Early Marine Isotope Stage Research Articles

Late Quaternary geomorphology, seabed evolution, and terrigenous sediment delivery to the Pandora and Moresby Troughs, Gulf of Papua

An integrated geology and geophysics investigation has been carried out to study the late Quaternary deepwater depositional system in the Gulf of Papua (NSF-MARGINS focus area) focusing on two contrasting depocentres, Pandora and Moresby troughs. The studies incorporate multi-beam bathymetry, sub-bottom sonar, and core data in order to define and map acoustic and lithofacies; and relate depositional processes, sediment routing, timing and geomorphic products that have developed since Marine Isotope Stage (MIS) 3, ca. 40calka. 3D seafloor visualisation is used to infer sedimentary processes responsible for observed morphology, which are then placed into a chronostratigraphic framework using recently published age models of sediment cores.The peak depositional period in Pandora Trough occurred during MIS 2. At that time a large deep-sea channel network linked the Pandora and Moresby troughs, allowing long-distance sediment transport by large turbidity currents from the Papuan mainland to the Coral Sea Basin. Near the LGM, shelf-edge failure led to emplacement of mass-transport deposits on the floor of the Pandora Trough, blocking this pathway for large turbidity currents. Intermittent turbidity currents continued to feed minibasins upslope of the MTD complex until early MIS 1 (earliest Holocene).Along the shelf edge of the Papuan Peninsula, substantial sediment delivery by turbidity currents continued until middle Holocene and perhaps later; combined with bottom currents, these flows contributed to the formation of large sediment waves of Moresby Fan. However, this Holocene turbidite sedimentation does not extend much farther into the Moresby Trough, based on negligible Holocene sediment accumulation deeper in the basin.This study has shown that sediment delivery from fluvial sources to deep basins in the GoP is controlled by a complex interplay of changing sea level, evolving basin bathymetry (influenced by depositional and tectonic processes), and oceanic transport of sediment from shelf to slope. These conditions have created highly localised conduits for shelf to slope sediment delivery that respond both to global forcing (eustatic sea level) as well as local conditions (shelf gradient, mass wasting, currents, and source proximity), resulting in a complex network of deep-sea depositional morphologies active from the Last Glacial Maximum to Holocene time.

Strong coupling of centennial-scale changes of Asian monsoon and soil processes derived from stalagmite δ18O and δ13C records, southern China

The paleoclimate application of speleothem δ13C is influenced by site-specific processes. Here we present four stalagmite δ13C records from two caves in southern China, covering early and late Marine Isotope Stage (MIS) 3 and the Holocene, to investigate the spatio-temporal pattern of calcite δ13C changes and the relationship with Asian monsoon (AM) variability. In each growth period, precessional- to millennial-scale changes are clear in the δ18O record. In contrast, millennial variability is absent in the δ13C record, which characterizes persistent centennial oscillations. However, centennial-scale δ18O variations agree well with those of δ13C, with a larger amplitude in δ13C changes (about twice that of δ18O). This suggests that soil humidity balance associated with regional hydrological circulations is important for these centennial δ13C changes, although evaporation-related kinetic fractionation can induce concurrent enrichments in δ18O and δ13C. In frequency, the detrended δ18O and δ13C records are coupled at a periodicity of about 300 yr during the last glacial period and 150 yr during the Holocene. Those centennial-scale δ13C variations are generally consistent with Greenland temperature variability, indicating a climate response over broad regions. Thus, strong co-variation of δ18O and δ13C records should have a climatic origin, even if it is amplified by kinetic effects.

