Abstract: A new ice core drilled at the Russian station of Vostok in Antarctica reached 2755 m depth in September 1993. At this depth, the glaciological time scale provides an age of 260 ky BP (±25). We refine this estimate using records of dust and deuterium in the ice and of δ18O of O2 in the entrapped air. δ18O of O2 is highly correlated with insolation over the last two climatic cycles if one assumes that the EGT chronology overestimates the increase of age with depth by 12% for ages older than 112 ky BP. This modified age-depth scale gives an age of 244 ky BP at 2755 m depth and agrees well with the age-depth scale of Walbroeck et al. (in press) derived by orbital tuning of the Vostok δD record. We discuss the temperature interpretation of this latter record accounting for the influence of the origin of the ice and using information derived from deuterium-excess data. We conclude that the warmest period of stage 7 was likely as warm as today in Antarctica. A remarkable feature of the Vostok record is the high level of similarity of proxy temperature records for the last two climatic cycles (stages 6 and 7 versus stages 1–5). This similarity has no equivalent in other paleorecords.

Abstract: The oldest ice rafted material (IRD) on the Voring Plateau is dated to about 11 Ma, and is regarded as evidence that glaciers extended to sea level somewhere around the Nordic Sea at this time We estimate that the major glaciations of Scandinavia and the Barents Sea-Svalbard area started at 25–28 Ma, when the amount of IRD on the Voring Plateau increased strongly, the deep sea δ18O curves indicate that onset of Northern Hemisphere glaciations, and the climate in The Netherlands was so cold that a major glaciation of Scandinavia is inferred Most of the time until 09 Ma, the ice sheets were of intermediate size; they probably reached the coastal zone of western Norway for long periods The center of glaciation is inferred to have been further north than during the later glaciations, and we speculate that this was the period of maximum glacial erosion of the Barents Sea The largest glaciations, and also the warmest interglacials occurred during the last 900 kyrs, when the 100 kyr astronomic cycle became important For the last glaciation, the Weichselian, the glacial fluctuations are known in greater detail both for Scandinavia and the Svalbard-Barents Sea region In Scandinavia the glacial fluctuations apparently followed the 23 kyr precession cycle, whereas in the Barents Sea they followed the 41 kyr tilt cycle In both areas more than one advance reached beyond the coast We use the Weichselian record to “calibrate” the interpretation of more indirect evidences of glacial fluctuations, and apply the latter to the Scandinavian and Barents Sea glacial history since 25 Ma

Abstract: Rapid and abrupt relative sea-level changes within the last interglacial (substage 5e) are recorded in the island geology of the tectonically stable Bahamas. From 132 to 118 ka, reef growth reached a maximum elevation near +2 m, as indicated by fossil reef elevation across the platform, whereas bioeroded notches are incised in coastal cliffs as high as +6 m. The end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions. It is inferred that sea level for most of the interval remained near +2 m, restraining reef growth, and that the notch at +6 m represents a rapid and brief excursion just before the close of the substage. The subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them. In order to explain the rapid rise to +6 m, glacial surging is invoked. The subsequent fall, also rapid, may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown.

Abstract: THE apparent similarity of climate variability in the North Atlantic region in the last interglacial period1–5 and the present interglacial (Holocene) has recently been challenged by the rapid oscillations in climate conditions indicated by some marine6,7 and terrestrial climate records8–10 for the last interglacial. Ocean circulation in the northern North Atlantic seems to be intimately coupled to the processes of climate change on various time-scales11,12, so that climate variability—and the associated mechanisms of change—should be well recorded by sediments from these high latitudes. Previous studies in this region5,13 have indeed indicated an apparently less stable last-interglacial climate than at middle latitudes of the North Atlantic Ocean4. Here we present detailed records from marine sediments in the Nordic seas of oceanographic conditions during the last interglacial. The records show three large sea surface temperature fluctuations, a weakening of the east–west sea surface temperature gradient with time, and changes in deep-water properties. In contrast, similar analyses of a core from the same region indicate that sea surface temperature during the Holocene has been relatively stable. Our data—along with those from the Labrador Sea7—indicate rapid changes in ocean circulation and oceanic heat fluxes at high northern latitudes during the last interglacial, which may have been associated with marked temperature changes on adjacent continents.

