform Infrared Spectroscopy (FTIR) is commonly applied in the amber and resin studies to identify their hydrocarbon structure and origin (Langenheim and Beck, 1965; Najarro et al., 2009; Poinar
and Mastalerz, 2000; Tappert et al., 2011, 2013; and many others). In
this study, it was used for the same purpose, focusing on differentiating
the color varieties of the Voznovo amber.
Fig. 3 shows the FTIR spectra of the three studied samples from
lignite of the Voznovo Formation: blue (two spectra determined for
different parts of the same sample) and greenish-yellow hard ambers,
and yellow-orange friable amber. In addition, it presents the spectra of
reference materials (water, carbon dioxide, perylene, conifer resin,
and amber from the three well-studied locations) for comparison
(Hudgins and Sandford, 1998; Khanjian et al., 2013; Najarro et al.,
2009; Smith, 1982; Tappert et al., 2011). As shown, all of the Voznovo
samples are characterized by infrared spectra basically similar to each
4.1. Amber findings
Amber is widely distributed in the Voznovo lignite. It commonly
forms small (up to 0.5 cm), irregularly-shaped and friable clasts that
are yellow and yellow-orange in color (Fig. 2f). Much harder pieces of
amber are rarer, larger (up to 1–2 cm in size), and appear blue (under
reflected sunlight and, more brightly, under ultraviolet light) and
greenish-yellow in color (Fig. 2a–e). Some of them contain abundant
wood microfragments (Fig. 2d). Both blue and greenish-yellow hard
amber pieces were concentrated directly below and above the clay parting in the lower part of lignite seam (Fig. 1). The amber-bearing lignite,
carbonaceous mudstone, and sandstone are characterized by abundant
fragments of charcoal and fusain (photo in Fig. 1). The blue amber has
4.3. Fourier Transform Infrared Spectroscopy
8
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
Fig. 2. The Voznovo amber under optical microscope: a — blue amber under reflected light; b — blue amber in transmitted light; c — a thin section of blue amber under ultraviolet light;
d — a thin section of blue amber with abundant wood debris in transmitted light; e — greenish-yellow amber under reflected light; f — small pieces of yellow-orange amber in lignite under
reflected light. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
other, suggesting origin from the same plant resin. They resemble both
Baltic and Spanish (El Soplao) ambers, which originated from the conifer resin. Modern examples of these types of resins are represented by
Cedrus libani (Pinales) in the graph. The El Soplao amber, sourced by
the Cupressaceae resin (Menor-Salván et al., 2010; Najarro et al.,
2009), produces an FTIR spectrum most similar to the yellow-orange
varieties of the Voznovo amber. The Dominican amber, which originated from angiospermous (Hymenaea) resin (Iturralde-Vincent, 2001;
Langenheim and Beck, 1965), produces a considerably different FTIR
spectrum (Langenheim and Beck, 1965; Tappert et al., 2011, 2013).
One of the FTIR spectra of the blue amber (Blue-1 in Fig. 3) is distinctly different from those of other amber and resin we studied and found in
literature. It has high absorption peaks around 3650, 2300 and 650 cm−1
corresponding to O\C\O bonds (carbon dioxide), as well as 3400 cm−1
corresponding to O\H bonds (hydroxyl radicals). Even the most
volatile-rich previously studied resins, characterized by spectra with
the largest O\H stretch, do not indicate considerable amounts of carbon
dioxide (Tappert et al., 2011). The presence of these volatile compounds
in only the blue Voznovo varieties may suggest that they play some role
in causing the blue color and fluorescence. This spectrum has also a characteristic FTIR pattern in the 2800–3000 cm−1 stretching region. In addition to the common absorption peaks of methylene and methyl groups, it
has a distinct peak at 2902 cm−1, indicating stretching vibrations of the
methyne (CH) group. The presence of this group has not been documented in previous studies of amber or resin (Langenheim and Beck,
1965; Poinar and Mastalerz, 2000; Tappert et al., 2011, 2013). Unfortunately, we could not confirm this result in several repeated FTIR analyses
of the same sample. Other blue amber analyses, represented by the
Blue-2 spectrum in Fig. 3, show patterns very similar to those of the
greenish yellow amber.
4.4. Scanning Electron Microscopy (SEM-EDA analysis)
SEM study was used to identify the amber impurities and fabric.
