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Copyright of Acta Sedimentologica Sinica is the property of Acta Sedimentologica Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fault slip rates are critical for understanding the evolution of active faults, earthquake recurrence, and crustal deformation. Yet variations in slip rate along the Haiyuan Fault Zone (HYFZ), a large-scale sinistral strike-slip fault in the northeastern margin of the Tibetan Plateau, remain disputed. Here, we investigate in detail late Quaternary and present-day fault slip rates for several segments across the HYFZ based on previously published geologic and geodetic (i.e. GNSS and InSAR) estimates. Our results reveal that the strike-slip rates increase from ~1.6±0.4–1.8±0.3 mm/a on the Halahu (HLH) fault to ~5.2±1.3–6.2±0.9 mm/a on the Lenglongling (LLL) and Jinqianghe (JQH) faults, then decrease to ~3.9±0.8–4.6±0.3 mm/a on the Maomaoshan (MMS) and Laohushan (LHS) faults, subsequently remain relatively constant (i.e. ~4.6±0.8–4.8±0.7 mm/a) on the Haiyuan (HY) fault (in narrow sense), and finally decrease to ~1.3±0.1–1.5±0.3 mm/a on the Liupanshan (LPS) fault, from west to east. These results indicate that the strike-slip rates on the LLL and JQH faults are highest and decrease toward fault tips along the HYFZ, approximating an asymmetrical bell-shaped distribution. Furthermore, geodetic (short-term) and geologic (long-term) slip rates are in general agreement, indicating that the slip rates were relatively constant in the recent geologic history. Despite the shallow creep on the LHS fault, the Tianzhu Seismic Gap, Tuolaishan (TLS), LLL, and LPS faults have a large locking depth, strain accumulation, and/or long seismic quiescence period, underscoring the substantial seismic hazard in these areas. Our study contributes to characterizing the total slip rate budget across the HYFZ and provides insight into further understanding of seismic hazard and regional crustal deformation.

The slip rate of strike-slip active faults is crucial for fault rupture behavior analysis and seismic hazard assessment. Although many segments of the Yilan-Yitong Fault Zone (YYFZ) in NE China have been strongly deformed since the late Quaternary, little progress has been made on its slip rate. With the help of highresolution satellite images, detailed field investigations, seismic reflections, and Quaternary chronological dating, we mainly studied the late Quaternary rightslip rate of the YYFZ. Field investigations revealed an ~15 km long by ~1-2 m high-surface scarp belt extending along the Tangyuan graben interior, with a series of sag ponds and small parallel bulges. Research has revealed that the most recent paleoearthquake (~M 7.0) occurred between 2,800± 600 a BP and 1,700 ± 200 a BP, with evidence of coseismic surface rupture. The T2 terrace abandonment age of the Heijin River is approximately 55.13 ± 1.78 ka (OSL), and the maximum cumulative right-lateral offset may reach 110 ±5 m. Thus, the maximum right-slip rate of the Tangyuan segment of the YYFZ since the late Quaternary is constrained to 1-2 mm/a according to the upper terrace model. This study suggests that the presence of a new fault in the basin interior merits more attention when assessing the influential surface range and earthquake potential along the YYFZ, and the features of "low tectonic loading rate, activity migration in space, and clustering in time separated by ten thousand years of seismic quiescence" observed along the YYFZ are highly important for earthquake model construction and tectonic deformation studies in stable continental regions (SCRs). [ABSTRACT FROM AUTHOR]

The slip rate of strike-slip active faults is crucial for fault rupture behavior analysis and seismic hazard assessment. Although many segments of the Yilan-Yitong Fault Zone (YYFZ) in NE China have been strongly deformed since the late Quaternary, little progress has been made on its slip rate. With the help of highresolution satellite images, detailed field investigations, seismic reflections, and Quaternary chronological dating, we mainly studied the late Quaternary rightslip rate of the YYFZ. Field investigations revealed an ~15 km long by ~1-2 m high-surface scarp belt extending along the Tangyuan graben interior, with a series of sag ponds and small parallel bulges. Research has revealed that the most recent paleoearthquake (~M 7.0) occurred between 2,800± 600 a BP and 1,700 ± 200 a BP, with evidence of coseismic surface rupture. The T2 terrace abandonment age of the Heijin River is approximately 55.13 ± 1.78 ka (OSL), and the maximum cumulative right-lateral offset may reach 110 ± 5 m. Thus, the maximum right-slip rate of the Tangyuan segment of the YYFZ since the late Quaternary is constrained to 1-2 mm/a according to the upper terrace model. This study suggests that the presence of a new fault in the basin interior merits more attention when assessing the influential surface range and earthquake potential along the YYFZ, and the features of "low tectonic loading rate, activity migration in space, and clustering in time separated by ten thousand years of seismic quiescence" observed along the YYFZ are highly important for earthquake model construction and tectonic deformation studies in stable continental regions (SCRs). [ABSTRACT FROM AUTHOR]

Copyright of Journal of Geodesy & Geodynamics (1671-5942) is the property of Editorial Board Journal of Geodesy & Geodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To reveal the characteristics and environmental indications for the combination of the grain size and magnetic susceptibility of coastal sediments, we provided a necessary basis for further study on their genetic mechanisms. Based on the data of grain size and magnetic susceptibility of the 36.10 m long core 07SR01 sediments in the Xiyang tidal channel of western South Yellow Sea, we analyzed their variations and correlations and further revealed their environmental indications and corresponding regional sedimentary evolution via the combination of the aforementioned analysis results, the reinterpretation results of the sedimentary sequence and the age of core 07SR01 and shallow seismic profiles, and the findings of climate and glacial–eustatic cycles during Late Quaternary. The three stages of the sedimentary evolution of the Xiyang tidal channel between marine isotope stage (MIS) 7 and MIS 5 were summarized as follows: First is the stage of marginal bank and riverbed developments in the tidal estuary under a relatively high sea level and strong hydrodynamic conditions during MIS 7 (core section: 36.10–26.65 m). The sediments deposited in this stage were mainly affected by the paleo-Changjiang River and characterized by a coarse grain size (mean: 4.02 Φ) and relatively high magnetic susceptibilities (mean: 27.06 × 10−8 m3·kg−1), with small fluctuations which were strongly and positively correlated with the sand component. Second is the stage dominated by fluviolacustrine and littoral environments with the weak hydrodynamics during MIS 6–5, in which the climate changed from cold and dry to warm and humid as the sea level rose after a drop (core section: 26.65–15.77 m). The sediments deposited in this stage were characterized by a fine grain size (mean: 5.27 Φ) and low magnetic susceptibilities with minor variations (mean: 10.83 × 10−8 m3·kg−1) which were weakly and positively correlated with the coarse silt component. Third is the stage of delta front in the tidal estuary with a relatively high sea level and strong hydrodynamics during MIS 5 (core section: 15.77–0 m). The sediments deposited in this stage were strongly influenced by the paleo-Yellow River and characterized by a relatively coarse grain size (mean: 4.86 Φ), and high magnetic susceptibilities (mean: 37.15 × 10−8 m3·kg−1) with large fluctuations which were weakly and positively correlated with the sand and coarse silt components. [ABSTRACT FROM AUTHOR]

