Marine Isotope Stage 5a Research Articles

The climatic control of sedimentary environment changes during the Weichselian – An example from the Middle Vistula Region (eastern Poland)

This study presents the sedimentary facies, stratigraphic framework and palaeoenvironmental conditions of the Weichselian sediments in the Middle Vistula Region. Based on sedimentological, palynological, palaeopedological and absolute age studies (luminescence and radiocarbon dating), a succession of three lithofacial complexes and the pattern of their evolution was distinguished. The lowermost, fluvial complex is composed of two parts separated by an extensive erosional surface. They were deposited in a braided river system during two distinct periods of Weichselian climate cooling: first at the end of the Marine Isotope Stage 5a and during the entire Marine Isotope Stage (MIS) 4, and then at the end of MIS 2 (Late Glacial). The middle, fluvio-aeolian complex was deposited during the Late Glacial as an effect of alternating fluvial and aeolian processes on abandoned, higher river terraces under periglacial conditions (discontinuous permafrost). It represents a record of climatic amelioration, culminating in the succession of tundra vegetation and sparse pine-birch forests, causing the formation of a soil in the top part of the middle complex. The uppermost, aeolian complex was deposited during the Older and Younger Dryas as a result of permafrost degradation. The deposition was interrupted by the expansion of boreal forest during the Allerød and the development of soils. Climate has been recognized as a major factor determining changes in sedimentary environments. The cooling of the climate during the Weichselian was conducive to the aggradation of sediments and permafrost. In contrast, climate warming resulted in increased erosion in the valley and creation of terraces.

Small mammals from Marine Isotope Stage 5 at Klasies River, South Africa–Reconstructing the local palaeoenvironment

Klasies River, a significant Middle Stone Age (MSA) site, preserves remains of anatomically modern humans and a 21 m sequence of human habitation that shows use of sophisticated lithic technology and systematic exploitation of marine and terrestrial resources. In this paper micromammals recovered from the lower MSA sequence (MSA I and MSA II) at Klasies River Main site have been analysed to provide proxy data for palaeoenvironmental reconstruction. Small mammals recovered from 183 separate layers ensure a detailed record of local climate and vegetation during Marine Isotope Stage (MIS) 5. Taphonomic analyses indicate that avian predators accumulated the micromammals. Analysis of post-depositional processes has provided information on intra-site variability and utilisation. The palaeoenvironmental reconstruction shows changes in rainfall seasonality within MIS 5. There was transient movement towards more aseasonal rainfall and significant alterations in the vegetation composition from MIS 5e to MIS 5a. Our study adds new insights to palaeoenvironmental conditions on the Cape coast during MIS 5.

Palaxius floridanus n. isp., a new structured callianassid crustacean microcoprolite from the Pleistocene of south Florida

AbstractThe crustacean microcoprolite Palaxius floridanus n. isp. is described from shallow-water carbonate platform deposits of Pleistocene limestones of south Florida. Palaxius floridanus n. isp. occurs in moderate-energy packstones and grainstones of the oolite facies of the Miami Limestone, and in skeletal packstones of the Key Largo Limestone, ranging in age from marine isotope stage (MIS) 11 to MIS 5a (ca. 400–80 kyr BP). The new ichnospecies resembles P. decemlunulatus, which has been described previously from Oligocene deposits. Late Jurassic and Late Cretaceous forms described as P. decemlunulatus belong to a new ichnogenus and new ichnospecies, respectively, yet to be described.

Quantitative reconstruction of paleoclimate in central Japan for the past 158,000 years based on a modern analogue technique of pollen composition

