Physicochemical structural characterization of ambers from deposits in Poland

AppliedGeochemistry,Vol. 11, pp. 811-834, 1996

Pergamon PII:S0883-2927(96)00046-7

Copyright © 1996ElsevierScience Ltd Printed in Great Britain. All rights reserved 0883-2927/96 $15.00+ 0.00

Physicochemical structural characterization of ambers from deposits in Poland Franciszek Czechowski* Institute of Chemistry and Technology of Petroleum and Coal, Technical University of Wroclaw, 7/9 Gdafiska St., 50-344, Wroc/aw, Poland

Bernd R. T. Simoneit Petroleum and Environmental Geochemistry Group, College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, U.S.A.

Micha/Sachanbifiski Institute of Geological Sciences, University of Wroctaw, 30 Cybulskiego St., 50-202, Wrociaw, Poland

Jan Chojcan Institute of Experimental Physics, University ofWrocaw, PI. Maxa Borna 9, 50-204, Wroc/aw, Poland

and Stanislaw Wo/owiec Institute of Chemistry, University of Wroctaw, 14F Joliot-Curie St., 50-383, Wroclaw, Poland

(Received 14 February 1995; accepted in revisedform 12 April 1996)

Al~tract--The physical and chemical properties of 8 samples of amber from different localities in Poland (Baltic Coast, Belehatrw Tertiary brown coal, and Jaroszrw clay mine) were investigated by N2 sorption at 77 K, positron annihilation spectroscopy for chemical analysis (PASCA) and by organic geochemical methods (FT-IR, I H and 13C NMR, GC, and GC-MS). The porosity of the ambers as determined by PASCA consists of narrow micropores with diameters ranging from 0.8 to 0.9 nm and a volume 0.025 crn3 g - i. In the external eroded part of the amber samples (rind) the concentration of pores where positronium atoms can form is lower and consists of approximately 1/2 the concentration as in their interior. Values of pore parameters determined from sorption of N2 are comparable with those found by the PASCA method. The average diameter of pores ranges from 2 to 12 nm, while their volume varies from 0.018 to 0.048 cm 3 g-1. The chemical character of the ambers is similar based on FT-IR spectroscopy. However, noticeable differences in concentrations of ester and hydroxyl groups are observed in both exterior and interior regions, where the abundances of the ester groups are lower in the exterior rind. The proportion of organic material extractable with chloroform-methanol (1:1, v/v) ranges from 15 to 50% and correlates inversely to the average reflectances (Rr) of polished amber surfaces which range from 1.7 to 0.1%. These variations are attributed to differing concentrations of oxygenated groups in the respective amber samples. The FT-IR spectra of the non-polar fractions (NP) from the extracts resemble the spectra of the source ambers. However, the intensities of the absorbance for the hydroxyl group are much lower, while absorbances for exomethylene groups are not present. The I H and 13C NMR data of NP fractions showed a complex diversity of components in mixtures with different relative concentrations but predominantly aliphatic in character for the respective samples. GC and GC-MS analyses of these fractions revealed that they are comprised of a mixture of compounds typical for Baltic amber but with variable relative concentrations. Two groups of compounds are found to be common to all NP fractions. The first is a minor concentration of homologous n-alkanes with a characteristic Gaussian distribution in the range from C22 to C32 and maximizing at C26-C27. In addition C22 is characteristically slightly higher in concentration compared to C23. The second group 0fcompounds is comprised of succinates with methyl, fenchyl, bornyl and isobornyl alcohols. The composition of these diesters revealed the same equilibrium ratio between compounds with fenchyl, bornyl and isobornyl alcohols in all NP fractions. We suggest an early enzymatically controlled (bacterial) process in the formation of succinates during resin diagenesis from the biotic precursors, yielding the same characteristic ratio of the respective suceinates in these ambers. These results show that all the ambers analyzed here fall into a c o m m o n class of fossil resin, suecinite (class Ia) independent of the sample location in Poland. Copyright (c) 1996 Elsevier Science Ltd *Correspondence to this author. 811

812

F. Czechowski et al. INTRODUCTION

Ambers occur in the form of finely dispersed small grains in sedimentary rocks and coal beds, as well as different sized lumps not occluded and easily recognized macroscopically. They are associated mainly with Tertiary and Quaternary deposits (KociszewskaMusiaL 1988) and rarely with Cretaceous formations (Nissenbaum, 1975). As is well documented by numerous reports, different kinds of Baltic amber (mainly represented by succinite and glessite) belong to the commonly occurring family of fossil resin in Europe. It is also known as Ukrainian amber (this kind occurs in Poland near the Parczew region) and Bitterfeld amber in Germany. Similar fossil resin as individual specimens have been found on the Asiatic and American (South Carolina) continents. The unequivocal origin of Baltic amber still remains unknown, however, it is commonly accepted that it derives from a hypothetical conifer of the Pinus succinifera family. Literature reports suggest that the resinous source tree for amber in other regions is recognized for example as Hymenaea courbaril L. for Mexican amber (Langenheim, 1969), and Cupressaceae osperum saxonicum Mai for Bitterfeld amber, also known as gtessite (Schlee and Glrckner, 1978; Kosmowska-Ceranowicz, 1986, 1993). Ambers in Poland are found mainly in Tertiary deposits and only occasionally in Quaternary and Cretaceous formations. At present over 600 regions are known where amber was mined or single pieces were found (Kosmowska-Ceranowicz, 1986) (Fig. 1). In the past it was mined on a commercial scale in the Narvia river basin in the Tucholskie forest district. At present the richest occurrence of amber in Poland is localized in the region between the Stogi and Vistula (Wisla) river mouths around Gdahsk. It is worth mentioning that the richest amber deposit known in the world is on the Sambian peninsula in Russia. It is an Upper-Eocene deposit genetically associated with sands and clays of the delta prograded into the sea. It was recently documented by drilling around Chtapowo, that the eastern part of this delta reaches Poland (Kosmowska-Ceranowicz, 1986). Sambian ambers were redeposited to a limited extent in the Miocene and Oligocene, while during the interglacial period of the Pleistocene the deposits underwent extensive erosion. Additionally during glacial transport large amounts of these ambers were spread over Poland. The subject of this work is twofold and concerns the new discoveries of ambers in the Midlands of Poland associated with the Tertiary Betehat6w brown coal bed (Miocene) and in SW Poland associated with a Quaternary (Pleistocene) refractory clay deposit with a detrital stratum near Jaroszrw. First, the characterization of the physicochemical properties of these samples was carried out to assess their genetic relation either to resinite of brown coal or to fossil resin typical

of Baltic amber (succinite). These materials differ in chemical composition. The bulk structure of Baltic amber has been established as polymers oflabdatriene diterpenoid carboxylic acids, with the presence of accessory structures like succinates and others (Beck et al., 1965; Mills et al., 1984/85; Anderson et al., 1992). Resinites in brown coals are generally rich in diterpanes with phyllocladane, kaurane, abietane and other skeletons (Grimalt et al., 1988; Wang and Simoneit, 1990; Anderson and Botto, 1993). Phyllocladane in particular was proposed as a marker for the Podocarpaceae family of conifers (Hagemann and Hollerbach, 1980). The second aspect was a general physicochemical characterization of the amber pieces by positron annihilation, N2 sorption and F T - I R techniques, while the compositions of the non-polar extractable components (NP) were determined by FT-IR, 1H and ~3C NMR, GC, and GC-MS methods.

SAMPLES AND EXPERIMENTAL METHODS

Geological setting The locations of the ambers collected for this investigation are marked in Fig. 1 with asterisks. Samples from the Tertiary Betchat6w brown coal (Tertiary, Midlands of Poland) were occluded in detrital material Fig. 2, (Hatuszczak, 1987), while those from Jarosz6w (Quaternary, SW Poland) occurred in clay minerals associated with detritus of highly altered plant remains. For the comparative studies a piece of amber from the Baltic coast near Gdafisk (Fig. 3), (Tomczak et al., 1990) as well as a sample of the detrital matrix from the Belehat6w brown coal were also selected. The locations of the samples, their symbols used in the text, their macroscopic appearances and elemental compositions are given in Table 1. The observed values for C, H and N contents are within a narrow range and in agreement with earlier data for amber occurring in Poland (Katinas, 1971; Kosmowska-Ceranowicz, 1986). Additional elemental composition data have been determined over the past century (e.g. Dahms, 1901) and the trends are most useful as a measure of the degree of oxidation. Reflectance Reflectances of the ambers were measured on polished surfaces of cross-sectioned pieces using an automated Opton (Germany) optical microscope linked to a computer data processing system. Measurements were taken in monochromatic light at the standard wavelength of 546 nm in oil immersion with a refractive index ~3"c = 1.518. An average value of 50 independent readings was taken as the amber mean

reflectance, Rr.