Southeastern China's coastal region is considered one of the key areas for studying prehistoric human–land relationships in the Western Pacific region. This region, which is rich in records of marine civilization, provides an ideal location for recording coastal environmental evolution. In this study, the chronological framework of three borehole cores recovered from Haitan Island, South China, near the Keqiutou group of sites, was established using both optically stimulated luminescence (OSL) and accelerator mass spectrometry radiocarbon (AMS 14C) dating techniques. Various analyses, including lithologic characteristics, chroma, clay–water electric conductivity (EC), grain size and elemental geochemistry, were conducted to elaborate the sedimentary sequence and its paleoenvironmental implications. The findings suggest that (i) since the late Quaternary, the Haitan Island sedimentary sequence can be divided into three deposition stages: Old Red Sand formed during Marine Isotope Stage 3 (MIS3), intermittent sedimentation during the Last Glacial Maximum and coastal aeolian deposition during the Holocene. Furthermore, the study reveals that terrestrial debris was significant as a material source for Haitan Island. (ii) Due to the absence of tectonic uplift, Haitan Island has no thick marine sedimentary record during the Holocene period of high sea level. The Luyangpu coastal sand sheet can be dated to 2.78 ka, which is consistent with previous reports giving dates of 2.4 ka. Prior to the formation of the sand sheet, the sedimentary environment in the area was characterized by lagoon or marsh facies. (iii) Paleoanthropological activities were influenced by sedimentary environmental evolution and geomorphic processes, among others. The Keqiutou Culture experienced high sea levels, which created an intertidal environment near the site and facilitated fishing. However, regression at 5.7 ka led to terrestrial environments, which prompted the inhabitants to migrate. Approximately 3 ka ago, sea levels rose again, coinciding with the initiation of rice cultivation. These factors may have influenced the transition from the Neolithic to Bronze Age culture. This study reconstructs evolution of the sedimentary sequence since the late Quaternary, enhancing our understanding of past human–terrestrial relationship in the region. [ABSTRACT FROM AUTHOR]

Recent research has shown the potential of speleothem δ13C to record a range of environmental processes. Here, we report on 230Th-dated stalagmite δ13C records for southwest Sulawesi, Indonesia, over the last 40,000 yr to investigate the relationship between tropical vegetation productivity and atmospheric methane concentrations. We demonstrate that the Sulawesi stalagmite δ13C record is driven by changes in vegetation productivity and soil respiration and explore the link between soil respiration and tropical methane emissions using HadCM3 and the Sheffield Dynamic Global Vegetation Model. The model indicates that changes in soil respiration are primarily driven by changes in temperature and CO2, in line with our interpretation of stalagmite δ13C. In turn, modelled methane emissions are driven by soil respiration, providing a mechanism that links methane to stalagmite δ13C. This relationship is particularly strong during the last glaciation, indicating a key role for the tropics in controlling atmospheric methane when emissions from high-latitude boreal wetlands were suppressed. With further investigation, the link between δ13C in stalagmites and tropical methane could provide a low-latitude proxy complementary to polar ice core records to improve our understanding of the glacial–interglacial methane budget. [ABSTRACT FROM AUTHOR]

The documentation and understanding of variations in the Earth's magnetic field through time is fundamental for several disciplines, but current geomagnetic models rely on datasets heavily biased toward the mid‐ and high northern latitudes. The African continent and surrounding islands and oceans are particularly underrepresented. Here, we present a new record of paleo‐secular variation (PSV) of the inclinations over the last 23 ka from Lake Chala, situated at 3°S near Mt Kilimanjaro in eastern equatorial Africa. This groundwater‐fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well‐constrained age model based on 210Pb and 14C dating. The magnetic mineralogy of the sediments is tested with rock magnetic analyses. The Lake Chala inclination record shows four highs and lows over 20 ka and compares well with that of Lake Malawi (10°S) between 20 and 16.2 ka, and from 9.8 to 2.6 ka. This record is linked to PSV records at Lakes Victoria and Malawi using a sequence slotting technique to generate a composite PSV model for east Africa. Analyzed at best‐possible resolutions up to 200 years, the Lake Chala PSV record not only represents an important contribution to improve our understanding of local and global features of the Earth's magnetic field. It also expands the utility of paleomagnetism as a key tool for dating and correlation both for archeological sites throughout East Africa and the many volcanoes, active or dormant, of the East African Rift System. Plain Language Summary: The understanding of the behavior of the Earth's Magnetic field in the geological past is based on an even spatial and temporal distribution of data collections. Nonetheless, data from large areas, such as from the African continent, remain sparse. In this study, we present new data from Lake Chala in equatorial East Africa, near Mount Kilimanjaro. The new inclination data are measured in lacustrine sediments covering the last 23 ka. We combine the data from Lake Chala with other data from Lake Victoria and Lake Malawi to produce a composite record for east African Lakes, using sequence slotting which improves the coherence between the records, whilst still constrained by the sediment age models. The composite record, centered on Lake Chala, improves our understanding of how the Earth's magnetic field changed in the recent past and can serve as an independent tool for dating nearby archeological sites as well as volcanic deposits from the African Rift emplaced in the last 23 ka. Key Points: Lake Chala contains an exceptionally well‐dated paleosecular variation record for east AfricaSequence slotting is used to refine a match to other secular variation records from east African lakesA composite paleosecular variation for equatorial east Africa is produced utilizing the combined set of control dates and magnetic records [ABSTRACT FROM AUTHOR]

The Yunnan-Tibet railway is located in the southeastern edge of the Tibetan Plateau, where tectonic plates collide and the terrain rapidly changes. Along the line, active faults develops, earthquakes occur frequently, and the intensity of earthquakes is strong, moreover, geological disasters are frequent. Hence its planning, construction, and long-term operation face severe geological safety risks. More than 10 active fault zones have been developed along the Shangri La-Bomi section of the Yunnan-Tibet railway, including the Haba-Yulong Snow Mountain east foot fault zone, Zhongdian-Longpan fault zone, Deqin-Zhongdian-Daju fault zone, Weixi-Qiaohou fault zone, Jinsha river fault zone, Batang fault zone, Lancang river fault zone, Nujiang fault zone, Bianba-Luolong fault zone, and Jiali-Chayu fault zone. These active fault zones are highly affected by fault slip dislocations, creep deformation, and the risk of triggering strong earthquakes. There is an urgent need to determine the geometric distribution and activity of regional active fault zones. Based on previous research, remote sensing interpretation, and field investigations, this article summarizes and analyzes the geometric distribution, kinematic properties, slip rate and paleoearthquake sequence of more than 10 active fault zones along the route, providing basic information for the planning, construction and safe operation of major national projects such as the Yunnan-Tibet railway.

Palynological analyzes of sediments from glacial lakes in Northern Priokhot'ye provide the first continuous records of regional vegetation responses to climate change at the end of the Pleistocene and during the Holocene. The pollen stratigraphy from these coastal sites is like that described for more northern regions of Western Beringia. Herb dominated tundra with Poaceae-forb meadows characterized the Late Pleistocene and was replaced c. 12,100 cal BP by Betula shrub tundra and then by shrub Betula-Alnus tundra. In the Middle Holocene (c. 8900-4700 cal BP), Larix-Betula platyphylla forests with an undergrowth of Pinus pumila , shrub Betula, and Alnus became widespread. Pinus pumila also formed a high shrub tundra zone above altitudinal treeline. Finds of Betula platyphylla macrofossils suggest that summer temperatures were 2–4 °C warmer than today between c. 7700 and 6700 cal BP. Variations in Pinus pollen percentages during the Middle and Late Holocene suggest changes in altitudinal treeline related to intervals of relatively cooler or warmer climates. The timing of the postglacial thermal maximum and possible shifts in altitudinal treeline suggest paleoclimatic patterns that are more like southern areas of the Russian Far East than northern regions of Western Beringia. A Late Holocene tephra was found for the first time in the lake sediments and peat exposures of Northern Priokhotye. The most likely source of this important chronostratigraphic horizon is the Shiveluch volcanic eruption (Kamchatka Peninsula) dated to 2500–2600 BP (2580–2730 cal BP). [ABSTRACT FROM AUTHOR]

