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1

Fluvial response to environmental conditions during MIS 4-3 : a sedimentary record at the Brześnica site, central-western Poland

Moskalewicz Damian, Tylmann Karol, Woźniak Piotr Paweł, Kopyść Natalia, Moska Piotr

Geological Quarterly

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2020

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Vol. 64, No. 4

915--930

EN

Fluvial deposits subjected to this study are exposed at the Brześnica site, in the south-western part of the Wielkopolska region in Poland, which was close to the ice-sheet limit during the Last Glacial Maximum (LGM). Sedimentological analyses, including lithofacies descriptions, palaeocurrent measurements, grain size and rounding analyses and heavy mineral compositions indicate that the fluvial deposits at Brześnica were deposited in braided river environment. The following fluvial sedimentary processes were inferred: (1) shallow, rapid flow alternating with waning flow, (2) infilling of erosional channels with fluvial sediments during flood events, (3) changes from supercritical to subcritical flows, and (4) shallow sheet floods. The results of OSL dating indicated sediment deposition ~65.2 ±1.5 ka, i.e. in MIS 4, that was here characterized by cold environmental conditions and a general shift from meandering to braided fluvial sedimentation style. This finding contrasts with accumulation/erosion phases interpreted previously in this region for that time interval; however, it is consistent with recent studies of fluvial systems functioning during MIS 5-2 and of factors responsible for sedimentation style.

2

Chronology of the last ice sheet decay on the southern Baltic area based on dating of glaciofluvial and ice-dammed lake deposits

Uścinowicz Szymon, Adamiec Grzegorz, Bluszcz Andrzej, Jegliński Wojciech, Jurys Leszek, Miotk-Szpiganowicz Grażyna, Moska Piotr, Pączek Urszula, Piotrowska Natalia, Poręba Grzegorz, Przezdziecki Piotr, Uścinowicz Grzegorz

Geological Quarterly

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2019

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Vol. 63, No. 1

193--208

EN

The paper presents the results of the first OSL dating of glaciofluvial and ice-marginal lake sediments which occur between end moraines of the Słupsk Bank and the Polish coast. The sand and gravel of glaciofluvial deltas on the Słupsk Bank were deposited most likely during a period from 14.3 ±1.2 to 16.6 ±1.4 ka ago. The deposition of silty-sandy sediments of the ice-marginal lake is dated at 14.51 ±0.81 and 14.6 ±1.4 ka years. Likewise, dates ranging from 13.74 ±0.84 to 16.70 ±1.1 ka obtained from low sandy ridges, related to the southern range of the ice-marginal lake in the Gardno-Łeba Lowland, indicate the most likely timing of their deposition. It can be concluded that a short stop of the ice sheet on the Słupsk Bank took place approximately 15.2 ka ago, which could be correlated with the position of the ice sheet front in central Skåne and in northern Lithuania at that time. Older and younger results were also obtained, except the dates mentioned above. The older ages show little sunlight exposure of sediments during their deposition. The younger dates indicate a marine origin of the sediments and show that some parts of glaciofluvial sediments were redeposited and exposed to sunlight at a later stage, most probably when dead-ice blocks were melting.

3

Eruption age of Kannabe volcano using multi-dating: Implications for age determination of young basaltic lava flow

Shitaoka Yorinao, Saito Takeshi, Yamamoto Junji, Miyoshi Masaya, Ishibashi Hidemi, Soda Tsutomu

