Interglacial Age Research Articles

Decoding the Interplay Between Tidal Notch Geometry and Sea‐Level Variability During the Last Interglacial (Marine Isotope Stage 5e) High Stand

AbstractRelic coastal landforms (fossil corals, cemented intertidal deposits, or erosive features carved onto rock coasts) serve as sea‐level index points (SLIPs), that are widely used to reconstruct past sea‐level changes. Traditional SLIP‐based sea‐level reconstructions face challenges in capturing continuous sea‐level variability and dating erosional SLIPs, such as tidal notches. Here, we propose a novel approach to such challenges. We use a numerical model of cliff erosion embedded within a Monte Carlo simulation to investigate the most likely sea‐level scenarios responsible for shaping one of the best‐preserved tidal notches of Last Interglacial age in Sardinia, Italy. Results align with Glacial Isostatic Adjustment model predictions, indicating that synchronized or out‐of‐sync ice‐volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology, with sea level confidently peaking at 6 m and only under a higher than present erosion regime. This new approach yields insight into sea‐level trends during the Last Interglacial.

A tale of two islands: tectonic and orbital controls on marine terrace reoccupation, Channel Islands National Park, California, USA

AbstractIn areas of low uplift rate on the Pacific Coast of North America, reoccupation of emergent marine terraces by later high sea‐stands has been hypothesised to explain the existence of thermally anomalous fauna (mixtures of warm and cool species) of last interglacial age. If uplift rates have been low for much of the Quaternary, it follows that higher (older) terraces should also show evidence of reoccupation. Strontium isotope analyses of fossils from a high‐elevation marine terrace on Anacapa Island, California, yield ages ranging from ~2.4–2.3 Ma to ~1.4–1.5 Ma. These results indicate that terrace reoccupation and fossil mixing on Anacapa Island could have taken place over several interglacial periods in the early Pleistocene. Terrace reoccupation over this time period is likely a function of both a low uplift rate and the timing of orbital forcing of glacial–interglacial cycles. Climate change in the early Pleistocene was modulated by the 41 ka obliquity cycle, and glacial–interglacial cycles were much shorter than later in the Pleistocene. Nearby San Miguel Island also has evidence of terrace reoccupation, with Sr isotope ages of shells from several high‐elevation terraces ranging from ~1.21–1.25 Ma to ~0.43–0.50 Ma. However, the frequency of terrace reoccupation was lower than on Anacapa Island. The uplift rate of San Miguel Island is higher than that of Anacapa Island and terraces formed when glacial–interglacial cycles were longer. The frequency of marine terrace reoccupation is controlled by the rate of tectonic uplift and the timing of orbital forcing of sea level change during glacial–interglacial cycles.

Last interglacial lake sediments preserved beneath Laurentide and Greenland Ice sheets provide insights into Arctic climate amplification and constrain 130 ka of ice‐sheet history

AbstractSediment cores from 13 lakes in a 1500 km transect along the eastern North American Arctic contain up to four superposed stratified interglacial units. All 13 lakes contain one unit with sediment similar in character and mass to Holocene gyttja, with 14C ages >40 ka, luminescence ages 90 to 120 ka, and pollen assemblages that require nearly complete Laurentide deglaciation, supporting a Last Interglacial (LIG; MIS 5e) age. Two lakes preserve an older interglacial, with luminescence ages suggesting an MIS 7 age. Four adjacent lakes record a thin, stratified organic unit between the LIG and Holocene units with 14C ages >50 ka, that is probably from late in MIS 5. Temperature estimates from biotic proxies suggest LIG summer temperatures 4–6°C above mid‐20th century values; pollen, chironomids and DNA document a poleward expansion of woody plants and invertebrate species during the LIG, supporting arguments that positive feedbacks native to the Arctic amplified insolation‐driven summer temperature increases. The stratigraphic succession implies the Laurentide Ice Sheet remained intact with sea level below ‐40 m from ~115 ka to ~11 ka, and places new constraints on the interpretation of cosmogenic radionuclide inventories in erratic boulders older than the Holocene throughout this region.