The high-resolution analysis of radiolarians and silicoflagellates in sediments from Holes U1545A and U1549A drilled during IODP Expedition 385 in the Guaymas Basin, in the Gulf of California provides detailed insights into the evolution of ocean circulation and water masses, and its relation to Eastern Tropical Pacific Ocean climate conditions, over the past 31,000 cal years BP (based on AMS radiocarbon dates). In the pre-Last Glacial Maximum, the Guaymas Basin experienced alternating circulation patterns of California Current Water (CCW) and Gulf of California Water (GCW), with an extended presence of the Pacific Intermediate Water (PIW) owing to: amplified jet streams; southern movement of the California Current System (CCS) and the incursion of CCW into the gulf; and increased North Pacific Intermediate Water (NPIW) formation. The Last Glacial Maximum witnessed the incursion of CCW due to the stronger CCS. The dominance of the PIW indicates the expansion and formation of NPIW. The Heinrich-I event as manifested in the core record, displays two distinct patterns, one suggesting GCW-like dominance and the other, the occurrence of CCW. The Bølling-Ållerød interstadial featured the entry of Tropical Surface Water (TSW), GCW, and CCW, linked with the northward migration of the Intertropical Convergence Zone. In the Younger Dryas, CCW dominated, transitioning to GCW as colder climatic conditions and more intense CCS. The Holocene displayed alternating periods of TSW and GCW, with a modern monsoon regime from 7,600 to 1,000 cal years BP. From 1,000 cal years BP to the present the ITCZ shifted to the south. [ABSTRACT FROM AUTHOR]

Incised valleys are commonly investigated based on outcrop, modern setting and seismic data, which are often limited by data availability, especially for broad (ca >100 km wide) shelf settings. Consequently, few have described complete depositional systems of the incised valleys, especially those linked to their corresponding modern rivers in a source‐to‐sink framework to determine comprehensive controlling factors. This study documents Late Quaternary incised valleys and their characteristics in the Balingian – Central Luconia shelf based on regionally‐extensive three‐dimensional seismic data, two‐dimensional high‐resolution seismic data and boreholes. The three‐dimensional seismic data show that the main Tatau incised valley and tributary Suai incised valley fed the Tatau–Suai shelf‐edge delta. The Tatau incised valley is interpreted as the main incised valley based on its broader width, thicker infill, two‐tier stratigraphic architecture and its larger drainage basin area compared to the tributary Suai incised valley. The Tatau incised valley shifted its direction towards an active tectonic lineament (West Baram Line) and bypassed sediments to the deep‐water via a series of upper slope channels. The Tatau incised valley system comprises the following elements: (i) an upstream segment characterized by rivers dissecting an uplifted hinterland comprising Neogene sedimentary rocks, humid‐tropical vegetation, monsoonal climate, extremely high river discharge and sediment supply; (ii) a midstream segment comprising an emergent, vegetated (tropical rainforest to mangroves) and relatively narrow (ca 150 to 200 km wide) shelf, which was characterized by basinward‐increasing, tectonically‐driven accommodation space, valley incision and deposition; (iii) a downstream segment with increasing tidal‐influence where the Tatau and its tributary valley merged; and (iv) a short (15 to 20 km), narrow (10 to 15 km), tectonically‐controlled shelf‐edge delta and channelized upper slope. This study demonstrates the value of documenting an incised valley system in the context of its broader source‐to‐sink setting, which may provide a useful analogue for ancient incised valleys in comparable geological settings. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Earthquake Sciences is the property of China Earthquake Administration, Institute of Geophysics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Sedimentary records from the Kumtag (also known as Kumtagh) Desert (KMD) in northwestern China are investigated to better understand Late Quaternary paleoenvironmental changes in this hyper-arid region. Presented here are the results of probably the first systematic survey of sedimentary sequences from the KMD, with the chronology determined by the optically stimulated luminescence dating. The variation of sedimentary facies, supported by granular and geochemical paleoenvironmental proxies, is used to decipher the history of Late Quaternary environment changes. The results demonstrate that a constantly dry condition characterized the eastern KMD since the last glacial maximum, but with occurrences of wetter periods. From ca. 17 to 15 ka, fluvial activity was probably triggered by melting of glaciers in mountains located south of the KMD. A distinctly drier stage (ca. 13-7 ka) was recognized due to the prominent occurrence of aeolian sands. A wetter environment likely persisted between ca. 4.4 and 2.2 ka, consistent with evidence of human activities. While the causes of paleoenvironmental changes in the eastern KMD are still a matter of debate, the melting of glaciers in the Altyn-Tagh Mountains in the south must be considered as an important factor. [ABSTRACT FROM AUTHOR]

Major shifts in hydroclimate have been documented during the last deglacial period and the Holocene in south‐central Alaska. Rare freshwater calcium carbonate (marl) deposits in lakes on the Kenai Peninsula can be used to reconstruct past changes in hydroclimate, including the influence of groundwater inflow to lakes. Here, the postglacial sediment sequence from groundwater‐fed Kelly Lake (60.514°N, 150.374°W) was analyzed for multiple proxies including isotopes of carbon and oxygen in marl calcite (δ13Cmarl and δ18Omarl), and isotopes of carbon (ẟ13COM) and abundances of C and N in organic matter. Bulk sediment analyses include organic matter and calcium carbonate (CaCO3) contents, visual stratigraphy and sediment flux. These analyses extend those of a previous paleoenvironmental reconstruction from Kelly Lake, which focused on sedimentary diatom oxygen isotopes and mass balance modeling over the past 10 000 years. Here, we show that Kelly Lake was deglaciated prior to 14.6 ka, and that by 14.0 ka marl dominated the sediments, with CaCO3 precipitation probably driven by groundwater input and mediated by shallow‐water charophytes. Marl accumulation decreased as organic and clastic inputs increased between ~12.2 and 11.5 ka. This shift, together with an increase in both δ13Cmarl and δ18Omarl values and a decrease in CaCO3 content, indicates an increase in the influence of meteoric water on the hydrologic budget under wet conditions, possibly driven by a strengthened Aleutian Low atmospheric pressure cell. A shift to lower δ13Cmarl and δ18Omarl values at ~11.5 ka is interpreted as an increase in the proportion of groundwater relative to meteoric water in the lake. Beginning around 9 ka, the proportion of meteoric water input continued to increase, the surrounding coniferous forest was established, and by 8 ka, CaCO3 accumulation ended. Our results elucidate the environmental conditions under which marl was deposited during the Lateglacial and early Holocene in this part of Alaska, and demonstrate how a variety of synoptic‐ and local‐scale climatic variables can converge to influence sedimentation in a groundwater‐fed lake. [ABSTRACT FROM AUTHOR]

Abstract The documentation and understanding of variations in the Earth's magnetic field through time is fundamental for several disciplines, but current geomagnetic models rely on datasets heavily biased toward the mid‐ and high northern latitudes. The African continent and surrounding islands and oceans are particularly underrepresented. Here, we present a new record of paleo‐secular variation (PSV) of the inclinations over the last 23 ka from Lake Chala, situated at 3°S near Mt Kilimanjaro in eastern equatorial Africa. This groundwater‐fed crater lake is characterized by a high sedimentation rate (ca. 1 cm/10 years) and a particularly well‐constrained age model based on 210Pb and 14C dating. The magnetic mineralogy of the sediments is tested with rock magnetic analyses. The Lake Chala inclination record shows four highs and lows over 20 ka and compares well with that of Lake Malawi (10°S) between 20 and 16.2 ka, and from 9.8 to 2.6 ka. This record is linked to PSV records at Lakes Victoria and Malawi using a sequence slotting technique to generate a composite PSV model for east Africa. Analyzed at best‐possible resolutions up to 200 years, the Lake Chala PSV record not only represents an important contribution to improve our understanding of local and global features of the Earth's magnetic field. It also expands the utility of paleomagnetism as a key tool for dating and correlation both for archeological sites throughout East Africa and the many volcanoes, active or dormant, of the East African Rift System.

