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Thermoluminescence dating of Loess-paleosol sequences in the carpathian basin (East-Central Europe): A suggestion for a revised chronology
307
Chemical Geology (Isotope Geoscience Section), 73 (1989) 307-317 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
THERMOLUMINESCENCEDATING OF LOESS-PALEOSOL SEQUENCESIN THE CARPATHIAN BASIN (EAST-CENTRAL EUROPE):A SUGGESTION FOR A REVISEDCHRONOLOGY A.K. SINGHVI’*2,
A. BRONGER3,
W. SAUER’
and R.K. PANT’
‘Physical Research Laboratory, Ahmedabad 380 009 (India) 2Max-Planck-Znstitut fiir Kernphysik, D-6900 Heidelberg 1 (Federal Republic of Germany) 3Geographisches Znstitut der Uniuersiti-it Kiel, D-2300 Kiel 1 (Federal Republic of Germany) (Received February 2,1988; revised and accepted July 27,1988)
Abstract Singhvi, A.K., Bronger, A., Sauer, W. and Pant, R.K., 1989. Thermoluminescence dating of loess-paleosol sequences in the Carpathian Basin (East-Central Europe): A suggestion for a revised chronology. Chem. Geol. (Isot. Geosci. Sect.), 73: 307-317. Detailed thermoluminescence (TL) dating of the loess-paleosol sequences in the Carpathian Basin, suggests that the conventional chronology of Mende-Base soil (soil F,) representing the Riss-Wtirm interglacial is not tenable, because it is much older. The results also suggest that the recently reported TL-age underestimation effect in some loess and sand samples from Northwestern Europe does not occur in the samples analyzed in this study.
1. Introduction
Of the terrestrial sediments, perhaps the most extended and continuous records of Pleistocene climatic changes are provided by the loesspaleosol sequences in the periglacial regions of the continents. Extensive efforts have been made to correlate climatic and proxy-climatic data provided by various loess-paleosol sequences with the deep-sea oxygen-isotopic records (Kukla, 1977). Such correlations have, however, been constrained by limited time resolution of a chronology based predominantly on the records of paleomagnetic reversals. The loess-paleosol sequences along the river Danube (Fig. 1) have been considered particularly suitable for land-sea correlations be-
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cause of the following reasons: (a) these deposits are in an ideal geographic location, being close enough to the Atlantic Ocean to record its influence during interglacials, and far enough inland to develop continental steppes during warmer episodes (Zeuner, 1959; Kukla, 1977); (b ) these sequences (especially from paleosol F5 to F,; Fig.2) provide an almost continuous and a complete succession of paleosols that are separated by thick loess deposits. This permits reliable stratigraphic correlation between various profiles (Bronger, 1975,1976,1979); (c) these sequences are in principle stratigraphically correlatable to the Pleistocene river terraces of the region (P&s& 1985; Pecsi et al., 1985); and (d) the river Danube also drains the Alpine
B.V.
308
Loess-
Exposures
lnvestlgated
Fig. 1. Map of the Carpathian investigated.
m
Basin, depicting
foothills, where the classical Alpine quences have been defined.
the River Danube and the locations of the loess-paleosol
glacial se-
2. Stratigraphy Fig. 2 provides a summary of the stratigraphical subdivisions and paleosol types in various loess-paleosol profiles in the Carpathian Basin. These are principally based on soil micromorphological and clay mineralogical studies by Bronger (1975,1976,1979; Bronger et al., 1976), who concluded that: (a) the sequence F, - F, is almost complete and can be reliably correlated between various profiles; (b ) the rate of pedochemical weathering (i.e. the rate of clay mineral formation, especially the < 0.2-pm fraction) in soils Fq, F3 and Fz (all identified as Chernozems ) is essentially similar to that exhibited by the modern soils of the same
sequences being
genesis in the region, the latter having developed in an ustic soil moisture regime (Soil Survey Staff, 1975); (c ) Chernozems F3 and Fz are well preserved in the northern part of the basin and generally are at least as thick as, and in southern parts are nearly twice, as thick as recent Chernozems. This suggests that the three soils Fq, F3 and Fz must have formed under a climatic regime very similar to the present, i.e. an interglacial climate. (d) the interglacial represented by the Brown Forest soil F5 also suggests a climate similar to the present but perhaps somewhat moister. In the literature these soils have been variously designated by different groups. Table I provides a broad correspondence between the nomenclatures used by different groups and the one used in the present study (see, e.g., Bronger, 1975,1976; PQcsi, 1984).
309 TABLE
I
Equivalence
chart between different
nomenclatures
F-notation Bronger
used to designate the loess-paleosol
MF-notation (1975,1976)
PBcsi (1984)
horizons in the Carpathian
Remarks
PBcsi (1984) Dunaujvaros-Tapiosuly developed in Paks)
F,
F2
f-1
F-3 F4 F,
F,(+Fs?) F4 F,
Basin
MF BD1 +BD, BA MB
3. Chronology 3.1. Present status The chronology of the loess-paleosol sequences has been much debated relying largely on the investigations made on sequences at Paks, Mende and Dolni Vestonice (Fig. 1). Basically two chronological assignments have been advocated. The first assignment, based on the INQUAstratigraphic guiding principle, suggests that the Mende-Base soil (i.e. soil F5) represents the last interglacial, being the “youngest” Brown Forest soil (Fink, 1964). Several radiocarbon dates were compiled by PQcsi et al. (1979). These range from N 16.5 to 20 ka ( hl and h2 humic soils), from N 27 to 30 ka (MF soils) or are 2 32 ka (soils BD, and BDz), and are correlatable to soils F1, F, and FB, respectively. In addition, thermoluminescent dating of samples from Paks and Mende by Borsy et al. (1979) and by Butrym and Maruszczak (1984) provided the age of the MendeBase soil as N 110-120 ka. These thermoluminescence (TL) dates cannot be accepted per-se in view of the inadequate methodology used in their determination [see Singhvi and Mejdahl (1985) for a discussion; also A. Wintle and V. Mejdahl’s private communication to A.K. Singhvi (1985) 1. On the other hand, radiocarbon dates on paleosol are in general grossly underestimated as has been demonstrated by studies by Geyh et al. (1983) and Fink1 (1984).