Reconstructing Permafrost Sedimentological Characteristics and Post-depositional Processes of the Yedoma Stratotype Duvanny Yar, Siberia

Cryogenic weathering is a key driver of periglacial sediment composition and properties. Selective mineral-grain weathering caused by freeze-thaw cycles in permafrost environments has the ability to dominate this process, leading to silt-rich grain-size distributions. The cryogenic weathering index (CWI) is a promising tool to quantify cryogenic weathering and freezing conditions. It considers the low resistance of quartz to freeze-thaw cycles compared to feldspars. Using this approach, this study aims to decipher post-depositional weathering by reconstructing cryogenic late Pleistocene Yedoma origins of the Yedoma stratotype exposure Duvanny Yar. To estimate the recent environmental endmember and to determine the initial mineral composition of sediment until freezing, the distribution of CWI in the active layer was studied. In addition to CWI, we studied mineral composition, heavy mineral distribution, grain size distribution and grain morphology. We suggest that cryogenic weathering likely altered polygenetic deposits (fluvial, nival, colluvial, lacustrine, alluvial, and aeolian processes) during sediment and ground ice accumulation. Moreover, we found two CWI distribution peaks in the late Pleistocene - Holocene sediments at the boundaries between glacial and interglacial ages. In conclusion, we see that the Duvanny Yar sediment facies varied by CWI, but also with grain-size distribution, suggesting environmental changes during formation. Nevertheless, post-depositional processes like cryogenic weathering have influenced sediment characteristics and should be considered in paleoenvironmental reconstructions.

Liolophura species discrimination with geographical distribution patterns and their divergence and expansion history on the northwestern Pacific coast

The chiton Liolophura japonica (Lischke 1873) is distributed in intertidal areas of the northwestern Pacific. Using COI and 16S rRNA, we found three genetic lineages, suggesting separation into three different species. Population genetic analyses, the two distinct COI barcoding gaps albeit one barcoding gap in the 16S rRNA, and phylogenetic relationships with a congeneric species supported this finding. We described L. koreana, sp. nov. over ca. 33°24′ N (JJ), and L. sinensis, sp. nov. around ca. 27°02′–28°00′ N (ZJ). We confirmed that these can be morphologically distinguished by lateral and dorsal black spots on the tegmentum and the shape of spicules on the perinotum. We also discuss species divergence during the Plio-Pleistocene, demographic expansions following the last interglacial age in the Pleistocene, and augmentation of COI haplotype diversity during the Pleistocene. Our study sheds light on the potential for COI in examining marine invertebrate species discrimination and distribution in the northwestern Pacific.

Change of Potential Distribution Area of a Forest Tree Acer davidii in East Asia under the Context of Climate Oscillations

The climate oscillations of the quaternary periods have profoundly affected the geographic distributions of current species. Acer davidii is a deciduous forest tree species mainly distributed in East Asia and China, playing a dominant role in the local forest ecosystem. In order to study the potential changes of geographic distributions of A. davidii in climate fluctuations, we collected the relate geographical distribution data and six climatic variables, using maximum entropy modelling to determine the species distribution. The results showed that the Areas Under Curve (AUC) values of the working characteristic curves of the subjects in the five historical periods were all greater than 0.93, suggesting that the results of maximum entropy modelling were accurate. The simulation of species distribution showed that the suitable area of A. davidii was mainly concentrated in central and northern China in contemporary times. From the Last Interglacial Age (LIG) to the Last Glacial Maximum (LGM), and then to the future (2050, 2070), the distribution area of this species experienced a decrease (LGM~Current; the high adaptability areas of central China became moderate) then an increase (Current~2050, the adaptation areas expanded to South Asia, Southeast Asia, and Siberia), and finally decreased (2050~2070, the suitable areas of South Asia, Southeast Asia, and Siberia shrank returning to China at latitude 25 °N). Compared to the LGM, the area of contemporary suitable area increased. Interestingly, the area of suitable growth range under future climatic conditions (2050) increased by half than before, and the suitable distribution area moved from Midwest China to Northeast China. This study on the change of species distribution can provide a typical case for the model study on the response of plants to climate change in the north temperate and subtropical zones of East Asia. Meanwhile, it can also give a basis for planting planning, species protection, and management.