Characterization of Polish ambers

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Fig. 1. Occurrence o f ambers in Poland (according to Kosmowska-Ceranowicz, 1986). Legend: Dots are locales where amber clusters have been found. Amber regions in Tertiary sediments: A - - in the delta of the Ch/apowo-Sambia area and At - - in the Parczew region. In boulders of Tertiary age occurring within Pleistocene deposits: B - - near Slupsk and B1 - - Zielnowo near Grudzi~dz. The other locales where amber is found are in Quaternary sediments.

Table 1. Macroscopic and elemental characteristics of the investigated ambers Elemental composition, % Sample location Gdaflsk Belchat6w Betehat6w Betchat6w Belchat6w Belchat6w Jarosz6w Jarosz6w

Assigned symbol

Macroscopic appearance

C

H

N

GD BE 1 BE2 BE3 BE4 BE5 JA 1 JA2

yellow, transparent citrine, cloudy honey, cloudy honey, transparent yellow, transparent cherry, part transparent milky, cloudy light-sienna, cloudy

75.42 74.24 75.44 74.57 77.02 75.93 76.22 74.49

9.67 9.51 9.51 9.66 9.60 9.95 9.70 9.63

0.06 0.07 0.10 0.07 0.15 0.11 0.27 0.20

814

F. Czechowski et al.

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Lawki

I!1 Formation

Odro 5tacintion

Fig. 2. Geological cross-section showing the amber occurrence in Belehatdw brown coal of the Midlands region of Poland (according to Hat~szczak, 1987). Legend: 1 =glacial clays, 2=sand with gravels, 3 = stagnant basin deposits, 4 = amber-bearing deposits.

relative pressure, p/po=0.21. An average pore diameter was calculated based on the cylindrical pore model.

Sorption o f nitrogen Sorption of N2 at a temperature of 77 K was carried out with the use of a Micrometrics Instrument Corporation model A S A P 2000 vacuum apparatus. Pieces o f amber samples of about I g mass were used for the measurements. Prior to sorption the samples were degassed at r o o m temperature until a stable vacuum of 10 - s T o r r was attained. The standard BET (Brunauer-Emmett-Teller) surface area was calculated from the N2 isotherm data. The total pore volume with diameters lower than 770 nm was determined from the N2 sorption capacity at a

N

The one-dimensional angular correlation of annihilation radiation ( A C A R ) of photons originating from the 2 photon annihilation of an electron-positron pair were determined for these ambers using an annihilation radiation spectrometer built in the Institute of Experimental Physics of the University of Wroctaw,

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Fig. 3. Geological cross-sections of the amber occurrences on the Vistula Bay Bar near Gdafisk. Legend: 1 = mineral-biogenie deposits; 2 = sandy deposits; 3 = gravelly deposits; 4 = till; 5 = varvexi days; 6 = radiocarbon dates in years BP; e = eolian; m = marine, f= fluvial; j = limnic, b = ice dammed; g = glacial deposits; H = Holoeene; E = Eemian age; S = Sanian age; pb = preboreal; a = Atlantic; sa = sub-Atlantic (according to Tomczak et al., 1990).

Characterization of Polish ambers with long slits, and a half-width of angular resolution function of 2 mrad. The positron source for these measurements was the 22Na isotope with an activity of about 2 x 10s Bq. The measurements were performed at room temperature under atmospheric pressure in air for angles in the range from - 34 to + 34 mrad in steps of 0.5 mrad. Positronium annihilation life (PAL) time spectra were measured on an annihilation spectrometer with a half-width time resolution function of about 350 ps. The measurement interval was from 0 to 14 ns. A 22Na activity of 4 x 105 Bq was used as the positronium source. The positronium source was sandwiched between 2 pieces of the same sample during measurements. A more detailed description of the method and the operating conditions are given elsewhere (Jean, 1990; Chojcan and Sachanbifiski, 1993).

Extraction and fractionation Samples were pulverized to pass though 0.1 x 0.1 mm square screens and subjected to onestep batch extraction with a mixture of chloroform-

815

methanol (1:1 v/v) under reflux for 60 h. About 50 ml of solvent was used per 1 g of amber sample. After extraction, the solution was filtered and concentrated by solvent evaporation to a volume of about 2 ml. Then a 20 fold excess of n-bexane was added to precipitate the insoluble fraction which was filtered off. The solution, after solvent evaporation, was chromatographed on 20 x 20 cm thin layer chromatography (TLC) plates (0.25 mm thick silica gel 60 H, Merck). The plates were eluted with the solvent system: n-hexane-dichloromethane-methanol = 8:1:1 (v/v). Bands were visualized under UV irradiation. Bands with higher Rf values than about 0.4 were taken as the non-polar compound fraction (NP). The intensively milky-violet fluorescing band (Rf~0.4, Fig. 4) is considered to be the polymeric terpenoid component (polymer of labdatriene acid derivative) (Crelling et al., 1991). Therefore, to avoid gas chromatographic separation problems, the components of this band and others with lower Rf values were combined into a polar fraction. Components which remained at the origin were collected as a strongly polar fraction (Fig. 4). The yields of the extracts and respective TLC fractions are given in

Fluorescence Colour

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Fig. 4. TLC separation of extracts from ambers. AG ll/6-O

Strongly polar fraction

F. Czechowski et al.

816

Table 2. Chloroform-methanol extract yield from the amber samples and contents of extract fractions differingin polarity Extract mass (fraction, %) GD

BE1

Amber sample BE2 BE3 BE4

BE5

JA1

JA2

18.5

25.1

30.7

31.5

48.6

30.6

15.6

44.7

percent of extract fraction in amber 3.4 7.7 7.3 3.3 6.5 8.6 0.5 1.4 1.7 11.3 9.4 13.1

4.1 4.4 0.7 22.1

9.3 11.6 1.6 26.1

0.8 3.4 0.7 25.6

3.3 3.6 0.8 7.9

6.3 5.2 1.4 31.7

19.0 23.9 3.3 53.8

2.8 11.1 2.4 83.7

21.3 22.8 5.1 50.8

13.2 11.7 3.1 71.0

Total extract a) non-polar fraction* b) polar fraction c) strongly polar fraction d) fraction not soluble in n-hexane

percent of extract fraction in relation to total extract mass. a) non-polar fraction* 18.3 30.6 23.7 12.9 b) polar fraction 17.7 26.1 28.1 14.0 c) strongly polar fraction 2.8 5.6 5.4 2.7 d) fraction not soluble in n-hexane 61.2 37.7 42.8 70.4 *Fraction characterized by GC-MS analyses.

Table 2. They are within the range of values observed earlier for such materials (Katinas, 1971), but a particularly low content of NP was found in the BE5 amber.

quadrupole MS was scanned from m/z 50 to 540 at 1 s per decade. The instrument Chem Station data system was used for data acquisition, storage, and processing. Structural assignments are based on interpretation of mass spectra, library and literature data, and consideration of chromatographic retention data.

Infrared spectrometry Fourier transformed infrared spectra (FT-IR) were obtained with the use of a Nicolet Impact 400 spectrophotometer linked with a computer data processing system. Transmittances of bulk ambers were taken in KBr pellets. NP fractions were transferred in dichloromethane onto the non-absorbing window and their transmittances were measured after solvent evaporation.

Nuclear magnetic resonance spectrometry ( NMR ) IH and 13CN M R spectra were determined for the NP fractions on a Bruker AMX 300 spectrometer operating at a frequency of 300 MHz for protons. Spectra were obtained at 300 K in chloroform solution. The chemical shift values were referred to the residual solvent resonance and recalibrated to TMS.