Geochronometria

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2019

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Vol. 46, no. 1

49--56

EN

We estimated the eruption age of Kannabe volcano, located in southwestern Japan. Although the eruption age had been estimated using tephrochronology and K-Ar dating, the precision of its age determination left some room for improvement. The latest eruption age of Kannabe volcano is well constrained by wide spread tephras to ca. 7.2–30 ka. We applied paleomagnetic dating to a basaltic lava and optically stimulated luminescence (OSL) dating to a soil layer, which are associated with the Kannabe volcano. The soil layer above the Kannabe scoria was newly dated to be 21 ± 6 ka, as inferred from OSL dating. We also made paleomagnetic investigation to estimate the eruption age of the Kannabe basaltic lava. Paleomagnetic data of 23 rock samples from six locations in the Kannabe basaltic lava showed good mutual agreement. The average of remanent magnetizations yields declination of 0.3° and inclination of 65.9° with 95% confidence limit of 2.7°. This paleomagnetic direction with a relatively steep inclination is thought to be correlated with the paleomagnetic secular variation data of sediments in Lake Biwa at ca. 21.5 ka. Based on that information from multi-dating, we inferred that the Kannabe volcano erupted at ca. 22 ka. This result presents profound scientific implications for the precise age determination of young basaltic lava flow, for which few dating methods exist.

4

Optically stimulated luminescence techniques applied to the dating of the fall of meteorites in Morasko

Moska P., Stankowski W., Poręba G.

Geochronometria

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2018

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Vol. 45, no. 1

74--81

EN

Geological materials used for luminescence dating and associated with the fall of meteorites on the Earth’s surface are extremely rare. The Morasko region has gained fame over the past 100 years because of a cosmic catastrophe which took place there. After thousands of years, the remains of a large metal meteorite which fell in this area have been found. In this article, we would like to state whether it is possible, using luminescence methods, to determine the moment when the iron meteorite fell on the surface of the Earth. The material which was analysed consisted of meteorite crust layers – melt/fusion and “semi melt/fusion”, including sintered ones, along with the sediments surrounding the meteorite. The final results are connected with four objects of different sizes (large ones and small shrapnel – 261 kg, 34 kg, 970 g and 690 g). The obtained results show a large discrepancy, which is most likely associated with the problem of resetting the luminescence signal of the tested materials.

5

Identifying the degree of luminescence signal bleaching in fluvial sediments from the Inner Mongolian reaches of the Yellow River

Li F., Pan B., Lai Z., Gao H., Ou X.

Geochronometria

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2018

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Vol. 45, no. 1

82--96

EN

The partial bleaching of the luminescence signal prior to deposition results in age overestimation, and can be a problem in delineating fluvial evolution within an OSL chronological framework. The Inner Mongolian reaches of the Yellow River are characterised by a high sediment load and complex sources of sediments. To test the incomplete bleaching occurring in this type of environment, the residual doses and the luminescence signal characteristics of different particle size fractions from 14 modern fluvial sediment samples were investigated. Furthermore, 26 OSL ages derived from drilling cores were compared with 11 radiocarbon ages. Our results show that the residual equivalent doses principally range between 0.16 and 0.49 Gy for silt grains, and between 0.35 and 3.72 Gy for sand grains of modern samples. This suggests that medium-grained quartz has been well bleached prior to deposition, and is preferable to coarse-grained quartz when dating fluvial sediments in this region. The results also show that the De values of coarse-grained fractions display a stronger correlation with distance downstream. In addition, a comparison of OSL and radiocarbon ages from drilling cores establishes further confidence that any initial bleaching of these sediments was sufficient. As a result, we believe that the studied fluvial samples were well bleached prior to deposition.

6

Methodological study on single grain OSL dating of mortars: Comparison of five reference archaeological sites

Urbanová P., Guibert P.