Peesey Swamp—a Last Interglacial (MIS 5e) marine corridor across southern Yorke Peninsula, southern Australia

Peesey Swamp on southern Yorke Peninsula, southern Australia, is a north-northwesterly—south-southeasterly trending lowland depression, approximately 24 km long and 4 to 10 km wide. The richly fossiliferous mollusc and foraminiferal faunal assemblages of the last interglacial Glanville Formation in Peesey Swamp indicate that the paleoenvironment was a low- to medium-energy, sheltered sandflat to shallow-water seaway during the Last Interglacial Maximum (Marine Isotope Substage [MIS] 5e; 128–116 ka). The presence of the fossil bivalve molluscs Katelysia rhytiphora, Chlamys (Equichlamys) bifrons and Fulvia tenuicostata, in life position, indicate that the paleowater depth was ≤4 m in Peesey Swamp. The seaway cut across southern Yorke Peninsula, establishing a marine connection between southern Spencer Gulf and Investigator Strait during deposition of these taxa. Amino acid racemisation dating of the fossil marine molluscs Katelysia sp. and Fulvia tenuicostata confirms that the shelly assemblages at Peesey Swamp are correlative with the last interglacial Glanville Formation, a succession of richly fossiliferous, mixed quartz–skeletal carbonate sands documented from many sites along the southern Australian coastline. This study illustrates the significant changes in the geographical configuration of coastlines that may accompany relatively modest (<5 m) sea-level changes on low-gradient coastal landscapes. KEY POINTS Peesey Swamp on southern Yorke Peninsula was flooded by seawater forming a 4 to 10 km-wide seaway during the Last Interglacial Maximum (MIS 5e). Fossil mollusc and foraminiferal assemblages reveal deposition within shallow subtidal to intertidal sandflat environments indicating that the paleowater depth and height of sea-level in Peesey Swamp was ≤4 m. Amino acid racemisation dating of fossil marine molluscs confirms that the shelly assemblages at Peesey Swamp are of last interglacial (MIS 5e) age. The distribution of the foraminifer Marginopora vertebralis indicates that the eastward flow of the warm-water Leeuwin Current, during the Last Interglacial Maximum, was retarded by the biogeographical barriers of Kangaroo Island and Fleurieu Peninsula.

The MIS 5a (~80 ka) Middle Stone Age lithic assemblages from Melikane Rockshelter, Lesotho: Highland adaptation and social fragmentation

Multidisciplinary research suggests that Marine Isotope Stage 5 (~130–74 ka) was an important evolutionary stage in African deep history. Population expansion and growth spurred changes in material culture as well as the exploration of previously unoccupied regions and ecosystems. The archaeological sequence at Melikane Rockshelter (1860 masl) in the Maloti-Drakensberg Mountains of highland Lesotho, southern Africa, stretches from the late Holocene back to sub-stage 5a, ~80 ka. The site's earliest strata represent one of the earliest known examples of a sustained human presence in high mountain systems worldwide. This paper deals with the lithic assemblages from those levels, which are currently the oldest radiometrically dated archaeology in Lesotho and one of the few stratified assemblages of Last Interglacial age in the southern African interior. The results of a typo-technological analysis of the assemblages are presented. They suggest that the afromontane foragers who resided at Melikane employed both blade-focussed and bipolar flaking systems, curated a maintainable toolkit suited to frequent residential moves, and used a hybrid provisioning system adapted to their immediate environment. Comparisons with other late Last Interglacial assemblages across the subcontinent suggest that highland populations at this time were largely disconnected from their lowland counterparts. This implies that as Last Interglacial populations in southern Africa expanded into new environments, they also fragmented, adapting to local conditions rather than adhering to a universal technological system.