Gas chromatography-mass spectrometry ( GC-MS) G C - M S analyses of NP fractions were conducted with a Hewlett-Packard model 5871 gas chromatograph coupled to a model HP 5970 mass selective detector. Separation was achieved on 25 m x 0.25 mm i.d. fused capillary column (HP-5). The GC operating conditions were as follows: temperature program from 35 to 290°C at 3°C min - l , hold isothermal at 290°C for 20 min and using He as carrier gas. The

PHYSICAL PROPERTIES OF AMBERS

Reflectance Vitrinite reflectance is commonly accepted as a physical maturity parameter in applied petrology (Teichmiiller and Durand, 1983; Espitalir, 1986; Burnham and Sweeney, 1989). Reflectance of an absorbing material such as vitrinite (symbol Ro) is described by Beer's equation (1): (/Z --//,0) 2 -}-//,2k2 Ro -- (/z +/zo) 2 +//,EKE 100

(1)

where /z and k are the refractive and absorption indices, respectively, of the sample under consideration, and/z 0 is the refractive index of an immersion oil. The ambers examined here are nonabsorbing, glassy and highly homogeneous materials. In such cases where the refractive index has a predominant influence the Fresnel expression is used to evaluate the reflectance of the materials as R(2): R = (/z - / t o ) 2 ' 100 [%] (~t + ~0) 2

(2)

The refractive index la and consequently the R value are related to the chemical constitution of solid molecules by the correlation (3): /z2 =

I'm+ 2Nm

V,.-N,,,

(3)

where Vm is a molar volume (era 3 m o l - l) and Nm the

Characterization of Polish ambers

60 50

Table 3. Molar bond refractivities at 589 nm (after Atkins, 1986) Bond

Molar refractivity, em3 mol- i

C-C C-O C-H O-H C=C C=O 047 = O

1.20 1.41 1.65 1.85 2.79 3.34 4.75

817

~" -: 40 ~--, ~-o .g, 30

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t_

RI20 10 molar refractivity (cm3mol-X). Also Vr"=Mr"/r, where Mr. is the molar mass ( g m o l - ] ) and r, the material density (g cm-3). Molar refractivities constitute the total molar value of individual functional groups comprising the resin structure. Because the analyzed ambers were transparent as well as cloudy their reflectances in oil were determined by direct comparison with a reflectance standard, and without recourse to these equations. Molar refractivity values for certain bonds or groups are given in Table 3. The higher values of an overall molar refractivity for an average molecule are consistent with the contribution from C--C double bonds and O containing groups (carbonyl and hydroxyl). Ambers are predominantly polymers of terpenoid alcohols and acids. In a polymeric system these groups remain preserved, while in molecules not associated with the macromoleeular matter (i.e. extractable) their number is lower. This is clearly observed from F T - I R analysis, where the concentrations of those groups are lower in the extracts. An inverse correlation between yield of volatile matter and vitrinite reflectance was found for coals of different rank. Therefore, by analogy it was expected that a correlation between the percentage of extractable material and its reflectance could be established. The reflectance data (Rr) obtained for the ambers are presented in Table 4. A correlation plot of the solvent extract yields versus reflectances of these ambers is presented in

Table 4. Amber reflectance, R, (oil) Amber Sample GD BEI BE2 BE3 BE4 BE5 JA1 JA2

Reflectance, % Range -0.62-1.36 0.48-1.08 0.02-0.57 0.01-0.27 0.01-0.68

---

Mean value 1.67 0.96 0.71 0.16 0.08 0.13 0.55 0.11

0,00

I

I

I

0.50

1.00

1,50

2.00

Fig. 5. Correlation of amber reflectance and yield of chloroform-methanol extract.

Fig. 5. In general, the correlation shows that with increasing extract yield, the amber reflectance decreases. Therefore, this can be used as an indicator for predicting the extraction behavior of amber and resin. However, it must be clearly pointed out that Rr values for ambers and resins do not indicate their maturation level, but only the degree of polymerization and preservation of structures bearing oxygenated and olefinic groups, and the amounts of accessory, non-chemically bound molecules.

Amber porosity Variations in the macroscopic appearance of ambers are characterized by different degrees of transparency, which reflect the numbers of small bubbles in the matrix and the presence of accessory organic matter. According to Katinas (1971) and Laciejewicz and Mierzejewski (1983), size and number of bubbles determine the transparency of ambers (Table 5). Amber opacity has been well understood and studied much earlier (e.g. Helm, 1877). These samples have different transparencies (Table 1). Mercury porosimetry and sorption of N2 were used to assess whether the bubbles in the ambers are connected via an open pore system or are closed. Porosimetry measurements did not show any penetration of Hg under pressure into the amber matrix. The pore parameters of selected samples evaluated from the N2 isotherms are given in Table 6. The BET surface areas are small, below 0.34 m 2 g - 1, and do not differ markedly between the cloudy JA1 amber and the transparent G D amber. A much lower value is observed for transparent sample BE4. The pore

F. Czeehowski et al.

818

Table 5. Bubble structure of typical ambers Amber type

Bubble diameter (mm)

transparent non-transparent, yellow non-transparent, milky

Number of bubbles in 1 mm 3

Percentage of bubble volume in amber (% v/v)

600-2500 up to 900,000

up to 10 10-25 42-50

0.05-1.0 0.05-0.0025 0.001-0.0008

Table 6. Pore parameters of ambers evaluated from sorption of N2 at 77 K Amber sample

BET surface area (m 2 g-1)

Total pore volume (cln 3 g - t )

Average pore diameter (nm)

GD BE4 JA1

0.27 0.06 0.34

0.048 0.018 0.018

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Characterization of Polish ambers

819

Table 7. Positronium characteristics of ambers volume accessible to N2 molecules at 77 K is very small for the samples examined, suggesting that the Amber sample x3 (ns) I3' (%) FI (mrad) I) (%) bubbles present in the cloudy amber are closed and not connected through pores. The calculated average GD 1.84 26.0+0.3 2.564-0.05 6.34-0.1 radius of the pores accessible to N2 molecules is within BFA 1.85 25.74-0.3 2.664-0.05 6.4+0.1 BE5 - - interior 1.89 25.0+0.3 2.404-0.05 6.0+0.1 a narrow meso- and micropore range. 1.82 14.44-0.2 2.244-0.08 3.4___0.1 It is of interest to compare these findings with the BE5--rind JA1 1.79 25.3+0.5 2.464-0.06 5.6+0.1 claim by (Berner and Landis, 1988) of having determined the composition of gas bubbles in ambers to be 'ancient air' containing up to 3 0 0 02 and high but variable amounts of CO2 (expressed on a mole percent water free basis). We suggest that gases can be encapsulated and preserved in amber, but they are to 0.9 nm, however, their concentration in the external mixtures of varying proportions of original ambient zone (rind) of sample BE5 constitutes only 1/2 of the air, respiration gases from the source plant and in situ value found for the interior zone of the sample. The microbial activity, and subsequent alteration due to calculated average values of pore diameter (d) from reactions in the organic matrix such as defunctionali- the positron annihilation experiments, as well as their zation, reduction and oxidation as polymerization/ concentrations (nv) and volumes (Vp) are presented in Table 8. Taking into account the F T - I R data diagenesis proceed. New insight into the microporosity of ambers was obtained for sample JA2, where a lower intensity of obtained by positron annihilation spectroscopy for carbonyl absorbance from ester groups was observed chemical analysis (PASCA). These studies consisted for the rind of the amber, it can be suggested that ester of measurements of positron annihilation lifetime components in the resin matrix may be responsible for spectra (PALS) and one dimensional angular correla- spheres where positronium atoms can be formed. tion of annihilation radiation (ACAR) of positronium. Representative PALS and A C A R for these ambers are shown in Fig. 6 (a) and (b), respectively. The decay rates of the acquired PALS were expressed Structural characterization o f bulk ambers as 3 exponentials with different mean lifetimes (rl, r2 and r3) and intervals (I~, I~, and I~). The values Various instrumental techniques have been determined for r3 and 15 characterizing the long-lived employed for the assessment of the chemical nature component of PALS (the mean lifetime greater than of ambers and fossil resins. The most common 0.6 ns) are given in Table 7. methods used in characterization of their bulk The recorded A C A R were analysed in terms of a structure are: FT-IR, solid state NMR, electron spin sum of 3 gaussians with different full widths at half resonance, mass spectrometry and others. Structural maximum (FWHM) (FI, F2, and F3) and intensities data on this subject has been presented in a large (11, I2 and 13). The presence of the narrow component number of publications, as for example work by: in the ACAR, as well as the long-lived component in Schwochau et al. (1963); Beck et al. (1964, 1965); the PALS, indicate that positronium atoms are Savkevich and Shakhs (1964); Murehison (1966) formed in the ambers, or there are empty spheres in Brooks and Steven (1967); Savkevich (1970); Savkethe material with diameters larger than 0.1 nm vich and Shakhs (1970); Urbafiski et al. (1971); (ultramicropores). The data were interpreted assum- Urbafiski (1977); Savkevich (1981); Cunningham et ing the commonly used pore volume (Bartenev et al., al. (1983); Lambert and Frye (1983); Brackman et al. 1971; Jean, 1990) in which the positronium atoms are (1984); Theil and Grey (1988); Kosmowska-Ceranotrapped. The estimated sizes of the pores in the wicz (1990); Meuzelaar et al. (1991); Yu et aL (1991); samples examined are similar within the range of 0.8 Wilson et al. (1992); and many others.