The last glacial inception was characterised by rapid changes in temperature, atmospheric pCO2, and changes in the water mass geometry of the major ocean basins. Although several climatic feedback mechanisms have been proposed to explain the glacial/interglacial cycles witnessed in the Quaternary, the exact mechanistic responses of these processes are still under constrained. In this study we use proxies including planktonic foraminifera compositional assemblages and oxygen stable isotopes to reconstruct past changes in sea surface productivity, stratification, and carbonate dissolution. We use core SIS-249 (2,091 mbsl, western South Atlantic 30°S 47°W), spanning 30–110 thousand years ago (ka), and currently bathed by modern Northern Component Water. We test existing hypotheses suggesting that the orbital obliquity cycle modulates the biological pump in the study area. Spectral analysis run on our synthesised productivity proxies recognises a ~43 kyr-cycle, related to the obliquity cycle. We propose that the enhanced productivity is produced by two mechanisms: i) the glacial upwelling of subsurface nutrient-rich waters and, ii) the continental (wind-driven dust and riverine outflows) fertilisation of the photic zone, with the latter process being obliquity-paced. We also suggest that not only the increased organic matter export but also a change in its bioavailability (from refractory to labile) led to calcium carbonate dissolution, as the degradation of the more soluble organic matter decreased the pH of the glacial bottom water, partially dissolving the calcium carbonate. Although our correlation analyses show a strong benthic-pelagic coupling through the relation between the enhanced biological pump and carbonate dissolution (ρ

The cliff embankments are covered as sediments from the floodplain run on both sides of the river. Various sediments transportation and depositional mechanism are contained in these floodplain deposits. For better understanding of depositional history of the floodplain sediments cliff embankments along the Sai River at the villages of Chaukhada and Khatihara in the districts of Pratapgarh and Jaunpur, respectively, were analysed using a laser particle size analyser. The common facies observed in the studied sections are very silty sandy mud, very silty sand, slightly silty sand and very silty slightly sandy mud accordingly. Indurated calcretes are also observed in the very silty sandy mud layer in the Chaukhada section. The Chaukhada section has mean size value ranging from 2.80 phi to 4.98 phi while Khatihara section has these values ranging from 3.80 phi to 4.27 phi, implying coarse silt to very fine sand size range for both the cliff section. The sediments in both of the investigated cliff sections are poorly to very badly sorted, as seen by the sorting (standard deviation) values for the Chaukhada section, which are ranging from 1.12 phi to 2.22 phi, and the Khatihara section, ranging from 1.30 phi to 1.84 phi. The sediment samples displayed the skewness values ranging from 0.23 to 0.34 for the Chaukhada section and 0.09 to 0.32 for the Khatihara section, indicating that the sediments are very finely skewed. The kurtosis value ranging between 1.24 to 1.73 for the Chaukhada section and 1.22 to 1.72 for the Khatihara sections shows that the sediments are leptokurtic to very leptokurtic in nature. Bivariate plots of textural parameters have been also utilized to figure out the depositional environment. The C–M plot indicates that the graded to uniform suspension was the primary mechanism of transportation for all the sediments.

The Sheyang estuary is located on the northern Jiangsu muddy coast, in the western South Yellow Sea, and in the transition area between the eroded coast of the abandoned Yellow River delta and the silted coast of the central Jiangsu. This area is also one of the key areas of interactions between the paleo-Yellow River and paleo-Changjiang River during the late Quaternary. In order to investigate deeply the late Quaternary sedimentary sequence models of coasts and continental shelves under the interactions of the above two large rivers, the sedimentary sequence and age of the core NTCJ1 drilled at the Sheyang estuary were re-examined and re-interpreted recently, based on the existing data on lithology, grain size, ostracods, foraminifera, clay minerals, geochemical elements, and Electron Spin Resonance (ESR) dating, together with other adjacent key cores and shallow seismic profiles. The three new perspectives were summarized as follows: Firstly, the 22.00 m-long core NTCJ1 recorded the evolution of the sedimentary environments since Marine Isotope Stage 5 (MIS 5), and the first continental facies layer formed in MIS 4-2 is supposed to be missing; therefore, the MIS 1 marine facies layer directly overlays on the MIS 5 marine facies layer. Furthermore, the second continental facies layer formed in MIS 6 and/or the stage of the relatively low sea-level of MIS 5 has not been drilled yet. Secondarily, the middle-upper part of the NTCJ1 core sediments (0.00–17.95 m) are characterized by a finer grain, with a predominantly silty texture and dark yellow tone, and from bottom to top it shows a change from fine to coarse and then to fine in grain size, which could be substantially interpreted as the abandoned Yellow River deltaic deposits mainly formed in 1128–1855 CE, and may contain a small amount of Holocene coastal-shallow marine deposits at the bottom; however, it is difficult to identify them currently. Thirdly, the lower part of the NTCJ1 core sediments (17.95–22.00 m) have not yet been drilled through and are characterized by a coarser grain, with a predominantly fine sandy texture and dark grey tone, which could be interpreted as a delta front deposit in the MIS 5 tidal estuary and were obviously influenced by the paleo-Yellow River. [ABSTRACT FROM AUTHOR]

Sedimentary records from the Kumtag (also known as Kumtagh) Desert (KMD) in northwestern China are investigated to better understand Late Quaternary paleoenvironmental changes in this hyper-arid region. Presented here are the results of probably the first systematic survey of sedimentary sequences from the KMD, with the chronology determined by the optically stimulated luminescence dating. The variation of sedimentary facies, supported by granular and geochemical paleoenvironmental proxies, is used to decipher the history of Late Quaternary environment changes. The results demonstrate that a constantly dry condition characterized the eastern KMD since the last glacial maximum, but with occurrences of wetter periods. From ca. 17 to 15 ka, fluvial activity was probably triggered by melting of glaciers in mountains located south of the KMD. A distinctly drier stage (ca. 13–7 ka) was recognized due to the prominent occurrence of aeolian sands. A wetter environment likely persisted between ca. 4.4 and 2.2 ka, consistent with evidence of human activities. While the causes of paleoenvironmental changes in the eastern KMD are still a matter of debate, the melting of glaciers in the Altyn-Tagh Mountains in the south must be considered as an important factor. [ABSTRACT FROM AUTHOR]

Submarine CO2 emissions are a recent (probably younger than about 5 ka) expression of volcanism at Vulcano Island (off NE Sicily), a Mediterranean natural laboratory for the study of ocean acidification. An impoverished molluskan association is known from the naturally acidified waters of Vulcano, at Levante Bay, where pH drops to 5.64. Here we describe a new gastropod, Alvania acida sp. nov., living in the bay, and found at the nearby site of Capo Milazzo (NE coast of Sicily) within a Late Pleistocene paleocommunity related to vegetated bottoms. The study species underwent a habitat change during its short evolutionary history, resulting in the recent adaptation to the CO2 seep at Vulcano. Similarly to the gastropods Tritia corniculum and T. neritea from the same seep, A. acida was up to 24% smaller than fossil shells from Milazzo, showing a further probable case of adaptation to high‐CO2 waters through dwarfing. The new species shows distinctive features: an inflated shell; very convex, axially ribbed whorls; weak spiral cords. Because of its current distribution, limited to Levante Bay, and anthropogenic pressure from tourism affecting the site, A. acida deserves protection. [ABSTRACT FROM AUTHOR]

