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1.
In Argentina, loess/palaeosol sequences were studied from the two sections at Monte Ralo and Corralito, located near to the city of Córdoba in the east of the Pampean ranges. Infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques were applied to set up a more reliable chronological framework for the Upper Pleistocene loess record. IRSL ages increase with depth and are stratigraphically consistent. The oldest loess exposed correlates at least to the penultimate glaciation. The luminescence dating study gives evidence for humid climate conditions with soil formation during the last interglacial period and the middle pleniglacial correlating to Marine Isotope Stage (MIS) 5 and 3, respectively. Three extended periods of soil formation are recorded in the loess/palaeosol sequences at the Corralito section. These buried soils most likely correlate with the last interglacial and early last glacial period. During the Middle Pleniglacial, two palaeosols are intercalated in the loess successions. In the Córdoba area, the periods of increased loess accumulation and deposition of loessic sediments correlate with more arid and glacial periods during the Early Pleniglacial, the Middle Pleniglacial and the Late Glacial. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

2.
《Quaternary Science Reviews》2003,22(10-13):961-966
Luminescence dating of loess has generally been restricted to a maximum of 100–150 ka, due primarily to the anomalous fading behaviour of feldspar. Recent studies have shown that the far-red luminescence from feldspar does not suffer from anomalous fading, and as such may have the potential to extend the age range of the luminescence dating method. The purpose of the present project is to further develop luminescence dating techniques using red and far-red emissions to date loess older than 100–150 ka. We present results demonstrating the presence of a far-red (λ>665 nm) IRSL emission in Chinese loess, and describe a series of basic experiments which seek to characterise aspects of this emission. These include an examination of sensitivity change, and dose reconstruction tests via the employment of a modified single aliquot regeneration (SAR) protocol. It is demonstrated that (a) far-red IRSL can be observed from Chinese loess; (b) far-red IRSL signal is highly reproducible; and (c) a range of laboratory doses from 100 up to 600 Gy can be accurately recovered using a modified SAR procedure.  相似文献   

3.
Loess/palaeosol sequences from the Loess plateau in China were investigated by combined infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques in order to study the luminescence properties of the loessic sediments and to provide a direct chronological link for correlation and position of the last interglacial soil in Central Asia and the Loess plateau in China. Sensitivity changes were found for all samples through artificial bleaching of the samples. The greatest sensitivity changes, of up to 50%, were found for very old loess samples designated to be older than the Matu-yama/Brunhes magnetic boundary and hence older than 788,000±1,800 years. The upper dating limit, as investigated by the very old loess samples, ranges from 250,000 to 300,000 years, if the TL additive dose method is applied. The chronological position of the last interglacial soil S1 at the section near Lanzhou indicates luminescence age estimates ranging from 82,000 to 75,000 years for the marine-isotope stage 5 to 4 transition. However, the loess from below S1 yielded luminescence age estimates between 153,200±14,200 and 110,100±20,100 years for TL and IRSL additive dose methods, respectively. Thus, a direct correlation between the S1 and the first intercalated pedocomplex PC1 in Central Asia is most likely. Received: 31 March 1998 / Accepted: 25 October 1998  相似文献   

4.
Multidisciplinary Quaternary investigations in the Minusinsk Basin in the upper Yenisei River region and other southern Siberian continental depressions have produced evidence of prehistoric peopling pre‐dating the last glacial stage (>100 ka BP). Abundant ‘pebble tools’ and bone artefacts exposed from eroded alluvia of the Yenisei River terraces indicate repeated occupation of this territory since the Middle Pleistocene. A new stage of expansion of the early human occupation habitat occurred around the last interglacial (OIS 5e) by a Middle Palaeolithic (Neanderthaloid?) population characterized by a core and flake stone industry and open‐air occupation sites. The key camp/kill‐processing site at Ust‘‐Izhul’, dated to c. 125 ka BP and documenting complex behavioural activities, is so far the most complete in situ pre‐Late Palaeolithic site found in Siberia. This unique record provides new insights into the timing and the palaeoenvironmental conditions of the Pleistocene colonization of north‐central Asia.  相似文献   