Geochronometria

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2017

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Vol. 44, no. 1

77--97

EN

The paper focuses on single grain OSL dating of quartz extracted from known age archaeological mortars, potentially representing a new tool for dating the construction of historical buildings. Apart from SG-OSL measurements and annual dose rate determination, the samples are systematically studied by means of optical microscopy, EDX-SEM cartography and beta autoradiography in order to evaluate the possible microdosimetric heterogeneity of each sample, arising principally from local variations of potassium content. Besides the practical aspects concerning sampling, preparation and appropriate choice of measurement conditions, the paper aims at the differences in microstructure and in elementary composition between different mortars and attempts to evaluate the impact of these aspects on the dispersion of equivalent dose distributions. Finally, archaeological doses (paleodoses) are calculated by using central age model (CAM), minimum age model (MAM) and internal-external consistency criterion (IEU). The appropriateness of these models for the exploitation of the measured SG-OSL data as well as for a hypothesis on the estimation of the input parameter needed to run these models are discussed. Three categories of mortars were identified: samples without any exploitable SG-OSL signal, samples that could have been reliably dated and poorly bleached samples affected by microdosimetric variations whose dating still remains complicated. Finally, the hypothesis on distinguishing between reliable and questionable dating results is raised and the potentials of the method for dating mortars are pointed out.

7

Employing Minimum age model (MAM) and Finite mixture modeling (FMM) for OSL age determination of two important samples from Ira Trench of North Tehran Fault

Fattahi M., Heidary M., Ghasemi M.

Geochronometria

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2016

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Vol. 43, no. 1

38--47

EN

Ira trench site is in a point where, the surface trace of North Tehran Fault (NTF) joins the Mosha Fault (MF) in the north-eastern margin of Tehran and can provide important paleosismological information for Tehran. The Ira trench, were divided into 6 packages (I to VI), described, according to their composition, relative and absolute ages. Package I consists of units 23, 25, 26, 27, 28, 29, 30 and 31. The whole package I mainly belongs to Holocene, and provides essential constraints for the recent paleo-earthquake activity of the EMF and NTF zone. Therefore, finding accurate ages for the units of this package is very important. Three colluvial wedges (units 23, 26, 28) are present between 20 and 36.5 m north in package I, which are assigned to 3 episodes of activity on Fault 13. Central age model (CAM) provided OSL ages of 35.0 ± 6.1, 7.3 ± 1.3, 6.4 ± 0.9 and 56 ± 6.5 ka for units 23, 26, 28 and 29, respectively. The conflicting ages of 56 ± 6.5 and 35.0 ± 6.1 ka (for units 23 and 29, respectively) as compared to the underlying younger units suggest that these ages are overestimated. MAM provided OSL ages of 13.1 ± 4.3 and 3.5 ± 0.4 ka for units 23 and 29, respectively. The contribution of the new statistical age model of sample IRA4 to the paleoseismic data is discussed.

8

Reconstruction of Late Quaternary neotectonic movements and fluvial activity in Sikkimese-Bhutanese Himalayan Piedmont

Starkel L., Płaskonka D., Adamiec G.

Studia Geomorphologica Carpatho-Balcanica

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2015

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Vol. 49

71--82

EN

In the part of Sikkimese-Bhutanese Himalaya the youngest Siwalik overthrust had not developed, and the piedmont zone with extensive fans forms a semicircular gulf dismembered by several faults and minor overthrusts. Some uplifted parts of older deformed alluvial fans contain the lenses of organic clays which were earlier dated at 22–34 ka BP by 14C method. Various elevated levels differ also in soil maturity. It means that the main tectonic activity with overthrusting could occur later. To distinguish various alluvial formations and phases of tectonic activity the authors dated older levels in several localities by OSL method as well as investigated soil profiles. Most mature soils over elevated blocks built of coarse alluvia were dated between 50 and 60 ka BP. Probably the previous 14C dates from clays are too young, and on the contrary OSL dates are overestimated. The younger generation of fans (10–15 m high) dated at about 14 ka coincide with the start of monsoonal pre-Holocene activity. The authors try to correlate these phases with terraces and tectonic activity in the most eastern part of the Himalayas (two phases of overthrusting: after 50 ka and 10–5 ka BP) as well as with events outside the piedmont zone: glacifluvial aggradation in the Tista valley during advance of glaciers in Sikkim and with sequence of deposits in the Brahmaputra delta.