Fig. 4 shows micrographs of blue and greenish-yellow amber varieties
under magnifications of 100, 1000, and 5000 ×. One can see that the
blue amber contains a rounded and highly porous fragment of amber inside of a larger piece (Fig. 4a). This fragment is characterized by large
bubbles (Fig. 4b) and smaller tubular hollows (Fig. 4c), as well as numerous mineral inclusions, which are especially abundant along the
fragment margins (Fig. 4a and d). Porosity is unevenly distributed
through the rounded fragment. The greenish-yellow amber studied
lacks pores, but contains some mineral inclusions and is cut by tiny
(0.5–1.3 microns) fractures (Fig. 4e and f).
According to our EDS INCA analyses, the mineral inclusions are
mostly quartz, clay, iron hydroxide, and salt. This mixture occurs on
the rims of the rounded porous fragment inside the blue amber and
other “dirty” areas of the blue and greenish-yellow amber samples.
Salt separately fills the cracks in the greenish-yellow amber sample
(Fig. 4f). Cations of this salt, in particular sodium (as in seawater) and
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
O-C-O
9
O-C-O
O-C-O
Carbon Dioxide
Methane
Water
0.50
2930-CH2
2950-CH3
0.45
2902-CH(methyne)
Perylene
0.40
2838-CH2
O-H
0.35
Absorption
Perylene
2870-CH3
3434
1726
0.30
2369
0.25
3575
0.20
384
1182
1154
1093
1462
539
1078
1377
883 676
1645.5
1228
471
1618
819
1324
971
Voznovo amber
2333.5
3675
3751.5
Blue 1
0.15
0.10
Greenishyellow
Blue 2 (common)
Yellow-o
range
0.05
El Sop
lao am
ber
Cedrus libani volatilerich resin (Pinaceae)
Baltic amber
Dominican amber
3500
3000
2500
2000
1500
1000
500
-1
Wavenumber, cm
Fig. 3. FTIR spectra of the Voznovo blue and greenish-yellow hard ambers and yellow-orange amber, as well as some reference materials (water, carbon dioxide, perylene, conifer resin,
and amber from the three well-studied locations) after Smith (1982), Hudgins and Sandford (1998), Najarro et al. (2009), Tappert et al. (2011), and Khanjian et al. (2013). The reference
spectra are shown out of scale. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
calcium (as in fresh water) with some magnesium and potassium indicate brackish water as its source (Holland, 1978). On the other hand, the
amber-bearing mud- and sandstones of the lignite seam are characterized by very low Na2O/Al2O3 ratio (Fig. 1) indicating a fresh-water environment. These data evidence that the amber studied was redeposited.
It likely came into the brackish water initially and accumulated in the
fresh-water basin finally.
4.5. Fluorescence and fluorescence excitation measurements
All the Voznovo amber varieties have blue fluorescence under
ultraviolet light (Fig. 5). However, the blue sample studied in details is
characterized by a significantly brighter blue glow.
The fluorescence and fluorescence excitation measurements of the
blue and greenish-yellow samples from the Voznovo Formation are
very similar to those determined in the Dominican amber (Fig. 6). The
blue varieties in both cases have the characteristic multiple peaks and
the mirror symmetry between fluorescence-excitation and fluorescence
curves that indicate, according to Bellani et al. (2005), an aromatic
hydrocarbon, particularly perylene. The yellow amber curves show
low blue fluorescence which peaks are not well shaped.
5. Discussion: what caused the blue amber glow?
FTIR study of the Voznovo blue amber has not found any distinct
signature of aromatic hydrocarbons, such as perylene (Fig. 3), which
are believed to be responsible for the classical blue fluorescence of
Dominican amber (Bellani et al., 2005). The presence of the fluorescent
aromatic substances in the blue amber, however, may not be excluded,
but their content must be so low that their infrared vibrations have been
completely buried among others.
Meanwhile, a methyne (CH) group peak was found in one of the blue
amber spectra. The CH group, in particular, forms cyanines, which are
synthetic dyes with fluorescence that span the infrared-ultraviolet
10
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
Fig. 4. SEM micrographs of blue (a–d) and greenish-yellow (e–f) amber. White rectangles with arrows indicate the areas of detailed (with a higher magnification or using EDA) study.
spectrum (CF Dye Selection Guide). This spectrum includes the visible
wavelength region between 430 and 530 nm (Fig. 6) reported for the
blue Dominican amber (Bellani et al., 2005; Zanotti et al., 2011). Some
of these dyes, particularly CF405S that is blue, have multiple
fluorescence-excitation patterns resembling those of blue amber from
both Dominican and Primorye locations. In addition, some small
fluorescence-excitation peaks of the Dominican and Primorye blue
ambers at 350 nm correspond to those of CF350.