Mende-Basaharc
complex (weakly
complex
In the case of loess-paleosol profiles of Kashmir, India, it was also seen that the radiocarbon ages were grossly underestimated (Singhvi et al., 1987). The second chronological assignment is based on the magnetostratigraphical results and suggests a much older chronology (Kukla, 1977, figs. 13 and 21). In this scheme the Mende-Base soil (F5 in Fig. 2) belongs to the loess cycles F and G, which have been assigned a date of N 500 ka. As supporting evidence, the presence of Elephas throgentherii (a middle-Pleistocene fauna), in the loess horizon beneath the MendeBase soil is cited. Lastly, a number of uraniumseries disequilibrium dates on travertines from Tata, Hungary, have been reported (Schwartz et al., 1982; Hennig et al., 1983). Geomorphological correlations suggest that these travertines correspond to the “young Mende-Basahart loess” sequence, i.e. the sequence encompassing the soils F, and F3 should have formed sometime during 100 ka B.P. which is substantially older than that suggested by radiocarbon dates. 3.2. Thermoluminescence
dating
Developments in TL dating during the past decade have offered the possibility of providing absolute chronologies for sediments for which a finite pre-depositional sun exposure could be assumed (see Singhvi and Mejdahl, 1985;
310
311
Singhvi and Wagner, 1986, for reviews). In general, the TL dates on loess-paleosols provide the age of the depositional event of the loess itself. However, in the case of some soil horizons (i.e. the A-horizons), fauna1 pedoturbation causes churning of the sediment, resulting in an on-site sun-bleaching of the TL. In such cases, TL provides the age of the soil formation itself (Huntley et al., 1983; Wintle and Catt, 1985). In view of the “absolute” nature of TL dates, derived by an analysis of the very minerals that constitute loess, it was considered necessary to re-examine the chronological framework of the globally important loess-paleosol sequences of the Carpathian basin. The “completeness” of the sequences in the basin extending up to and beyond the Brunhes-Matuyama boundary at N 730 ka provided an additional incentive for research into the TL methodology. In particular, such a continuous sequence provides a unique opportunity to examine the TL-age underestimation effect reported by Debenham (1985) in respect of some of the North-western European sand and loess sequences. This observation indicated that no matter how old the depositional age of loess and/or sands, their TL age is limited to - loo-150 ka. At this time, the exact cause of the anomaly is not yet understood, though various mechanisms such as a possible decay of recombination centres, radiation-dose-dependent changes in the TL sensitivity, and an alteration of TL sensitivity following an optical bleaching in the laboratory have been proposed (see Mejdahl, 1986 for a concise discussion). The sequences in the Carpathian basin thus provide good stratigraphic control on TL dates to examine the validity and universality of the age underestimation effect.
4. Samples and methods The details of basic TL methodology, relevant assumptions and procedural aspects are described in a recent publication (Singhvi et al., 1987). Briefly, the fine-grain technique was
used and the 4-11-pm grain size was extracted after pre-treatment of the samples with 0.1 N HCl to remove carbonates, with Hz02 to remove organic fraction, and with 0.01 N Na-oxalate to deflocculate the sample. The equivalent dose of the sediment was measured using the total bleach-regeneration method (Proszynska, 1983; Debenham, 1985) and with an optical window corresponding to transmission through a Schott@ UGll filter coupled to a Chance-Pilkington@ HA-3 filter. The photomultiplier tube used was EMI@ 9635 QA. In the total bleach-regeneration method (TBregen), the growth of TL in the sample during antiquity is simulated by optically bleaching the sample in the laboratory using sunlight or a sunlamp or the like, and then regenerating the TL in the sample by laboratory irradiations. The laboratory irradiation which provides a TL intensity equal to that observed in the sample (natural TL) is the sediment equivalent dose D (Id). Implicit in this approach is the assumption that the laboratory optical bleaching in no way alters the TL sensitivity of the samples, i.e. the laboratory induced growth faithfully replicates the TL growth during antiquity. This fact is examined for each sample by comparing the TL sensitivity of samples before and after optical bleaching, in the dose region corresponding to the natural TL [i.e. D (&) 1. In the present study, a 300-W Ultra-Vitalux Wotan@ sunlamp (Osram@ ) was used for laboratory photo-bleaching. The laboratory irradiations were made using a “Sr-“Y P-plaque (30 mCi) and 241Am under vacuum. The radioactivity of the samples was analyzed using the thick-source ZnS (Ag) cx-counting as well as the elemental neutron activation analysis (NAA). The 40K concentration was estimated using atomic absorption spectrophotometry.
5. Results The results are compiled in Table II. Fig. 3 provides a typical glow curve along with a TL growth curve with P-dose and TL age plateau.
312 TABLE
II
Thermoluminescence Site and horizon No.
data on loess sequences in the Carpathian Plateau region*’ (“Cl
D(Z,)(‘”
Basin
a’**’
u bpm)
Th bpm)
K (%)
0.10
3.16
10.73
0.10 0.08 0.11
3.09 2.95
10.51 10.9
1.4
15
3,900
0.06 0.09 0.07
2.76 3.1 3.1 2.8
9.4 12.5 11.5
1.5'3 1.6 1.63
15 15
0.10
2.9
11.1 13.6
1.68 1.61
10 10 20
(GY)
Water fraction (%o)
Dose rate WY a-‘)
4s @a)
5.5’3
15
1.5'3
15
4,320 4,250 3,940 3,960 4,520 4,380
75'4 63'4 82 85 128 121 L186'5
4,910
2314’5
St. Slankamen: S-50 F, F, S-29 F, S-120 F, S-26 F, S-25 loess below F3 S-23 loess below F, S-22 F,
320-400 300-420 300-420 300-460 320-420 340-460 340-400 340-460
331 518 494 793 1,542
Er-43 F,
300-460
150
0.08
4.24
14.42
2.04
15
5,450
29
Er-45 loess below F,
300-440
207
0.08
3.51
11.94
1.56
10
4,504
45
300-380 300-380
335 581
0.11
3.2
10.94
1.53
10
0.10
3.12
10.68
1.41
15
4,670 4,135
71** 125'4
S-30
325 271
319
Erdut:
TiteljMosorin: TM-30 loess below F, TM-32 F3
“A somewhat delayed onset of plateau is quite probably due to the optical filter combination of Schott@ UG-II and ChancePilkingtone HA-3 filter. “Data refers to 360 ’ C on the glow curve temperature. *3K content assumed. *%-Counting data used for dose rate analysis. ‘5The growth of signal with dose was marginal and much more work needs to be carried out before a firm estimate can be provided.
Fig. 4 provides a comparison of the results obtained using the NAA and ZnS(Ag) a-counting methods. The concordance suggests that the radioactive decay series are not grossly in disequilibrium. Some comments on TL measurements may be appropriate at this stage. Recent work by Debenham and Walton (1983) has indicated that a Schott@ UG-11 filter with a peak transmission at around 320 nm provides a greater selectivity for K-feldspar emissions. In the present case, the detection optics has a HA-3@’ filter in addition to a UG-11@ filter causing N 20-nm shift of the peak transmission towards the blue. Despite this shift in peak transmission, it is considered that the combination still
provides a greater selectively to K-feldspar emissions, both due to their substantially higher TL sensitivity compared to the other dominant luminescent mineral quartz (Sutton and Singhvi, 1983) and due to their emission spectral characteristics (Debenham and Walton, 1983; Rendell et al., 1983). This is further substantiated by the glow curve shapes (Fig. 3) and by the fact that the residual TL intensities (after laboratory sunlamp bleaching) range from 6% to 16% of the natural TL (at 360°C). The TL dates implicitly assume that any systematic error arising from the spectral mismatch between the laboratory sunlamp with line emissions and the sunlight exposures experienced by the sample during its pre-depositional
313
TL:e-43
/ ‘\\ : -t, :I \\ 1 \;---NTL+sL+2.5t).B
f “5
100
200
300
0.6 400
500
0.5
0.6 aZnS(Counts
0.7 mid
1
Fig. 4. A comparison of the neutron activation analysis with the result of ZnS (Ag) a-counting method. The S series refers to samples from Stari Slankamen and Hu series refers to samples (also loess) from Plaidter Hummerich, F.R. Germany (not discussed in the present work).