9

Testing the standardized growth curve (SGC) to OSL dating coastal sediments from the South Bohai Sea, China

Guang-Quan Ch., Liang Y., Xing-Yong X, Hong-Jun Y., Jian-Rong C., Qiao S., Lin-Hai Y., Yong-Hang X., Jun-Yi G., Zhong-Ping L.

Geochronometria

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2013

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Vol. 40, no. 2

101--112

EN

It has been suggested that the standardized growth curve (SGC) method can be used to ac-curately determinate equivalent dose (De) and reduce measurement time. However, different opinions regarding the applicability of the SGC method exist. In this paper, we evaluated quartz OSL SGCs of marine and coastal sediments of different grain sizes and different cores in the south Bohai Sea in China, and tested their applicability to the determination of De values. Our results suggested as fol-lows: (1) The SGC method is applicable to both multiple- and single- aliquot regenerative-dose (MAR and SAR) protocols of OSL dating and efficiently provides reliable estimates of De. (2) Fine-sand quartz of different palaeodoses showed highly similar dose-response curves and an SGC was de-veloped, but old samples using the SGC method have large uncertainties. (3) For coarse-silt quartz, two different types of dose-response curves were recorded: low-dose (≤60Gy) and high-dose (≥100Gy). The growth curves of low-dose quartz were similar to each other, facilitating the use of SGC in De estimations, but errors tended to be larger than those obtained in the SAR method. For high-dose (100-300Gy) quartz, the SGC was also found to be reliable, but there was large uncertainty in De (>300Gy) estimation. We suggest that SGC could be employed for the dating of marine and coastal sediments dating using either MAR or SAR OSL protocol and either fine-silt, coarse-silt or fi-ne-sand quartz.

10

OSL dating using quartz fine grains extracted from loess in Upper Palaeolithic sites of Nihewan Basin, northern China

Shitaoka Y., Nagatomo T.

Geochronometria

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2013

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Vol. 40, no. 4

311--316

EN

Although radiocarbon (14C) dating, uranium-series dating, and optically stimulated lumi-nescence (OSL) dating have been conducted for Upper Palaeolithic sites in the Nihewan Basin, north-ern China, there is room for constructing a detailed chronological framework. In this study, loess sed-iments collected from two Upper Palaeolithic sites, Youfang site and Hutouliang site, were dated us-ing the single-aliquot regenerative-dose (SAR) OSL protocol. OSL measurements for palaeodoses es-timation used fine-grained quartz samples extracted from loess. OSL dating results were obtained as 10-17 ka. These OSL ages were consistent with the related stratigraphy of Palaeolithic sites, archaeo-logical evidence and independent 14C ages.

11

Chronology of red dune aggradations of South India and its Palaeo-environmental significance

Alappat L., Seralathan P., Shukla A. D., Thrivikramji K. P., Singhvi A. K.

Geochronometria

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2013

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Vol. 40, no. 4

274--282

EN

Red sand dunes occur in the coastal plains of south east and west of Tamil Nadu, India be-tween the co-ordinates of 8°00’ to 9°30’ N; 77°18’ to 79° 00’ E. OSL dating of these sands indicated aggradations between ~16-9 ka and ~9-3 ka in the west and east coasts respectively. Dating results from inland red dunes at the foothills of Western Ghats show a break in deposition at ~6 ka and ag-gradation since ~2 ka. The sand aggradations in the west coast occurred during the transition period when SW monsoon in the area was re-establishing. The dunes attained their stability by 9 ka. In the coastal region, the aggradations were controlled by sea level changes and a local recycling of earlier dunes (in the east coast). In the inland areas, the dune building was controlled by sand supply from fluvial sources.

12

Quartz OSL dating of sand dunes in Ghaggar Basin, northwestern India

Shitaoka Y., Maemoku H., Nagatomo T.