New Datings of Deposits From Odra River Valley - Stratigraphic Consequences and Interpretation at Fluvial Succession

Abstract This paper presents organic sediments age analysis in Odra river valley in Słubice, western Poland. In this middle reach of Odra valley reach the uppermost fluvial deposits contain several alternate layers of organic sediments. These deposits have been mostly interpreted as the Holocene fluvial (floodplain) sediments, even if visible admixture of organic matter is not observed. However, there is also another hypothesis. Geotechnical studies conducted in several locations in Słubice, have questioned this interpretation. The main argument was the values of preconsolidation ratio in the range of 0.8 to 5.4, which may suggest, that the analysed sediments were covered by an ice sheet. Also, based on the presence of a clay layer devoid of organic matter impurities in the top of organic deposits, the second one presumes an interglacial (possibly Eemian) age of the discussed fluvial/organic sediments (peats and silts). To verify these hypotheses, six samples from six different boreholes drilled in the Odra river valley, in the centre of Słubice were collected. The results of 14C dating and its interpretation allowed to determine the age of the tested material. All analysed samples from Słubice (Odra river valley) were formed within the last 10,000 years - in Preboreal, Atlantic and Subboreal. Such a result contradicts the earlier stratigraphic interpretations.

Lake sedimentation as an agent of postglacial transformation of interfluves and fluvial landscapes of the Borisoglebsk Upland, Central European Russia

Abstract. Borisoglebsk Upland is considered an example of a secondary upland plain in the marginal zone of the last Middle Pleistocene glaciation. Moraine hills and kames were reworked by glaciofluvial processes and incised by small fluvial forms later. Its postglacial surface drift cover is regularly defined as an undivided complex of mantle loams of dominantly subaerial origin with characteristic cryogenic features and remnants of paleosols. However, some previous studies suggest that lake sedimentation played an important role in the postglacial history of the Borisoglebsk Upland. This paper presents results of a detailed investigation of postglacial sedimentary cover of the eastern part of the Borisoglebsk Upland aimed to reconstruct the co-evolution of surface deposits, soil cover and geomorphic landscapes since degradation of the last Middle Pleistocene glaciation about 150 ka (MIS-6). The study is essentially based on a comprehensive lithological, pedological and geocryological description of postglacial deposits in cores (hand or machine-driven) and open sections, systematic sampling for grain size analysis and selective sampling for 14C absolute dating and monoliths structural examination. The results indicate that most of the surface drifts in this feature consists of stratified lacustrine deposits. Their Late Pleistocene age is stratigraphically confined by the underlying paleosols and incorporated peats of the Mikulino interglacial age (MIS-5) and several organic-rich layers within the lake sequence 14C dated to the Middle Valdai interstadial (MIS-3). Overlying mantle loams and colluvial deposits with cryogenic features and low organic matter content those facially substitute lacustrine sediments were attributed to the Late Valdai stadial (MIS-2). After the Mid-Holocene stabilization, relatively thin colluvial cover identified by the increased amount of organic matter also deposited. We conclude that lacustrine sedimentation is the primary Late Pleistocene agent that transformed the initial glacial topography and most characteristic type of lithodynamics of the eastern Borisoglebsk Upland.

Accuracy of ESR dating of small gastropods from loess and fluvial deposits in the Bavarian Alpine Foreland

This study focuses on the accuracy of the Electron Spin Resonance (ESR) dating method applied to small land snail shells from eolian loess deposits, and from shell bearing clods of sandy loam and marl in fluvial gravel deposits in the Bavarian Alpine Foreland. Due to the small size of land snail shells and lack of specimens available for ESR analysis it was necessary to reduce individual aliquot sample weights to 0.02–0.07 g. While the reduction in sample weight inevitably lowers the signal-to-noise ratio and thus may also negatively influence the precision on the equivalent dose due to even smallest weight variations between the single aliquots, the dating results are in good agreement with independent age control. In general, the ESR ages are mostly within the age interval of previous and new luminescence or radiocarbon dating results. We show that ESR dating of small terrestrial gastropods in most cases allows differentiating between shells of Holocene, Late or Middle Würmian (last glacial, MIS 3, 2), penultimate glacial (MIS 6) or penultimate interglacial (MIS 7) age with errors between c. 10%–15%.