Abstract: Rock-magnetic characteristics of late Pleistocene loess-paleosol sequences in the Czech Republic show patterns of variation that reflect climate-related depositional and diagenetic processes which acted on the sedimentary profiles. Mass-normalized magnetic susceptibility is high in interglacial and interstadial paleosols, while uniformly low values are measured in unweathered loess horizons. Normalized ferrimagnetic susceptibility and anhysteretic remanent magnetization show an enhancement of ultrafine (superparamagnetic, SP) and fine (single-domain, SD, and pseudo-single-domain, PSD) grains in chernozem paleosols correlated with δ18O substages 5c and 5a as well as in the Holocene soil. The parabraunerde paleosol associated with peak interglacial conditions, correlated with δ18O substage 5e, shows evidence of diagenetic loss of fine grained magnetic minerals, although coarse (multidomain, MD) grains appear to be preserved. Low temperature remanence behavior plus high temperature susceptibility measurements of representative samples from each lithologic unit indicate that magnetite and maghemite are the dominant magnetic minerals within the sediments. Variations in concentration-independent rock-magnetic parameters are therefore primarily a function of grain size variations through the profile. It is anticipated that with additional magnetic and non-magnetic sedimentological and geochemical tests, a quantitative rock-magnetic — paleoclimate model can be developed for the central European loess region.

Abstract: The central problem of late Quaternary circulation in the South Atlantic is its role in transfer of heat to the North Atlantic, as this modifies amplitude, and perhaps phase, of glacial- interglacial fluctuations. Here we attempt to define the problem and establish ways to attack it. We identify several crucial elements in the dynamics of heat export: (1) warm-water pile-up (and lack thereof) in the western equatorial Atlantic, (2) general spin-up (or spin-down) of central gyre, tied to SE trades, (3) opening and closing of Cape Valve (Agulhas retroflection), (4) deepwater E-W asymmetry. Means for reconstruction are biogeography, stable isotopes, and productivity proxies. Main results concern overall glacial-interglacial contrast (less pile-up, more spin-up, Cape Valve closed, less NADW during glacial time), dominance of precessional signal in tropics, phase shifts in precessional response. To generate working hypotheses about the dynamics of surface water circulation in the South Atlantic we employ Croll’s paradigm that glacial - interglacial fluctuations are analogous to seasonal fluctuations. Our general picture for the last 300 kyrs is that, as concerns the South Atlantic, intensity of surface water (heat) transport depends on the strength of the SE trades. From various lines of evidence it appears that stronger SE trades appeared during glacials and cold substages during interglacials, analogous to conditions in southern winter (August).

Abstract: This paper reviews the evidence from terrestrial palaeoenvironmental records in north-central Europe and, in particular, central Germany, which relates to the controversial proposition that there were strong climate oscillations during the last interglacial (oxygen isotope substage 5e). In contrast to the evidence from the GRIP ice core at Summit, Greenland, and a recent palaeoclimate reconstruction based on the pollen profile from Bispingen, Germany, the evaluation of the palaeobotanical and the stable isotope data presented here strongly suggests relatively stable temperature for most of the Eemian and with instability confined to the beginning and end of the interglacial. High amplitude temperature variations can be seen in both the Early Weichselian pollen and isotope records. It is argued that this pattern of climate development is applicable to most of continental north-central Europe.