Geochronometria

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2012

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Vol. 39, no. 3

221-226

EN

Several studies have used luminescence dating to investigate sand mobilization activity in extreme western areas and the southern margin of the Thar Desert, India. However, room exists for a chronology of sand profiles for the northern margins of the Thar Desert. The Ghaggar River flood plain at Rajasthan, northwestern India, in the northern margin of the Thar Desert, is bordered by sand dunes. Elucidation of the environmental changes of the Ghaggar Basin requires knowledge of many aspects of sand dune formation. We measured optically stimulated luminescence (OSL) using the single aliquot regenerative-dose (SAR) protocol for sand of eight palaeo-dunes and two flood silts of both sides of the present Ghag-gar Basin and Chautang Basin flood plains. Their OSL ages were obtained respectively, as 15-10 ka or 5 ka, and 9-8 ka. Results of this study reinforce the hypothesis that sand dune deposition had start-ed or had already been completed by 15-10 ka. Aeolian deposition was subdued by enhanced mois-ture during 9-8 ka. Our interpretation is that, at least since 5 ka, the scale of the flood plain of the Ghaggar River has remained equivalent to that of the present day.

13

Optical dating of alluvial deposits at the orogenic front of the Andean Precordillera (Mendoza, Argentina)

Schmidt S., Tsukamoto S., Salomon E., Frechen M., Hetzel R.

Geochronometria

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2012

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Vol. 39, no. 1

62-75

EN

Well constrained numerical ages of alluvial fan sediments are key to understanding the chronology of alluvial episodes and tectonic activity at the front of the Andean Precordillera. We tested the application of radiocarbon and optically stimulated luminescence (OSL) dating in the distal part of an alluvial fan five kilometers north of Mendoza. For OSL dating a large number of aliquots (n > 70) – each composed of ~50 quartz grains – were measured in order to obtain reliable burial ages despite scattered dose distributions. Owing to a feldspar contamination in all samples, an infrared stimulation was inserted before each OSL measurement, which reduced the feldspar OSL signal suc-cessfully. By using the minimum age model we obtained stratigraphically consistent burial ages of alluvial deposits in a depth profile. The uppermost ~1 m of sediment is composed of debris flow deposits buried 770š76 years ago. Three plant remnants used for radiocarbon dating from the same layer, however, yielded ages younger than 350 years, which are interpreted to underestimate the depositional age. Underneath the debris flow, a major unconformity cuts a series of distal alluvial fan sediments with interstratified floodplain deposits, which are composed of sandy and calcite-rich silt layers, respectively. Three samples from this unit which were distributed over one meter of sediment thickness yielded statistically concordant OSL ages of 12.3š1.2 ka, 12.3š1.2 ka, and 11.7š1.1 ka. The deposi-tion of these sediments during the latest Pleistocene coincides with a phase of cool and humid climate, which occurred before the alluvial fan propagated farther into the foreland. The overlying debris flow sediments are associated with alluvial fan incision during the arid Late Holocene.

14

Luminescence age constraints on palaeo-earthquake events along the lingwu fault in the Yinchuan basin, China

Xulong W., Chizhang Ch., Peng D., Qiyun L., Gongming Y., Yanchou L.

Geochronometria

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2012

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Vol. 39, no. 1

57-61

EN

Optically stimulated luminescence (OSL) dating was applied to sediment samples in order to provide age constraints on the palaeo-earthquake events that are recorded in a trench on the Lingwu fault near Yinchuan on the northeastern margin of the Tibetan Plateau, China. Combining seventeen OSL ages with field observations in the trench shows that at least four events took place at this specif-ic site, and that this fault has been active over the past 200 ka.

15

Mesolithic occupations and environments on the Island of Ikaria, Aegean, Greece

Sampson A., Kaczanowska M., Kozłowski J. K., Athanassas C., Bassiakos Y., Liritzis I., Laskaris N., Tsermegas I.