A continuous stable isotope record of last interglacial age from the Bulgarian Cave Orlova Chuka

AbstractRecent research shows that the last interglacial climate was more unstable in comparison to Holocene. Lack of suitable dating techniques and precisely defined absolute age benchmarks is one from main problems for present LIG studies. Therefore many of LIG chronologies base on indirect dating techniques like record alignment strategies. In this context, speleothems are valuable paleoclimate archives because of their capability to be dated by U-series method. In Europe LIG speleothem records are known mostly from western and central part of the continent. In this paper we present a 1,650 mm long stalagmite (ocz-6) from Bulgarian Cave Orlova Chuka. The ocz-6 stalagmite records the period of timeca. 129–112 ka. Ocz-6 stalagmite was analyzed in terms of stable isotopic composition of calcite and trace elements content. All analyzed geochemical proxies point to dynamic changes in the environment during the Last Interglacial time. At the time of interglacial development (129–126.5 ka), ocz-6 records shows systematic change in proportion of moisture delivered from Atlantic source and other sources. The beginning of last interglacial optimum is connected with a rapid change to more humid and warm conditions. During interglacial demise local climate become more dependent from regional settings.

Reconstructing the mass and thermal ecology of North American Pleistocene tortoises

AbstractResearchers often interpret the presence of tortoises in Pleistocene assemblages as evidence of an interglacial age, based on an assumption that these fossils indicate thermic climates, as modern giant tortoises require. Since the Paleocene, tortoises have been common components of terrestrial fossil assemblages and have repeatedly evolved species of giant size. Whereas extant giant tortoises are found only on islands off the coasts of South America and Africa, at least two species persisted in North America until the terminal Pleistocene. These tortoises,Hesperotestudo crassiscutataandGopherus“hexagonatus,” both of which reached carapace lengths of &amp;gt;1 m, were distributed across the southern United States. This study provides new metrics to derive quantitative weight estimates from measurements of the tortoise shell. The linear measurements of 69 anatomical features of the shells of 108 live tortoises indicate that the regression between straight carapace length and weight is most significant, with a maximumr2&amp;gt; 0.99. This regression is useful for tortoises that weigh between 1.8 and 339 kg. This mass estimate, coupled with a heat dissipation rate derived from thermoregulation modeling, provides estimates of how long tortoises can maintain a viable body temperature at low ambient temperatures. Depending on size, a tortoise can survive a maximum of 2.3 to 33 hours of freezing temperatures, which corresponds to a mean annual temperature ≥22°C and a mean winter low temperature ≥7.5°C. This analysis infers warmer temperatures at Pleistocene sites with fossil tortoise occurrences than previous qualitative estimates.

The Moyjil site, south-west Victoria, Australia: fire and environment in a 120,000-year coastal midden — nature or people?

At Moyjil (Point Ritchie), a cliffed site at the mouth of the Hopkins River at Warrnambool, south-eastern Australia, an erosional disconformity of Last Interglacial age on both a rock stack and the adjacent headland represents a surface of possible human occupation. Shells of edible marine molluscs occur on the disconformity, together with a distinctive population of transported stones derived from a calcrete of MIS 7 age and bearing variable dark grey to near-black colouration suggestive of fire. Experimental fire produced similar thermal alteration of calcrete. A strong correlation exists between intensity and depth of dark staining on one hand and increased magnetic susceptibility on the other. Thermal luminescence analyses of blackened stones provide ages in the MIS 5e range, 100–130 ka, consistent with independent stratigraphic evidence and contemporaneous with the age of the surface on which they lie. The distribution of fire-darkened stones is inconsistent with wildfire effects. Two hearth-like features closely associated with the disconformity provide further indications of potential human agency. The data are consistent with the suggestion of human presence at Warrnambool during the Last Interglacial.

The Moyjil site, south-west Victoria, Australia: excavation of a Last Interglacial charcoal and and burnt stone feature — is it a hearth?