5.
Two high-resolution loess-palaeosol sections from the Ob Loess Plateau (Iskitim) and the Minusinsk Basin (Kurtak 33) provide new detailed information on the last interglacial climate variations and landscape development in the parkland-steppe zone of southern Siberia. The complete last interglacial sensu lato (130-74 ka BP) records of the two sites, documented by magnetic susceptibility, grain-size, CaCO 3 and organic carbon content as proxy climatic data, and supplemented by thin-section studies, indicate several short warm and very cold intervals correlated with OIS 5e-5a. A strongly continental warm climate culminated around the peak of the last interglacial sensu stricto (OIS 5e) and cooler conditions occurred during the following interstadial stages (OIS 5c and 5a), corresponding to shifts in palaeolandscape development with gradual replacement of parkland-steppe and mixed southern taiga by boreal forest. During stadial stages (OIS 5d and 5b), the palaeolandscape was transformed into a cold arid periglacial tundra-steppe. Evidence for a major cooling in Siberia during OIS 5d, corroborating the palaeolimnological record from Lake Baikal, is provided by deep frost-wedge casts distorting the OIS 5e chernozemic palaeosol, suggesting formation of permafrost shortly after the last interglacial climatic optimum. The pedosedimentary record, reflecting the effects of syndepositional pedogenic processes, attests to a dynamic climate pulsation during the last interglacial stage.  相似文献   

6.
This study contributes to the paleoenvironmental reconstruction of the loess–paleosol sequence of Nussloch, Germany, by using n-alkanes as plant leaf-wax-derived lipid biomarkers. We found that n-alkane patterns and concentrations in the Saalian loess and the last interglacial Eemian paleosol of Nussloch point to very strong degradation and prevailing deciduous vegetation. Degradation effects in the overlying paleosols and loess layers are less pronounced and allow for the application of an end-member mixing model to estimate vegetation changes semi-quantitatively. Our findings highlight the potential for the interpretation of degradation-corrected n-alkane ratios. n-Alkane modelling results for loess layers, paleosols and an in-filled paleochannel dated to ~ 60–32 ka suggest that up to ~ 50% of the n-alkanes were derived from deciduous trees or shrubs. This finding is in agreement with the abundant occurrence of wood fragments and indicates a highly variable and dynamic landscape dominated by tundra shrubland. On the other hand, deciduous trees or shrubs did not contribute significantly to the soil organic matter in the late Weichselian loess layers and the intercalated Gelic Gleysols (~ 32–18 ka).  相似文献   

7.
The establishment of a chronology of landscape-forming events in lowland and mid-altitude Tasmania, essential for assessing the relative importance of climatic and human influences on erosion, and for assessing present erosion risk, has been limited by the small number of ages obtained and limitations of dating methods. In this paper we critically assess previous Tasmanian studies, list published radiocarbon ages considered to be dependable, present new radiocarbon and thermoluminescence (TL) ages for 25 sites around Tasmania, and consider the evidence for the hypotheses that erosion processes at low and mid altitudes have been: (1) purely climatically controlled; and (2) influenced both by climatic and anthropogenic (increased fire frequency) effects. A total of 94 dependable finite ages (calibrated for radiocarbon and ‘as measured’ for TL and optically stimulated luminescence (OSL) determinations) are listed for deposits comprising dunes, colluvium, alluvium and loess-like aeolian deposits. Two fall in the >100 ka period, 15 fall in the period 65–35 ka, and 77 fall in the period 35–0.3 ka. There was a sustained increase in erosion recorded in the period 35–15 ka, as reflected by a greater number of dated aeolian deposits during this period.We considered three possible biases that may have affected the age distribution obtained: the limitations of radiocarbon dating, sampling bias, and preservation bias. Sampling bias may have favoured more recent dune strata, but radiocarbon dating and preservation biases are unlikely to have significantly distorted the age distribution obtained.Long but intermittent aeolian deposition is recorded at two sites (Southwood B; c. 59–28 ka and Dunlin Dune; c. 29–14 ka) but there is no evidence of regional loess deposits such as found in New Zealand. The timing of increased erosion in Tasmania between 35 and 30 ka approximately coincides with the intermittent ten-fold increase of dust accumulation between 33 and 30 ka in the Antarctic Dome C ice core. The absence of widespread erosion before 35 ka, the abrupt increase of erosion around this time, the frequent association of erosion products with charcoal, the arrival of people in Tasmania at c. 40 cal ka, and the known use of fires by Aborigines to maintain areas of non-climax vegetation suggest that ecosystem disturbance by anthropogenic fires, in a drier climate than that presently prevailing, may have contributed to erosion in lowland and mid-altitude Tasmania after 35 ka. Thus the Tasmanian erosion record provides circumstantial support for the proposition that human dispersal in southeast Australia was accompanied by significant ecological change.  相似文献   

