An MIS 8 terrestrial record retrieved from a glacially overdeepened basin in the northern foreland of the European Alps

Climatic control on magnetic mineralogy during the late MIS 6 - Early MIS 3 in Lake Chalco, central Mexico

We investigated the late Quaternary abyssal benthic foraminiferal faunas from the upper 209 cm of sediment core (KODOS PC5101) in order to understand the biotic response of abyssal benthic foraminifera to the glacial-interglacial cycle in the eastern equatorial Pacific Ocean. Three factor assemblages were identified in the benthic foraminiferal faunas of core PC5101: the common deep-sea fauna for which there is some seasonal food supply (Factor 1 assemblage), the fauna that suffer from possible carbonate undersaturation in the deep waters of the Southern Ocean or low food supply (Factor 2 assemblage), and the fauna for which there is seasonal food supply (Factor 3 assemblage). The low Horn’s index of overlap indicates the instability of benthic faunal association during the Marine Isotope Stage (MIS) 5. There are reasonably good correlations between the Factor 1 or 2 assemblages and the CaCO3 or biogenic opal content in the earlier part of the studied interval (early MIS 5 to MIS 7), whereas there is no significant correlation in the later part (MIS 1 to late MIS 5), except for a weak correlation between the Factor 1 assemblage and biogenic opal content. It is suggested that carbonate undersaturation at the sediment-water interface on the seafloor was one of major factors that influenced benthic foraminiferal fauna at the site of our study, particularly from early MIS 5 to MIS 7. However, additional factors also affected benthic foraminifera from MIS 1 to late MIS 5. For example, enhanced periodicity of the food supply from the surface ocean (i.e., seasonality or ENSO variability) might be another factor responsible for the shift in the biotic response of abyssal benthic foraminifera deposited after MIS 5.

A benthic foraminiferal proxy record of 290 kyr, acquired from Core SH7B in the northern continental slope of the South China Sea, was studied to identify the bottom-water environment changes since marine isotope stage (MIS) 8. The changes, including oxygenation and types of organic matter flux to the seafloor, reflect the palaeoproductivity fluctuations linked to monsoon variability. Four assemblages, characterizing different palaeoenvironmental changes, have been recognized by factor and cluster analysis with 32 foraminiferal species in 93 samples (>150 µm size fraction). AssemblagePyrgospp.–Hoeglundina elegansmainly dominates during interglacial periods of MIS 7, MIS 5 and MIS 3, suggesting well-oxygenated bottom environments with low sea surface productivity linked to a weak East Asian Winter Monsoon (EAWM). AssemblageUvigerinaspp.–Globocassidulina subglobulosais composed of a constantly high percentage of shallow infaunal species, occurring in intervals of MIS 4, MIS 5, MIS 7 and MIS 8, which indicates that an enhanced EAWM led to a low seasonality of palaeoproductivity, a constant high flux of fresh and labile marine-derived organic particles to the seafloor and a low oxygen bottom environment. AssemblageMelonis barleeanus–Clavulinaspp. is characterized by species that depend on seasonal supplies of more altered refractory organic matter and is mainly distributed in interglacial periods (late MIS 5, MIS 3 and MIS 1), suggesting a high seasonality of palaeoproductivity associated with a seasonal intensification of the EAWM. With low benthic foraminiferal diversity and abundance, assemblageGlobobulimina affinis–Chilostomella mediterranensiswas identified during the intermediate MIS 8 and early MIS 2. Both substantial input of terrigenous nutrients from an increased river run-off and an increased primary productivity correlated with an enhanced EAWM have led to abundant nutrient supplies and severe bottom-water oxygen depletion. As suggested by the composition of benthic foraminiferal in Core SH7B, changes in bottom-water environments of the northern South China Sea over the last 290 kyr were driven by the fluctuating palaeoproductivity linked to the high variability of the EAWM.