In this study, quantitative climate information for central Japan for the past 158 ka is reconstructed on the basis of pollen composition data of NJ88 core from Lake Nojiri and those of TKN-2004 core from the lacustrine Takano Formation using a modern analogue technique. Reconstructed values at the sites around 36.6°N and 700 m altitude are as follows.In marine isotope stage (MIS) 6, the average annual mean temperature was about 2.1 °C, with a coldest month temperature of −11.8 °C, which suggest very cold climate conditions. The climates of MIS 4 and 2 were similarly cold, and the precipitation was low with ∼1050 mm for mean annual precipitations during these cold periods. In contrast, the annual mean temperatures of MIS 5e and MIS 1, among the warmest periods, averaged about 5.5 °C and 9.1 °C, respectively. The annual mean temperature of MIS 5e was significantly lower than that of the Holocene. We estimate that an intensely cold winter controlled the vegetation, which resulted in the lower temperature reconstruction for MIS 5e. The annual mean temperatures of intermediately warm periods such as MIS 5c and 5a were a slightly high, with averages of 4.4 °C and 5.1 °C, respectively. Annual precipitations increased up to ∼1400 mm on average in these warmer periods. Annual mean temperatures of MIS 5d and 5b were low with averages of about 3.0 °C.Annual mean temperatures reconstructed for MIS 3 fluctuated over short periodicities that correspond to Dansgaard–Oeschger cycles. For example, the annual mean temperature of the interstadial GI-8 (Greenland Interstadial 8), 38–39 cal ka BP (calendar ka before 1950 CE) was about 4.0 °C, and that of the stadial HE 4 (Heinrich event 4) in 42–43 cal ka BP was about 2.6 °C. From 14 to 12 cal ka BP, annual mean temperature increased significantly in a relatively short period, from 1.3 to 9.5 °C, and annual precipitation also increased from 1040 to 1380 mm. A cool event corresponding to the Younger Dryas was identified in this deglaciation process, but its intensity was much weaker than that in the North Atlantic region. The climate in the Holocene (MIS 1) was warm, with an average annual mean temperature of 9.0 °C with wide variation, by a maximum of about 2 °C, which suggests temporal change of the Arctic polar front situated in mid-latitude regions.

Predicted bounds on peak global mean sea level during marine isotope stages 5a and 5c

Estimates of marine isotope stage (MIS) 5c and 5a global mean sea level (GMSL) based on marine terraces and coastal indicators range from 15–37 m and 9–30 m below present, respectively. Tectonic displacement and glacial isostatic adjustment (GIA) complicate efforts to refine this range. We revisit this issue using numerical predictions of post-glacial sea-level change and updated estimates of site-specific tectonic signals based upon these predictions. Laurentide and Cordilleran peripheral bulge dynamics and variations in the gravitational effect of these ice masses dominate the GIA signal along the east and west coasts of North America. Published compilations suggest that MIS 5 sea-level indicators extending from Virginia to the Caribbean lie on the outer flank of the peripheral bulge, while those along a transect from Oregon to Baja California sit on the inner flank of the bulge. Our GIA modeling reconciles these data by adopting a significantly weaker (i.e., lower viscosity) upper mantle in analyzing data on the Pacific coast relative to the Atlantic, an inference supported by seismic tomography. We present a sensitivity analysis that compares the observed elevation of globally distributed high stand markers to a suite of GIA simulations that vary the Earth model and GMSL from the Last Interglaciation (MIS 5e, ∼130-115 ka) to 70 ka. We conclude that GMSL peaked at −8.5 ± 4.6 m (1σ) during MIS 5a and −9.4 ± 5.3 m during MIS 5c. A more restrictive analysis yields slightly wider bounds corresponding to −10.5 ± 5.5 m and −11.1 ± 6.6 m, respectively.

The Small Mammal Sequence from the c. 76 - 72 ka Still Bay Levels at Blombos Cave, South Africa - Taphonomic and Palaeoecological Implications for Human Behaviour.

The Still Bay, c. 76–72 ka, a prominent techno-tradition during the Middle Stone Age of southern Africa, has yielded innovative technologies, symbolic material culture, and shows evidence of expansion of hunting techniques and subsistence strategies. In this paper we present the results of the first systematic, taphonomic and palaeoenvironmental study of micromammals from the Still Bay levels at Blombos Cave. Our taphonomic analysis indicates that the micromammals were accumulated by avian predators occupying the cave. Post-depositional processes affecting the micromammal assemblage include organic waste decomposition and conditions associated with a limestone cave environment. The palaeoenvironmental reconstruction shows that Marine Isotope Stage (MIS) 5a at Blombos Cave had diverse micromammal communities occupying a variety of habitats and with rainfall pattern equal to present. The transition from MIS 5a to 4 is indicated by less diverse micromammal assemblages, increase in grassland and scrub vegetation, shifts in seasonal precipitation, and a decline in shrubs associated with fynbos. The onset of the glacial conditions associated with MIS 4 is visible in the micromammal assemblage. However humans occupying Blombos Cave during this c. 5 ka period showed an ability to cope with changing environmental conditions and were able to adapt and utilise a variety of available resources.