Fig. 3. a. Typical natural TL and regenerated TL glow curves b. TL growth with /I-dose. c. TL-age plateau.
transport are small. Some support for this assumption comes from recent results of Jungner (1987) whose comparison of bleaching by blacklamp and sunlight suggests that the K-feldspars do not have significant wave-length dependence on bleaching. Further the non-linear growth of TL also reduces the extent of error caused by any possible over-bleaching. Thus, even if the bleached TL level is overestimated by lOO%, the nett error in the sediment equivalent dose will be less than a few percent (notice that the initial TL sensitivity is substantially higher ) . For all samples the change in TL sensitivity subsequent to laboratory sunlamp exposure was examined. In view of the intrinsically low TL sensitivity at higher doses and the variability of 5 10% in the TL output of different fine-grain discs, a variation in the TL sensitivity (before (54,) and after (S,) the sunlamp bleach) of up
to 20% was considered acceptable. In the present case, usually there existed at least one temperature on the plateau region where SN and S,-, matched reasonably well. The growth curves generally exhibited nonlinearity for doses of > 200 Gy*. All growth curves were fitted to a second-order polynomial using a Chebyshev polynomial expansion of the type: Y= $2&(X)
+a,T,(X)
+&T,(X)
where T,(X) is the Chebyshev polynomial of the first kind of degree i, and X is restricted to a range of -1 < X < 1, using the linear transformation: x =
(2X,-x,"""-XT) (qlaxxp)
in which X, are the data values; and Xy and Xpare the largest and smallest value of the input data (i.e. Xd’s ) , respectively. *l Gy= 1 Gray= 100 rads=
1J kg-l absorbed dose.
314
A numerical analysis group, Oxford’s library program (NAGLIB, EO~ADF ) was used. Fig. 5 shows typical plots of the regenerated growth curves for three samples which provided different’ equivalent doses. Further, the dates reported are uncorrected for the difference in the nature of TL growth with cy- and P-irradiation, which might result in their overestimation by up to - 10% for older samples (Aitken, 1984). In view of some of the above-mentioned yet
to be quantified factors in TL dating of sediments, a rigorous error estimate is not possible. Experimental errors (excluding the possible systematic errors mentioned on pp. 312 and 313) are estimated to be -12-15%. An error estimate of -20% may be appropriate for intercomparisons. It is, however, considered that none of the conclusions are affected by these uncertainties. 6. Discussion To aid the discussion Table I and Fig. 6, which provide a summary of the results and the correspondence between various nomenclatures used in the literature (e.g., Bronger, 1975; Kukla, 1977; PQcsi et al., 1979), are referred to. The TL dates (Table II; Fig. 2 ) enable the following observations: (1) The TL dates depict clear stratigraphic correlations both within the profiles and between different profiles. The TL dates also provide additional confirmation of the soil stratigraphy proposed by Bronger (1975). Thus five TL dates on soil F2 at St. Slankamen and Titel (Fig. 1) show a close grouping at - 75 ka. This is supported by TL dates of 29-45 ka for soil F, and loess beneath it at Erdut. Similarly, TL dates on soil F, at St. Slankamen and Titel show a close grouping at - 125 ka. The soil horizons
r
SO
100
APPLIED DOSE (mid (I min~Gy1 Fig. 5. Regenerated TL growth with dose and the nature of TL growth beyond natural TL for three samples with different equivalent doses.
Fig. 6. Schematic presentation of two principally used nomenclatures and available chronological assignments. The present TL dates are also provided. The solid half-triangles on the TL dates indicate that generally the event of loess deposition is dated.
315
F4and F, havebeen assigneda minimum ageof 2 186 and >,315 ka, respectively. (2) The TL dates suggest that the soil F3 probably representsthe last interglacial corresponding to substage5e of the oxygen-isotope stratigraphy (Shackleton and Opdyke, 1973)) thus questioning the traditional view that the Mende-Base soil (i.e. soil F5) representsthe last interglacial. This suggestion is supported by several factors, such as: (a) If soil F5 really representsthe last interglacial, then it is difficult to explain the presence of three chernozem soils (F4, F, and F,) during this period. As aforementioned, soil micromorphological and clay mineralogical analyses and comparisons with modern soils unambiguously suggest that these soils were formed in an interglacial climate (akin to the present climate) and not in an interstadial climate. (b) Considerations of the averageloess accumulation rates also make it difficult to reconcile soil F5 with the Riss-Wiirm interglacial, and soils Fs and Fg with the Brunhes-Matuyama boundary. It thus seemsdifficult to explain a high accumulation rate of N 25 m of loesscontaining four well-developedsoils during the past 100ka and almost ten-fold lower accumulation rate during the preceding 600 ka. Although it is possible to visualize several erosional episodes to cause this time hiatus, the mechanism and reason why such erosional processessceased abruptly during the past 100ka would then need an explanation. (c) The TL chronology is in excellent agreement with the U-series disequilibrium dates on travertines at Tata (Schwartz and Skoflek, 1982;Hennig et al., 1983). With respect to soil Fg, the TL date of >,315 ka is in general agreement with the estimates of Kukla (1977) based on paleomagnetic data. For soils FP, F, and F, the TL dates are somewhat younger than those predictedby Kukla’s ( 1977) loesscycle analysis. Methodologically, the present study suggests that TL dates on loess of > 300 ka are obtainable and thus indicate that the age underesti-
mation effect reported by Debenham (1985) does not affect the samples examined in this study, at least not to the same degreeof severity. This conclusion is supported by the results of Proszynska (1983), who obtained sediment equivalent dosesof 750-1000 Gy on two samples from Paks (near the Brunhes-Matuyama boundary) and at Stranzendorf, Austria (from the Matuyama-Gauss boundary). Although these TL dates are also underestimated, nonetheless, these results clearly suggestthat sediment equivalent dosesof 750-1000 Gy are obtainable. This is in contrast with the results of Debenham (1985), which indicated a limiting value of - 200-250 Gy. It may be appropriate to indicate that the underestimate in the above two casesof samples from Paks and Stranzendorf (particularly the latter) could quite likely be reflecting an equilibrium betweenthe growth and decay of TL, thereby pointing at a minimum age. 7. Conclusions
(a) The present study unambiguously demonstratesthat the traditional view of the loesspaleosol chronology in the Carpathian Basin is not tenable. More specifically, it can be definitively concludedthat the Mende-Base soil (soil F5) was not formed during the last interglacial becauseit is much older. The uncertainties involved in the TL dating methodology will not upset this conclusion in any way. The concordancewith available isotopic and paleomagnetic dates also supports this inference. (b) Soil F3 is inferred to have developedduring the Riss-Wtirm interglacial, soil F, probably correspondsto substage5a of the oxygenisotopestratigraphy. This is in conformity with the micromorphological and clay mineralogical evidencethat F3 and F, formed under an interglacial climate and not under an interstadial one. Efforts are in progressto locate the Blake event in this part of the sequence. (c) The underestimation effect of TL dates reported by Debenham (1985) does not affect
316
the present extent.