Abstract: Pleistocene marine terraces along the Marlborough coast, South Island, New Zealand, have been re‐examined with detailed stratigraphic observations, accurate height data, and amino acid and thermo‐luminescence (TL) geochronology. Marine terraces range in age from c. 220 ka (oxygen isotope stage 7) to c. 60 ka (oxygen isotope stage 3), in the area from Cape Campbell to Conway River. At Kaikoura Peninsula, five marine terraces are preserved. The marine fauna, loess stratigraphy, and amino acid dating of Tawera spissa, from the Kaikoura I (highest) terrace and from the highest terrace at Haumuri Bluffs (Tarapuhi Terrace), indicate a correlation to oxygen isotope substage 5c, with an age of 100 ka. North of the Clarence River, marine terraces (including the Parikawa Formation) are correlated to oxygen isotope substage 5e of the last interglacial. TL dating of loess supports this interpretation. The Winterholme Formation terrace at Kekerengu is reinterpreted as a last glaciation fluvioglacial terrace g...

Abstract: A stratigraphic sequence of unconsolidated sediments ranging in age from Late Pliocene to Late Pleistocene is recorded in the Canyon Ranges of the Mackenzie Mountains. Three of the sections (Katherine Creek, Little Bear River, and Inlin Brook) expose bedrock and Tertiary gravel overlain by colluvium and a multiple till sequence of montane origin, separated by paleosols and capped by a till of Laurentide origin. The sections are correlated on the basis of lithology, paleosol development, paleomagnetism, and chlorine dating of surface boulder erratics. A formal stratigraphic nomenclature is proposed for the deposits of this region. The sequence of glacial tills separated by paleosols reflects a long record of glacial–interglacial cycles. Soil properties from the oldest paleosol to modern soil show a general decrease in the degree of soil development, suggesting a progressive deterioration of interglacial climatic conditions. A normal–reverse–normal sequence of remanent magnetization was determined within th...

Abstract: We present atmospheric simulations of three different time slices of the late Quaternary using the ECHAM 3 general circulation model in T42 resolution. In this work we describe the results of model runs for the time slices 6000 years BP (last climate optimum), 21 000 BP (last glacial maximum) and 115 000 years BP (glacial inception). Although the solar insolation is known for all time slices, a complete data set of the other boundary conditions which are necessary for running the atmospheric model exists only for the last glacial maximum in the form of the CLIMAP reconstruction. For the other two time slices, which are interglacial states like the modern climate, sea surface temperatures, land albedo and ice sheet topography are kept at modern values and only the solar insolation is changed appropriately. The response of the model to solar insolation changes is quite reasonable. The modelled anomalies are small and roughly opposite in sign for 6000 BP and 115 000 BP, respectively. In the case of last glacial maximum, the glacial ice sheet topography and ice albedo produce a much larger climate anomaly in the model. However, to enable a real test of model performance under glacial boundary conditions, the CLIMAP sea surface temperatures, which are now known to be partly inaccurate, should be replaced by an updated “state-of-the-art” reconstruction.

Abstract: Unconsolidated carbonate sands and cobbles on Kapapa Island, windward Oahu, are 1.4-2.8 (± 0.25) m above present mean sea level (msl). Agreeing with Stearns (1935), we interpret the deposit to be a fossil beach or shoreline representing a highstand of relative sea level during middle to late Holocene time. Calibrated radiocarbon dates of coral and mollusc samples, and a consideration of the effect of wave energy setup, indicate that paleo-msl was at least 1.6 (± 0.45) m above present msl prior to 3889-3665 cal. yr B.P, possibly as early as 5532-5294 cal. yr B.P., and lasted until at least 2239-1940 cal. yr B.P. Hence, the main phase of deposition on Kapapa Island lasted a minimum of c. 1400 yr and possibly as long as c. 3400 yr. No modern samples have been recovered from the fossil beach on Kapapa Island, and samples from potential source sites offshore of the island show modern ages, indicating that sediments on the island are not deposited by modern-era storm and tsunami overwash. Because antecedent sediments are uncommon offshore but common on the island, deposition must have been time-transgressive rather than related to a single event. Radiocarbon ages of coral and mollusc clasts from a breccia lining an emerged (1.4 ± 0.25 m msl) intertidal notch, cut into emerged coralline-algal carbonate of presumed last interglacial age, on south Mokulua Island (15 km to the southeast of Kapapa Island) correlate to the history recorded on Kapapa Island. Calibrated ages range from 2755-2671 to 3757-3580 cal. yr B.P. (averaging c. 3100 cal. yr B.P.) suggesting that a higher than present sea level formed the notch prior to 3757-3580 cal. yr B.P. A storm or tsunami origin for the features on Kapapa and south Mokulua islands is highly unlikely. Their age and elevation indicate, instead, a history of higher relative sea level (and subsequent fall) on windward Oahu during the middle to late Holocene. This history is consistent with geophysical models of postglacial geoid subsidence over the equatorial ocean first predicted by Walcott (1972) and later refined by Clark et al. (1978) and Mitrovica and Peltier (1991).