Folia Quaternaria

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2012

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nr 80

1--87

EN

The most important Mesolithic site on the Island of Ikaria, Kerame 1, extends 80 m along the sloping edge of the cliff and is up to 40 m wide. The site is a sum of repeated sojourns of Mesolithic groups that had left behind concentrations of lithic artefacts, which were subsequently displaced by post-depositional agents, first of all by erosion. As a result, the site reveals now a large concentration of finds in Trenches E, C, and G. Moreover, post-depositional agents caused the destruction of permanent features such as the hearths associated with the various khsemenitsas, or — possibly — stone rings surrounding the dwelling structures. Only in trenches D, B and E the remains of a circular stone rings, probably around hearths, were registered. The lithic industry of Kerame 1 displays considerable similarity to the site of Maroulas on Kythnos; the techno-morphological differences are, probably, the effect of differing raw materials structure at Kerame 1 and at Maroulas. At Kerame 1, the distant interregional contacts and the influx of extralocal raw materials (documented by the flow of obsidian nodules from Melos and Yali) caused that production in a full cycle was carried out on-site. Thus, there was no specialization of lithic production, and unworked nodules of raw material were exploited in the particular social clusters in a full cycle, whose outcome were tools to be used by a given unit. Regretfully, because organic materials (also bones) have not been preserved we have no data to determine seasonality at Kerame l. Nevertheless, we can say with all certainty that Mesolithic groups visiting Kerame 1 were mobile, which is evidenced by the network of interregional contacts. The most noticeable similarity between Kerame 1 and Maroulas can be accounted for by the chronological closeness of the two sites. The AMS determinations from Maroulas concentrate in the first half of the 9th millenium cal. BC (Facorellis et a1. 2010). Similarly, the dates from obsidian dehydration from Kerame 1 (if their broad standard deviation is overlooked) correspond to the first half of the 9th millenium cal. BC.

16

Potential geoarchaeological sites for luminescence dating in the Ganga Bhagirathi-Hugli Delta, west Bengal, India

Rajaguru S. N., Deotare B. C., Gangopadhyay K., Sain M. K., Panja S.

Geochronometria

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2011

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Vol. 38, no. 3

282-291

EN

Archaeological studies in the upper and lower part of the Ganga-Bhaghrathi-Hugli delta were taken up to understand the nature of site formation and human adaptation in a dynamic fluvial zone. This aspect has been neglected in Indian archaeology. However archaeological dating using ty-pological information, has an error margin of a couple of centuries and hence, is of limited use. We suggest that high resolution chronology using Optically Stimulated Luminescence (OSL) and radio-carbon dating can be quite effective in the study of archaeology and human environment relationship in the Ganga-Brahmaputra Delta (GBD).

17

Construction of a quartz osl standardised growth curve (SGC) for Aeolian samples from the horqin dunefield in northeastern China

Yang L., Lai Z., Long H., Zhang J.

Geochronometria

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2011

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Vol. 38, no. 4

391-396

EN

It has been suggested that the standardised growth curve (SGC) method can be used to determinate De accurately and reduce the measurement time. However, different opinions regarding the applicability of the SGC method exist. In this paper, we report the construction of quartz OSL SGC for 35 aeolian samples from different parts of the Horqin dunefield in northeastern China, and then test their applicability for De determination. Our results suggest that: 1) up to a regeneration dose of 80 Gy, the SGC of the Horqin dunefield can be fitted using the exponential plus linear equation, with the r2 value of 0.97, and all the regeneration dose points closely stick to the fitting line, implying that all samples share a very similar dose-response curve; 2) for samples with De s ranging from 1 to 50 Gy, the ratios of SAR De to SGC De fall within the range of 0.9-1.1, and the average ratio of SAR De to SGC De is 1.01š0.01, close to unity. Therefore, the construction of SGC is correct, and the SGC is an effective procedure for accurate De determination for samples from the study area.

18

Comparison of three K-feldspar luminescence dating methods for Holocene samples

Li G. Q., Zhao H., Chen F. H.