samples, at least not to the same
Acknowledgement We thank Professors M.J. Aitken, G.A. Wagner and V. Mejdahl and Dr. A.G. Wintle for constructive suggestions. We also thank Dr. N.C. Debenham and Professor G. Kukla for useful discussions. A.K.S. acknowledges the Alexander-von-Humboldt Foundation, F.R. Germany, for a fellowship during which part of the work was accomplished. We thank Professor G.A. Wagner for providing free access to the experimental facilities and Dr. L. Zijller for his willing cooperation. R.K.P. thanks D.A.A.D. (F.R. Germany) for a grant to cover the field excursions and A. Bronger acknowledges the Deutsche Forschungsgemeinschaft for supporting this research (Br-303/18). We thank Dr. E. Pernicka and Mr. W. Bach for their help with the neutron activation analysis. References Aitken, M.J., 1976. Thermoluminescent age evaluation and assessment of error 1imits:revised system. Archaeometry, 18(Z): 233-238. Aitken, M.J., 1984. Non-linear growth Allowance for alpha particle contribution. Ancient TL, 2: 2-6. Borsy, Z., Felszerfalvy, J. and Szabo, P.P., 1979. Thermoluminescence dating of several layers of loess sequences at Paks and Mende (Hungary). Acta Geol. Acad. Sci. Hung., 22: 451-459. Bronger, A., 1975. Paliioboden als Klimazeugen - dargestellt an Loss-Boden-Abfolgen des Karpatenbeckens. Eiszeitalter Ggw., 26: 131-154. Bronger, A., 1976. Zur quartliren Klima- und Landschaftsentwicklung des Karpatenbeckens auf (palgo-)pedologischer und bodengeographischer Grundlage. Kiel. Geog. Schr., No. 45,268 pp. Bronger, A., 1979. The value of mineralogical and clay mineralogical analyses of loess soils for the investigations of Pleistocene stratigraphy and paleoclimate. Acta Geol. Sci. Hung., 22: 141-152. Bronger, A., Kalk, E. and Schroeder, D. 1976. Uber Glimmer- und Feldspatverwitterung sowie Entstehung und Umwandlung von Tonmineralen in rezenten un fossilen Lbssboden. Geoderma, 16: 21-54. Butrym, J. and Maruszczak, H., 1984. Thermoluminescence chronology of younger and older loesses. In: M.
Pecsi (Editor), Lithology and Stratigraphy of Loesses and Paleosols. Hung. Acad. Sci., Budapest, pp. 195199. Debenham, N.C., 1985. Use of UV emissions in TL dating of sediments. Nucl. Tracks Radiat. Meas., 10(4-6): 717724. Debenham, NC. and Walton, A.J., 1983. TL properties of some wind blown sediments. PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 531-538. Fink, J., 1964. Report of the VIth International Congress on the Quaternary, Warsaw, 1961, Vol. IV. Symp. on Loess, pp. 451-462. Finkl, Jr., C.W., 1984. Chronology of weathered materials and soil age determination in pedostratigraphic sequences. Chem. Geol., 44: 311-335. Geyh, M.A., Roeschmann, G., Wijmstra, T.A. and Middeldorp, A.A., 1983. The unreliability of ‘*C dates obtained from buried sandy podzols. Radiocarbon, 25: 409-416. Hennig, G.J., Grun, R., Brunnacker, K. and Pecsi, M., 1983. Th-230/U-234 sowie ESR-Altersbestimmungen einiger Travertine in Ungam. Eiszeitalter Ggw., 33: 9-19. Huntley, D.J., Berger, G.W., Diwigalpitiya, W.M.R. and Brown, T.A., 1983. Thermoluminescence dating of sediments PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 607-618. Jungner, H.,1987. Result from a comparison of UV and sunlight bleaching of feldspars and quartz. Preprint pap. presented at 5th Specialist’s Semin. on TL/ESR Dating, Cambridge, July 1987. Kukla, G., 1977. Pleistocene land-sea correlations, I. Europe. Earth-Sci. Rev., 13: 307-374. Mejdahl, M., 1986. Thermoluminescence dating of sediments Radiat. Prot. DOS., 17: 219-227. Pecsi, M., 1984. Is typical loess older than one million years? In: M. P6csi (Editor), Lithology and Stratigraphy of Loess and Paleosols. Hung. Acad. Sci., Budapest, pp. 213-224. Pecsi, M., 1985. Chronostratigraphy of Hungarian loesses and the underlying sub-area1 formation. In: M. PCsi (Editor), Loess and the Quaternary: Chinese and Hungarian Case Studies. Akademiai Kiado, Budapest, pp. 33-50. PBcsi, M., Pevzner, M.A. and Szebenyi, E., 1979. In: Guide Book for Conference and Field Workshop on the Stratigraphy of Loess and Alluvial Deposit. Geophys. Res. Inst., Budapest, pp. 11-38. PBcsi, M., Scheuer, Gy., Schweitzer, F., Hahn, Gy. and Pevzner, M.A., 1985. Neogene and Quaternary geomorphological surfaces in the Hungarian Mountains. In: M. Kretzoi and M. P&i (Editors), Problems of the Neogene and the Quarternary. Akademiai Kiadd, Budapest, pp. 51-63. Proszyriska, H., 1983. TL dating of some subareal sediments from Poland. PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 539-546. Rendell, H.M., Gordon, D. and Strain, J.A., 1983. Investi-
317 gation of relationship between TL response and composition of polymineral mixtures. PACT J. (J. Eur. Stud. Group. Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 473-478. Schwartz, H.P.and Skoflek, I., 1982. New dates from the Tata, Hungary, archaeological site. Nature (London), 295: 590-591. Shackleton, N.J. and Opdyke, N.D., 1973. Oxygen isotope and paleomagnetic stratigraphy of Equatorial Pacific core V28-238: Oxygen isotope temperature and ice volumes on a lo5 year and lo6 year scale. Quat. Res., 3: 3955. Singhvi, A.K. and Mejdahl, V., 1985. Thermoluminescence dating of sediments. Nucl. Tracks Radiat. Meas., lO(l-2): 137-161. Singhvi, A.K. and Wagner, G.A., 1986. Thermoluminescence dating of young sedimentary deposits. In: Dating Young Sediments, CCOP Comm. Coord. Joint Prospect. Miner. Resour. Asian Offshore Areas (U.N.),
Bangkok, Tech. Publ. No. 16, pp. 159-198. Singhvi, A.K., Bronger, A., Pant, R.K. and Sauer, W., 1987. Thermoluminescence dating and ita implications for the chronostratigraphy of loess-paleosol sequences in the Kashmir Valley (India). Chem. Geol. (Isot. Geosci. Sect.), 65: 45-56. Soil Survey Staff, 1975. Soil Taxonomy. In: Agriculture Handbook No. 436. U.S. Dep. Agric., Washington, D.C., pp. l-754. Sutton, S. and Singhvi, A.K., 1983. A cathodoluminescence/X-ray microprobe study of various sediments. Ancient TL, l(3): 2-4. Wintle, A.J. and Catt, J.A., 1985. Thermoluminescence dating of soils developed in late Devensian loess at Pegwell Bay, Kent. J. Soil Sci., 36: 293-298. Zeuner, F.E., 1959. The Pleistocene: Its Climate, Chronology and Fauna1 Succession. Hutchinson, London, 447 PP.