Abstract: Caves overrun by glaciers are known to accumulate dateable evidence of past glacial and interglacial events. Results are reported from an investigation of Aurora Cave on the slopes above Lake Te Anau in Fiordland. The cave commenced to form before c. 230 ka B.P. Sequences of glacifluvial sediments interbedded with speleothems are evidence of the number and timing of glacial advances and the status of intervals between them. Twenty‐six uranium series dates on speleothems underpin a chronology of seven glacial advances in the last 230 ka, with the peak of the late Otira glaciation, Aurora 3 advance, at c. 19 ka B.P. With five advances in the Otiran, the last glaciation is more complex than previously recognised. Comparison of the record with that recorded offshore from DSDP Site 594 reveals little matching, but the correspondence of the Aurora sequence with that interpreted from other onshore deposits is more convincing. Glacial deposits on slopes above the cave for a further 660 m may be evidence ...

Abstract: Well-dated surface and subsurface deposits in semiarid Fish Lake Valley, Nevada and California, demonstrate that alluvial-fan deposition is strongly associated with the warm dry climate of the last two interglacial intervals, and that fans were stable and (or) incised during the last glaciation. Fan deposition was probably triggered by a change from relatively moist to arid conditions causing a decrease in vegetation cover and increases in flash floods and sediment yield. We think that this scenario applies to most of the other valleys in the southern Basin and Range. Radiocarbon, tephra, and a few thermoluminescence and cosmogenic ages from outcrops throughout Fish Lake Valley and from cores on the Leidy Creek fan yield ages of >100–50 ka and 11–0 ka for the last two periods of alluvial-fan deposition. Mapping, coring and shallow seismic profiling indicate that these periods were synchronous throughout the valley and on the proximal and distal parts of the fans. From 50 to 11 ka, fan deposition ceased, a soil formed on the older alluvium and the axial drainage became active as runoff and stream competence increased. Slow deposition due to sheet flow or aeolian processes locally continued during this interval, producing cumulic soil profiles. The soil was buried by debris-flow sediment beginning at about 11 ka, coincident with the onset of relatively dry and warm conditions in the region. However, ground-water discharge maintained a large freshwater marsh on the valley floor throughout the Holocene. Pulses of deposition during the Holocene are recorded in the marsh and fan deposits; some pulses coincided with periods of or transitions to warm, dry climate indicated by proxy climate records, whereas others may reflect local disturbances associated with volcanism and fires. Within the marsh deposits, much of the clastic material is probably desert loess. In addition, the deposition of coppice dunes within the fan deposits coincides with two dry periods during the late Holocene.

Abstract: Sea‐surface temperature trends in planktonic foraminifers, isotopic and population abundance trends in benthic foraminifers, and abundance trends in calcareous nannofossils of V18–222 (38°34'S, 140°37'E, southeast Australia: 1904 m water depth) reveal an interglacial interval (oxygen isotope stage 1) distinctly different from underlying glacial intervals (isotope stages 10 and 12). During the glacial times mean sea‐surface temperatures (FI‐2 planktonic foraminiferal transfer function) ranged between 12°C and 9°C, indicating the close proximity of the Subtropical Convergence Zone. The cooler waters were unfavourable for the existence of the nannofossil Florisphaera profunda, while cooler water flora like Coccolithus pelagicus and Gephyrocapsa caribbeanica flourished. Absence of tropical and subtropical nannoflora suggest that the Leeuwin Current did not flow across the area at this time. High surface productivity, associated with strong upwelling during this time is indicated by Bulimina aculeata‐dominated...