Constraining the chronology of Pleistocene glaciations on Svalbard: Kapp Ekholm re‐visited

The Kapp Ekholm site, in central Spitsbergen, shows alternating units of glaciomarine sandy silt and diamicton representing three glacial cycles and is key in reconstructing the Late Pleistocene glacial history of Svalbard. Part of the site is reinvestigated here by focusing on re‐dating two units (B and F) interpreted as interglacial/interstadial glaciomarine deposits, in order to constrain the controversial chronology. A combination of Optical Stimulated Luminescence (OSL) on quartz, infrared stimulated luminescence with a 50 °C readout temperature (IRSL50) and post infrared‐infrared stimulated luminescence (pIR), both on feldspar, was applied. While Formation B was beyond the dateable range of OSL, IRSL50 and pIR ages lead to the conclusion that this unit represents the Last Interglacial, Marine Isotope Stage (MIS) 5e, and the underlying diamicton the MIS 6 glacial. Formation F yielded ages implying that the formation represents the MIS 5a interstadial and the underlying diamicton is interpreted to represent the MIS 5b stadial. This agrees with conclusions drawn concerning the Pleistocene glaciations elsewhere on Svalbard.

Palaeohydrological corridors for hominin dispersals in the Middle East ∼250–70,000 years ago

The timing and extent of palaeoenvironmental connections between northeast Africa, the Levant and the Arabian Peninsula during the Middle and Late Pleistocene are critical to debates surrounding dispersals of hominins, including movements of Homo sapiens out of Africa. Although there is evidence that synchronous episodes of climatic amelioration during the late Middle and Late Pleistocene may have allowed connections to form between northern Africa and western Asia, a number of palaeoclimate models indicate the continued existence of an arid barrier between northern Arabia and the Levant. Here we evaluate the palaeoenvironmental setting for hominin dispersals between, and within, northeast Africa and southwest Asia during Marine Isotope Stages (MIS) 7–5 using reconstructions of surface freshwater availability as an environmental proxy. We use remotely sensed data to map palaeohydrological features (lakes, wetlands and rivers) across the presently hyper-arid areas of northern Arabia and surrounding regions, integrating these results with palaeoclimate models, palaeoenvironmental proxy data and absolute dating to determine when these features were active. Our analyses suggest limited potential for dispersals during MIS 7 and 6, but indicate the formation of a palaeohydrological corridor (the ‘Tabuk Corridor’) between the Levant and the Arabian interior during the MIS 6-5e glacial–interglacial transition and during MIS 5e. A recurrence of this corridor, following a slightly different route, also occurred during MIS 5a. These palaeohydrological and terrestrial data can be used to establish when proposed routes for hominin dispersals became viable. Furthermore, the distribution of Arabian archaeological sites with affinities to Levantine assemblages, some of which are associated with Homo sapiens fossils, and the relative density of Middle Palaeolithic assemblages within the Tabuk Corridor, are consistent with it being utilised for dispersals at various times.

Morphology and evolution of drowned carbonate terraces during the last two interglacial cycles, off Hilo, NE Hawaii

The eastern side of Hawaii Island is a rapidly subsiding margin dominated by drowned carbonate platforms. We present detailed bathymetric and backscatter data, remotely operated vehicle and submersible observations, sedimentological and 14C accelerator mass spectrometry and U/Th age data from seven submerged terraces (H7, H2a–d, H1a–b) in water depths between 1100 and 25m off Hilo, north-eastern Hawaii. The main carbonate deposits on these terraces are coral deposits, rhodolith beds, coralline algal mounds, crusts, pavements and tabular sheets. We identified five previously described sedimentary shallow- to deep-water facies and one new facies type that are consistent with reef drowning on a rapidly subsiding margin. We used palaeobathymetric data derived from the sedimentary facies, age versus depth relationships, and published sea-level curves, to estimate a uniform long-term subsidence rate of 2.80±0.36m/ky for the eastern side of Hawaii over the last 150ky. Terrace H7 developed about 380ka based on data from the western side of the island. Active coral growth on terrace H2d occurred during the Marine Isotope Stage (MIS) 6 to 5 transition, and the terrace drowned during the peak of MIS 5e when sea level rose faster than reefs could grow. Favoured by the gentle platform gradient, reefs established progressively landwards with a backstepping pattern during MIS 5e to form the terraces H2c and H2b 122ka. Final turn-off of shallow water carbonate production on terraces H2b–d coincided with the relative sea-level rise of the interstadial MIS 5a. Bathymetry and submersible data suggest that carbonate sediments on terraces H2a and H1b were deposited over an antecedent topography of local lava deltas emplaced during rising sea levels at ca. 85 and 65ka, while terrace H1a established on lava delta substrates of the Mauna Loa volcano ca. 11ka. We conclude that the initiation, growth and drowning of coral-reef terraces off Hilo differ in some ways from the pattern observed in the submerged terraces in the western side of Hawaii and that the platform evolution off Hilo is more strongly influenced by emplacement of offshore lava flows.

Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

Abstract. Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d–6. Therefore, we hypothesize that the causes of the DFO2006–AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d–6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, −230 years (minimum) at MIS 7a and +60 to +126 years on average.

Late Pleistocene montane vegetation and climate history from the Dajiuhu Basin in the western Hubei Province of Central China

A continuous 775-cm-long sediment core (Core B) was collected from the Dajiuhu Basin in the western Shennongjia Forest Region of Central China. The core between 775 and 144cm in depth spanning the period from 83.4 to 9.6ka (calibrated age, throughout this study) was studied for pollen analysis. The high-resolution pollen record revealed the histories of the vegetation succession and climate changes from 83.4 to 9.6ka in the mountainous regions at an altitude of approximately 1,700ma.s.l. in Central China. The results show that five evident climate changes disclosed by the pollen record in Core B correspond to MIS (Marine Isotope Stage) 5a, MIS 4, MIS 3, the LGM (Last Glacial Maximum) of MIS 2, and the period from the deglacial of MIS 2 to the early Holocene, respectively. The temperature changes in the Dajiuhu Basin are consistent with the solar insolation in the Northern Hemisphere, the climate records in the Greenland and Guliya ice cores, the stalagmite, and the loess. However, the precipitation changes during the late Quaternary in the study area were roughly reversed with the temperature changes in the Northern Hemisphere. Therefore, the climatic patterns from 83.4 to 9.6ka in the Dajiuhu Basin are cold and humid conditions and warm and dry conditions, which may be caused by the middle latitude position, the humid monsoon climate, and the steep mountainous geomorphology of the study area.

Marine terraces and rates of vertical tectonic motion: The importance of glacio-isostatic adjustment along the Pacific coast of central North America

Differences in marine terrace elevations across the Pacific coast of North America have long been assumed to be a result of differences in the rates of tectonic motion. However, other processes, particularly glacio-isostatic adjustment, lead to regional variations in sea levels. In this study, we compiled the elevations of marine isotope stage (MIS) 5e (ca. 119–129 ka), 5c (ca. 106 ka), and 5a (ca. 84 ka) terraces across the Pacific coast of central North America and compared these regional variations in elevation with model predictions of glacio-isostatic adjustment after correcting for tectonics. These predictions are generally consistent with the observed trends in the elevations of the terraces and show that this process created up to 20 m of coeval variation in local sea levels along the Pacific coast of central North America (between 20°N and 45°N) during MIS 5c and MIS 5a, but less, ~4 m, during MIS 5e. Accounting for glacio-isostatic adjustment reduces the variability in uplift rates calculated at individual locations using different-aged terraces as datums. Ignoring glacio-isostatic adjustment leads to overestimated uplift rates by an average of 40%, but up to 72%, across the Pacific coast of central North America. An understanding of regional variations in glacio-isostatic adjustment–corrected sea levels also contributes to the correct identification of marine terraces with mistaken ages.