Chemical Geology (Isotope Geoscience Section), 73 (1989) 307-317 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
THERMOLUMINESCENCEDATING OF LOESS-PALEOSOL SEQUENCESIN THE CARPATHIAN BASIN (EAST-CENTRAL EUROPE):A SUGGESTION FOR A REVISEDCHRONOLOGY A.K. SINGHVI’*2,
A. BRONGER3,
W. SAUER’
and R.K. PANT’
‘Physical Research Laboratory, Ahmedabad 380 009 (India) 2Max-Planck-Znstitut fiir Kernphysik, D-6900 Heidelberg 1 (Federal Republic of Germany) 3Geographisches Znstitut der Uniuersiti-it Kiel, D-2300 Kiel 1 (Federal Republic of Germany) (Received February 2,1988; revised and accepted July 27,1988)
Abstract Singhvi, A.K., Bronger, A., Sauer, W. and Pant, R.K., 1989. Thermoluminescence dating of loess-paleosol sequences in the Carpathian Basin (East-Central Europe): A suggestion for a revised chronology. Chem. Geol. (Isot. Geosci. Sect.), 73: 307-317. Detailed thermoluminescence (TL) dating of the loess-paleosol sequences in the Carpathian Basin, suggests that the conventional chronology of Mende-Base soil (soil F,) representing the Riss-Wtirm interglacial is not tenable, because it is much older. The results also suggest that the recently reported TL-age underestimation effect in some loess and sand samples from Northwestern Europe does not occur in the samples analyzed in this study.
1. Introduction
Of the terrestrial sediments, perhaps the most extended and continuous records of Pleistocene climatic changes are provided by the loesspaleosol sequences in the periglacial regions of the continents. Extensive efforts have been made to correlate climatic and proxy-climatic data provided by various loess-paleosol sequences with the deep-sea oxygen-isotopic records (Kukla, 1977). Such correlations have, however, been constrained by limited time resolution of a chronology based predominantly on the records of paleomagnetic reversals. The loess-paleosol sequences along the river Danube (Fig. 1) have been considered particularly suitable for land-sea correlations be-
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cause of the following reasons: (a) these deposits are in an ideal geographic location, being close enough to the Atlantic Ocean to record its influence during interglacials, and far enough inland to develop continental steppes during warmer episodes (Zeuner, 1959; Kukla, 1977); (b ) these sequences (especially from paleosol F5 to F,; Fig.2) provide an almost continuous and a complete succession of paleosols that are separated by thick loess deposits. This permits reliable stratigraphic correlation between various profiles (Bronger, 1975,1976,1979); (c) these sequences are in principle stratigraphically correlatable to the Pleistocene river terraces of the region (P&s& 1985; Pecsi et al., 1985); and (d) the river Danube also drains the Alpine
B.V.
308
Loess-
Exposures
lnvestlgated
Fig. 1. Map of the Carpathian investigated.
m
Basin, depicting
foothills, where the classical Alpine quences have been defined.
the River Danube and the locations of the loess-paleosol
glacial se-
2. Stratigraphy Fig. 2 provides a summary of the stratigraphical subdivisions and paleosol types in various loess-paleosol profiles in the Carpathian Basin. These are principally based on soil micromorphological and clay mineralogical studies by Bronger (1975,1976,1979; Bronger et al., 1976), who concluded that: (a) the sequence F, - F, is almost complete and can be reliably correlated between various profiles; (b ) the rate of pedochemical weathering (i.e. the rate of clay mineral formation, especially the < 0.2-pm fraction) in soils Fq, F3 and Fz (all identified as Chernozems ) is essentially similar to that exhibited by the modern soils of the same
sequences being
genesis in the region, the latter having developed in an ustic soil moisture regime (Soil Survey Staff, 1975); (c ) Chernozems F3 and Fz are well preserved in the northern part of the basin and generally are at least as thick as, and in southern parts are nearly twice, as thick as recent Chernozems. This suggests that the three soils Fq, F3 and Fz must have formed under a climatic regime very similar to the present, i.e. an interglacial climate. (d) the interglacial represented by the Brown Forest soil F5 also suggests a climate similar to the present but perhaps somewhat moister. In the literature these soils have been variously designated by different groups. Table I provides a broad correspondence between the nomenclatures used by different groups and the one used in the present study (see, e.g., Bronger, 1975,1976; PQcsi, 1984).
309 TABLE
I
Equivalence
chart between different
nomenclatures
F-notation Bronger
used to designate the loess-paleosol
MF-notation (1975,1976)
PBcsi (1984)
horizons in the Carpathian
Remarks
PBcsi (1984) Dunaujvaros-Tapiosuly developed in Paks)
F,
F2
f-1
F-3 F4 F,
F,(+Fs?) F4 F,
Basin
MF BD1 +BD, BA MB
3. Chronology 3.1. Present status The chronology of the loess-paleosol sequences has been much debated relying largely on the investigations made on sequences at Paks, Mende and Dolni Vestonice (Fig. 1). Basically two chronological assignments have been advocated. The first assignment, based on the INQUAstratigraphic guiding principle, suggests that the Mende-Base soil (i.e. soil F5) represents the last interglacial, being the “youngest” Brown Forest soil (Fink, 1964). Several radiocarbon dates were compiled by PQcsi et al. (1979). These range from N 16.5 to 20 ka ( hl and h2 humic soils), from N 27 to 30 ka (MF soils) or are 2 32 ka (soils BD, and BDz), and are correlatable to soils F1, F, and FB, respectively. In addition, thermoluminescent dating of samples from Paks and Mende by Borsy et al. (1979) and by Butrym and Maruszczak (1984) provided the age of the MendeBase soil as N 110-120 ka. These thermoluminescence (TL) dates cannot be accepted per-se in view of the inadequate methodology used in their determination [see Singhvi and Mejdahl (1985) for a discussion; also A. Wintle and V. Mejdahl’s private communication to A.K. Singhvi (1985) 1. On the other hand, radiocarbon dates on paleosol are in general grossly underestimated as has been demonstrated by studies by Geyh et al. (1983) and Fink1 (1984).