Abstract: This study represents an attempt to extract paleoclimatic data from the deep-sea record by analyzing foraminiferal shells individually. Using the oxygen (δ18O) and carbon (δ13C) isotopic composition of individual Orbulina universa and Neogloboquadrina dutertrei, we present an approach to reconstruct the δ18O of seawater (δ18Ow), the δ13C of ΣCO2, and seasonal maximum sea surface temperatures (SST) in the western and eastern equatorial Atlantic. We examine the glacial and interglacial extremes of the last 150,000 years (isotope stages 1, 2, 5e, and 6). Comparison of recent water column hydrography with reconstructions from core top assemblages shows that O. universa and N. dutertrei δ18O and δ13C values accurately record hydrographic conditions in the mixed layer and upper thermocline at both sites. By analyzing shells individually, we can evaluate the effect of bioturbation on the range of δ18O and δ13C values in each interval and take it into consideration in our data interpretations. Downcore results show that N. dutertrei δ18O values in the western equatorial Atlantic reflect glacial to interglacial changes in δ18Ow due to continental ice formation (Δδ18O=1.30 ‰). We use changes in N. dutertrei δ18O values between core intervals to estimate the ice-volume effect in paleotemperature calculations for the mixed layer. To validate the use of O. universa for mixed layer reconstructions, we have added individual Globigerinoides sacculifer data for stages 1 and 2 at both sites. Paleotemperature reconstructions from O. universa δ18O values indicate that maximum seasonal mixed layer temperatures in the equatorial Atlantic decreased by at most 2.6°C between isotope stages 1 and 2 and by no more than 3.4°C between stages 1 and 6. Individual shell data from G. sacculifer yield similar results indicating that maximum O. universa δ18O values reflect the mixed layer environment. In agreement with Climate: Long-Range Investigation, Mapping, and Prediction (CLIMAP) [1981] SST reconstructions for stage 2, these data indicate little change between glacial and interglacial paleotemperatures in the equatorial Atlantic. An electronic supplement of this material may be obtainedon a diskette or Anonymous FTP from KOSMOS.AGU.ORG.(LOGIN to AGU's FTP account using ANONYMOUS as theusername and GUEST as the password. Go to the rightdirectory by typing CD APEND. Type LS to see what files areavailable. Type GET and the name of the file to get it.Finally, type EXIT to leave the system.) (Paper 95PA03773,Reconstructing the stable isotope geochemistry andpaleotemperatures of the equatorial Atlantic during the last150,000 years: Results from individual foraminifera,Katharina Billups and Howard J. Spero). Diskette may beordered from American Geophysical union, 2000 FloridaAvenue, N. W., Washington, DC 20009; $15.00. Paymentmust accompany order.

Abstract: Styles of glacial sedimentation and erosion in Prydz Bay respond to glacial and interglacial cycles and fall into three zones; an inner zone of net erosion, a middle zone of subglacially eroded and deformed transitional glacial marine deposits and an outer zone of subglacial till deposition and shelf progradation. The inner zone is the region of maximum basal shear stress and inner-shelf deep formation by enhanced erosion in areas where tributary glaciers converge with the extended Lambert Glacier. The middle zone is underlain by sediments deposited near the ice-grounding zone during retreat, both as blanket like deposits and as grounding-line moraines. This material is then deformed into elongate subglacial bedforms (megaflures or drumlins), a process that probably involves some erosion. Deforming subglacial bed conditions extend to the shelf edge within a valley crossing the shelf on the western side of Prydz Bay. The outer zone is a zone of net deposition of compact subglacial till and prograding continental slope deposits formed during full glacial conditions and glacial marine sediment formed during ice retreat. The inferred build up of ice on the Ingrid Christensen Coast may have been responsible for the development of the western ice stream that flowed in Prydz Channel. The geometry of seismic sequences in Prydz Channel suggests that this ice stream and its associated trough mouth fan developed after a major episode of shelf and slope erosion during the Pliocene.