8.
The infrared stimulated luminescence (IRSL) dating method is applied to alkali feldspar coarse grains from the two distinct Middle Pleistocene interglacial estuarine deposits of Tourville, located along the Seine Valley. The upper deposit (unit D), previously dated at 200 ka by ESR on in situ shells and correlated with a stage 7 high sea-level stand (186–245 ka), yields a measured IRSL age of 176 ± 21 ka. The lower deposit (unit B) assigned to a distinctly older high sea-level event (stage 9: 303–339 ka) yields a measured IRSL age of 273 ± 28 ka. The nearby stage 7 raised beach of Sangatte, in Northwestern France, previously dated by TL on quartz (229 ± 18 ka) yields a measured IRSL age of 186 ± 19 ka. These IRSL age estimates systematically underestimate the expected geological ages. This could be due to the long-term fading or instability of the luminescence signal in alkali feldspars. The correction for long-term fading has been tested on these samples. At Tourville, it yields corrected IRSL ages of 196 ± 23ka and 314 ± 32ka, for the upper and lower units respectively and, at Sangatte, a corrected IRSL age of 206 ± 20 ka. These corrected IRSL age estimates are in better agreement with the expected geological ages. This study demonstrates the potential of the feldspar luminescence dating method to provide chronological information on Middle Pleistocene interglacial estuarine sediments within the North Sea-English Channel Basin.  相似文献   

9.
《Quaternary Science Reviews》2003,22(18-19):1835-1857
Upper Pleistocene loess/palaeosol sequences provide excellent high-resolution terrestrial archives of climate forcing. Due to improvements in numerical age determinations, especially in luminescence dating methods, a more reliable time-based reconstruction of the past climate and environmental change has become available for the loess record in Europe. Chronological information was collected from 43 sites along a northwest to southeast transect in Europe. Thirty-three of these sites had sufficient age information to allow estimation of mass accumulation rates, and it was possible to isolate the mass accumulation rates of primary loess during the Last Glacial Period (∼28–13 ka BP) at 21 of these locations. These sites fall along a coarse climatic gradient from the relatively coastal climate of Belgium and France to the drier, more continental climate of Central Europe. Interpreting mass accumulation rates of loess in terms of this climatic gradient is not straightforward as these deposits are dominated by sources in floodplains and large river systems. Thus accumulation rates are influenced strongly by regional wind and precipitation patterns, but mostly by the availability of glacially derived material from the Alps and the periglacial terrains that characterized European fluvial systems during and immediately following glaciation.  相似文献   

10.
Curaçao has reef terraces with the potential to provide sea-level histories of interglacial periods. Ages of the Hato (upper) unit of the “Lower Terrace” indicate that this reef dates to the last interglacial period, Marine Isotope Stage (MIS) 5.5. On Curaçao, this high sea stand lasted at least 8000 yr (~ 126 to ~ 118 ka). Elevations and age of this reef show that late Quaternary uplift rates on Curaçao are low, 0.026–0.054 m/ka, consistent with its tectonic setting. Ages of ~ 200 ka for corals from the older Cortalein unit of the Lower Terrace correlate this reef to MIS 7, with paleo-sea level estimates ranging from ? 3.3 m to + 2.3 m. The estimates are in agreement with those for MIS 7 made from other localities and indicate that the penultimate interglacial period was a time of significant warmth, on a par with the present interglacial period. The ~ 400 ka (MIS 11) Middle Terrace I on Curaçao, dated by others, may have formed from a paleo-sea level of + 8.3 to + 10.0 m, or (less likely) + 17 m to + 20 m. The lower estimates are conservative compared to previous studies, but still require major ice sheet loss from Greenland and Antarctica.  相似文献   