Mende-Basaharc
complex (weakly
complex
In the case of loess-paleosol profiles of Kashmir, India, it was also seen that the radiocarbon ages were grossly underestimated (Singhvi et al., 1987). The second chronological assignment is based on the magnetostratigraphical results and suggests a much older chronology (Kukla, 1977, figs. 13 and 21). In this scheme the Mende-Base soil (F5 in Fig. 2) belongs to the loess cycles F and G, which have been assigned a date of N 500 ka. As supporting evidence, the presence of Elephas throgentherii (a middle-Pleistocene fauna), in the loess horizon beneath the MendeBase soil is cited. Lastly, a number of uraniumseries disequilibrium dates on travertines from Tata, Hungary, have been reported (Schwartz et al., 1982; Hennig et al., 1983). Geomorphological correlations suggest that these travertines correspond to the “young Mende-Basahart loess” sequence, i.e. the sequence encompassing the soils F, and F3 should have formed sometime during 100 ka B.P. which is substantially older than that suggested by radiocarbon dates. 3.2. Thermoluminescence
dating
Developments in TL dating during the past decade have offered the possibility of providing absolute chronologies for sediments for which a finite pre-depositional sun exposure could be assumed (see Singhvi and Mejdahl, 1985;
310
311
Singhvi and Wagner, 1986, for reviews). In general, the TL dates on loess-paleosols provide the age of the depositional event of the loess itself. However, in the case of some soil horizons (i.e. the A-horizons), fauna1 pedoturbation causes churning of the sediment, resulting in an on-site sun-bleaching of the TL. In such cases, TL provides the age of the soil formation itself (Huntley et al., 1983; Wintle and Catt, 1985). In view of the “absolute” nature of TL dates, derived by an analysis of the very minerals that constitute loess, it was considered necessary to re-examine the chronological framework of the globally important loess-paleosol sequences of the Carpathian basin. The “completeness” of the sequences in the basin extending up to and beyond the Brunhes-Matuyama boundary at N 730 ka provided an additional incentive for research into the TL methodology. In particular, such a continuous sequence provides a unique opportunity to examine the TL-age underestimation effect reported by Debenham (1985) in respect of some of the North-western European sand and loess sequences. This observation indicated that no matter how old the depositional age of loess and/or sands, their TL age is limited to - loo-150 ka. At this time, the exact cause of the anomaly is not yet understood, though various mechanisms such as a possible decay of recombination centres, radiation-dose-dependent changes in the TL sensitivity, and an alteration of TL sensitivity following an optical bleaching in the laboratory have been proposed (see Mejdahl, 1986 for a concise discussion). The sequences in the Carpathian basin thus provide good stratigraphic control on TL dates to examine the validity and universality of the age underestimation effect.
4. Samples and methods The details of basic TL methodology, relevant assumptions and procedural aspects are described in a recent publication (Singhvi et al., 1987). Briefly, the fine-grain technique was
used and the 4-11-pm grain size was extracted after pre-treatment of the samples with 0.1 N HCl to remove carbonates, with Hz02 to remove organic fraction, and with 0.01 N Na-oxalate to deflocculate the sample. The equivalent dose of the sediment was measured using the total bleach-regeneration method (Proszynska, 1983; Debenham, 1985) and with an optical window corresponding to transmission through a Schott@ UGll filter coupled to a Chance-Pilkington@ HA-3 filter. The photomultiplier tube used was EMI@ 9635 QA. In the total bleach-regeneration method (TBregen), the growth of TL in the sample during antiquity is simulated by optically bleaching the sample in the laboratory using sunlight or a sunlamp or the like, and then regenerating the TL in the sample by laboratory irradiations. The laboratory irradiation which provides a TL intensity equal to that observed in the sample (natural TL) is the sediment equivalent dose D (Id). Implicit in this approach is the assumption that the laboratory optical bleaching in no way alters the TL sensitivity of the samples, i.e. the laboratory induced growth faithfully replicates the TL growth during antiquity. This fact is examined for each sample by comparing the TL sensitivity of samples before and after optical bleaching, in the dose region corresponding to the natural TL [i.e. D (&) 1. In the present study, a 300-W Ultra-Vitalux Wotan@ sunlamp (Osram@ ) was used for laboratory photo-bleaching. The laboratory irradiations were made using a “Sr-“Y P-plaque (30 mCi) and 241Am under vacuum. The radioactivity of the samples was analyzed using the thick-source ZnS (Ag) cx-counting as well as the elemental neutron activation analysis (NAA). The 40K concentration was estimated using atomic absorption spectrophotometry.
5. Results The results are compiled in Table II. Fig. 3 provides a typical glow curve along with a TL growth curve with P-dose and TL age plateau.
312 TABLE
II
Thermoluminescence Site and horizon No.
data on loess sequences in the Carpathian Plateau region*’ (“Cl
D(Z,)(‘”
Basin
a’**’
u bpm)
Th bpm)
K (%)
0.10
3.16
10.73
0.10 0.08 0.11
3.09 2.95
10.51 10.9
1.4
15
3,900
0.06 0.09 0.07
2.76 3.1 3.1 2.8
9.4 12.5 11.5
1.5'3 1.6 1.63
15 15
0.10
2.9
11.1 13.6
1.68 1.61
10 10 20
(GY)
Water fraction (%o)
Dose rate WY a-‘)
4s @a)
5.5’3
15
1.5'3
15
4,320 4,250 3,940 3,960 4,520 4,380
75'4 63'4 82 85 128 121 L186'5
4,910
2314’5
St. Slankamen: S-50 F, F, S-29 F, S-120 F, S-26 F, S-25 loess below F3 S-23 loess below F, S-22 F,
320-400 300-420 300-420 300-460 320-420 340-460 340-400 340-460
331 518 494 793 1,542
Er-43 F,
300-460
150
0.08
4.24
14.42
2.04
15
5,450
29
Er-45 loess below F,
300-440
207
0.08
3.51
11.94
1.56
10
4,504
45
300-380 300-380
335 581
0.11
3.2
10.94
1.53
10
0.10
3.12
10.68
1.41
15
4,670 4,135
71** 125'4
S-30
325 271
319
Erdut:
TiteljMosorin: TM-30 loess below F, TM-32 F3
“A somewhat delayed onset of plateau is quite probably due to the optical filter combination of Schott@ UG-II and ChancePilkingtone HA-3 filter. “Data refers to 360 ’ C on the glow curve temperature. *3K content assumed. *%-Counting data used for dose rate analysis. ‘5The growth of signal with dose was marginal and much more work needs to be carried out before a firm estimate can be provided.
Fig. 4 provides a comparison of the results obtained using the NAA and ZnS(Ag) a-counting methods. The concordance suggests that the radioactive decay series are not grossly in disequilibrium. Some comments on TL measurements may be appropriate at this stage. Recent work by Debenham and Walton (1983) has indicated that a Schott@ UG-11 filter with a peak transmission at around 320 nm provides a greater selectivity for K-feldspar emissions. In the present case, the detection optics has a HA-3@’ filter in addition to a UG-11@ filter causing N 20-nm shift of the peak transmission towards the blue. Despite this shift in peak transmission, it is considered that the combination still
provides a greater selectively to K-feldspar emissions, both due to their substantially higher TL sensitivity compared to the other dominant luminescent mineral quartz (Sutton and Singhvi, 1983) and due to their emission spectral characteristics (Debenham and Walton, 1983; Rendell et al., 1983). This is further substantiated by the glow curve shapes (Fig. 3) and by the fact that the residual TL intensities (after laboratory sunlamp bleaching) range from 6% to 16% of the natural TL (at 360°C). The TL dates implicitly assume that any systematic error arising from the spectral mismatch between the laboratory sunlamp with line emissions and the sunlight exposures experienced by the sample during its pre-depositional
313
TL:e-43
/ ‘\\ : -t, :I \\ 1 \;---NTL+sL+2.5t).B
f “5
100
200
300
0.6 400
500
0.5
0.6 aZnS(Counts
0.7 mid
1
Fig. 4. A comparison of the neutron activation analysis with the result of ZnS (Ag) a-counting method. The S series refers to samples from Stari Slankamen and Hu series refers to samples (also loess) from Plaidter Hummerich, F.R. Germany (not discussed in the present work).