Great Basin hydrology, paleoclimate, and connections with the North Atlantic: A speleothem stable isotope and trace element record from Lehman Caves, NV

We present a record of speleothem stable isotope (δ18O, δ13C) and trace element (Mg/Ca, Sr/Ca) variations from Lehman Caves, Nevada for an interval of time (139–128 ka) that encompasses the penultimate glacial termination, Termination II (T-II). Additional growth phases provide data from about 123 ka, a time that correlates with Marine Isotope Stage (MIS) 5e, and about 84 ka and between 82 and 81 ka (MIS 5a). Chronologies from two new stalagmites are anchored by thirty-six uranium–thorium dates. We also present new trace element data from stalagmite LC-2, which has a previously published uranium–thorium chronology and stable isotope record of T-II (Shakun et al., 2011). Our T-II δ18O record broadly replicates that of the Shakun et al. (2011) and Lachniet et al. (2014) records of this time, recording low values from 139 to 135 ka followed by an approximately 3.5‰ increase over an extended interval between 134 and 129 ka. This rise in δ18O values occurs during Heinrich Stadial 11 and the associated Weak Monsoon Interval observed in Chinese caves; our record broadly follows the marine termination, rising boreal summer insolation, and the rise in atmospheric CO2. We infer that this shift results from temperature increase due to increasing atmospheric CO2 and potentially a change in moisture source or precipitation seasonality from greater influence of the North American Monsoon accompanying summer insolation increase. It is also plausible that the melting of the ice sheet itself may have contributed to both temperature and precipitation seasonality changes. Trace element ratios and δ13C values are largely decoupled from δ18O values, showing minimal variation between 139 and 130 ka, for the duration of the Chinese Weak Monsoon Interval. However, these values increase sharply between 130 and 128 ka, which we interpret as increased prior calcite precipitation driven by a transition from wet to dry conditions. This abrupt drying event coincides within dating uncertainties with the abrupt strengthening of the East Asian summer monsoon, which marks the end of both the Weak Monsoon Interval and Heinrich Stadial 11. Our records demonstrate a link between North Atlantic climate and Great Basin moisture during this time that is consistent with the interpretation of data from the last glacial period and may result from abrupt shifts in Atlantic Meridional Overturning Circulation affecting the strength of the Aleutian Low.

Revisiting tectonic corrections applied to Pleistocene sea-level highstands

Tectonic displacement contaminates estimates of peak eustatic sea level (and, equivalently, minimum continental ice volumes) determined from the elevation of Quaternary interglacial highstand markers. For sites at which a stratigraphic or geomorphic marker of peak Marine Isotope Stage (MIS) 5e sea level exists, the standard approach for estimating local tectonic uplift (or subsidence) rates takes the difference between the elevation of the local highstand marker and a reference MIS 5e eustatic value, commonly chosen as +6 m, and divides by the age of the marker. The resulting rate is then applied to correct the elevation of all other local observed sea-level markers for tectonic displacement, including peak highstands of different ages (e.g., MIS 5a, MIS 5c and MIS 11), under the assumption that the tectonic rate remained constant over those periods. This approach introduces two potentially significant errors. First, the peak eustatic value adopted for MIS 5e in most previous studies (i.e., +6 m) is likely incorrect. Second, local peak sea level during MIS 5e is characterized by significant departures from eustasy due to glacial isostatic adjustment in response to both successive glacial–interglacial cycles and excess polar ice-sheet melt relative to present day values. We use numerical models of glacial isostatic adjustment that incorporate both of these effects to quantify the plausible range of the combined error and show that, even at sites far from melting ice sheets, local peak sea level during MIS 5e may depart from eustasy by 2–4 m, or more. We also demonstrate that the associated error in the estimated tectonic rates can significantly alter previous estimates of peak eustatic sea level during Quaternary highstands, notably those associated with earlier interglacials (e.g., MIS 11).

Photic zone changes in the north-west Pacific Ocean from MIS 4–5e

Abstract. In comparison to other sectors of the marine system, the palaeoceanography of the subarctic North Pacific Ocean is poorly constrained. New diatom isotope records of δ13C, δ18O, δ30Si (δ13Cdiatom, δ18Odiatom, and δ30Sidiatom) are presented alongside existing geochemical and isotope records to document changes in photic zone conditions, including nutrient supply and the efficiency of the soft-tissue biological pump, between Marine Isotope Stage (MIS) 4 and MIS 5e. Peaks in opal productivity in MIS 5b/c and MIS 5e are both associated with the breakdown of the regional halocline stratification and increased nutrient supply to the photic zone. Whereas the MIS 5e peak is associated with low rates of nutrient utilisation, the MIS 5b/c peak is associated with significantly higher rates of nutrient utilisation. Both peaks, together with other smaller increases in productivity in MIS 4 and 5a, culminate with a significant increase in freshwater input which strengthens/re-establishes the halocline and limits further upwelling of sub-surface waters to the photic zone. Whilst δ30Sidiatom and previously published records of diatom δ15N (δ15Ndiatom) (Brunelle et al., 2007, 2010) show similar trends until the latter half of MIS 5a, the records become anti-correlated after this juncture and into MIS 4, suggesting a possible change in photic zone state such as may occur with a shift to iron or silicon limitation.