11.
Irene Zembo 《Sedimentary Geology》2010,223(3-4):206-234
The sedimentary record of the Val d'Agri basin is of great importance for understanding the Quaternary tectonic activity and climatic variability in the Southern Apennines. Changes in tectonic controls, sediment supply and climatic input have been identified. The interval from ～ 56 to ～ 43 ka was associated with asymmetric subsidence restricted to the north-eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems. Short-lasting Mediterranean-type pedogenesis between ～ 43 and ～ 32 ka (MIS Stage 3) coexisted with progradation–aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor. Aggradation ended with consumption of accommodation space after 32 ka. During a subsequent stage of decline of vegetation cover, possibly as a consequence of climatic cooling (probably MIS Stage 2), active progradation of alluvial fans occurred. Breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest Pleistocene to Holocene age. The first stages of basin opening and fill, predating ～ 56 ka have only been inferred by stratigraphic considerations: the earliest lacustrine sedimentation should be middle Pleistocene or older in age. The following south-eastward basin widening allowed progradation of alluvial fan systems, which completely filled the lacustrine area (tentatively late middle Pleistocene). Pedogenesis in “Mediterranean-like” climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces, in areas of morpho-tectonic stability, plausibly during MIS Stage 5. The study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the Pleistocene glacial–interglacial cycles.  相似文献   

12.
《Quaternary Science Reviews》2003,22(15-17):1717-1728
Sedimentological and geochemical proxy records of a deep-sea sediment core from the southern central Nordic seas were used to reconstruct the development of glacial and interglacial conditions during the Early and Middle Pleistocene, i.e., late Matuyama to middle Brunhes Chron (1.5–0.35 Ma). An enhancement of both glacial and interglacial characteristics is observed during early Brunhes oxygen isotope stages (OIS) 16 and 15, respectively. Any intensification of the climatic conditions prior to this, as was previously described for the eastern part of the Nordic seas, is not recognized at our study site. It is further shown that the glacial–interglacial environmental contrasts increased from the early to the middle Bruhnes Chron. Of all glacial periods investigated OIS 12 is characterized by the most severe conditions, showing both maximum input of iceberg-rafted debris (IRD) as well as planktic foraminiferal δ18O values comparable to those of the Last Glacial Maximum. Among the interglaciations, OIS 11 is by far the longest interval and the first to show fully developed interglacial conditions, i.e., Holocene-like δ18O values and a minimum of IRD deposition. Hence, our comparison supports bottom water δ18O studies that have indicated the existence of a gradual intensification of glacial–interglacial climate contrasts during the Middle Pleistocene.  相似文献   

13.
An abrupt climatic change during the MIS 5a/4 transition is evident in the loess records of China (S1/L1). Proxies including geochemical elements, grain size, soil color, magnetic susceptibility and carbonate (CaCO3) content indicate a warming interval, which lasted approximately 3 ka, during the MIS 5a/4 transition in both the Wangguan and Shagou loess sections, located in Sanmenxia (Henan Province) and Wuwei (Gansu Province), respectively. Both the winter and summer monsoon proxies demonstrate that this warming interval occurred at the same time in both sections (nearly 70.5–73.6 ka BP), with maximum warming from 71.4 to 72.0 ka BP. This study suggests a universal abrupt warming interval in the East Asia monsoon region at this time. Comparisons with marine, terrestrial and ice-core records indicate this event was very likely an abrupt global warming interval during the last glacial–interglacial transition.  相似文献   

14.
Late Pleistocene loess‐palaeosol sequences are widespread in the Vojvodina region, with thicknesses reaching a maximum of about 20 m. Our investigations include more than 40 of these loess sections. Geochronology of the last glacial loess‐palaeosol sequences, based on luminescence dating and amino acid racemisation, provides correlations between Upper Pleistocene loess‐palaeosol sediments in Vojvodina and comparable deposits at other European localities. Sedimentary logs of magnetic susceptibility, grain‐size measurements and carbonate content, combined with malacological evidence, indicate two main relatively cold and arid phases during the last glacial period, related to intensive accumulation of loess units L1L1 and L1L2, as well as many brief episodes of dry and windy climatic conditions, suggesting a possible relationship with cold events recorded in the North Atlantic region. Generally, late Pleistocene climate in the region was dry and relatively warm, compared with glacial period sites in central Europe, and was characterised by sharp differences between glacial and interglacial modes. New data and interpretations presented in this study emphasise the significance of loess‐palaeosol sequences in Vojvodina for the reconstruction of the temporal and spatial evolution of late Pleistocene palaeoclimate in this part of Europe. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