Fig. 3. a. Typical natural TL and regenerated TL glow curves b. TL growth with /I-dose. c. TL-age plateau.
transport are small. Some support for this assumption comes from recent results of Jungner (1987) whose comparison of bleaching by blacklamp and sunlight suggests that the K-feldspars do not have significant wave-length dependence on bleaching. Further the non-linear growth of TL also reduces the extent of error caused by any possible over-bleaching. Thus, even if the bleached TL level is overestimated by lOO%, the nett error in the sediment equivalent dose will be less than a few percent (notice that the initial TL sensitivity is substantially higher ) . For all samples the change in TL sensitivity subsequent to laboratory sunlamp exposure was examined. In view of the intrinsically low TL sensitivity at higher doses and the variability of 5 10% in the TL output of different fine-grain discs, a variation in the TL sensitivity (before (54,) and after (S,) the sunlamp bleach) of up
to 20% was considered acceptable. In the present case, usually there existed at least one temperature on the plateau region where SN and S,-, matched reasonably well. The growth curves generally exhibited nonlinearity for doses of > 200 Gy*. All growth curves were fitted to a second-order polynomial using a Chebyshev polynomial expansion of the type: Y= $2&(X)
+a,T,(X)
+&T,(X)
where T,(X) is the Chebyshev polynomial of the first kind of degree i, and X is restricted to a range of -1 < X < 1, using the linear transformation: x =
(2X,-x,"""-XT) (qlaxxp)
in which X, are the data values; and Xy and Xpare the largest and smallest value of the input data (i.e. Xd’s ) , respectively. *l Gy= 1 Gray= 100 rads=
1J kg-l absorbed dose.
314
A numerical analysis group, Oxford’s library program (NAGLIB, EO~ADF ) was used. Fig. 5 shows typical plots of the regenerated growth curves for three samples which provided different’ equivalent doses. Further, the dates reported are uncorrected for the difference in the nature of TL growth with cy- and P-irradiation, which might result in their overestimation by up to - 10% for older samples (Aitken, 1984). In view of some of the above-mentioned yet
to be quantified factors in TL dating of sediments, a rigorous error estimate is not possible. Experimental errors (excluding the possible systematic errors mentioned on pp. 312 and 313) are estimated to be -12-15%. An error estimate of -20% may be appropriate for intercomparisons. It is, however, considered that none of the conclusions are affected by these uncertainties. 6. Discussion To aid the discussion Table I and Fig. 6, which provide a summary of the results and the correspondence between various nomenclatures used in the literature (e.g., Bronger, 1975; Kukla, 1977; PQcsi et al., 1979), are referred to. The TL dates (Table II; Fig. 2 ) enable the following observations: (1) The TL dates depict clear stratigraphic correlations both within the profiles and between different profiles. The TL dates also provide additional confirmation of the soil stratigraphy proposed by Bronger (1975). Thus five TL dates on soil F2 at St. Slankamen and Titel (Fig. 1) show a close grouping at - 75 ka. This is supported by TL dates of 29-45 ka for soil F, and loess beneath it at Erdut. Similarly, TL dates on soil F, at St. Slankamen and Titel show a close grouping at - 125 ka. The soil horizons
r
SO
100
APPLIED DOSE (mid (I min~Gy1 Fig. 5. Regenerated TL growth with dose and the nature of TL growth beyond natural TL for three samples with different equivalent doses.
Fig. 6. Schematic presentation of two principally used nomenclatures and available chronological assignments. The present TL dates are also provided. The solid half-triangles on the TL dates indicate that generally the event of loess deposition is dated.
315
F4and F, havebeen assigneda minimum ageof 2 186 and >,315 ka, respectively. (2) The TL dates suggest that the soil F3 probably representsthe last interglacial corresponding to substage5e of the oxygen-isotope stratigraphy (Shackleton and Opdyke, 1973)) thus questioning the traditional view that the Mende-Base soil (i.e. soil F5) representsthe last interglacial. This suggestion is supported by several factors, such as: (a) If soil F5 really representsthe last interglacial, then it is difficult to explain the presence of three chernozem soils (F4, F, and F,) during this period. As aforementioned, soil micromorphological and clay mineralogical analyses and comparisons with modern soils unambiguously suggest that these soils were formed in an interglacial climate (akin to the present climate) and not in an interstadial climate. (b) Considerations of the averageloess accumulation rates also make it difficult to reconcile soil F5 with the Riss-Wiirm interglacial, and soils Fs and Fg with the Brunhes-Matuyama boundary. It thus seemsdifficult to explain a high accumulation rate of N 25 m of loesscontaining four well-developedsoils during the past 100ka and almost ten-fold lower accumulation rate during the preceding 600 ka. Although it is possible to visualize several erosional episodes to cause this time hiatus, the mechanism and reason why such erosional processessceased abruptly during the past 100ka would then need an explanation. (c) The TL chronology is in excellent agreement with the U-series disequilibrium dates on travertines at Tata (Schwartz and Skoflek, 1982;Hennig et al., 1983). With respect to soil Fg, the TL date of >,315 ka is in general agreement with the estimates of Kukla (1977) based on paleomagnetic data. For soils FP, F, and F, the TL dates are somewhat younger than those predictedby Kukla’s ( 1977) loesscycle analysis. Methodologically, the present study suggests that TL dates on loess of > 300 ka are obtainable and thus indicate that the age underesti-
mation effect reported by Debenham (1985) does not affect the samples examined in this study, at least not to the same degreeof severity. This conclusion is supported by the results of Proszynska (1983), who obtained sediment equivalent dosesof 750-1000 Gy on two samples from Paks (near the Brunhes-Matuyama boundary) and at Stranzendorf, Austria (from the Matuyama-Gauss boundary). Although these TL dates are also underestimated, nonetheless, these results clearly suggestthat sediment equivalent dosesof 750-1000 Gy are obtainable. This is in contrast with the results of Debenham (1985), which indicated a limiting value of - 200-250 Gy. It may be appropriate to indicate that the underestimate in the above two casesof samples from Paks and Stranzendorf (particularly the latter) could quite likely be reflecting an equilibrium betweenthe growth and decay of TL, thereby pointing at a minimum age. 7. Conclusions
(a) The present study unambiguously demonstratesthat the traditional view of the loesspaleosol chronology in the Carpathian Basin is not tenable. More specifically, it can be definitively concludedthat the Mende-Base soil (soil F5) was not formed during the last interglacial becauseit is much older. The uncertainties involved in the TL dating methodology will not upset this conclusion in any way. The concordancewith available isotopic and paleomagnetic dates also supports this inference. (b) Soil F3 is inferred to have developedduring the Riss-Wtirm interglacial, soil F, probably correspondsto substage5a of the oxygenisotopestratigraphy. This is in conformity with the micromorphological and clay mineralogical evidencethat F3 and F, formed under an interglacial climate and not under an interstadial one. Efforts are in progressto locate the Blake event in this part of the sequence. (c) The underestimation effect of TL dates reported by Debenham (1985) does not affect
316
the present extent.