Table 8. Characteristics of free volumes in the ambers from PAL spectra Amber sample GD BFA BE5 interior BE5 - - rind JA 1 -

-

Average pore diameter, d (nm)

Pore concentration, nv (nm-3)

Pore volume, Vp (cm3 g-Z)

0.80 4-0.04 0.78 4-0.04 0.86 4-0.04 0.92 4-0.04 0.84 4-0.04

0.097 4-0.005 0.101 4-0.006 0,083 4-0.005 0,045 4-0.003 0.084 + 0.005

0.026 4-0.003 0.025 4-0.003 0.028 + 0.003 0.0 t8 4-0.002 0.026 4-0.003

820

F. Czeehowski et al.

FT-1R o f ambers

The chemical character of the ambers was investigated from their F T - I R spectra, which had similar features for all samples. The F T - I R spectra for selected samples are presented in Fig. 7 and the absorbances are discussed in the text. It is well known that ambers contain large numbers of compounds (e.g. Mills et aL, 1984/85; Grimalt et al., 1988; Anderson and Winans, 1991; Anderson and Botto, 1993) even so, the absorption bands observed are well resolved, suggesting a closely related nature of these structural moieties. Information deduced from the F T - I R spectra on the chemical constitution of the samples yields only a general qualitative--quantitative assessment of the presence of various kinds of bonds and functional groups. The presence of a substantial quantity of hydroxyl groups is illustrated by the broad absorbance at 3450 c m - i, which derives from stretching vibrations of the O - H bond. Associated with these are stretchings of C--O bonds observed at a higher frequency in the range of 1005-1030 crn- 1. Sharp, not completely resolved absorbances in the range 28403000 c m - 1 result from symmetrical and asymmetrical C-H bond stretching in methyl and methylene groups. The bending vibration absorbances of C - H bonds in these groups are observed at 1385 and 1460 cm -1, while the presence of wagging and twisting C-H vibrations in methylene groups is manifested by bands in the 1230-1265 cm -1 range. A low intensity band at 3070 c m - 1 is attributed to C - H stretching in olefinic groups (olefins, aromatics). Absorbances of

0

similar intensity from C-H bending deformations of the group above and depending on the structure type where it is present, are observed at 980, 995 and 1416cm -1. A small absorbance at 1648cm -J is associated with the C = C stretching of the olefinic group. Sample GD in comparison to the other samples exhibits the lowest relative absorbance at 895 c m - l indicating the lowest concentration of cisolefins and structures bearing an exomethylene group. Two incompletely resolved bands at a high intensity in the range of 1720-1733 cm -1 are due to C = O stretching, The absorbance with a maximum at 1720 c m - 1 relates to the carbonyl group in ketones, while that at 1735 cm -~ to the carbonyl in esters. Absorbances in the higher frequency range of 11601190 c m - i due to C-O stretching in esters supports their presence. Additionally, the range of these vibrations is typical for esters in solids which is the case for the materials examined. The F T - I R spectra for the 2 different parts of sample JA2, i.e. the homogeneous interior (core) and the weathered exterior (rind), show marked quantitative differences in absorbances (Fig. 8). Namely, the exterior region exhibits lower absorbance intensities due to ester group vibrations (1165 and 1730 c m - i ) and higher absorbances attributed to hydroxyl, methyl and methylene groups in comparison to the interior region. This observation suggests that during the weathering process hydrolysis of esters and removal of the released, water soluble acids takes place in the region in contact with the surrounding environment. It is, however, not possible to attribute

ov t~ JD

0 e~ <

i t~

~ i O r

I

. . . . .

4000

t

. . . . .

3400

i

. . . . .

2800

J . . . . .

2200

t

. . . . .

1600

i

. . . . .

1000

i

400

Wave numbers[cmq Fig. 7. FT-IR spectrafor selectedambers.

. . . . .

4000

i

. . . . .

3400

i

. . . . .

2800

i

. . . . .

2200

t

. . . . .

1600

i

. . . . .

t

1000 400

Wave numbers [cm "1]

Fig. 8. FT-IR spectra for the interior and the rind of amber sample JA2.

Characterization of Polish ambers these samples to a specific class of resin on the basis of bulk structural characteristics from the F T - I R technique.

CHEMICAL COMPOSITION AND STRUCTURAL CHARACTERISTICS OF THE NP FRACTIONS A proportion of the organic matter in ambers is comprised of lower molecular weight molecules which are not bound to the polymeric matrix. These molecules have structures (or diageneticaily, altered analogous products) which can be related to the biogenetic source material. Therefore, they are of particular interest in geochemical studies and can be considered as specific molecular markers characteristic of their biogenetic source. These compounds are separated by solvent extraction and characterized by various instrumental techniques. Methods used for separation of components from amber and fossil resin extracts are thin layer chromatography (e.g. Lebez, 1968; Kucharska and Kwiatkowski, 1979; Grimalt et al., 1987) and gas chromatography (e.g. Gough and Mills, 1972; Urbafiski et al., 1976; Urbafiski and Molak, 1984; Grimalt et al., 1987; Szykula et al., 1990; Vavra, 1990). Both of these techniques alone, however, do not provide unambiguous identification of the separated components. The use of gas chromatography coupled with mass spectrometry (GC-MS) as well as pyrolysis coupled with GC-MS, yield more detailed and specific identification of the molecular components in ambers. Extensive research has been

r

GD

2 o~

821

carried out recently in this area and the GC-MS data have been reported (e.g. Thomas, 1966, 1969; Grantham and Douglas, 1980; Brackman et al., 1984; Mills et al., 1984/85; Noble et al., 1985; Simoneit et al.. 1986; Grimalt et al., 1987; Shedrinski et al., 1989/90/91; van Aarssen et al., 1990; Anderson and Winans, 1991; Crelling et al., 1991; Meuzelaar et al., 1991; van Aarssen et al., 1991; Anderson and Botto, 1993; Kosmowska-Ceranowicz et al., 1993). A new classification of fossil resins based on their molecular composition has been proposed in the work of Anderson et al. (1992) and Anderson (1994). This classification differentiates fossil resins and ambers into 5 classes (I-V), and class I is additionally divided into 3 subclasses (Ia, Ib and Ic). This classification shows that useful information on the structural nature and biogenetic origin of fossil resins and ambers can be evaluated from their molecular composition.

F T - I R o f non-polar extracts

The F T - I R spectra for the NP extracts isolated from the ambers are presented in Fig. 9. Their patterns qualitatively resemble the IR spectra of the source material (Fig. 8). This is not surprising, because a similar correlation has been reported for other sedimentary organic materials like coals, kerogens and their extracts, showing that the chemical nature of the extracts and the source materials is interrelated (Leythaeuser and Welte, 1969; Hagemann and Hollerbach, 1980). Significant differences are only observed for olefinic and O bearing moieties in the F T - I R spectra of the ambers and their NP extracts. The absorbances of the hydroxyl group (1005-1030 and 3450 c m - 1) have much lower intensities for the NP extract fractions, while absorbances of olefinic vibrations (895, 980, 1416, 1648 and 3070 cm -1) are present at trace intensities or below detection. Also additional absorbance bands of low intensities at 695 and 725 cm - l observed in NP fractions were not present in the F T - I R spectra of the ambers. Yu et al. (1991) observed these latter bands in resin samples separated from coal from the Wasatch Plateau (Utah) and attributed these absorbances to in phase rocking vibrations of the methylene group in cycloalkanes. Concentrations of ester groups in the NP fractions are similar as in the ambers. However, for sample BE5 (cherry colored amber) the concentration of this group is lower in the NP fraction than in the bulk sample. This may be due to a higher amount of ester groups bonded to the bulk matrix than esters occurring in the extractable form.

i

4000

3400

2800

2200

1600

1000

400

Wave numbers [em "1]

Fig. 9. FT-IR spectra for non-polar extract fractions from selected ambers.