The Sunda Shelf plays a key role in the sedimentation of the southern South China Sea (SCS). However, the impact of past climate changes on sediment transfer to the Sunda Shelf and the southern SCS is still unresolved. Here, we present new data on grain size, clay mineralogy, and Sr‐Nd isotopes of three marine cores, river sediments, and surface sediments of the Sunda Shelf. The results indicate that clay fractions of the central Sunda Shelf and the Gulf of Thailand derived mainly from the Mekong River and the rivers of northern Thailand since the last deglaciation. Significant changes in sediment sources are observed at 7.5 cal ka BP. From 13.3 to 7.5 cal ka BP, sediments in the Gulf of Thailand mainly originated from the rivers of northern Thailand, with contributions from the Mekong River increasing after 7.5 cal ka BP. An opposite shift is observed in the central Sunda Shelf. Such variations in the spatial distribution result from a combination of sea level and East Asian monsoon effects. After 7.5 cal ka BP, less Mekong River sediments were transported southeastwards into the southern SCS, and more sediments were gradually trapped within the delta and transported in a southwesterly direction into the Gulf of Thailand due to intense East Asian winter monsoon, which forced a strong southwestward coastal current. Our results demonstrate the important impact of East Asian winter monsoon strengthening and sea level rise in the mid‐Holocene, which can change sediment sources and transport processes on the Sunda Shelf. Plain Language Summary: Sea level and monsoon are two important factors controlling sediment transfer in the tropical and subtropical continental marginal seas. However, the impact of past sea level and monsoon changes on mineralogical composition and sediment transfer to the Sunda Shelf (the largest low‐latitude continental shelf) and the southern South China Sea (SCS) is unclear. This study provides new data on grain size, clay mineralogy, and Sr‐Nd isotopes of sediment from marine cores, river sediments, and surface sediments of the Sunda Shelf to constrain sediment sources and climatic control on sediments deposited on the Sunda Shelf since the last deglaciation. We find that the Mekong River and the rivers of northern Thailand are two major sediment sources to the Sunda Shelf. An opposite shift of sediment sources at 7.5 cal ka BP is observed between the Gulf of Thailand and the central Sunda Shelf, which results from the transfer of the Mekong River sediments between the southern SCS and the Sunda Shelf caused by sea‐level rise and East Asian winter monsoon strengthening in the mid‐Holocene. Our results highlight that sea level and East Asian winter monsoons can significantly change sediment sources and transport processes on the Asian low‐latitude continental shelf. Key Points: Clay minerals and Sr‐Nd isotopes identified sediment sources to the Sunda Shelf since the last deglaciation as Mekong and Thailand riversEstimation of the Mekong and Thailand river inputs to the sedimentation of the Sunda Shelf and the southern South China SeaSea‐level rise and East Asian winter monsoon strengthening drove major sediment‐source changes on the Sunda Shelf at 7.5 ka BP [ABSTRACT FROM AUTHOR]

We inferred the annual isotopic diet (δ13C) of an individual of the giant ground sloth Eremotherium laurillardi found in Toca dos Ossos (Ourolândia, Bahia, Brazil) through the extension of its third inferior molar. This individual lived in the region at 40,779-39,617cal yr BP. One year of its life was recorded in a length of 67 mm in the tooth. Two years were recorded in this molariform, during which the diet and climate did not change much, and substantial precipitation occurred during the middle of the year, which is in opposition to the modern pattern. The mean carbon (μδ13C=-13.9 ± 1.8‰) and oxygen (μδ18O = 22.5 ± 2.9‰) isotopic values were similar to values for other individuals of the species found in the same cave but different from the values found in other localities of the Brazilian Intertropical Region, which allows us to suggest that this region had more precipitation and lower temperatures in comparison to today. The oxygen isotopic values found in dated fossils of E. laurillardi and from two other taxa found in the same cave (Toxodon platensis, and Notiomastodon platensis) could help in the understanding of the climatic variation that occurred in the region. [ABSTRACT FROM AUTHOR]

Shelter caves serve as crucial repositories that provide valuable insights into Late Pleistocene–Holocene depositional mechanisms and environmental changes. In this study, we conducted a stratigraphic analysis of the easternmost cave-fill succession within the Santuario della Madonna cave, located along the Tyrrhenian coasts of southern Italy. By examining the cave-fill deposits and their relationship with archaeological successions from previous excavation campaigns, we aimed to enhance our understanding of sedimentary evolution, specifically, the interplay between local and global environmental factors. A comprehensive sedimentological analysis was conducted, enabling the identification of three distinct sedimentary facies within the clastic succession that overlays the calcareous cave roof. Our findings reveal a noticeable shift in cave sedimentation processes, characterized by a gap in detritus accumulation followed by the deposition of flowstones. Furthermore, the presence of oversized boulders within the succession was attributed to failures from the cliffs that overhang the cave opening. We interpret these boulders as possible evidence of cave collapses induced by earthquakes, similarly to rockfall phenomena observed in the archaeological test pits within the shelter, which show a strong correlation with paleoseismic events. [ABSTRACT FROM AUTHOR]

Close relationship exists between the Mg/Ca ratio in foraminiferal shells and the calcification temperature. Even when most paleoceanographic studies focused on near-surface property reconstructions leaving the deep ocean less explored, during the last years, new Mg/Ca-temperature calibrations were established for the benthic genera Uvigerina and Cibicidoides. Among the main conclusions, it has been established that secondary factors exist affecting the Mg incorporation into the benthic shells, particularly at low temperatures. In order to establish a potential relationship between the Mg/Ca ratios of the aforementioned genera for the western South Atlantic and tropical Atlantic, 38 core-top samples are analyzed here. Our results confirm the existence of other parameters than just temperature affecting Cibicidoides and Uvigerina Mg/Ca, suggesting that the effect of all these other parameters together produces a variable "offset" between both genera that can be linearly approached. We develop an algorithm that allows transforming the Mg/Ca data measured on one of these two genera into the other. This not only would allow performing a continuous Mg/Ca record independent of which benthic genera is available for study but also potentially leads to new and more accurate Mg/Ca-temperature calibrations allowing to get more, high-resolution bottom water temperature reconstructions. [ABSTRACT FROM AUTHOR]

The Belt of Schuppen (BoS) of Nagaland is a NE-SW trending linear zone lying adjacent to the Brahmaputra Valley of Assam in Northeast India. Geomorphic, stratigraphic and chronologic data from the Dzüdza and Chathe river valleys that cut across the BoS have been studied to understand the influence of climate on landform evolution in parts of the BoS. Fluvial landforms in the Dzüdza and Chathe river valleys evolved in four major phases bracketed between 22–17 ka (Phase IV), 13–9.0 ka (Phase III), 7–5 ka (Phase II) and 3.5–1.5 ka (Phase I), indicating multi-centennial to millennial changes in monsoon intensity. Climatically, Phase-III was dominated by valley aggradation initiated by onset of the Indian Summer Monsoon (ISM) and persisted intermittently till the early Holocene-strengthened ISM. The other phases of aggradation are attributed to transient or weak ISM. The present study suggests that fluvial aggradation was associated with enhanced precipitation and sediment supply in the BoS valley, whereas the transient and weak ISM is manifested in episodic pulses of alluvial ingression from the tributaries to the trunk valleys; along with post depositional tectonic modifications of the landforms. [ABSTRACT FROM AUTHOR]

To reveal the characteristics and environmental indications for the combination of the grain size and magnetic susceptibility of coastal sediments, we provided a necessary basis for further study on their genetic mechanisms. Based on the data of grain size and magnetic susceptibility of the 36.10 m long core 07SR01 sediments in the Xiyang tidal channel of western South Yellow Sea, we analyzed their variations and correlations and further revealed their environmental indications and corresponding regional sedimentary evolution via the combination of the aforementioned analysis results, the reinterpretation results of the sedimentary sequence and the age of core 07SR01 and shallow seismic profiles, and the findings of climate and glacial–eustatic cycles during Late Quaternary. The three stages of the sedimentary evolution of the Xiyang tidal channel between marine isotope stage (MIS) 7 and MIS 5 were summarized as follows: First is the stage of marginal bank and riverbed developments in the tidal estuary under a relatively high sea level and strong hydrodynamic conditions during MIS 7 (core section: 36.10–26.65 m). The sediments deposited in this stage were mainly affected by the paleo-Changjiang River and characterized by a coarse grain size (mean: 4.02 Φ) and relatively high magnetic susceptibilities (mean: 27.06 × 10−8 m3·kg−1), with small fluctuations which were strongly and positively correlated with the sand component. Second is the stage dominated by fluviolacustrine and littoral environments with the weak hydrodynamics during MIS 6–5, in which the climate changed from cold and dry to warm and humid as the sea level rose after a drop (core section: 26.65–15.77 m). The sediments deposited in this stage were characterized by a fine grain size (mean: 5.27 Φ) and low magnetic susceptibilities with minor variations (mean: 10.83 × 10−8 m3·kg−1) which were weakly and positively correlated with the coarse silt component. Third is the stage of delta front in the tidal estuary with a relatively high sea level and strong hydrodynamics during MIS 5 (core section: 15.77–0 m). The sediments deposited in this stage were strongly influenced by the paleo-Yellow River and characterized by a relatively coarse grain size (mean: 4.86 Φ), and high magnetic susceptibilities (mean: 37.15 × 10−8 m3·kg−1) with large fluctuations which were weakly and positively correlated with the sand and coarse silt components.