15.
《Quaternary Science Reviews》2003,22(10-13):1051-1058
The Great Plains of the Mid West USA contain dunefields which display stratigraphic evidence of episodic sand drift throughout the Holocene and, in some cases, the Late Pleistocene. Widespread aeolian activity has been linked to persistent megadroughts caused by a weakening of the tropical moisture-laden circulation from the Gulf of Mexico and equatorial Pacific. Infrared stimulated luminescence (IRSL) dating has been applied to two exposures in the Fort Morgan dunefield of northeastern Colorado where radiocarbon-dated buried soils provide ages for land surface stability. IRSL ages show that sand drift occurred episodically during the Late Holocene at 4.85, 2.37, 1.06, 0.80, 0.6–0.53 and 0.37 ka.  相似文献   

16.
Improved chronological control on the penultimate advance of the Cordilleran Ice Sheet in northwest Canada (the Reid glaciation) is required for a better understanding of late Quaternary palaeoclimatic and palaeoenvironmental change in eastern Beringia. However, reliable dating of glaciation events beyond the last glacial maximum is commonly hindered by a lack of directly dateable material. In this study we (i) provide the first combined minimum and maximum age constraint on the Reid glaciation at Ash Bend, its reference locale in the Stewart River valley, northwestern Canadian Cordillera, using single-grain optically stimulated luminescence dating of quartz; and (ii) compare the timing of the Reid glaciation with other penultimate ice sheet advances in the region with the aim of establishing improved glacial reconstructions in eastern Beringia. We obtain ages of 158 ± 18 ka and 132 ± 18 ka for glaciofluvial sands overlying and underlying the Reid till, respectively. These ages indicate that the Reid advance, at its reference locale, occurred during MIS 6. This precludes an earlier MIS 8 age, and suggests that the Reid advance may have been synchronous with the Delta glaciation of central Alaska, and is likely correlative with the Mirror Creek glaciation in southern Yukon.  相似文献   

17.
Based on the concepts (a) that the stable C and O isotopes combined with the Sr isotope ratios of fracture fills should reflect the source groundwater from which the solid phases precipitated and (b) that U-series disequilibria (USD) enable the calculation of residence time for the U by using Fe oxides as the best candidate, an “isotopic toolbox” was applied to fracture fill from the crystalline basement of the Vienne district. The fracture fills are formed mainly of carbonates, clays and Fe oxides. The isotope data indicate two main generations of carbonate that originated from hydrothermal circulation and equilibrium with present-day groundwaters but the Sr isotope ratios highlight another component with a higher 87Sr/86Sr ratio reflecting the complexity of the water–rock interactions.For the USD, the Fe-hydroxides located at 207 m depth yield an age of 102 ± 5 ka (St. Germain I interglacial stage), whereas those located at 277 m and 300 m yield respective ages of 173 ± 15 ka and 181 ± 10 ka. These corresponding to the transition between the penultimate glacial period (isotopic stage 6) and the end of the preceding interglacial stage (isotopic sub-stage 7a). Investigating water–rock interaction (87Sr/86Sr, 18O, 13C, USD) in the fracture-fill minerals from the crystalline basement has shown that such an approach is relevant to developing an understanding of how the groundwater system has changed over time.  相似文献   

18.
Relict sand wedges are ubiquitous in southern Patagonia. At six sites we conducted detailed investigations of stratigraphy, soils, and wedge frequency and characteristics. Some sections contain four or more buried horizons with casts. The cryogenic features are dominantly relict sand wedges with an average depth, maximum apparent width, minimum apparent width, and H/W of 78, 39, 3.8, and 2.9 cm, respectively. The host materials are fine-textured (silt loam, silty clay loam, clay loam) till and the infillings are aeolian sand. The soils are primarily Calciargidic Argixerolls that bear a legacy of climate change. Whereas the sand wedges formed during very cold (?4 to ?8 °C or colder) and dry (ca. ≤100 mm precipitation/yr) glacial periods, petrocalcic horizons from calcium carbonate contributed by dustfall formed during warmer (7 °C or warmer) and moister (≥250 mm/yr) interglacial periods. The paleo-argillic (Bt) horizons reflect unusually moist interglacial events where the mean annual precipitation may have been 400 mm/yr. Permafrost was nearly continuous in southern Patagonia during the Illinoian glacial stage (ca. 200 ka), the early to mid-Pleistocene (ca. 800–500 ka), and on two occasions during the early Pleistocene (ca. 1.0–1.1 Ma).  相似文献   