1H and 13C nuclear magnetic resonance o f non-polar extracts

Further insight into the structural composition of the NP extract fractions was achieved by nuclear

822

F. Czechowski et al.

GD

BE2

BE3

,,

BE5

_2, I

8

6

~

I

I

4

2

i

I

0

(~ ppm Fig. 10. =H NMR spectra for non-polar extract fractions from selected ambers (the peak at 7.2 ppm marked with an asterisk is the response from residual chloroform).

magnetic spectrometry. The IH N M R spectra for the NP extract fractions are presented in Fig. 10 and indicate complex mixtures of components. The resonances of alkyl protons predominate for all NP fractions. Their integrated areas in the alkyl proton region (0.75-2.0 ppm) show a prevalence for protons in olefinic and aromatic structural groups (4.07.5 ppm) and differ among the samples. Numerous resonances differing in relative intensities observed at low chemical shift values for respective NP fractions show their complexities as mixtures of compounds having mainly an aliphatic character, with differing relative concentrations. Namely, the prevailing signal intensities in the 0.8-1.25 ppm region are singlet resonances of peripheral methyls on alicyclic rings and isolated methylene and methine groups in rings. Marked differences in peak intensities are observed within this spectral window for the subregions 0.780.90, 0.90-1.00, and 1.15-1.25 ppm (Fig. 10). The resonances of the first subregion are assigned to protons of normal chain alkanes, while those at 0.90-1.00 ppm to protons of branched chain hydrocarbons and peripheral methyls of alicyclic rings. The resonances in the 1.15-1.25 ppm range are singlets of isolated methylene and methine groups in rings. The

other resonance patterns and integrated intensities vary among the NP fractions. Unresolved resonance bands of alicyclic methylene protons occur within the chemical shift range of 1.30-2.0 ppm. Sharp single resonances at 3.6-3.7ppm represent the methyl protons of the methoxy group in methyl esters. The well resolved, sharp resonances of low intensity around 7.15 ppm, particularly for sample JA2, are due to aromatic protons. Multiple resonances at 5.7 and 4.9 ppm are present only in the NP fractions from samples GD, BE2, BE3 and JA1 and are practically not observed in the NP fractions from the other amber samples. So, their presence or absence is not associated with the source locality of the amber (Belchat6w or Jarosz6w). These resonances have a consistent integrated signal ratio of ca. 1:2 and show a specific pattern and coupling. The resonance multiplicity at 5.7 ppm (doublet of doublets) and at 4.9 ppm (4 pairs of resonances, where 2 internal pairs overlap), and the chemical shift values are characteristic for the vinyl group with 2 magnetically nonequivalent methylene protons, i.e. vinyl with the AB system -CHx = C ~ . The observed coupling constants between the respective protons have values: JAX = 10.6 Hz, Jax = 17.3 Hz and JAa = 1.5 Hz, and the chemical shift values for the protons are HA =4.83, HB =4.88 and Hx = 5.72 ppm. The resonance pattern and shift values are typical for terpenoidal structures. For example in a related structure (methyl oblongifolate, Aiyar and Seshadri, 1970) these values for the vinyl group are as follows: coupling constants JAX = 10.0 Hz, Jax = 17.7 Hz and JAB = 1.5 Hz, with values of HA = 4.84, Ha = 4.89 and H x = 5 . 8 3 ppm. It can be assumed that the vinyl substituent in these amber samples is present in an isopimarane-related skeleton on the basis of biogeochemistry and consideration of the structural relationship to Baltic amber. The lack of resonances at 5.35.4 ppm from olefinic protons of a ring C = C bond (the presence of a C = C bond in ring B or C is characteristic for tricyclic diterpenoids) with an intensity corresponding to that of the quartet resonances at 5.7 ppm suggests that if the C = C bond is present in the terpenoid structure bearing a vinyl group, it is placed between the quaternary C-8 and C-9 carbons common to both rings. This may suggest that the structure with the vinyl group is represented mainly by the A8 isomer of isopimarane. A 2D IH COSY experiment was performed for the NP fraction from sample JA1 to provide unambiguous identification of the vinyl group in the mixture (Fig. 11). Indeed, the quartet assigned to the Hx proton at 5.72 ppm shows a cross peak with the methylene protons of the vinyl group at 5.8-5.9 ppm. The latter has a cross peak with protons at resonance values of 2.3 and 1.18 ppm. The resonance multiplicities in the region around these chemical shift values do not allow further interpretation of the compound structure bearing the vinyl group. The 13C N M R spectra obtained for the NP fractions of 2 representative amber samples are

Characterization of Polish ambers

823

x,, L'~ | It

t.

I , ' ; . , , ' . , , ,

.....

, ' ' 1 ' , , ,

. . . . . . .

;,

',,,

wrT--I~TrI'rT

~"r ;-r'l~-r'lw'r~

' T [ r'r ~ I-rl

""

I1

' ; ' ; ; r-r

; 1 ' ' ~

ppm Fig. ] ]. 2D 1H COSY NMR spectrum for the non-polar extract fraction from amber sampleJA1.

GD

BE2 / - -

L..zu

I

200

I

150

I

100 ppm

,~||..

50

I

0

Fig. 12. 13C NMR spectra for non-polar extract fractions from amber samples GD and BE2 (the peaks at 78 ppm marked with an asterisk arc due to residual solvent).

shown in Fig. 12. Sample GD exhibited the presence of a vinyl group in the 1H N M R spectrum while it was not present in sample BE2. Even though the intensities of the 13C resonances are not comparable for different types of C atoms, the representative spectra show a marked prevalence of aliphatic C resonances (1060 ppm). For both NP fractions the common and dominant resonances in this region are at values of 16.2, 18.1, 19.5, 20.9, 27.8, 29.2, 29.6, 31.8, 36.7, 41.9, 44.6 and 46.1 ppm. The relative intensities of the aliphatic C resonances differ for both NP fractions suggesting quantitative differences in their molecular composition. The total number of resonances for sample BE2 is greater than for sample GD, which also indicates qualitative molecular differences. The high intensity resonance at 80 ppm is assigned to C associated with a hydroxylic group. The number of resonances representing olefinic and/or aromatic carbons ( l l 0 - 1 ? 0 p p m ) is much smaller. Five resonances at 110.8, 124.6, 128.4, 136.3 and 146.1 ppm are present within this spectral window for the NP fraction of sample G D (a vinyl group is

824

F. Czechowski et al.

a)

GD 4

3

5 . . . . .

10

.]~,li

i I..k

30

20

40

50

60

70

b)

BE3 I

,..,[I Ib......L....... ~b~o_[....tJ~]

3o

•

"

'

~o . . . .

~o . . . .

6o . . . .

q

o

"

7 0

"

c)

JA2

. .

~, .

.IJll,., ,

,

I0

•

•

"

2 ' 0

"

"

3b ....

~;o ....

Retention

time

~ o

"

6o

"

"

"

[min]

Fig. 13. Total ion current traces from GC-MS analyses of the non-polar extract fractions from selected amber samples GD, BE3 and JA2 (numbers refer to Table 9).

Characterization of Polish ambers observed in its IH N M R spectrum), while for the NP fraction of sample BE2 only 2 resonances at 110.8 and 128.4 ppm are observed. The resonances which are not common, i.e. at 124.6, 136.3 and 146.1 ppm, are typical for structures with a diterpenoid skeleton (Aiyar and Seshadri, 1970). The resonance of the exocyclic methylene C=CH2, observed at 108 ppm for fossil resins in solid state ~3C N M R spectra (Lambert and Frye, 1983; Cunningham et al., 1983; Grimalt et al., 1987), is not present in the 13C N M R spectra of both NP extract fractions. This fact is consistent with the observation of Wilson et al. (1992), who also did not report this resonance for resin extracts, while it was present for bulk resin. This is consistent with the F T - I R data, supporting the suggestion that an exomethylene group is associated with the insoluble polymeric matrix. Resonances representing carboxylic C are very weak. Only one significant resonance at 172.5 ppm is observed in the spectra, indicating that one dominant structural moiety of carboxylic C prevails (possibly succinates). In general, the data of the IH and ~3C N M R spectra are consistent and exhibit both qualitative and quantitative variations in the molecular compositions of the non-polar extract fractions of the ambers.