The climate of Africa's southwestern Cape is characterised by a strongly seasonal winter precipitation regime, with late Quaternary climate variability generally considered to have been driven by the position of the southern westerlies. This paper presents a unique ∼70,000 year-long palaeoclimatic record from a rock hyrax midden from South Africa's winter rainfall zone, enabling the analysis of regional climate systems since the beginning of marine isotope stage 4. The data suggest that the last glacial period was relatively humid compared to the Holocene, likely due to cooler temperatures, more extensive Antarctic sea-ice extent and an equatorward displacement of the westerly storm track. However, orbital-scale climate variability associated with the 23 kyr precessional cycle primarily correlates with changes in upwelling intensity in the Benguela system, implying an important role for the blocking of tropical easterly flow in driving long-term climatic variability. These factors combined during glacial periods to significantly amplify rainfall seasonality in the southwestern Cape, bringing more winter rainfall via mid-latitude frontal systems, while reducing the proportion of summer rainfall, particularly during the glacial periods of the late Quaternary. The results therefore highlight the need to consider a complex suite of circulation systems and dynamics when inferring drivers of long-term environmental change in the region.

This study used the comparative analysis of 3 gravity cores (GCs) obtained from the shallow offshore at ~40 m water depth to reconstruct the morphological evolution of the delta (East Equatorial Atlantic). The focus of this study is on the interpretation of elemental tracers and their justification between these tracers and microfossil data to understand the impact of climate-sea level controls on the evolution of the Niger Delta during the Late Quaternary. Key elemental tracers comprising Ti, Zr, Fe and S were explored to strengthen this concept. High Ti/Zr ratio values down-hole indicate fluvial transport of terrestrial components to the marine setting (20–11.7 ka), whereas high values of Fe/S ratio up-hole provide an extent of inherent marine shale of the Niger Delta (11.7–6.5 ka). In addition, the integrated multiple proxy (mangrove and hinterland pollen, planktonic foraminifera and sedimentary facies) with elemental tracer ratios provided robust and coherent information for delineating the late glacial (MIS2) prograding and interglacial (MIS1) retrograding deltaic transition, respectively. The overall trends of the two elemental tracer ratios (Lower and Mid-upper depths of the GCs) provide a new distinction on the depositional patterns (prograding and retrograding delta) to determine the proximal/upper (clay, silt and very fine sand) and distal offshore/lower shorefaces (coarse-medium sand), and gross palaeoenvironments based on planktonic foraminifera records. These sequential records provide a new clue as evidence of the morphological evolutionary stages (delta plain, delta front and prodelta) of the Niger Delta landscape, gross palaeoenvironments, and vegetation dynamics (pollen data) during two distinct time-bound intervals (20–6.5 ka), which potentially delineate the climate and sea level regime of the coastal offshore. [ABSTRACT FROM AUTHOR]

This article aims to refine the description of the artefacts and the geomorphological, geological, pedological and chronological (optically stimulated luminescence (OSL) analyses of sedimentary deposits) characterisation of the Rincão I site (southeastern Brazil) to contribute to the understanding of early human–environment interactions. The archaeological site occupation took place on hillslopes truncated by the Mogi‐Guaçu River's lateral (~1200 m) and vertical (~5 m) movements during the Late Quaternary, in an area where in situ bedrock outcrops are uncommon. This geological context favoured human groups simultaneously having access to the resources provided by the alluvial plain and hillslopes. Here we describe how about three hundred lithic artefacts are associated with soils that originated from sandy colluvium with OSL ages between 20.3 and 5.5 thousand years. These ages are consistent with the local palaeopedological and geomorphological contexts of landscape changes, and partly controversial from the perspective of models currently in vogue for the human occupation of southeastern Brazil. The vestiges of past human presence amid the hillslope sandy colluvium deposits include: 1) a set of flakes and formal artefacts (one stemmed point and three convex artefacts) made of sandstone obtained from hillslopes near (<10 km) the site; and 2) predominant detritus and flakes of quartz and flint obtained mostly from the adjacent (<1.5 km) alluvial plain, linked to flaking sequences other than those of the formal artefacts. Only quartz artefacts were found in the lower levels of the site stratigraphy, whereas in the intermediate and upper levels quartz, flint and sandstone artefacts were found, suggesting that there were changes in the raw materials used for flaking over time. The formal artefacts from the site have technological attributes like the ones observed in assemblages associated with a previously known lithic industry (Rioclarense), but a different pattern of choice of raw materials. This suggests that technical standards underwent a process of adaptation to the environmental particularities surrounding the Rincão I site. [ABSTRACT FROM AUTHOR]

Research into river processes in different climatic and geomorphic areas is vital for a clearer understanding of the non-linear responses of rivers to climate change. The Huaihe River (HHR) Basin, located in China's North–South Transition Zone (NSTZ), provides an ideal environment in which to explore river responses to climate change within a humid/semi-humid transitional area. Based on optically stimulated luminescence (OSL) and 14C dating, combined with sedimentary stratigraphic analyses, we reconstructed the river processes of three sedimentary sequences in the upper HHR since the Late Quaternary. Our results showed that the upper HHR was characterized by aggrading meandering channels from the Last Glacial Maximum (LGM) to 0.5 ka, and an aggrading wandering channel from 0.2 ka to the present. Two periods of downcutting occurred during 5.8–3.0 and 0.5–0.2 ka, respectively. The river incision is potentially linked to changes in the climate during the Mid–Late Holocene transition and the Little Ice Age (LIA). However, there have been no marked changes in channel patterns in the upper HHR since the LGM. This phenomenon reflects the influence of vegetation on channel patterns during climate change. Our results showed that the fluvial processes in different climatic and geomorphic areas are controlled by the local hydroclimatic regime. [ABSTRACT FROM AUTHOR]

The temporal distribution of trace elements in a sediment core (SK117/GC-08) indicates minor changes in oxygenation during the last 100 kilo years in the bottom waters of the deeper eastern Arabian Sea. The high values of Mn, Co, Cu, Mn/Al, Co/Al, Cu/Al, V/Cr, and V/(V + Ni) in the sediments during interglacials and interstitials collectively indicate oxic conditions during warm periods. The high values of Cr, Ni, V, Mo, Cr/Al, Ni/Al, and Ni/Co in sediments during glacials and stadials collectively indicate dysoxic to suboxic conditions during the colder last glacial maximum and during the entire marine isotope stage two. The bottom waters have never experienced anoxic conditions. Multivariate statistics showed the attribution of the trace elements in two factors: cluster 1 (Co, Cu, Mn) was enriched during oxic conditions and cluster 2 (Cr, Mo, Ni, V) was enriched during dysoxic to suboxic conditions. Oxygenation conditions are mainly driven by variations in monsoon-controlled surface water productivity and changes in the flux of circumpolar deep water. The dysoxic to suboxic bottom water conditions developed at the core location during colder climates are very well synchronised with an increased organic matter flux. The main factor that controls the accumulation of the organic-rich sediments in the eastern Arabian Sea during a glacial is the increase in the supply of organic matter from increased primary productivity in the surface waters, controlled by winter monsoon winds, and localized convective mixing. During warmer interglacials and interstadials, the core location has remained well ventilated. [ABSTRACT FROM AUTHOR]