Geochronometria

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2011

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Vol. 38, no. 1

14-22

EN

The luminescence dating of the K-feldspar fraction is an alternative way for samples that cannot yield reasonable equivalent dose (De) from quartz fraction with very weak luminescence signal. For testing the reliability of the infrared stimulated luminescence (IRSL) dating of K-feldspar, luminescence dating was applied to quartz and K-feldspar fractions respectively for several Holocene samples in this study. K-feldspar apparent ages using routine single aliquot regenerative-dose (SAR) protocol, K-feldspar ages using g value correction method and ages from isochron dating method were compared with quartz ages. It is found that the g value correction method cannot give reliable ages due to the large errors induced during measurements. The isochron dating method is effective to the sample with problematically external dose rate. However, isochron dating may introduce a relatively greater error during grain sizes – De curve fitting, therefore this method could obtain lowresolution ages for Holocene samples. Even K-feldspar apparent age from routine SAR protocol is relatively younger by about 10% than the quartz age, it still could establish reasonable chronological framework for Holocene samples.

19

Age and sedimentological features of fluvial series in the Toruń Basin and the Drwęca Valley (Poland)

Weckwerth P., Przegiętka K., Chruścińska A., Woronko B., Oczkowski H. L.

Geochronometria

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2011

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Vol. 38, no. 4

397-412

EN

The deposits of the Toruń Basin are dominated by a few-metre thick sand series which fill up buried valley-like depressions. In many cases they underlie the Weichselian till which builds up the ice marginal streamway (pradolina) terraces or they are exposed at the basin slopes. As the results of the geological and sedimentological studies, as well as of the dating of the deposits at the sites in the Toruń Basin indicate, the deposits include two fluvial series accumulated before the advancement of the Leszno Phase ice sheet, i.e. in Middle Weichselian and at the beginning of Late Weichselian. The oldest fluvial series connected with the Saalian Glaciation was found at the mouth section of the Drwęca Valley. The fluvial system of the Toruń Basin during Middle Weichselian and at the begin-ning of Late Weichselian developed in two phases of the sand-bed braided river. During the first one the river channel were dominated by large mid-riverbed sandbars, while during the second phase the water flow was smaller and, as a result, low transverse sandbars and two-dimensional dunes devel-oped. Other active river channel also showed low-energy flows, more intensive meandering than in the case of the braided rivers, as well as sandy side-bars. Analysis of the rounding and frosting of the quartz grains indicate that the studied series of the Weichselian sandy deposits represent alluvia of a river which were fed from two diverse sources. The first one might have represented the alluvia of a warm river which transformed its load, while the other one might have mainly carried the underlying Quaternary deposits.

20

Optical dating of sediments in Khari River basin and slip rate along Katrol Hill Fault (KHF), Kachchh, India

Kundu H. K., Thakkar M. G., Biswas R. H.

Geochronometria

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2010

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Vol. 37

21-28

EN

In the central region of Mainland Kachchh, Western India, the Katrol Hill Fault (KHF) is one of the major E-W trending faults. An understanding of the episodes of reactivation during the past has a bearing on the future seismicity in the region. These reactivations are manifested by offset of elevation of fluvial sediments and scarp-derived colluvium in the Khari River basin, SE of Bharasar (23°11'36.5"N, 69°35'22.6"E). Stratigraphic offsets of the sediments at this site suggest three episodes of reactivation of the KHF during the late Quaternary. Optical dating of samples from sediment strata and top layer of scarp-derived colluvium using Natural Sensitivity Corrected – Single Aliquot Regenerative (NCF-SAR) protocol suggested that these events occurred during the past ~30 ka, with the most recent historic episode around 3.0 ka. Given that a part of the slip recorded in the form of sediments offset, was lost due to erosion after faulting, a lower bound to the time averaged slip rate of the segment of KHF, is inferred to be > 0.23 mm/a during the past 30 ka.