Claims for a human presence in Australia beyond 60,000 years ago must have a strong evidence base associated with rigorous methodology and intense scrutiny. In this light we present excavation results for Charcoal and Burnt Stone Feature #1 (CBS1) located within coastal dune sediments at Moyjil (Point Ritchie), Warrnambool, that independent geomorphic and OSL dating indicates is of Last Interglacial age (~120,000 years ago). While on plausibility grounds the cultural status of a feature of such great antiquity in Australia is unlikely, a cultural origin for CBS1 is less easily dismissed if assessed with an age-independent methodology. A broad range of macroscale discrimination criteria has been used to assess whether CBS1 is either a cultural hearth or a natural feature such as a burnt tree stump. On balance, evidence marginally supports a cultural origin over a natural origin. However, the absence of associated stone artefacts and faunal remains and the presence of burnt root wood precludes definitive statements on the cultural status of the feature. Our case study is methodologically instructivein terms of the potential complexities and issues of equifinality involved in the archaeological identification of ancient hearths.

中国亚热带地区阔叶林植物的谱系地理历史

PDF HTML阅读 XML下载 导出引用 引用提醒 中国亚热带地区阔叶林植物的谱系地理历史 DOI: 10.5846/stxb201606031072 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金青年科学基金项目（31600301）；上海科技馆引进人才项目 Phylogeographic history of broad-leaved forest plants in subtropical China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:中国亚热带地区因丰富的植物物种多样性备受生物地理学研究关注，丰富的多样性与中新世以来的地质气候变化密切相关。谱系地理学已成为探讨植物分布模式和遗传格局受地质气候变化影响的主要手段。总结了该地区阔叶林植物对中新世以来地质气候变化的响应模式和种群分化的历史成因。在中新世和上新世时，由于全球变冷、青藏高原抬升和亚洲内陆干旱，阔叶林植物被迫向南退缩，形成不同的谱系。同时，亚洲季风的增强为遗传多样性的增加提供了良好的环境。在更新世冰期和间冰期时，大部分落叶阔叶林和常绿阔叶林植物在多个避难所间存在长期隔离，不同的避难所种群各自经历局部地区的收缩和扩张。长期的隔离使不同谱系间进一步分化，形成高水平的遗传多样性和遗传分化。少部分植物在冰期时向南退缩，并在间冰期时明显向北扩张。最后，就分化时间的准确估计和探究遗传格局背后的机制两方面展望了未来的研究趋势。 Abstract:Subtropical China has drawn considerable attention for biogeography studies because of its high plant species diversity, which has been closely related to geo-climate changes since the Miocene. Phylogeography has become the main method for studying the influence of geo-climate changes on the distribution and genetic structure of plants. In this paper, we review the response patterns to geo-climatic changes since the Miocene and the historical causes of population-level genetic differentiation of broad-leaved forest plants in this region. During the Miocene and Pliocene, broad-leaved forest plants were forced to contract southward and form different lineages because of global cooling, the Qinghai-Tibet Plateau uplift, and Asian interior aridity. Meanwhile, the escalation of Asian monsoons provided suitable environment for diversification. During the glacial and interglacial ages in the Pleistocene, both deciduous and evergreen broad-leaved forests plants mainly underwent long-term isolation in multiple separated refugia. Different refugia populations respectively experienced localized contractions and expansions. Long-term isolation caused further divergence of different lineages, resulting in high genetic diversity and high differentiation. Few plants experienced southward contraction in glacial ages and obvious northward expansion in the interglacial ages. Finally, we speculate on the directions of future research based on accurate divergence time estimations and on mechanisms underlying the genetic structure. 参考文献 相似文献 引证文献

The impact of solar radiation and solar activity on climate variability after the end of the last glaciation

This paper analyzes climate changes since the end of the last glaciations 19–20 thousand years ago, including the modern warm interglacial Holocene age, which started about 11.5 thousand years ago. The connection between the impact of the orbital effect and solar activity on the Earth’s climate is studied. This is important for estimation of the duration of the modern interglacial period. It is shown that there is significant inconsistency between temperature variations in Holocene, which is deduced from the large amount of recently obtained indirect data and the temperatures reproduced in the climate models. The trends of climate cooling in the Holocene on the whole and during the last 2000 years are investigated.