In recent years, coastal areas have been threatened by many potential hazards due to global warming, glacier melting and sea level rise. Understanding their evolutionary history and development trends can help predict disasters and further reduce the corresponding losses. The Hanjiang River delta in the southeastern part of China is the second largest delta in Guangdong Province and has such challenges. Studying the sedimentary evolution and delta initiation of the Hanjiang Delta is beneficial for understanding the response of the Hanjiang Delta to present and future sea level and climate changes. In this research, we drilled a series of cores from the Hanjiang subaqueous delta, which contains information on the sedimentary environment, climate change and sea level change during the late Quaternary. Combined with previous research results and under the constraint of high-precision and high-resolution AMS14C and OSL, we carried out a multi-proxy analysis that included micropaleontology and grain size to obtain information on the sedimentary environment, sea level change and climate change. We then further discussed the initiation of the Hanjiang delta and its primary factors. The Quaternary sediments began depositing in the early Late Pleistocene (MIS5), and three sedimentary cycles can be recognized from bottom to top. The dating results also indicate that the first two cycles were formed during the late Pleistocene, while the last cycle was formed during the Holocene. The initiation of the Hanjiang Delta was indicated by a progradation in the process of a transition from estuary to a typical delta. At this time, the rate of delta progradation seaward was fast, and increasing amounts of sediments moved through the third line of islands into the sea. The barrier–lagoon system began to develop in the estuary of Hanjiang during this period. With the sequential construction of the delta, the lagoon was filled and covered by delta deposition, and the barrier bar moved to the sea; thus, the barrier-coast delta depositional model was established in the study area. Since the last glacial period (LGM), the Hanjiang River Delta and other river deltas in the region seem to have experienced similar evolutionary histories, including the filling of incised paleo-valleys and estuaries in the Early Holocene and deltaic progradation in the Middle to Late Holocene, controlled by sea level change. [ABSTRACT FROM AUTHOR]

Speleothem oxygen isotope records (δ18O) of tropical South American rainfall in the late Quaternary show a zonal "South American Precipitation Dipole" (SAPD). The dipole is characterized by opposing east‐west precipitation anomalies compared to the present—wetter in the east and drier in the west at the mid‐Holocene (∼7 ka), and drier in the east and wetter in the west at the Last Glacial Maximum (∼21 ka). However, the SAPD remains enigmatic because it is expressed differently in western versus eastern δ18O records and isotope‐enabled climate model simulations usually misrepresent the magnitude and/or spatial pattern of δ18O change. Here, we address the SAPD enigma in two parts. First, we re‐interpret the δ18O data to account for upwind rainout effects that are known to be pervasive in tropical South America, but are not always considered in Quaternary paleoclimate studies. Our revised interpretation reconciles the δ18O data with cave infiltration and other proxy records, and indicates that the centroid of tropical South American rainfall has migrated zonally over time. Second, using an energy balance model of tropical atmospheric circulation, we hypothesize that zonal migration of the precipitation centroid can be explained by regional energy budget shifts, such as changing Saharan albedo associated with the African Humid Period, that have not been modeled in previous SAPD studies. This hypothesis of a migrating precipitation centroid presents a new framework for interpreting δ18O records from tropical South America and may help explain the zonal rainfall anomalies that predate the late Quaternary. Plain Language Summary: Paleoclimate data suggest that, in the last ∼25,000 years, tropical South American precipitation has changed substantially, but in opposite directions between the east and west. This opposing east‐west pattern in past rainfall is known as the "South American Precipitation Dipole," and its end‐member states approximately coincide with the Last Glacial Maximum (∼21,000 years ago) and mid‐Holocene (∼7,000 years ago), respectively. However, the cause of the dipole is debated because different models produce different results, and the interpretations of data are in conflict. Central in this conflict are oxygen isotope tracers of past precipitation which show different trends over space. We present a new interpretation of these data, backed by model results, which suggests that the dipole is driven by the centroid, or focus, of tropical South American precipitation migrating from west‐to‐east (and back) across tropical South America. We test this precipitation centroid migration hypothesis with an energy balance climate model which reproduces the expected east‐west differences for the Last Glacial Maximum and mid‐Holocene. The precipitation centroid migration hypothesis is a possible solution to the precipitation dipole enigma, but it remains to be tested in more sophisticated climate models. Key Points: The late Quaternary South American Precipitation Dipole drives opposing east‐west precipitation anomalies in tropical South AmericaDipole transitions can drive changes in rainfall greater than 1,000 mm/yrSpatial migration of the precipitation centroid can explain dipole transitions and reconcile proxy‐model conflicts [ABSTRACT FROM AUTHOR]

Current climatic trends raise concerns about the fate of boreal forests and associated communities. To understand forest vegetation dynamics in the face of future changes, it is necessary to know how trees have responded to past climatic fluctuations. We investigated genetic data and a past distribution based on paleorecords and species distribution modeling data to determine refugia and migration routes of Siberian stone pine (Pinus sibirica) from the late Pleistocene to the present. Thus, we gained a deep insight into the past of Siberian stone pine. We revealed four genetic clusters of Siberian stone pine located in the following mountain systems of Siberia: the West Sayan and the Altai (WSA), the East Sayan (ES), the Kuznetsk Alatau (KA), and the Urals (U). Paleorecords and species distribution modeling indicated preservation of Siberian stone pine in these mountains and near big lakes (Lake Baikal and Lake Teletskoe) during the Last Glacial Maximum (LGM). Nonetheless, processes of migration from these refugia were heterogeneous: WSA has never expanded after the LGM beyond its current range; ES occupied the eastern geographic range of the species; KA and U had common history before the LGM and got isolated during LGM. Moreover, refugia and migration routes of Siberian forest species (Larix sibirica and Abies sibirica) were different from those of P. sibirica despite similar ecological preferences. Pinus sibirica occupied the West Siberian Plain from the Urals and Kuznetsk Alatau, whereas A. sibirica and L. sibirica expanded from Lake Baikal and the Sayan Mountains, respectively. Thus, our results substantially complement existing notions of South Siberia Mountains, Lake Baikal area, and Urals as glacial refugia for Siberian stone pine. [ABSTRACT FROM AUTHOR]

This research was intended to interpret, by means of several empirical bases, the quaternary climate variabilities in the area of Fazenda Nova. The premise that guides the investigation is that the sedimentary fills of the weathering pits favors the understanding of the landscape and geomorphological changes in the area, by means of the investigation of a depositional environment that is still closely linked to the current landscape. Due to that, the analysis of the depositional events and climate variabilities was done based on a morphostratigraphic approach, dating by Optically Simulated Luminescence (LOE), O18 isotope of carbonatic crust and phytolith analysis. The results showed that the deposits that fill the weathering pits were derived from gravitational sedimentation of the debris flow type, under torrential conditions, evidencing that the genesis of these records was associated with cycles of pedogenesis/morphogenesis under several combinations of semiaridity at work in the area. [ABSTRACT FROM AUTHOR]

The “tablelands” in Taiwan are sedimentary terraces occurring in the foreland basin west of the Neogene mountain ranges. The Miaoli Tableland consists of elevated Late Quaternary sedimentary successions, representing a change from tidal to coastal and fluvial to eolian depositional environments. The present-day morphology is a result of combined processes, including differential tectonic uplift, ongoing fluvial aggradation, and incision. Selected deposits in 10 outcrops were sampled and studied by optical dating. The deposition of fluvial sediments started after the last interglacial (<100 ka) in the southeast of the tablelands. Uplift and sea-level lowering caused a base-level fall, resulting in a stepwise redeposition of the fluvial sediments. Additionally, enhanced remobilization of fluvial sediments occurred during the cold/dry climate during Marine Oxygen Isotope Stages (MIS) 4 and 2. The depositional ages of the coastal sediments enabled the estimation of long-term uplift rates of ca. 0.5 to 3.5 mm/yr. The eolian cover sediments yielded MIS 3 (east) to Holocene ages (west). Our results provide new insight into the interplay of climate, sea-level changes, remobilization of sediments, and tectonism leading to tableland formation during the Late Quaternary. [ABSTRACT FROM AUTHOR]