Quaternary Tectonic Deformation, Holocene Paleoseismicity, and Modern Strain in the Unusually–Wide Coupled Zone of the Central Cascadia Margin, Washington and Oregon, USA, and British Columbia, Canada

Vertical deformation and horizontal strains are analyzed in the central Cascadia margin, or the Juan de Fuca plate segment of the Cascadia subduction, zone to establish the widths of the inter–plate strongly–coupled zone and the transition zone. Local variability of marine terrace elevations, corresponding to marine isotope stages 5a–5e (~80-130 ka), in the south and central Oregon coast (32±23 m–to–10.5±7.4 m mean sea level) and in the northern Oregon and Washington coasts (9.5±3.2 m–to–7.6±2.1 m), constrain the width of the strongly coupled zone (~100 km) from the deformation front or buried trench along the central Cascadia margin in Washington and Oregon. Late Holocene tidal marsh sites (number = 25) in Washington demonstrate three conditions of cyclic coseismic subsidence, representing the first and second zero-isobases (< 0.5 m sea level rise) and the trough of maximum coseismic subsidence (1.0±0.5 m or > 1.5 m abrupt sea level rise) for most rupture events during the last 2.6 ka. Together with paleosubsidence data from the Oregon coast the tidal wetland records in Washington show that the first and second zero–isobases, respectively, reach distances of ~100 and ~200 km from the deformation front in the central Cascadia subduction zone. Global positioning system (GPS) baselines show that across–margin crustal shortening (strain rate -5 × 10-8 to -1.5 × 10-6 a-1) is about one order of magnitude larger than along–margin shortening (strain rate -2 × 10-8 to -5 × 10-7 a-1) near the coast during the last several years. Significant negative strain or shortening in the upper–plate is measured to 200 km distance from the deformation front, thereby establishing an unusually wide coupled zone (~200 km) in the central Cascadia margin. The landward limits of the west coupled zone, central uncoupled zone, and east coupled zone, respectively, could account for long–term uplift of the Coast Ranges, the lack of uplift in the Puget and Willamette forearc valleys, and uplift of the western margin of the Cascade volcanic arc.

Glacial history and paleoceanography of the southern Yermak Plateau since 132 ka BP

The southern Yermak Plateau (YP) is situated at the entrance to the Arctic Ocean in the narrow Marginal Ice Zone (MIZ) between the Polar and Arctic Fronts, north-west of Svalbard. A gravity core JM10-02GC has been analysed in order to reconstruct paleoceanographic conditions and the movement of the sea ice margin as well as the glacier ice conditions of the Svalbard–Barents Sea Ice Sheet (SBIS) during the Last Interglacial–Glacial cycle. The distribution of planktic and benthic foraminifera, planktic and benthic oxygen and carbon isotopes and variations in ice-rafted debris (IRD) has been investigated. The sediment core covers the time interval from the Marine Isotope Stage (MIS) 6/5e transition (Termination II, c. 132 ka BP) to the early Holocene. During Termination II (TII), the SBIS retreated and the sea ice margin was in distal position whereas during MIS 5 to MIS 4 the sea ice margin was close to the core site. Several core intervals interpreted as representing MIS 5e, MIS 5c, MIS 5a, MIS 3 and MIS 1 were barren of calcareous microfossils whereas the intervals representing MIS 4 and MIS 2 were characterised by high productivity (HP) of planktic and benthic foraminifera. These “glacial” HP zones were associated with the open water conditions resulting from the advection of Atlantic Water (AW) and retreat of the sea ice margin. The barren zones during MIS 5, MIS 3 and MIS 1 resulted from the proximity of the sea ice margin whereas during MIS 2 the likely cause was an advance of the SBIS.