The ELSA-Vegetation-Stack: Reconstruction of Landscape Evolution Zones (LEZ) from laminated Eifel maar sediments of the last 60,000 years

Laminated sediment records from several maar lakes and dry maar lakes of the Eifel (Germany) reveal the history of climate, weather, environment, vegetation, and land use in central Europe during the last 60,000years. The time series of the last 30,000years is based on a continuous varve counted chronology, the MIS3 section is tuned to the Greenland ice — both with independent age control from 14C dates. Total carbon, pollen and plant macrofossils are used to synthesize a vegetation-stack, which is used together with the stacks from seasonal varve formation, flood layers, eolian dust content and volcanic tephra layers to define Landscape Evolution Zones (LEZ). LEZ 1 encompasses the landscape dynamics of the last 6000years with widespread human influence. The natural oak and hazel forests of the early Holocene back to 10,500b2k define LEZ 2. LEZ 3, the late glacial between 10,500 and 14,700b2k, shows the development of a boreal forest with abundant grass and shallow water biomass in the lakes. The maximum of the last glaciation (LEZ 4: 14,700–23,000b2k) was characterized by sparse vegetation of moss and characeae. These sediments are generally devoid of clay and sand and reveal no indication of snow-meltwater events. Accordingly, the Last Glacial Maximum (LGM) must have been extremely arid in central Europe. The sediments of the subsequent LEZ 5 from 23,000–28,500b2k preserve distinct layers of clay and coarse sand, which indicates running water with clay in suspension and ephemeral coarse-grained fluvial sediment discharge. Abundant Ranunculaceae macroremains (used for 14C dating), insects, moss and fungi sclerotia reflect a tundra environment during a time of frequent strong snowmelt events. Total carbon content, Betula–Pinus pollen and diatoms reach increased concentrations during Marine Isotope Stage (MIS) 3 interstadials that occurred between 28,500 and 36,500b2k (LEZ 6). The entire MIS3 interstadials are well documented in the organic carbon record from the Auel dry maar. The main paleobotanical indicators of MIS3 are, however, grass pollen and heliophytes, which indicate a steppe environment with scattered/patchy trees during the interstadials. The stadial phases inferred during LEZ 6 reveal initiation of eolian dust deflation. The change of the early MIS 3 forested landscape to a steppe occurred with the LEZ 7–LEZ 6 transition. This is when modern man spread in central Europe. The principle vegetation change to a steppe at 36,500b2k must have favoured the spread of horses, an important hunting prey of modern humans. We propose accordingly that the migration of the modern humans into central Europe might have been at least partly driven by climate and associated vegetation change. The LEZ 7 encompassed the time interval 36,500 to 49,000b2k and was characterized by a boreal forest with high abundance of pine, birch, as well as spruce during the interstadial events. Abundant charcoal fragments indicate that this taiga was under frequent drought stress with regular burning. The most unexpected finding, but corroborated by all our maar records is the dominance of thermophilous tree taxa from 49,000 to 55,000b2k (LEZ 8). Greenland interstadials 13 and 14 were apparently the warmest of MIS 3 according to the Eifel pollen records. The preceeding LEZ 9 from 55,000 to 60,000b2k is also dominated by spruce, but thermophilous trees were sparse. A warm early MIS3 appears plausible, because summer insolation (at 60° N) was higher in the early MIS 3 than today, ice cover was low in Scandinavia and sea-surface temperatures of the North Atlantic were almost comparable to modern values during GI-14.

Last Glacial palaeoenvironments at Lascaux, southwest France, with special emphasis on MIS 4 (Ognon II interstadial)

A deep sequence of Last Glacial peats and slope deposits at the foot of the Lascaux hill was investigated using a large array of methods (geology, geophysics, 14C and OSL dating, palynology, macro-remain analysis, entomology). The peaty levels, OSL dated to between ~73 and 60ka, are found within a doline developed in a fluvial terrace of the Vézère River. These gyttja and chalky gyttja deposits covered by fen peat yielded abundant beetle and plant (seeds, pollen) remains. Palaeoecological reconstructions suggest a cool steppe with willow stands compatible with an interstadial of marine isotopic stage (MIS) 4, probably Ognon II (GI-19.2). Aquatic and hygrophilous plants (sedges), which reflect local vegetation, and their dependent insects are equally well represented in the record. The peats are covered by a sequence of slope deposits: a coarse-grained lower unit deposited during late MIS 4, overlain by a heavily decalcified sandy unit with a boreal soil complex correlated with early MIS 3, and finally, a coarse-grained, calcareous unit formed during late MIS 3 and MIS 2 in connection with slope dynamics typical of periglacial environments. The palaeosols yielded a small Middle Palaeolithic lithic assemblage.