samples, at least not to the same
Acknowledgement We thank Professors M.J. Aitken, G.A. Wagner and V. Mejdahl and Dr. A.G. Wintle for constructive suggestions. We also thank Dr. N.C. Debenham and Professor G. Kukla for useful discussions. A.K.S. acknowledges the Alexander-von-Humboldt Foundation, F.R. Germany, for a fellowship during which part of the work was accomplished. We thank Professor G.A. Wagner for providing free access to the experimental facilities and Dr. L. Zijller for his willing cooperation. R.K.P. thanks D.A.A.D. (F.R. Germany) for a grant to cover the field excursions and A. Bronger acknowledges the Deutsche Forschungsgemeinschaft for supporting this research (Br-303/18). We thank Dr. E. Pernicka and Mr. W. Bach for their help with the neutron activation analysis. References Aitken, M.J., 1976. Thermoluminescent age evaluation and assessment of error 1imits:revised system. Archaeometry, 18(Z): 233-238. Aitken, M.J., 1984. Non-linear growth Allowance for alpha particle contribution. Ancient TL, 2: 2-6. Borsy, Z., Felszerfalvy, J. and Szabo, P.P., 1979. Thermoluminescence dating of several layers of loess sequences at Paks and Mende (Hungary). Acta Geol. Acad. Sci. Hung., 22: 451-459. Bronger, A., 1975. Paliioboden als Klimazeugen - dargestellt an Loss-Boden-Abfolgen des Karpatenbeckens. Eiszeitalter Ggw., 26: 131-154. Bronger, A., 1976. Zur quartliren Klima- und Landschaftsentwicklung des Karpatenbeckens auf (palgo-)pedologischer und bodengeographischer Grundlage. Kiel. Geog. Schr., No. 45,268 pp. Bronger, A., 1979. The value of mineralogical and clay mineralogical analyses of loess soils for the investigations of Pleistocene stratigraphy and paleoclimate. Acta Geol. Sci. Hung., 22: 141-152. Bronger, A., Kalk, E. and Schroeder, D. 1976. Uber Glimmer- und Feldspatverwitterung sowie Entstehung und Umwandlung von Tonmineralen in rezenten un fossilen Lbssboden. Geoderma, 16: 21-54. Butrym, J. and Maruszczak, H., 1984. Thermoluminescence chronology of younger and older loesses. In: M.
Pecsi (Editor), Lithology and Stratigraphy of Loesses and Paleosols. Hung. Acad. Sci., Budapest, pp. 195199. Debenham, N.C., 1985. Use of UV emissions in TL dating of sediments. Nucl. Tracks Radiat. Meas., 10(4-6): 717724. Debenham, NC. and Walton, A.J., 1983. TL properties of some wind blown sediments. PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 531-538. Fink, J., 1964. Report of the VIth International Congress on the Quaternary, Warsaw, 1961, Vol. IV. Symp. on Loess, pp. 451-462. Finkl, Jr., C.W., 1984. Chronology of weathered materials and soil age determination in pedostratigraphic sequences. Chem. Geol., 44: 311-335. Geyh, M.A., Roeschmann, G., Wijmstra, T.A. and Middeldorp, A.A., 1983. The unreliability of ‘*C dates obtained from buried sandy podzols. Radiocarbon, 25: 409-416. Hennig, G.J., Grun, R., Brunnacker, K. and Pecsi, M., 1983. Th-230/U-234 sowie ESR-Altersbestimmungen einiger Travertine in Ungam. Eiszeitalter Ggw., 33: 9-19. Huntley, D.J., Berger, G.W., Diwigalpitiya, W.M.R. and Brown, T.A., 1983. Thermoluminescence dating of sediments PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 607-618. Jungner, H.,1987. Result from a comparison of UV and sunlight bleaching of feldspars and quartz. Preprint pap. presented at 5th Specialist’s Semin. on TL/ESR Dating, Cambridge, July 1987. Kukla, G., 1977. Pleistocene land-sea correlations, I. Europe. Earth-Sci. Rev., 13: 307-374. Mejdahl, M., 1986. Thermoluminescence dating of sediments Radiat. Prot. DOS., 17: 219-227. Pecsi, M., 1984. Is typical loess older than one million years? In: M. P6csi (Editor), Lithology and Stratigraphy of Loess and Paleosols. Hung. Acad. Sci., Budapest, pp. 213-224. Pecsi, M., 1985. Chronostratigraphy of Hungarian loesses and the underlying sub-area1 formation. In: M. PCsi (Editor), Loess and the Quaternary: Chinese and Hungarian Case Studies. Akademiai Kiado, Budapest, pp. 33-50. PBcsi, M., Pevzner, M.A. and Szebenyi, E., 1979. In: Guide Book for Conference and Field Workshop on the Stratigraphy of Loess and Alluvial Deposit. Geophys. Res. Inst., Budapest, pp. 11-38. PBcsi, M., Scheuer, Gy., Schweitzer, F., Hahn, Gy. and Pevzner, M.A., 1985. Neogene and Quaternary geomorphological surfaces in the Hungarian Mountains. In: M. Kretzoi and M. P&i (Editors), Problems of the Neogene and the Quarternary. Akademiai Kiadd, Budapest, pp. 51-63. Proszyriska, H., 1983. TL dating of some subareal sediments from Poland. PACT J. (J. Eur. Stud. Group Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 539-546. Rendell, H.M., Gordon, D. and Strain, J.A., 1983. Investi-
317 gation of relationship between TL response and composition of polymineral mixtures. PACT J. (J. Eur. Stud. Group. Phys. Chem. Math. Tech. Appl. Archaeol.), 9: 473-478. Schwartz, H.P.and Skoflek, I., 1982. New dates from the Tata, Hungary, archaeological site. Nature (London), 295: 590-591. Shackleton, N.J. and Opdyke, N.D., 1973. Oxygen isotope and paleomagnetic stratigraphy of Equatorial Pacific core V28-238: Oxygen isotope temperature and ice volumes on a lo5 year and lo6 year scale. Quat. Res., 3: 3955. Singhvi, A.K. and Mejdahl, V., 1985. Thermoluminescence dating of sediments. Nucl. Tracks Radiat. Meas., lO(l-2): 137-161. Singhvi, A.K. and Wagner, G.A., 1986. Thermoluminescence dating of young sedimentary deposits. In: Dating Young Sediments, CCOP Comm. Coord. Joint Prospect. Miner. Resour. Asian Offshore Areas (U.N.),
Bangkok, Tech. Publ. No. 16, pp. 159-198. Singhvi, A.K., Bronger, A., Pant, R.K. and Sauer, W., 1987. Thermoluminescence dating and ita implications for the chronostratigraphy of loess-paleosol sequences in the Kashmir Valley (India). Chem. Geol. (Isot. Geosci. Sect.), 65: 45-56. Soil Survey Staff, 1975. Soil Taxonomy. In: Agriculture Handbook No. 436. U.S. Dep. Agric., Washington, D.C., pp. l-754. Sutton, S. and Singhvi, A.K., 1983. A cathodoluminescence/X-ray microprobe study of various sediments. Ancient TL, l(3): 2-4. Wintle, A.J. and Catt, J.A., 1985. Thermoluminescence dating of soils developed in late Devensian loess at Pegwell Bay, Kent. J. Soil Sci., 36: 293-298. Zeuner, F.E., 1959. The Pleistocene: Its Climate, Chronology and Fauna1 Succession. Hutchinson, London, 447 PP.