Middle to Late Pleistocene ice extents, tephrochronology and paleoenvironments of the White River area, southwest Yukon

Sedimentary deposits from two Middle to Late Pleistocene glaciations and intervening non-glacial intervals exposed along the White River in southwest Yukon, Canada, provide a record of environmental change for much of the past 200 000 years. The study sites are beyond the Marine Isotope stage (MIS) 2 glacial limit, near the maximum regional extent of Pleistocene glaciation. Non-glacial deposits include up to 25 m of loess, peat and gravel with paleosols, pollen, plant and insect macrofossils, large mammal fossils and tephra beds. Finite and non-finite radiocarbon dates, and twelve different tephra beds constrain the chronology of these deposits. Tills correlated to MIS 4 and 6 represent the penultimate and maximum Pleistocene glacial limits, respectively. The proximity of these glacial limits to each other, compared to limits in central Yukon, suggests precipitation conditions were more consistent in southwest Yukon than in central Yukon during the Pleistocene. Conditions in MIS 5e and 5a are recorded by two boreal forest beds, separated by a shrub birch tundra, that indicate environments as warm or warmer than present. A dry, treeless steppe-tundra, dominated by Artemisia frigida, upland grasses and forbs existed during the transition from late MIS 3 to early MIS 2. These glacial and non-glacial deposits constrain the glacial limits and paleoenvironments during the Middle to Late Pleistocene in southwest Yukon.

MIS 5/4 transition in a mountain environment: herpetofaunal assemblages from Cueva del Camino, central Spain

The Cueva del Camino site (Pinilla del Valle, Madrid, Spain) is located in the upper valley of the Lozoya River in the Sierra de Guadarrama, a mountain range extending NE−SW within the Central Range System. Due to its location within a mountain range on the central Iberian Peninsula at an altitude of 1114 m a.s.l. and the numerical dating of its sediments, the palaeontological site of Cueva del Camino has proved a highly relevant location for studying the ecological changes linked to the climatic fluctuations at the end of Marine Isotope Stage (MIS) 5 and the beginning of MIS 4. Environmental reconstructions suggest a rather open, patchy landscape throughout the succession, with abundant evidence of dry meadows, scrublands and rocky habitats. The climate can be considered as generally warm, reaching mean annual temperatures (MATs) of up to 13.8°C (i.e. higher than today's by up to 2.9°C). Three cooler events can be seen throughout the succession as reflected by the presence of Rana iberica, Anguis fragilis and Coronella austriaca. The first of these events may correlate with MIS 5b; the second in the Central sector may correlate with the Stadial I pollen event occurring at the end of MIS 5a; and the third event, corresponding to the coldest MAT of the entire succession with MATs 0.9°C lower than today's, may correspond to the transition from MIS 5a to MIS 4. The evolution of mean annual precipitation (MAP) is characterized by warm periods, drier and cold periods, as well as wetter periods (up to +356 mm compared to today's MAP values), similar to what occurs today in the high‐elevation areas of the neighbouring mountains. Our study gives new quantitative estimations for the climatic fluctuations in mountain environments of central Spain at the MIS 5/4 transition and their associated ecological changes.

Speleothem constraints on marine isotope stage (MIS) 5 relative sea levels, Yucatan Peninsula, Mexico

ABSTRACTRates of sea‐level fall at the termination of the last interglacial are poorly defined and archives from which sea‐level elevations are constrained during marine isotope stage (MIS) 5 in the western North Atlantic–Caribbean region are restricted spatially to a few key sites. Here, growth periods of presently submerged but subaerially deposited speleothems from the Yucatan Peninsula, south‐east Mexico, are dated using the 230Th/234U multi‐collector inductively coupled plasma mass spectrometric method. The growth periods, used to constrain maximum elevations of relative sea level, are in agreement with glacio‐isostatic adjustment models for the near to intermediate region of the former North American ice sheets. Furthermore, our data provide additional constraints on the timing of peak relative sea levels during MIS 5a and 5c, and the timing of the regression following the last interglacial highstand. Combining our data with coral archives of minimum relative sea level from the same region provides a novel approach to calculating the rate of relative sea‐level fall, although initial estimates are poorly constrained because of the wide range in ages observed for the most suitable corals. Copyright © 2013 John Wiley &amp; Sons, Ltd.