Palaeoproductivity linked to monsoon variability in the northern slope of the South China Sea from the last 290 kyr: evidence of benthic foraminifera from Core SH7B

Abstract 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). Assemblage Pyrgo spp.– Hoeglundina elegans mainly 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). Assemblage Uvigerina spp.– Globocassidulina subglobulosa is 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. Assemblage Melonis barleeanus – Clavulina spp. 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, assemblage Globobulimina affinis – Chilostomella mediterranensis was 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.

Similar millennial climate variability on the Iberian margin during two early Pleistocene glacials and MIS 3

Although millennial-scale climate variability (<10 ka) has been well studied during the last glacial cycles, little is known about this important aspect of climate in the early Pleistocene, prior to the Middle Pleistocene Transition. Here we present an early Pleistocene climate record at centennial resolution for two representative glacials (marine isotope stages (MIS) 37–41 from approximately 1235 to 1320 ka) during the “41 ka world” at Integrated Ocean Drilling Program Site U1385 (the “Shackleton Site”) on the southwest Iberian margin. Millennial-scale climate variability was suppressed during interglacial periods (MIS 37, MIS 39, and MIS 41) and activated during glacial inceptions when benthic δ18O exceeded 3.2‰. Millennial variability during glacials MIS 38 and MIS 40 closely resembled Dansgaard-Oeschger events from the last glacial (MIS 3) in amplitude, shape, and pacing. The phasing of oxygen and carbon isotope variability is consistent with an active oceanic thermal bipolar see-saw between the Northern and Southern Hemispheres during most of the prominent stadials. Surface cooling was associated with systematic decreases in benthic carbon isotopes, indicating concomitant changes in the meridional overturning circulation. A comparison to other North Atlantic records of ice rafting during the early Pleistocene suggests that freshwater forcing, as proposed for the late Pleistocene, was involved in triggering or amplifying perturbations of the North Atlantic circulation that elicited a bipolar see-saw response. Our findings support similarities in the operation of the climate system occurring on millennial time scales before and after the Middle Pleistocene Transition despite the increases in global ice volume and duration of the glacial cycles.

Archeological deposits at Abric Romaní extend to 110 ka: U-series dating of a newly cored, 30 meter-thick section

Recent exploratory drilling at Abric Romaní reveals that carbonate tufas similar to the archeologically rich levels excavated to date extend at least 30m beneath the current base of excavation. The present project focused on sampling and measuring a suite of new U-series dates on core samples to determine whether reliable dates could be obtained from the older tufas and, if so, their temporal extent.Using relatively small (~100mg), carefully selected samples analyzed by inductively coupled plasma mass spectrometry, we obtained a total of 20 dates for 10 core samples and one sample near the base of the current excavation. Corrections for thorium from contaminating detritus were generally negligible, as indicated by a median 230Th/232Th activity ratio of 360. At selected levels in the sequence, two or three coeval samples were prepared and analyzed in order to determine the reproducibility of their dates. Reproducibility at most levels was similar to analytical errors, consistent with rapid carbonate deposition followed by evolution of closed U–Th systems. In contrast in the sample nearest the base of the core, scatter of dates beyond analytical errors was observed among sub-samples, probably indicating failure of the U–Th system to remain closed.The dates, which preserve stratigraphic order in all cases, range from ~55ka for a sample from level N of the existing excavation to ~110ka at the base of the core. The new dates show that tufas at Abric Romaní extend at least to early Marine Isotope Stage (MIS) 5. Mean accumulation rates in the core varied widely, from a minimum of 17cm/ka during the later parts of MIS 5 to a maximum of 130cm/ka during the Last Interglacial in early MIS 5, suggesting that a wetter hydroclimate prevailed in the region during periods of low global ice volume. The new dates show that burned travertine and sand intersected by the drill-core, which are likely indicators of human presence, are as old as ~100ka. Thus, evidence for human presence at Abric Romaní now extends over ~60thousandyears.