At the same time, the perylene fluorescence and fluorescence excitation patterns are very close to those determined in both Dominican and
Voznovo blue ambers. Thus, the data presented confirm that perylene is
a major source of blue fluorescence in amber. Some additional unknown
fluorescing dyes, however, may not be absolutely excluded at this stage
of study.
In addition, our FTIR spectra indicate some linkage between volatile
content and the blue amber color. These volatiles include free hydroxyl
group and carbon dioxide. As far as we know, the numerous FTIR studies
of amber from other locations have not found such distinct O–C–O
stretches. Meanwhile, high O\H peaks are common in the volatilerich resin and gum (Tappert et al., 2011), and become lower during
polymerization (Najarro et al., 2009; Tappert et al., 2011) and higher
during weathering (Khanjian et al., 2013).
CO2 has been identified in the gaseous inclusions of Baltic,
Dominican, and Canadian amber and modern resin, where its content
is varying between 3% and 22% of the whole gaseous phase (Berner
and Landis, 1988). Other components include N2, O2, CH4, Ar, and H2.
The authors of that study suggest that these gases represent original
air modified by the aerobic respiration of microorganisms partly
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
11
Fig. 5. Photographs of the multi-color Voznovo amber under white sunlight (left) and UV light (right): a and b — amber pieces collected, including the bright blue sample subjected to the
FTIR, SEM-EDA and fluorescence studies; and c and d — different color amber fragments in carbonaceous mudstone. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
replacing O2 with CO2. This mechanism, however, does not exclude the
hypothesis that some amount of carbon dioxide might be directly
trapped from the air during wildfires. This phenomenon is often proposed as one of the factors influencing the amber origin (for example,
Corday and Dittrich (2009) and Najarro et al. (2010)). It seems to be especially significant in our case, since one of the FTIR spectra of blue
amber we studied shows atypically high concentration of CO2. Irregularly distributed bubbles and tubular micropores in the Voznovo blue
amber (Fig. 2a–d) provide additional evidences for this hypothesis.
Wildfire heating followed by sharp cooling in brackish water might
result in rapid hardening of the primary resin encapsulating CO2 in its
micropores. An alternative explanation of rather high volatile contents
in the Voznovo amber may be that they were sorbed onto the amber
during degassing of the lignite. If so, we would expect distinct signs of
methane in the FTIR spectra, as methane is a common product of such
a process everywhere (Moore, 2012). These signs are not, however,
present.
Wildfire heating followed by sharp cooling in brackish water could
also promote extreme polymerization of the resin including formation
of some fluorescent aromatics, particularly perylene. Perylene might
also form later, after amber deposition in the reduced environment
(Bertrand et al., 2013). This suggestion is supported by our observation
that blue amber pieces are hosted by lignite and highly carbonaceous
mudstone only, while less carbonaceous sandstones contain just ordinary yellow amber.
A relatively large hydroxyl stretch of the friable yellow-orange amber
might be inherited from the primary volatile-rich resin (Tappert et al.,
2011) and, less likely, may have resulted from weathering (Khanjian
et al., 2013).
6. Conclusion
Small pieces of amber have been recently found in a lignite seam
from the Voznovo Formation, Zerkal'nenskaya depression, Primorsky
Krai, Far East Russia. They may be classified into three types, including
a common friable yellow-orange variety and two (blue and greenishyellow) hard ones. All the varieties seem to have been sourced by
Cupressaceae resin. The blue amber is distinguished by its unusual
blue coloration under normal sunlight and bright blue fluorescence
under ultraviolet light, as is typical for blue amber from the classical
Dominican sites. However, our FTIR study has not found any of the
distinct signatures of aromatic hydrocarbons which are believed to be
responsible for the blue color and fluorescence of Dominican amber
(Bellani et al., 2005). Their content is likely so low that their infrared vibrations have been completely buried among others. At the same time,
one of the FTIR spectra of blue amber shows a distinct signature of the
methyne (CH) group and atypically high concentrations of free hydroxyl groups and carbon dioxide in the blue Voznovo amber. This, along
with abundant charcoal and fusain fragments in the host rocks, may
suggest that wildfire had a role in its origin. Wildfire heating followed
by cooling in water might result in hardening of the primary resin and
encapsulating CO2 in its micropores. This process could also promote
extreme polymerization of the resin including formation of some
amounts of blue-fluorescing aromatic hydrocarbons. After deposition
among highly carbonaceous sediments, the amber remained in a reducing environment that could produce perylene (Bertrand et al., 2013).