Molecular constitution o f non-polar extract fractions

The NP fractions were analyzed by GC-MS and the total ion current (TIC) traces for selected samples are shown in Fig. 13. Their peak patterns reflect a similar overall molecular composition, however, with variable relative concentrations of the various compounds. This is the case for all NP fractions, even among those of a given locality (Belchatrw or Jarosz6w). The components constituting the mixtures were identified by analysis of their mass spectra, mainly with reference to literature data (Botta et al., 1982; Mills et al., 1984/85; Grimalt et al., 1988; Anderson and Winans, 1991; Anderson and Botto, 1993). The mass spectrometric data of respective chromatographic peaks and, where possible, the assigned compound names are presented in Table 9, while the structures of the identified compounds are shown in Scheme 1 (the compound numbers in Scheme 1 are also given in Table 9). The most abundant compounds common to all NP fractions are derivatives of fenchyl, bornyl and isobornyl alcohols, as well as succinic, abietic and isopimaric acid derivatives. The other compounds are present only in some of the samples. The monoterpenols have also been described to occur in the volatile fraction of Baltic amber (Mosini et al., 1980). A similar suite of volatile monoterpenoids was generated from various pine resins after heating at 110 C for 1-2 months (Mosini et al., 1980). The most significant aspect of these data is the presence of a specific group of compounds in all the NP fractions. This group is represented by diesters of

825

succinic acid with methyl, fenchyl, bornyl and isobornyl alcohols. The mass fragrnentograms for m/z 137 (fenchyl or bornyl ion) for selected NP fractions are shown in Fig. 14. Peaks at lower retention time (35) represent succcinic acid diesters with methanol and fenchyl, bornyl or isobornyl alcohols. The relative concentration of these monoterpenoid-methanol diesters is similar in all samples (at equilibrium) and for (3):(4):(5) equals 0.52:1:0.25-0.30. This parallels approximately the relative concentrations of the corresponding monoterpanols themselves (compounds 16, 18 and 19). The peaks in the medium range of retention time (52-58 min) are represented by succinate diesters of fenchyl, bornyl and isobornyl alcohols, i.e. difenchyl-(6), fenchyl-bornyl-(7), fenchyl-isobornyl-(8), dibornyl-(9), bornyl-isobornyl(10) and diisobornyl succinate (11). Similarly as for the diesters (3), (4) and (5) their relative concentration ratios are for (6):(7):(8):(9):(10):(11)=0.150.20:1:0.15--0.20:0.85-0.95:0.45:0.05. These relative ratio values are similar for all NP fractions except for sample BE5 (the most altered amber) where the overall concentration of succinates is lowest. It is assumed that amber components containing O in ester groups are more likely to be hydrolyzed and washed out (for instance in a limestone environment). The peaks observed around a retention time of 65-70 min are esters of isopimaric and abietic acids with fenchyl, bornyl and isobornyl alcohols. The latter esters are present in some NP fractions, and in general their higher overall concentration correlates with a lower overall concentration of diesters (6), (7), (8), (9), (10) and (11) in the sample. The characteristic relative concentrations of the various succinic acid diesters can be considered as specific molecular markers related to the biotic precursors of the ambers. To assess whether these biotic precursors are associated with the brown coal detritus of the Betchatrw deposit (BCB), its NP fraction was also analyzed by GC-MS and the mass fragmentogram of m/z 137 is presented in Fig. 14(e) for comparison. The diesters of succinic acid are not present, not even in traces in the NP fraction of sample BCB. The major compound in the m/z 137 trace of this fraction is 16ct(H)-phyllocladane which is a typical diterpenoid constituent of Tertiary brown coals (Simoneit et al., 1986; Alexander et al., 1987). On the other hand, phyllocladane is not observed in any NP fraction of the ambers that were examined. Another specific group of compounds is represented by homologous series of n-alkanes. Although their relative concentrations are low in all NP extract fractions, their distribution patterns in the key ion plots of m/z 71 (Fig. 15) are practically the same for all amber samples. Contamination by these compounds from solvents was excluded based on blank analysis. The series of n-alkanes exhibit a Gaussian distribution within a homolog range from C22 to C33 , maximizing at C26-C27, and additionally a characteristic slight C22 predominance. Such n-alkane distribu-

826

F. Czechowski et al. Table 9. Identification of constituents in the non-polar extracts of the ambers from the GC--MS data

MW Retention time (% relative intensity) (min)

Other fragment ions, m/z (% relative intensity)

5.90 7.04 7.17 7.24 7.34

136(30) 138(19) 146(I) 138(19) 154(37)

7.38 8.56 8.71 9.14

134(28) 152(13) 160(1) 154(2)

9.97

152(29)

0.18 10.26

136(10) 154(1)

10.50 12.24 12.53 14.13 17.04 17.26

154(1) 182(1) 164(37) ? 192(20) 204(12)

18.06

204(7)

18.54

222(1)

18.83

222(4)

18.87 19.06

192(10)

19.34 19.46

188(25) 204(1)

19.70

206(10)

19.96 21.22

190(15) 174(22)

121(82), 107(35), 93(100), 91(50), 79(43) 123(16), 95(100), 81(48),67(37) 115(100), 114(30), 87(17), 74(1), 59(52) 95(100), 81(34), 68(54), 67(54) 139(31), 136(5), 125(8), 115(13), 111(48), 108(65),97(12),96(32),93(50), 84(77), 81(90), 71(100), 69(77), 67(55), 59(48) ll9(100), 91(20) 137(3), 109(5), 101(7), 81(100), 69(48), 57(5) 129(15), 115(100), 101(44), 87(13), 73(9), 59(44) 139(4), 121(8), 114(15), 111(13), 107(9), 93(13), 84(21), 81(100), 80(74),71(25), 69(25), 57(16) 137(3), 123(2), 110(13), 108(44), 95(100), 83(32), 81(82), 69(57), 67(25), 56(3) 128(4), 121(12), 110(18),101(10),95(100),82(5), 67(10), 59(5) 139(6), 136(10), 122(24), 110(20), 105(29), 95(100), 83(11), 77(25), 67(15), 59(7) 139(5), 136(5), 121(4), 110(22), 95(100), 83(4),67(10), 57(3) 136(19),121(25),110(14),108(84),95(100),80(10),69(18),57(10) 121(15), 94(100), 79(37), 77(19), 70(13), 57(6) 157(1), 133(4), 115(100), 101(33), 87(7), 71(3), 56(18) 177(30), 163(4), 137(15), 121(10), 109(70),95(100), 82(95),67(55) 148(65), 135(15), 133(48), 124(11), 121(15), 119(23), 109(55), 107(100), 93(40), 91(36), 79(32), 69(32), 57(18) 189(20), 161(18), 148(65), 133(40), 119(40), 109(30), 106(80), 95(65), 93(100), 79(60), 69(55) 193(2), 179(5), 166(6), 139(14), 123(16), 121(14), 108(29), 95(20), 85(100), 83(85), 67(26), 57(7) 189(3), 179(2), 166(8), 151(4), 137(8), 123(22), 109(44), 108(44),95(52), 93(34), 83(64), 81(100),67(30), 56(7) 177(18), 153(15), 125(75), 109(50), 95(98), 82(100), 67(56) 175(60), 161(25), 147(30), 133(45), 121(80), 108(100), 93(95), 81(55), 69(35) 173(7), 159(3), 145(10), 132(50), 119(100), 105(7), 91(70), 69(20) 188(20), 173(4), 159(2), 145(9), 132(40), 119(100), 105(11), 91(11), 69(19), 57(7) 191(10), 180(20), 166(15), 151(35), 138(10), 123(50), 109(100), 95(75), 82(72), 67(55) 147(100), 133(15), 119(6), 95(5), 81(7), 69(5), 57(4) 159(100), 128(8), 109(4), 91(7), 71(10), 58(9)

22.37

188(18)

173(100), 158(11), 145(7), 128(7), 119(7), 115(6), 91(6), 67(6)

22.53 24.40

202(25) 220(2)

24.79

222(2)

25.06 25.76

222(3) 236(1)

26.68

222(8)

29.38 29.64 30.10 31.62 31.80 32.10 32.37

268(2) 206(10) 268(1) 204(7) 236(10) 268(2) 268(2)