Abrupt termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, California

AbstractThe Marine Isotope Stage 16–15 boundary (Termination VII) is the first deglacial warming step of the late Quaternary following the mid‐Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic event has remained unknown until now. Core MV0508‐19JPC from Santa Barbara Basin, California, contains a decadal‐scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (&lt;700 years), in a progression of three abrupt warming steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably abrupt with 4–5°C sea surface warming in ~50 years. The deglacial sequence contains the well‐dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal‐scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level. A warm interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox‐sensitive elements indicating sulfidic, oxygen‐deficient bottom and pore‐waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean‐atmosphere system following the MPT.

Patterns of vegetation and climate change in the northern South China Sea during the last glaciation inferred from marine palynological records

High-resolution marine palynological records from the northern South China Sea (SCS) provide new information concerning the regional history of vegetation and climate conditions during the last glaciation (~70–19cal ka BP). The preservation of rich pollen from tropical and subtropical broadleaf trees (largely composed of evergreen Quercus, Castanopsis, and Euphorbiaceae) suggests that a southern subtropical climate prevailed during the last glaciation, including the period of the Last Glacial Maximum. Relatively higher percentages of such pollen taxa occurred during Marine Isotope Stage (MIS) 3, when Phyllocladus pollen from the south also increased, indicating a warmer terrestrial climate and a strengthened East Asian summer monsoon comparing to MIS 4 and 2. Moreover, the maximum percentages of such pollen occurred during the early MIS 3, implying that an optimal climate prevailed in this period. The reconstructed terrestrial climate corresponds well to marine evidence such as δ18O values from planktonic foraminifer shell and records of sea surface temperature. This study confirmed that the regional terrestrial climate could be linked closely to changes in both global ice volume and the East Asian monsoon attributable to variations of the earth’s orbital parameters. Modern palynological investigations and statistical analyses of the pollen percentages in the profiles indicate that Pinus pollen and spores are easily transported by water flow in the northern SCS. Therefore, their relative abundance peaks suggest that several wet intervals occurred during the last glaciation.

Luminescence Dating of Fluvial Deposits from the Weser Valley, Germany

Luminescence dating was applied on coarse-grained monomineralic potassium-rich feld-spar and polymineralic fine-grained minerals of five samples derived from fluvial deposits of the Riv-er Weser in northwestern Germany. We used a pulsed infrared stimulated luminescence (IRSL) single aliquot regenerative (SAR) dose protocol with an IR stimulation at 50°C for 400 s (50 μs on-time and 200 μs off-time). In order to obtain a stable luminescence signal, only off-time IRSL signal was rec-orded. Performance tests gave solid results. Anomalous fading was intended to be reduced by using the pulsed IRSL signal measured at 50°C (IR&lt;sub&gt;50&lt;/sub&gt;), but fading correction was in most cases necessary due to moderate fading rates. Fading uncorrected and corrected pulsed IR50 ages revealed two major fluvial aggradation phases during the Late Pleistocene, namely during marine isotope stage (MIS) 5d (100 ± 5 ka) and from late MIS 5b to MIS 4 (77 ± 6 ka to 68 ± 5 ka). The obtained luminescence ages are consistent with previous &lt;sup&gt;230&lt;/sup&gt;Th/U dating results from underlying interglacial deposits of the same pit, which are correlated with MIS 7c to early MIS 6.