This highly fluorescent matter, as noted by Bellani et al. (2005) and in
our similar experiments, is most likely responsible for the major blue
amber glow. These suggestions, to be sure, require additional study.
Gas chromatography–mass spectrometry that successfully applied the
amber study by Menor-Salván et al. (2010) may be especially informative for this.
Acknowledgments
The authors are thankful to Nadezhda Khomyakova, a geologist for
the Voznovo Opencast mine for her assistance during the fieldworks,
Anna Poselyuzhnaya for the SEM-EDA study, and Anatoly Mirochnik
and Aleksey Mamaev for the fluorescence measurements. The manuscript reviewers, Drs. Jen M.K. O'Keefe from Morehead State University,
James C. Hower from University of Kentucky, and Shifeng Dai, Editor of
International Journal of Coal Geology, have done many efforts to improve the paper's language and improving the clarity of its conclusions.
12
I.Y. Chekryzhov et al. / International Journal of Coal Geology 132 (2014) 6–12
We also thank the anonymous reviewer, who made valuable suggestions for our future research.
Blue Cyanine Dyes
References
Cf350 (blue)
CF405S (blue)
300
350
400
450
500
550
600
Perylene
500
350
400
500
550
600
300
Blue Dominican
Amber
100
14
350
400
450
500
550
600
10
Yellow Dominican
Amber
6
2
350
400
450
500
550
600
45
Blue Voznovo Amber
Fluorescence Intensity, arb. un.
30
15
300
4.5
350
400
500
Fluorescence
Excitation
3
550
600
Bellani, V., Giulotto, E., Linati, L., Sacchi, D., 2005. Origin of the blue fluorescence in
Dominican amber. J. Appl. Phys. 97 (1). http://dx.doi.org/10.1063/1.1829395
(016101–1 - 016101–2).
Berner, R.A., Landis, G.P., 1988. Gas bubbles in fossil amber as possible indicators of the
major gas composition of ancient air. Science 239, 1406–1409. http://dx.doi.org/10.
1126/science.239.4846.1406.
Bertrand, O., Montargès-Pelletier, E., Mansuy-Huault, L., Losson, B., Faure, P., Michels, R.,
Pernot, A., Arnaud, F., 2013. A possible terrigenous origin for perylene based on a
sedimentary record of a pond (Lorraine, France). Org. Geochem. 58, 69–77.
CF Dye Selection Guide. Available at http://biotium.com/wp-content/uploads/2013/07/
2013-CF-dye-selection-guide-web.pdf.
Corday, A., Dittrich, H., 2009. Amber — The Caribbean Approach. pp. 2–6 (Available at
http://www.ambarazul.com/FallWinter2009.InColor.BlueAmber.pdf).
Holland, H.D., 1978. The Chemistry of the Atmosphere and Oceans. Wiley, New York
(351 pp.).
Hudgins, D.M., Sandford, S.A., 1998. Infrared spectroscopy of matrix isolated polycyclic
aromatic hydrocarbons. 1. PAHs containing two to four rings. J. Phys. Chem. A 102
(2), 329–343. http://dx.doi.org/10.1021/jp9834816.
Iturralde-Vincent, M.A., 2001. Geology of the amber-bearing deposits of the Greater
Antilles. Caribb. J. Sci. 37, 141–167.
Khanjian, H.,Schilling, M.,Maish, J., 2013. FTIR and PY-GC/MS investigation of archaeological amber. e-Preservation Science. 10, pp. 66–70 (Available at: http://www.moranartd.com/e-preservationscience/2013/Khanjian-28-08-2012.pdf).
Langenheim, J.H., Beck, C.W., 1965. Infrared spectra as a means of determining botanical
sources of amber. Science 149 (3679), 52–54. http://dx.doi.org/10.1126/science.149.
3679.52.