159(100), 144(15), 131(20), 128(15), 105(18), 91(10), 77(5) 204(4), 189(3), 179(7), 161(16), 135(7), 123(26), 111(100),95(24),81(26), 69(22), 59(16) 204(3), 179(7), 163(2), 151(14), 123(37),111(100),95(26),81(44),69(36), 57(9) 177(25),149(100) 221(2), 204(2), 193(11), 165(4), 137(8), 125(100), 109(4), 93(8), 81(15), 67(81), 57(2) 207(100), 166(7), 151(10), 137(7), 123(36), 111(23), 95(28), 81(23), 69(22), 57(10) 240(1), 153(4), 136(10), 115(100), 81(22), 69(4), 59(6) 191(7), 163(4), 143(15), 123(8), 109(11), 97(24), 87(54), 74(100), 57(19) 163(5), 136(10), 115(100),91(10), 81(28), 59(9) 189(2), 173(100), 158(15), 143(12), 128(11), 109(6), 81(7), 69(7), 57(5) 221(100), 143(33), 128(15), 115(18), 105(22), 91 (25) 153(3), 136(22), 121(14), 115(100),95(26), 81(11), 69(7), 59(12) 136(30), 115(100), 108(13), 95(26), 81(1), 69(7), 59(12)

33.50

226(15)

34.10

246(7)

190(55)

Compound (number in Scheme 1) camphene fenchane (12) dimethyl succinate (1) camphane (13) 1,8-cineole (14) p-and m-cymene (?) fenchone (15) ethyl methyl succinate (2) fenchol (16) camphor (17) tricyclene (?) isoborneol (18) endo-borneol(19)

bornylformate (20)

cadinene(e.g. 21,~-isomer) bergamotene sesquiterpenol ledol isomer (e.g. 22)

dihydro-ar-curcumene (23) dihydrocadinene 1,5,6-trimethyl- 1,2,3,4tetrahydronaphthalene (24, R = H) l,l,5,6-tetramethyl-l,2,3,4-tetrahydronaphthalene (24, R = CH3) calamenene (25) palustrol (26) diethyl phthalate

fenchylmethylsuccinate (3) (e.g., 24, R = CH2OH)

bomyl methyl succinate (4) isobornyl methyl succinate (5) 206(55), 179(20), 161(18), 148(80), 136(100), 135(95), 121(60), 109(40), 13-methyl- 16/17-norpodocarpa-6,8, I 1,1391(50),71(60) tetraene

228(17),213(54),157(47),131(100),105(30)

Characterization of Polish ambers Table 9. Retention MW time (% relative (rain) intensity)

34.13 35.79 36.71 38.07 38.91 40.13 41.37 42.90 43.20 44.34 46.30 47.55 48.74 49.15 0.71 52.40 54.75 55.38 57.00 57.37 57.79 59.00 64.68 65.10 70.64

827

(continued)

Other fragment ions, m/z (% relative intensity)

Compound (number in Scheme 1)

243(100), 221(10), 201(7), 187(30), 161(85), 147(25), 121(30), 120(40), 105(80),91(81), 81(70),65(50) 14-ethyl-13-methyl-16/17256(15) 241(80), 185(30), 159(100), 117(15) norpodocarpa-8,11,13triene(27, R = CH3) 171(3), 143(13), 119(6), 87(54), 74(100) methyl palmitate 270(6) dibutyl phthalate 223(8),149(100) 278(2) 19-norabieta-8,11,13256(23) 241(60), 213(5), 185(26), 159(100), 117(24),91(10),69(5) triene (28) 256(23) 241(72), 213(13), 185(27), 159(100), 129(15), 117(55), 91(13), 69(24), 18-norabieta-8,11,13triene (29) 55(10) 270(29) 255(100), 227(7), 199(15), 185(44), 173(66), 159(85), 129(29), 117(22), abietatriene (30) 91(30),69(100), 57(24) 272(20) 257(100), 229(7), 201(4), 175(6), 149(16), 123(16), 109(23), 91(29), abieta-7,13-diene (31) 79(27),69(20), 57(25) 255(6), 227(18), 199(7), 185(6), 171(14), 145(26), 129(14), 109(20), methyl stearate 298(6) 87(72), 74(100), 57(31) 306(10) 291(60), 177(85), 149(45), 121(50), 109(55), 95(100), 81(60), 68(50), 67(45) 13-methyl-14-propyl- 16270(38) 255(100), 227(8), 199(20), 173(95) norpodocarpa-8,11,13triene(27, R = C2H5) 13-methyl-14-propyl- 17270(48) 255(100), 227(13), 199(31), 173(87) norpodocarpa-8,11,13triene(27, R = CzHs) 14-butyl-13-methyl-16/17284(46) 269(100),227(33),199(53),187(64),69(19) norpodocarpa-8,11,13triene(27, R = C3H7) 302(30) 287(50), 257(15), 241(50), 185(40), 173(30), 159(25), 145(27), 133(45), methyl norisopimarate (32) 119(45), 105(90),91(100), 79(60), 67(40), 57(15) 275(15), 230(50), 180(5), 121(100), 107(95),95(15), 81(25),67(22) methyl 13318(2) +290(32) methylpodocarpa- 13-en16-oate (33) + unknown 137(100), 121(5), 109(4), 95(10), 81(70),69(10), 57(2) 390(1) difenchyl succinate (6) 137(100), 95(58), 81(100), 69(50), 57(40) bornylfenchyl sueeinate (7) 390(1) 279(4), 167(15), 149(100) dioctyl phthalate 390(0) 153(5), 137(100), 121(14), 109(8), 95(28), 81(65), 69(10), 57(5) 390(2) dibornyl succinate (9) 254(5), 153(5), 137(100), 121(10), 109(6), 95(21), 81(70), 67(15), 57(5) bornyl isobornyl succinate 390(2) (10) 137(100), 121(15), 109(20), 95(30), 81(67), 67(25), 57(18) 390(1) diisobornyl succinate (11) 57(100)...... 380(6) n-C27 alkane 268(17), 253(100), 211(9), 173(16), 115(37), 81(20), 69(20), 57(15) 400(5) dehydroabietyl methyl succinate (34, R = CH3) 287(12), 257(8), 187(9), 175(10), 137(100), 81(100), 69(50) 438(1) bornyl-8-pimarate (abietate?) (35) 282(73), 267(100), 187(100), 115(73),95(35), 81(45),69(55), 57(73) 414(9) dehydroabietyl ethyl succinate (34, R = C2H5) 258(35)

tions have been reported for biodegraded lipid detritus (Simoneit, 1978). An origin from plant wax lipids as found in the brown coal was excluded by comparison with the different pattern in the key ion plot for the NP fraction from sample BCB (Fig. 15d). Also, the presence of pristane (Pr) and phytane (Ph) in NP fractions BE4 and BCB support a biotic origin for both materials (i.e. resin and bulk plant detritus, respectively). The n-alkanes in the brown coal sample have a strong predominance of odd C numbered homologs in the range C25-'C33, characteristic for immature higher plant wax (Simoneit, 1978; Wang and Simoneit, 1990). This group of compounds shows

that the amber samples are biogenetically related and derive from different biotic source matter (resin) than the bulk detritus of the Betchat6w brown coal deposit. The other compounds which occur in some but not all NP fractions are monoterpenoids, sesquiterpenoids, diterpenoids, alkanoic acids as methyl esters (mainly C16 and C1s), various unknowns, and phthalate ester contaminants (Table 9). Some of these compounds have previously been reported to occur in Baltic amber (Mosini et al., 1980; Botta et al., 1982; Mills et al., 1984/85). The unbound monoterpenoids are found as the hydrocarbons, ketones and alcohols

828

F. Czechowski et al.

0

R1

Rlo~LV~.~

OR2 0

1.

2. 3. 4. 5. 6. 7. 8.

9. 10. 11. ~

R2

methyl methyl methyl methyl methyl fenchyl fenchyl fenchyl bornyl bornyl isobornyl

methyl ethyl fenchyl bornyl isobornyl 12. fenchane fenchyl bornyl isobornyl bornyl isobornyl isobornyl

do ~

\--

14. 1,8-cineole

1

H

.,oOH

16. fenchol

13. camphane

17. camphor 18. isoborneol

19. bomeol

OH

15. fenchone

I

OOCH

20. bornylformate

) 21.13-cadinene

22. ledol

J 23. dihydro-ar-curcumene

24. aromaticdrimanes

25. calamer//e~

5, 03H7

26. palustrol

27. dialkylnorpodocarpatrienes Scheme 1. Chemical structures identified in the non-polar extract fractions of the ambers (numbers refer to Table 9).