Palynostratigraphy and vegetation changes during the early Middle Pleistocene, based on new studies of deposits from Ferdynandów (central eastern Poland)

Abstract New palynological data from the Ferdynandów site are presented and interpreted against the background of the earlier division of this stratotype pollen sequence by Janczyk-Kopikowa (1975), with special attention to a comparison with the nearest profile of a complete Ferdynandovian succession in Łuków (Łuków Plain). The proposed division of the new pollen diagram from Ferdynandów - into two warm periods of interglacial rank separated by a succession typical of glacial periods - is based on the new division of the Ferdynandovian pollen sequence s.l., applied for the first time by Mamakowa (1996) to the Podgórze B1 pollen profile close to Nowe Miasto on the Pilica river. The two warm units and the cold one between them in the new pollen diagram from the Ferdynandów site correspond to the climatostratigraphic units named Ferdynandovian 1 and 2. Together with the cooling/glaciation (Ferdynandovian 1/2) separating them, the whole Ferdynandovian sequence s.l. can be related to the early Middle Pleistocene Cromerian Complex (Cromerian II Westerhoven and Cromerian III Rosmalen) and Marine Isotope Stages (MIS) 13-15.

A 94–10ka pollen record of vegetation change in Qaidam Basin, northeastern Tibetan Plateau

Drill core (ISL1A) was obtained from the Qarhan Salt Lake in central eastern Qaidam Basin, northeastern Tibetan Plateau (NE TP). Fossil pollen and the lithology of the core sediment were analyzed in conjunction with AMS C-14 and Th-230 dating. The results indicated that Artemisia and Chenopodiaceae dominated the steppe/desert steppe vegetation developed around the lake between 94 and 51.2 ka, corresponding with the organic-rich silty clay deposited in the core sediments. Pediastrum continuously appeared in the core sediments between 94 and 51.2 ka, indicating freshwater to oligohaline conditions of the paleo-Qarhan Lake during the late marine isotope stage (MIS) 5, MIS 4, and early MIS 3. During the 51.2 to 32.5 ka period, Ephedra dominated shrub-desert vegetation expanded in the basin, while, Pediastrum disappeared in the core sediments. The core sediments consisted of interbedded layers of halite silt and clay-rich halite between 51.2 and 32.5 ka, signifying a shift toward drier hydrologic conditions. Thus, the paleo-Qarhan Lake experienced periods of desiccation and shallow water levels. Artemisia and Chenopodiaceae dominated steppe/desert steppe vegetation appeared again from 32.5 to 253 ka, with clay-rich sediments in the core, thereby suggesting an increase of runoff from the lake under relatively wetter climatic conditions. Since 253 ka, however, pollen concentrations declined, corresponding with the amount of halite deposited in the core sediment and, suggesting a cold, dry climatic condition during MIS2. Our findings have important implications for understanding complex regional vegetation and climatic responses to large-scale forcings in the Qaidam Basin. (C) 2015 Elsevier B.V. All rights reserved.

Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal

The dispersal of human populations out of Africa into Arabia was most likely linked to episodes of climatic amelioration, when increased monsoon rainfall led to the activation of drainage systems, improved freshwater availability, and the development of regional vegetation. Here we present the first dated terrestrial record from southeast Arabia that provides evidence for increased rainfall and the expansion of vegetation during both glacial and interglacial periods. Findings from extensive alluvial fan deposits indicate that drainage system activation occurred during Marine Isotope Stage (MIS) 6 (ca. 160–150 ka), MIS 5 (ca. 130–75 ka), and during early MIS 3 (ca. 55 ka). The development of active freshwater systems during these periods corresponds with monsoon intensity increases during insolation maxima, suggesting that humid periods in Arabia were not confined to eccentricity-paced deglaciations, and providing paleoenvironmental support for multiple windows of opportunity for dispersal out of Africa during the late Pleistocene.