Paleontological sites composed of small vertebrate specimens can contain hundreds-of-thousands of identifiable fossils, which can reveal community responses to environmental and trophic changes. However, the composition of these communities may be skewed if the taphonomic signatures of the deposits change over time and across strata. Here, we discuss the taphonomic processes that led to dense deposits of microvertebrate fossils at Natural Trap Cave, Wyoming, USA. We then evaluate the nature and consistency of the taphonomic signature across stratigraphic layers using bone breakage rates and bone processing information. Natural Trap Cave is a pitfall cave that has an excellent record of vertebrate communities over the last 35,000 years. Along the North Wall of the excavation site, microvertebrate fossils form a dense accumulation, raining down from a packrat (Neotoma) nest located ∼20 m above the floor of the cave. Using the breakage rates of micromammal limb bones, we evaluate whether the accumulation mechanism appears consistent across strata. We demonstrate that the variation in breakage rates from Natural Trap Cave's strata cluster together when compared to breakage rates for different predator types (mammalian carnivores, raptors, and owls). We then demonstrate that the variation in breakage rates from the three strata is less than would be expected if it were the result of a change in major predator type across the strata. Our analysis of depositional taphonomy at Natural Trap Cave provides confidence in the reliability of the microvertebrate community record, paving the way for future paleoecological analyses. [ABSTRACT FROM AUTHOR]

This study aims to investigate Sabzevar playa in the northeast of the Great Kavir in terms of geomorphology, bulk and clay mineralogy, as well as the geochemistry of core sediments from the surface to a depth of 1 m. The results suggest that up to 50% of Sabzevar playa is made of clastic components (mostly quartz and clay minerals), which increases toward the depth, though this trend is bucked by evaporite minerals (mostly gypsum, calcium carbonate, and halite). According to the mineralogical trend and geochemical evidence, Sabzevar brine has evolved into a Na–SO4–Cl type. Granulometry studies suggest drastic fluctuations and higher energy costs during sediment deposition at a depth of 1 m compared to the surface. The micro-morphology of quartz grains is due to the windborne surface sediments and waterborne deep grains. A combination of clay mineralogy and geochemistry of elements exhibits a higher evaporation rate at the surface than at a depth of 1 m, suggesting that the area has witnessed a climate change from a warm humid climate in the past to a warm arid climate in recent years. Sabzevar playa is characterized by an unconventional Bull’s-eye pattern with a concentration of calcite around the playa, gypsum in the center, and halite in the west. This research also explores the hydrological characteristics of the study area based on geomorphologic surfaces findings revealing that the groundwater level was higher in the west than in the center and east of Sabzevar playa, leading to the formation of halite and the development of a salt pan in the margin. [ABSTRACT FROM AUTHOR]

Limited constraints on the variability of the deep‐water production in the Labrador Sea complicate reconstructions of the strength of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Quaternary. Large volumes of detrital carbonates were repeatedly deposited in the Labrador Sea during the last 32 kyr, potentially affecting radiogenic Nd isotope signatures. To investigate this the Nd isotope compositions of deep and intermediate waters were extracted from the authigenic Fe‐Mn oxyhydroxide fraction, foraminiferal coatings, the residual silicates and leachates of dolostone grains. We provide a first order estimation of Nd release via dissolution of detrital carbonates and its contribution to the authigenic ԑNd signatures in the Labrador Sea. During the Last Glacial Maximum the Nd isotope signatures in the Labrador Sea would allow active water mass mixing with more radiogenic ɛNd values (−12.6 and −14) prevailing in its eastern part whereas less radiogenic values (ɛNd ∼ −18.4) were found on the western Labrador slope. The deposition of detrital carbonates during Heinrich stadials (2,1) was accompanied by negative detrital and authigenic Nd isotope excursions (ɛNd ∼ −31) that were likely controlled by dissolution of dolostone or dolostone associated mineral inclusions. This highly unradiogenic signal dominated the authigenic phases and individual water masses in the Labrador Sea, serving as potential source of highly unradiogenic Nd to the North Atlantic region, while exported southward. The Holocene authigenic ɛNd signatures of the coatings and leachates significantly differed from those of the detrital silicates, approaching modern bottom water mass signatures during the Late Holocene. Plain Language Summary: The Labrador Sea is an important region for deep water formation and for the ocean circulation in the Atlantic region. Over the last 32 thousand years, numerous discharges from melting glaciers added freshwater to the Labrador Sea which could help understand the future effects of current melting glaciers. This information is necessary to better constrain climate predictions in order to gauge the effects on the Global Ocean Water Circulation. However, past deep water production in the Labrador is still poorly constrained, complicating reconstruction of the Atlantic Meridional Overturning Circulation on different timescales. In this study we investigated changes in deep and intermediate water mass circulation patterns over the last 32 kyr based on the radiogenic Nd isotope compositions that serve as a water mass circulation proxy. Analysis of four marine sediment cores show that the deposition of large volumes of detrital carbonates during studied period had a large effect on the recorded in the sediment column signals. New data suggest active water mass circulation during the maximum extent of glacial ice sheets. The modern day ocean circulation patterns have emerged during the Late Holocene (6 ka). Key Points: Estimation of Nd release via dissolution of detrital carbonates and its contribution to the authigenic ԑNd signatures in the Labrador SeaDissolution of detrital dolostones in the water column during Heinrich stadials at least partially controlled ɛNd signaturesDuring the LGM generally more radiogenic signatures possibly indicate active water mass advection and mixing in the Labrador Sea [ABSTRACT FROM AUTHOR]

Although central Iran is pivotal for palaeoclimatic correlations, palaeoenvironmental data for this region is very sparse and a reliable chronology for pedogenic features is lacking. We therefore tried to answer the question how the environmental conditions and, in particular, the climate developed over time by using the isotopic signatures of pedogenic carbonates. We present a chronology of pedogenic carbonates in association with stable carbon and oxygen isotopes in both the matrix and coating carbonates of a relict palаeosol (Baharan palaeosol) in central Iran to understand the dynamics of environmental changes in this region during the late Quaternary. The palаeosol experienced several episodes of leaching during pedogenesis as reflected in its morphology (carbonate coatings under the rock fractions) and geochemical characteristics (Ba/Sr ratios). The δ18O values of both the matrix and coating carbonates in the upper 60 cm (especially in the upper 20 cm) of the pedon are enriched (∼4‰) compared to the subsoil and are mainly related to the impact of evaporation. Moreover, the δ13C values of the carbonates are in isotopic disequilibrium with the modern vegetation cover (desert shrubs) of the study area and are enriched in different degrees. The carbonates in the top 60 cm are formed by the input of atmospheric CO2 and calcareous dust while deeper carbonates formed in an environment exhibiting a higher contribution of C4 plants. Based on the radiocarbon chronology of carbonate coatings, it seems that three main stages of palaeoenvironmental changes occurred in the region during the last 32 ka. The first stage lasted ca. 5,000 years (between 31.6 and 26.0 ka) and was accompanied by deep leaching under sub-humid climatic conditions and the expansion of C4 plants. Under the dominance of semi-arid conditions during the second stage until the late Holocene, a gradual increase in the δ18O values and aridity occurred in the region. The last phase in the late Holocene was characterised by the establishment of an arid and evaporative environment with a sparse vegetation cover. A climatic correlation using the oxygen isotopic composition of secondary carbonates from the Baharan palaeosol, Soreq Cave (the Levant) and Hoti Cave (Oman; both having speleothems records) suggested a climatic connection between central Iran and the eastern Mediterranean during the late Pleistocene and between central Iran and northern Oman during the late Holocene.