Menor-Salván, C., Najarro, M., Velasco, F., Rosales, I., Tornos, F., Simoneit, B.R.T., 2010.
Terpenoids in extracts of Lower Cretaceous ambers from the Basque-Cantabrian
Basin (El Sopalo, Cantabria, Spain): paleochemotaxonomic aspects. Org. Geochem.
41, 1089–1103. http://dx.doi.org/10.1016/j.orggeochem.2010.06.013.
Moore, T.A., 2012. Coalbed methane: a review. Int. J. Coal Geol. 101, 36–81. http://dx.doi.
org/10.1016/j.coal.2012.05.011.
Najarro, M., Peñalver, E., Rosales, I., Pérez de la Fuente, R., Daviero-Gomez, V., Gomez, B.,
Delclòs, X., 2009. Unusual concentration of Early Albian arthropodbearing amber in
the Basque-Cantabrian Basin (El Soplao, Cantabria, Spain): palaeoenvironmental
and palaeobiological implications. Geol. Acta 7, 363–387. http://dx.doi.org/10.1344/
105.000001443.
Okamura, S.,Martynov, Y.A.,Furuyama, K., Nagao, K., 1998. K–Ar ages of the basaltic rocks
from Far East Russia: Constraints on the tectono-magmatism associated with the
Japan Sea opening. Island Arc 7, 271–282. http://dx.doi.org/10.1046/j.1440-1738.
1998.00174.x.
Otofuji, Y.,Matsuda, T.,Itaya, T., et al., 1995. Late Cretaceous to early Paleogene paleomagnetic results from the Sikhote Alin, Far Eastern Russia: implications for deformation of
East Asia. Earth Planet. Sci. Lett. 130, 95–108. http://dx.doi.org/10.1016/0012821X(94)00254-V.
Pavlyutkin, B.I.,Chekryzhov, I.Yu.,Petrenko, T.I., 2011. The Voznovo Formation: the reflection of the early Oligocene stage in the geological history of East Sikhote-Alin. Russ. J.
Pac. Geol. 5, 47–63. http://dx.doi.org/10.1134/S1819714011010052.
Poinar Jr., G.O., Mastalerz, M., 2000. Taphonomy of fossilized resins: determining the
biostratinomy of amber. Acta Geol. Hisp. 35, 171–182 (Available at http://www.
geologica-acta.com/pdf/aghv3501a17.pdf).
Smith, A.L., 1982. The Coblentz Society Desk Book of Infrared Spectra, In: Carver, C.D.
(Ed.), The Coblentz Society Desk Book of Infrared Spectra, Second edition The
Coblentz Society, Kirkwood, MO, pp. 1–24 (Available at http://webbook.nist.gov/
chemistry/).
Tappert, R., Wolfe, A.P., McKellar, R.C., Tappert, M.C., Muehlenbachs, K., 2011. Characterizing modern and fossil gymnosperm exudates using micro-Fourier transform infrared
spectroscopy. Int. J. Plant Sci. 172, 120–138. http://dx.doi.org/10.1086/657277.
Tappert, R., McKellar, R.C., Wolfe, A.P., Tappert, M.C., Ortega-Blanco, J., Muehlenbachs, K.,
2013. Stable carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic. Geochim. Cosmochim. Acta 121, 240–262.
Zanotti, K.J., Silva, G.L., Creeger, Y., Robertson, K.L., Waggoner, A.S., Berget, P.B., Armitage,
B.A., 2011. Blue fluorescent dye–protein complexes based on fluorogenic cyanine
dyes and single chain antibody fragments. Org. Biomol. Chem. 9, 1012–1020. http://
dx.doi.org/10.1039/c0ob00444h.
Fluorescence
Greenish-Yellow
Voznovo Amber
1.5
250
300
350
400
450
Wavelength, nm
500
550
600
Fig. 6. Fluorescence and fluorescence excitation curves of the blue and greenish-yellow
Voznovo ambers in comparison with those of the blue Dominican amber, perylene, and
cyanine dyes (Bellani et al., 2005; CF dye selection guide). The fluorescence spectrum of
all the Voznovo and Dominican amber pieces was obtained under excitation with light
of wavelength λ = 413 nm (345 nm), whereas detection wavelength in the fluorescence
excitation spectrum was λ = 475 nm (433 nm). (For interpretation of the references to
color in this figure legend, the reader is referred to the web version of this article.)