Orbital-scale climate variability in Arabia as a potential motor for human dispersals

The Arabian Peninsula is situated at an important crossroads for the movement of Pleistocene human populations out of, and into, Africa. Although the timings, routes and frequencies of such dispersals have not yet been confirmed by genetic, fossil or archaeological evidence, expansion into Arabia would have been facilitated by humid periods driven by incursions of monsoon rainfall, potentially from both Indian Ocean and African monsoon systems. Here we synthesise terrestrial and marine core palaeoclimatic data in order to establish the spatial and temporal variability of humid periods in Arabia between late Marine Isotope Stage (MIS) 7 and 3. Incursions of monsoon rainfall occurred during periods of insolation maxima at ca. 200–190, 170, 155, 130–120, 105–95, 85–75 and 60–55ka, providing multiple ‘windows’ of favourable climatic conditions that could have facilitated demographic expansion through Arabia. Strong summer monsoons are generally associated with mid-high latitude interglacials, however, enhanced monsoon convection also brought rainfall into Arabia during global glacial phases, possibly due to a strengthened winter monsoon and a greater influence of southern hemispheric temperature changes. Key periods for dispersal into northern regions of Arabia correspond with the synchronous intensification of both eastern Mediterranean and monsoon rainfall systems at insolation maxima during MIS 7 and MIS 5, which may have facilitated demographic connectivity between the Levant and the Arabian interior. Environmental conditions throughout southern and southeast regions were also favourable to expansion during these times, although strong monsoons in these regions during MIS 6 and MIS 3 suggest further opportunities for demographic expansion and exchange. Terrestrial and marine evidence show that during early MIS 3 (ca. 60–50ka), a strengthened monsoon led to the activation of interior drainage systems and increased productivity in coastal zones, indicating that favourable environmental conditions existed along both coastal and interior routes at that time.

Deep water masses in the Iceland Basin during the Last Interglacial (MIS 5e): Evidence from benthic foraminiferal data

The Last Interglacial period, marine isotope stage (MIS) 5e, is a potential analogue for the Holocene. In this study, we investigated a marine sediment core, AMK-4442, recovered from the northern part of the Iceland Basin. The multiproxy approach used in this study, which includes foraminiferal and lithological analyses, identifies the difference in intensity of deep circulation between MIS 5e and the Holocene. Our data indicate that during early MIS 5e, the Iceland-Scotland Overflow Water (ISOW) flux into the Iceland Basin was suppressed. We suggest that the less active North Atlantic Deep Water (NADW) formation at this time was related to the obstruction of warm surface water inflow into the Nordic Seas.

A high-resolution Early Holocene-late MIS 3 environmental rock- and palaeomagnetic record from Lake Sf. Ana, Carpathian Mts, Romania

Lacustrine sediments are excellent sources of palaeoenvironmental and palaeoclimatic information because they usually provide continuous and high-resolution records. In centraleastern Europe however lacustrine records that extend beyond the Holocene are rather sparse. Palaeomagnetic records from this region are also insufficiently explored, and usually associated with terrestrial deposits such as loess. In this context, the lacustrine record of Lake Sf. Ana, a volcanic crater lake in the East Carpathians, Romania, provides an important archive for reconstructing past paleomagnetic secular variation in the region from early Holocene to late Marine Isotope Stage (MIS) 3.

Fluvio-lacustrine deposits reveal precipitation pattern in SE Arabia during early MIS 3

On a global scale, Marine Isotope Stage (MIS) 3 (ca. 55–30 ka) was characterised by frequent and abrupt changes in climate. At the same time, humans may have dispersed out of Africa and populated the planet. For the Arabian Peninsula, a key region in both contexts, the paucity of suitable terrestrial records leaves our knowledge of the environmental conditions during this important period enigmatic. Here, we elucidate the environmental history for part of the Oman Mountains by analysing luminescence-dated fine-grained playa-like sediments from Wadi Mistal that formed in a landslide-dammed ephemeral lake. We identified 112 individual fining-upward sequences in the distal facies of the lake that are interpreted to represent major precipitation events during early MIS 3. The nature of sedimentation together with the presence of desiccation cracks and the absence of any faunal remains imply that the lakes had a temporary nature. It appears that the time of deposition was characterised by strong short-lived precipitation events, rather than continuous rainfall under a monsoonal regime. This points towards a climatic situation during early MIS 3 that was not so different from that of the present, at least in this part of Arabia.