OSL chronology for lacustrine sediments recording high stands of Gahai Lake in Qaidam Basin, northeastern Qinghai–Tibetan Plateau

<p>Long-range atmospheric dust transport affects the climate by impacting radiative transfer, cloud formation and the global carbon cycle. Furthermore, dust plays an important role in pedogenesis, whereas Fe-rich dust in particular influences the primary productivity of the ocean. Transport of Saharan dust via the westerlies to the Caribbean is well recorded, even under present conditions, however, its variability over Quaternary glacial-interglacial cycles is less well understood. Here, we present initial investigations into the speleothem record of long-range Saharan dust transport to the Bahamas. A stalagmite collected from -25.6 m below sea level from Abaco Island, Bahamas, macroscopically displays a tripartite structure beginning and ending with opaque crystalline calcite, but with a middle section containing striking insoluble Fe-rich layers several mm thick that alternate with finer opaque layers. The red layers are interpreted to be formed under vadose conditions and not due to precipitation of an Fe-rich crust in an unsaturated mixing zone. U-Th dating reveals that the opaque calcite sections were deposited during Marine Isotope Stage (MIS) 10 and late MIS 8, with the intervening Fe-rich section being deposited during early MIS 8. Dripstone speleothem deposition during MIS 10 and 8 therefore places an upper constraint on relative sea-level elevation of -25.6 m during those glacial periods, with the interglacial MIS 9 hiatus considered to be sea-level controlled. The Fe-rich section indicates atmospheric dust transport to Abaco Island increased during early MIS 8 synchronous with an episode of cooler sea surface temperatures in the sub-tropical Atlantic. On the other hand, the decline in dust transport during late MIS 8 is associated with higher sea surface temperatures.</p>

This contribution summarizes the most informative loess–palaeosol sequences (LPS) and fluvial terrace records from the late Middle Pleistocene (LMP) of northern France demonstrating the reliability of the cyclostratigraphic approach for the interpretation of pedosedimentary sequences controlled by major glacial–interglacial climatic cycles. In this area, continental mollusc assemblages from interglacial fluvial silts and calcareous tufas are particularly rich and diverse and marker species define the malacological signatures of each interglacial optimum for Marine Isotope Stages (MIS) 11, 9 and 5e. This approach shows that the forest was less developed during MIS 7, suggesting that climatic conditions were either drier and/or cooler than during other Pleistocene interglacials. In the Somme basin, the terrace system shows that two alluvial formations were deposited between early MIS 8 and late MIS 7. In some LPS, the occurrence of two pedosedimentary sub‐cycles (IIa and IIb), separated by a relatively long (~12 ka) and cold period, corresponding to an ‘aborted glacial’ (MIS 7d), underlines the complex pattern of this unusual ‘interglacial’. Overall, during the LMP, each soil complex corresponding to interglacial and early‐glacial periods from MIS 11 to MIS 5 is broadly made up of the same soil facies but exhibits a specific succession pattern or signature. Throughout the area, LPS show a huge change in both the deposition rates and the geographical extent of typical calcareous loess at the beginning of MIS 6. This so‐called ‘Loess Revolution’ probably reflects a change in the palaeogeography of the southern North Sea and eastern Channel source areas at times marked by the coalescence of the British and Scandinavian ice sheets. MIS 6 is also characterized by the oldest evidence of permafrost development in the area. In addition, this work allows the age of the Lower/Middle Palaeolithic boundary to be confirmed, with the oldest occurrence of Levallois technology being around 300 ka.

Indian summer monsoon variability during the past ~75 ka based on stable isotope records of sediments from NW India