The Carrancas Formation, Bambuí Group: A record of pre-Marinoan sedimentation on the southern São Francisco craton, Brazil

The Carrancas Formation outcrops in east-central Brazil on the southern margin of the São Francisco craton where it comprises the base of the late Neoproterozoic Bambuí Group. It is overlain by the basal Ediacaran cap carbonate Sete Lagoas Formation and was for a long time considered to be glacially influenced and correlative with the glaciogenic Jequitaí Formation. New stratigraphic, isotopic and geochronologic data imply that the Carrancas Formation was instead formed by the shedding of debris from basement highs uplifted during an episode of minor continental rifting. Reddish dolostones in the upper Carrancas Formation have δ13C values ranging from +7.1 to +9.6‰, which is a unique C isotopic composition for the lowermost Bambuí Group but similar to values found in the Tijucuçu sequence, a pre-glacial unit in the Araçuaí fold belt on the eastern margin of the São Francisco craton. The stratigraphic position below basal Ediacaran cap carbonates and the highly positive δ13C values together indicate a Cryogenian interglacial age for the Carrancas Formation, with the high δ13C values representing the so-called Keele peak, which precedes the pre-Marinoan Trezona negative δ13C excursion in other well characterized Cryogenian sequences. Hence, The Carrancas Formation pre-dates de Marinoan Jequitaí Formation and represents an interval of Cryogenian stratigraphy not previously known to occur on the southern margin of São Francicso craton. Documentation of Cryogenian interglacial strata on the São Francisco craton reinforces recent revisions to the age of Bambuí Group strata and has implications for the development of the Bambuí basin.

A detailed post‐IR IRSL dating study of the Niuyangzigou loess site in northeastern China

In this study, we report standard quartz SAR OSL and post‐IR infrared (IR) stimulated luminescence (post‐IR IRSL; pIRIR290) measurements made on sand‐sized quartz and K‐feldspar extracts from the loess‐palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ~15 and ~80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ∼800 Gy. Otherwise, the dose recovery ratio deviates from unity. The De values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR290 results are compared with multiple elevated temperature ‐pIRIR (MET‐pIRIR) data. It appears that the low temperature MET‐pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR290 results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ~10% signal loss occurs in pIRIR signals. Long‐term laboratory bleaching experiments (&gt;80 days) show that a constant (or very difficult to bleach) residual pIRIR290 signal is reached after ~300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol.

Cryptokarst: A Case-Study of the Quaternary Landforms of Southern Apulia (Southern Italy)

Skriti kras (cryptokarst) je kras, razvit pod prepustnim, vendar netopnim pokrovom. Nastane zaradi vode, ki prenika skozi krovne plasti. V krovnih plasteh se zbira voda, se poeasi preceja skoznje in razjeda maticno kamnino. Zaradi tega nastanejo depresije, zapolnjene s pokrovnim sedimentom, in kraski stebri. Zaradi posedanja prepustnega pokrova, nastanejo na povrsju ulegnine. Ce erozija odtsrani krovnino, se razgali relief, za katerega so znacilni kraski stebri, razvalinasti relief in vrtace. Cryptokarst is a karst developed beneath a permeable and not karstifiable formation by percolating waters. The permeable rock acts as a storage of water which feeds slow seepage and infiltration enhancing the alteration of bedrock. The resulting forms consist of depressions, filled by the covering sediments, and pinnacles. The sinking of the permeable cover can produce depressions on the topographic surface. Erosion of the cover exposes a landscape characterised by pinnacles, ruinforms and dolines. In the Apulia region, cryptocorrosion surfaces are characterized by solution pipes 4-5 meters deep and with variable width (from a few centimeters to about one meter). Pipes walls are covered by a brownish carbonate crust, from a centimeter to more than 10 centimeters thick. The continental sands are only found in these depressions. The cryptocorrosion process took place late in the Middle Pleistocene on Quaternary marine abrasion terraces covered by no-carbonate sandy-silty continental deposits. The process stopped before the Last Interglacial age in response of an abrupt climatic change that induces a calcium carbonate precipitation and the formation of a carbonate crust.