Re-evaluation and extension of the Marine Isotope Stage 5 tephrostratigraphy of the Faroe Islands region: The cryptotephra record

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.

Vegetation response to climate change during the Last Interglacial–Last Glacial transition in the southern Bekaa Valley, Lebanon

During the late Quaternary, extensive forests covered the slopes of the southern section of the Lebanon Mountains. Investigating the response of these forests to the climate change at the Last Interglacial–Last Glacial transition provides insight into their response to an abrupt and extensive deterioration in climate. Here we present the results of a new sedimentary sequence from the southern Bekaa Valley, Lebanon, which spans the late Last Interglacial marine isotope stage (MIS) 5e to early MIS 5c of the Last Glacial. High-resolution analyses for pollen, carbon isotopes and total organic carbon have been undertaken and reveal dramatic shifts in the vegetation composition during this transition. At the Last Interglacial (MIS 5e) to glacial (MIS 5d) transition an environmental threshold was crossed in response to a significant reduction in precipitation with the development of grassland/steppe dominated by Chenopodiaceae and Artemisia. The arid conditions led to the loss of the temperate deciduous arboreal species (Betula, Alnus and Corylus) and significant reduction in the populations of coniferous trees Cedrus libani and Pinus that populated the slopes of the Lebanon Mountains during the Last Interglacial. At the onset of the MIS 5c interstadial an increase in arboreal pollen is observed, in particular Cedrus libani, as the grassland/steppe transitioned into an open forest-steppe. The response of the vegetation during the Last Interglacial to temperatures that were at least as high as or higher than present, and the onset of the Last Glacial, when precipitation declined significantly, has the potential to indicate how eastern Mediterranean biotic communities will respond to changes in these climatic parameters that are predicted to occur in the near future.

Millennial-scale versus long-term dynamics in the surface and subsurface of the western North Atlantic Subtropical Gyre during Marine Isotope Stage 5

Subtropical Gyres are an important constituent of the ocean–atmosphere system due to their capacity to store vast amounts of warm and saline waters. Here we decipher the sensitivity of the (sub)surface North Atlantic Subtropical Gyre with respect to orbital and millennial scale climate variability between ~140 and 70ka, Marine Isotope Stage (MIS) 5. Using (isotope) geochemical proxy data from surface and thermocline dwelling foraminifers from Blake Ridge off the west coast of North America (ODP Site 1058) we show that the oceanographic development at subsurface (thermocline) level is substantially different from the surface ocean.Most notably, surface temperatures and salinities peak during the penultimate deglaciation (Termination II) and early MIS 5e, implying that subtropical surface ocean heat and salt accumulation might have resulted from a sluggish northward heat transport. In contrast, maximum thermocline temperatures are reached during late MIS 5e when surface temperatures are already declining. We argue that the subsurface warming originated from intensified Ekman downwelling in the Subtropical Gyre due to enhanced wind stress.During MIS 5a-d a tight interplay of the subtropical upper ocean hydrography to high latitude millennial-scale cold events can be observed. At Blake Ridge, the most pronounced of these high latitude cold events are related to surface warming and salt accumulation in the (sub)surface. Similar to Termination II, heat accumulated in the Subtropical Gyre probably due to a reduced Atlantic Meridional Overturning Circulation. Additionally, a southward shift and intensification of the subtropical wind belts lead to a decrease of on-site precipitation and enhanced evaporation, coupled to intensified gyre circulation. Subsequently, the northward advection of this warm and saline water likely contributed to the fast resumption of the overturning circulation at the end of these high latitude cold events.