The fluctuating position of the boundary between the Kuroshio (warm) and Oyashio (cold) currents in the mid-latitude western North Pacific affects both heat transport and air–ocean interactions and has significant consequences for the East Asian climate. We reconstruct the paleoceanography of Marine Isotope Stages (MIS) 20–18, MIS 19 being one of the closest astronomical analogues to the present interglacial, through multiple proxies including microfossil assemblage data, planktonic foraminiferal isotopes (δ18O and δ13C), and foraminiferal Mg/Ca-based temperature records, from the Chiba composite section (CbCS) exposed on the Boso Peninsula, east-central Japan. Principal component analysis (PCA) is used to capture dominant patterns of the temporal variation in these marine records, and shows that the relative abundances of calcareous nannofossil and radiolarian taxa are consistent with the water mass types inferred from geochemical proxies. The leading mode (36.3% of total variance) mirrors variation in the terrestrial East Asian winter monsoon (EAWM), reflecting seasonal trends dominated by the winter monsoon system. In the CbCS, this mode is interpreted as reflecting the interplay between the warm Kuroshio and cold Oyashio waters, which is likely related to the latitudinal shift of the subtropical–subarctic gyre boundary in the North Pacific. The second mode (15.4% of total variance) is closely related to subsurface conditions. The leading mode indicates that MIS 19b and 19a are represented by millennial-scale stadial/interstadial oscillations. Northerly positions for the gyre boundary during late MIS 19c, the interstadials of MIS 19a, and early MIS 18 are inferred from the leading mode, which is consistent with a weak EAWM and consequent mild winter climate in East Asia. Nonetheless, the northerly positions for the gyre boundary during late MIS 19c and early MIS 19a were not associated with subsurface warming presumably due to the suppressed gyre circulation itself caused by the weak Aleutian Low. Intermittent southerly positions for the gyre boundary are inferred for the stadials of MIS 19b and 19a. Regional sea surface temperature (SST) comparisons in the western North Pacific reveal that the moderate SSTs during MIS 19a through early MIS 18 were restricted to the mid- to high latitudes, influenced by the weak EAWM. Comparison between MIS 20–18 and MIS 2–1 suggests that glacial MIS 20 and 18 had significantly milder winters than MIS 2, likely related to the relatively weak EAWM.

Previous studies of marine sequences from the Faroe Islands region have identified a series of coarse-grained tephra horizons deposited during Marine Isotope Stage (MIS) 5. Here we reassess the MIS 5 tephrostratigraphy of the Faroe Islands region and focus on the cryptotephra deposits preserved within the fine-grained fraction of marine core LINK 16. We also extend the record to encompass the late MIS 6 and early MIS 4 periods. A density separation technique, commonly used for tephra investigations in lacustrine settings but rarely applied to marine sediments, is utilised to explore the fine-grained material and EPMA and LA-ICP-MS are employed to determine the major and trace element composition of individual tephra shards. In total, 3 basaltic and 3 rhyolitic Icelandic cryptotephra deposits with homogeneous geochemical compositions are identified — all of which have the potential to act as isochronous tie-lines. Geochemical results highlight that the Grímsvötn volcanic system of Iceland is the predominant source of the basaltic horizons and the Öraefajökull or Torfajökull systems are the likely sources of the rhyolitic deposits. Three of the horizons have been previously recognised in Faroe Islands region marine sequences, with two of these deposits traceable into a Norwegian Sea sequence. An early MIS 4 rhyolitic horizon is the most widespread deposit as it can be traced into the Norwegian Sea and to the south into a record from the Rockall Trough. Basaltic and rhyolitic horizons deposited during late MIS 6 have not been recognised in other sequences and represent new additions to the regional tephrostratigraphy.

Climate variability during MIS 20–18 as recorded by alkenone-SST and calcareous plankton in the Ionian Basin (central Mediterranean)

The Ziegler Reservoir fossil site near Snowmass Village, Colorado, provides a rare opportunity to examine environmental conditions in the Rocky Mountains during marine isotope stage (MIS) 4 (71–57 ka). Although recognized as a global-scale cold event, MIS 4 is typically absent from Rocky Mountain glacial chronologies because the geologic evidence was covered or destroyed during the subsequent, and more extensive, MIS 2 (Pinedale; 29–14 ka) glaciation. Ziegler Reservoir lies beyond the Pinedale glacial extent, which allowed for the preservation of a long-lived sequence of eolian sediments deposited in a lacustrine environment that spans from late MIS 6 (ca. 140 ka) through early MIS 3 (ca. 55 ka). Sediments dating to MIS 4 exhibit a significant increase in clay-sized particles, suggesting that the source areas, most likely nearby glacio-fluvial deposits, were enriched with fine-grained material at that time. We hypothesize that the elevated clay content was the result of rock flour production by nearby valley glaciers that were active in the Rocky Mountains during MIS 4. The results of our study illustrate how recognizing indirect evidence of glacial activity can result in a more complete record of past climate conditions than what could be achieved by the study of moraines alone.

Mineralogical and isotopic evidence for the sediment provenance of the western South Yellow Sea since MIS 3 and implications for paleoenvironmental evolution

Quaternary glaciations in the Lopu Kangri area, central Gangdise Mountains, southern Tibetan Plateau

Eemian and post-Eemian fluvial dynamics in the Lesser Caucasus

Enhanced Asian hydroclimate instability during early MIS 6.5