(12-19) and as more extensively altered derivatives (e.g. cymenes). The sesquiterpenoids are comprised of isomeric derivatives of cadinene (21), bergamotene, ledol (22) and palustrol (26), and of structurally altered products such as dihydro-ar-curcumene (23), monoaromatic drimanes (24), dihydrocadinene, calamenene (25) and various unknown isomers (Table 9). The diterpenoids occur mainly as hydrocarbon and carboxylie acid derivatives of the abietane and pimarane skeletons (28-34), with a minor hydrocarbon series of 13,14-dialkylnorpodocarpatrienes (27) (Table 9). It should be noted that the norabietatrienes

(28 and 29) are in the elution order according to our reference standards which is opposite to their listing by Mills et al. (1984/85). Triterpenoids are not detectable.

CONCLUSIONS The ambers which were investigated have very low porosities. Positron annihilation spectroscopy and sorption of N2 at low temperatures gave similar values for pore volumes of about 0.018 to

Characterization of Polish ambers

829

D

28. 19-norabieta-8,11,13-triene

29. dehydroabietin

~ kT

30. abieta-8,11,13-triene

91 '~R2

J =% vinyl

v

92 vin9 methyl

COOCH3 31. abieta-7,13-diene

33. methyl 13-methylpodocarpa-13-en-16-oate

32. methyl 18-nor-8pimarenoates :l 2

*~Ra

H3~C2H5

R1 R2 R3 methyl methyl methyl fenchyl methyl vinyl fenchyl vinyl methyl bomyl methyl vinyl bomyl vinyl methyl isobomyl methyl vinyl isobomyl vinyl methyl

35. monoterpenylpimarates 0 34. alkyldehydroabietylsuccinate Scheme 1.

0.030 cm 3 g-1. These pore sizes are small. Spheres where positronium atoms are formed have diameters of 0.8 to 0.9 nm, while pore sizes accessible to N2 molecules are larger with an average diameter of 2 to 12 nm. The concentration of spherical voids in the core of the bulk amber is approximately twice as large as in its weathered rind. Lower concentrations of components with ester groups were found in the rind and based on this observation it was assumed that positronium atoms are formed in ester group proximity in the interior of the amber. F T - I R showed a similarity in the chemical nature of all amber samples. They are highly alicyclic with minor hydroxyl, carbonyl and carboxyl groups. The degree of polymerization was found to parallel the reflectances (Rr) of the polished surfaces of the

(Continued).

ambers. Furthermore, the solvent extract yields from the ambers correlate inversely with their R¢ values, analogous as observed for coals. The 1H and 13C N M R data supported the bulk chemical compositions of the NP fractions of the ambers as observed by FT-IR. The N M R data indicate that the amber extracts are highly aliphatic and alicyclic with low concentrations of compounds bearing oxygenated groups. Exocyclic methylene groups observed in resinous materials are not detectable in the NP fractions by either F T - I R or ~3C NMR, suggesting that this group is bound to the polymeric matrix, which is insoluble in organic solvents. The IH and 13C N M R data, however, do reflect the complex diversity of structures constituting the NP fractions.

830

F. Czechowski et al.

GD

a) 9 3

J,~l., . . . .. .. . . L . L . . . . .. . ., . .. .. .. .. . . . . ., 35 40 45 50

3O

-=. , iJ'-..--Jm - - - . ., . . . . 55 60

, ~ 65

b)

,

.

.

70

BE2

3

r

0

6

8

!

11 J!l....

%

30

4

.,

35

, , ..

40

.

45

.

,

I .... .h

50

55

60

65

70

BE5

c)

35

3

5

30

7

35

40

45

50

4

9

60

55 7

d)

65

70

J,~.

9

lo

3

1

6

/

30

3 35

40

45

50

.= 55

60

65

70

BCB trltelrpenu + trlterpe~es

e) l(~z(H)-phylk~ledmne

•

,

30

. . . .

,

35

. . . .

.

. . . . . . . . . . . . . .

40

45

50

ly

i L

55

.

60

. . . .

.

65

. . . .

. . .

70

Retention time [rnin] Fig. 14. Mass fragrnentograms for m/z 137 for the non-polar extract fractions from selected ambers and brown coal sample BCB (numbers refer to Table 9).

Characterization of Polish ambers

831

26 25

a)

GD

27 28 29

24

3O 31

22

17

118

30

[ 231

35

40

45

I

50

b)

65

60 27

55

70

26

BE4

2~ 3

25

75

'£a 30

24

17

c)

18

22

23

J

32

(4)

(3)

29

is)

18

24

22

i

17

LII 3O

•

JA2

26 27 28

25

•

J .

35

.

I

.

.

.

d IMill )11 llU .

40

.

.

.

.

.

45

.

i

50

. . . .

n

30

L,,

55

d)

60

65 29

27

70

75

31

25

BCB 22

• " 3'o ....

a's ....

4b ....

4~ ....

23 24

26

so ....

s~ ....

6b ....

6g ....

7'o ....

7;

Retention time [rain] Fig. 15. Massfragmentogramsform/zT1 (key ion for n-alkanes) for the non-polar extract fractions from selcctcd ambcrs and brown coal sample BCB (numbers refer to C chain length ofn-alkanes, numbers in parentheses refer to Table 9, Pr = pristan¢, Ph = phytane).

/~ II/6-E

832

F. Czechowski et al.

The molecular composition of the characteristic 2 groups of compounds, succinate diesters and nalkanes, revealed particularly useful information. First, it was concluded on the basis of their composition that the amber samples, independent of locality, are succinite representative of organic material of the same biogenetic origin. Second, the marked differences between the NP fractions of the ambers and the NP fraction of BelchatSw brown coal, even for the BE amber samples from the same bed, indicate a lack of biogenetic relation between the resin and coal materials, i.e. the amber is succinite and the coal is derived from resins and other plant detritus. In addition the nalkane profiles for the NP fractions from the ambers are more mature than that of the NP fraction for the BCB coal. Chemical and physical changes during the early stages of biogeochemical reworking and diagenetic maturation should affect the detrital material to a greater extent than the bulk amber because the latter is more stable and consolidated during that period of time results in better preservation of the marker compounds. Assuming the different biotic origin of both of these materials, yet similar age and mild geothermal maturation, the n-alkane profile for the amber NP fractions should show a lower degree of alteration compared to that observed for coal sample BCB, provided a plant wax signature was preserved in the precursor resin. In fact, the nalkane distributions show the opposite results. No plant wax was preserved in the amber. The traces of degraded n-alkanes may have become incorporated into the resin matrix from microbial sources active during resin evolution from the biotic source. It is also suggested that during the process of amber evolution from the biotic source a simultaneous biochemical fermentation took place to form succinic acid. This indicates that succinates may be specific markers for certain bacterial species (for instance Desulfovibrio) which were active on resinous material during its evolution from the biotic source by converting some compounds to succinates. This idea is supported by the specific composition of succinates preserved in the ambers as well as the presence of numerous bubbles. The trace n-alkane distribution may represent a microbial lipid residue. Therefore, fingerprinting of succinate esters with specific alcohols and n-alkanes in amber is proposed as a characteristic indicator for fossil resins of Class Ia according to Anderson et aL (1992) and Anderson (I 994). The overall data suggest that all the amber pieces analyzed are Baltic amber (suceinite), independent of sample location in Poland. The presence of amber in different localities and in various deposits (Tertiary Belchat6w brown coal, Quaternary Jaroszrw clay) indicates their spread over a large area during the redeposition process from the Chiapowo-Sambian delta. The molecular composition of succinite is

related to fossil Agathis resin. However, substantial amounts of naturally formed diesters (i.e. succinates of methyl, fenchyl, bornyl and isobornyl alcohols) are not found in the latter. Therefore, a direct relationship to precursor plant material cannot be unambiguously established for these ambers, but in general it is assumed they are derived from the hypothetical genus of Pinus succinifera. Acknowledgements--Financial support from the National Research Committee (KBN-grant number 60458 91 01) is gratefully acknowledged. We thank Professor Curt W. Beck for his excellent comments and suggestions which clarified and improved this manuscript. Editorial Handling: Dr Ron Fuge.

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