19.
This paper reports the main sedimentary characteristics, soil micromorphology and optically-stimulated luminescence (OSL) ages, and details the pedosedimentary reconstruction, of the Hudson site situated in the northern Pampas of Buenos Aires province. It also provides the OSL chronology and a reinterpretation of previously reported micromorphological features for the nearby site of Gorina. Finally, the stratigraphic records of both sites are compared and the main environmental events discussed in a regional context.At Hudson, situated at a low altitude environment close to the coastal plain, the basal fine-grained paludal deposits were unconformably covered by coastal marine sediments with an OSL age of ca. 128 ka supporting its correlation with the high stand of sea level of marine isotope stage 5e. A paleosol developed on the marine deposits and the underlying paludal sediments. OSL ages suggest that soil development and its subsequent erosion occurred over some period between ca. 128 and 54 ka. Fine sediment accumulation in a paludal environment continued until prior to ca. 23 ka when the accumulation of the uppermost loess mantle started. It continued until the early Holocene when present soil development began. At Gorina, OSL ages suggest that the upper part of the pedocomplex formed at some stage between ca. 194 and 56 ka. Loess then accumulated followed by an erosional phase; loess deposition restarted by ca. 29 ka and continued until the beginning of the Holocene (ca. 9 ka) when the present land surface was established.The stratigraphic and paleoenvironmental differences exhibited by the Hudson and Gorina records result from their contrasting geomorphological settings. The OSL geochronology suggests that the last interglacial (MIS 5) at Hudson is marked by the accumulation of marine deposits (MIS 5e) and the subsequent development of a paleosol. The equivalent soil-forming interval at Gorina is represented by the upper part of the buried pedocomplex. Both at Gorina and Hudson, loess accumulation was dominant especially during MIS 2. Loess accumulation continued during MIS 1 until the early Holocene with apparently somewhat higher sedimentation rates in Hudson. Pedogenesis has been predominant during the rest of the Holocene, resulting in the formation of the surface soil profiles.  相似文献   

20.
《Quaternary Science Reviews》2004,23(16-17):1733-1756
This study shows that successions of Pleistocene carbonate aeolian deposits can be placed successfully in a geochronologic framework using magnetostratigraphic and susceptibility stratigraphic analysis supplemented by luminescence dating, studies of wave-cut platforms, and biostratigraphic evidence. The investigated aeolian system covers a significant part of southernmost Mallorca and is exposed in impressive coastal cliff sections.At the study site at Els Bancals the aeolian system has a maximum thickness of 16 m and is composed of alternating dark red colluvial deposits and greyish red aeolian dune and sand-sheet deposits forming seven cyclostratigraphic units. Each cyclostratigraphic unit represents landscape stabilisation, colluviation, and soil formation followed by dunefield development, when marine carbonate sand was transported far inland by westerly or north-westerly winds. The aeolian system is located on top of a wave-cut marine platform 12–14 m a.s.l. This platform probably formed during a sea-level highstand in Marine Isotope Stage (MIS) 11 (427–364 ka), and renewed marine activity probably later in MIS 11 is indicated by the formation of beach deposits.Two sections at Els Bancals were sampled for a paleomagnetic study; additional samples were taken to detect variations in magnetic susceptibility (MS). The characteristic remanent magnetisation has been recovered for the most part of the succession in spite of diagenetic overprinting. There is evidence for two probably three reversal polarity excursions, possible connected to the Levantine, CR1 and CR0/Biwa III episodes. If this correlation is correct, the sampled succession represents a time interval in the Middle Pleistocene between ca 410 and ca 260 ka. This age estimate is supported by the MS study and by luminescence dates of 333±70 ka (aeolianite from lower part of the succession) and 275±23 ka (aeolianite from the top of the succession).The nature of the succession suggests deposition during alternating warm and moist (colluvial deposition; soil formation) and cold, dry and windy conditions (dunefield formation). The susceptibility signal can be correlated with the insolation signal at 65°N suggesting that environmental variation on Mallorca was linked to orbitally forced climate change, and it seems that aeolian activity and dunefield formation were linked to glacial or stadial periods.  相似文献   

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