Glacial Sections Research Articles

Paleogeographic records of glacial and terminal glacial palynozones related to the Late Paleozoic Ice Age in the Brazilian portion of the Paraná Basin, Western Gondwana

Among the four palynozones established for the Pennsylvanian–Permian sedimentary succession of the Paraná Basin, two are related to the glacial (AcZ: Ahrensisporites cristatus and CmZ: Crucisaccites monoletus zones) and one is related to the following terminal glacial phase (VcZ: Vittatina costabilis Zone) in this portion of Gondwana. The AcZ and the CmZ are typically recognized within the basal and middle portions of the Itararé Group and the Aquidauana Formation, while the VcZ corresponds to the upper portions of both units. In this paper we present a palynostratigraphic analysis of all occurrences of these palynozones from 66 boreholes and 29 outcrops. Two paleogeographic maps are depicted showing the distribution of all sections where the palyonozones related to glacial and terminal glacial sections occur within the Itararé Group and the Aquidauana Formation. Glacial palynozones (AcZ and CmZ) are recognized from outcrops and boreholes from Santa Catarina, Paraná, São Paulo, Mato Grosso do Sul, Mato Grosso and Goiás states, encompassing the thickest portion of the Itararé Group and the Aquidauana Formation. The terminal glacial palynozone (VcZ) was recognized from several boreholes and outcrops, well distributed throughout the basin, from the Rio Grande do Sul, Santa Catarina, Paraná, São Paulo and Mato Grosso do Sul states. Reworked palynomorphs from Devonian and Mississippian strata found together with indigenous species in assemblages assigned to the glacial palynozones (AcZ and CmZ) are used herein as a tool for interpretation of the source area and as indicators of transport direction. As observed elsewhere in Gondwana, palynozones related to the glacial and terminal glacial phases present dominance of spores and monosaccate pollen grains, whereas those linked to the latter phase record the income and the quantitative increase of certain species indicative of progressive climate amelioration. Further sedimentary and stratigraphical aspects are also discussed.

A SUMMARY OF RADIOCARBON MEASUREMENTS OF FLUVIAL AND COLLUVIAL DEPOSITS IN CATCHMENTS OF SOUTH-CENTRAL ONTARIO, CANADA

ABSTRACTFluvial and colluvial deposits of Late Holocene age in South-Central Ontario catchments have provided few 14C dates, most by conventional methods registering century-old ages. Other young deposits, dated by conventional and accelerator mass spectrometry radiocarbon (AMS 14C), have yielded bomb-affected post-1950 ages over variable time limits. Attempts to date the base of Ah and lower-in-section soil horizons, in Early to Late Holocene stream terrace deposits, have yielded atomic bomb effects. Comparing bomb contamination in Late Holocene fluvial deposits, using both conventional and AMS methods, identifies a mix of bomb-affected beds juxtaposed with dated beds, the latter yielding ages with narrow standard deviations. Colluvial deposits overlying key glacial sections in the Rouge Catchment, while rare, yield bracketed AMS ages for an Ahbk horizon that refines weathering times relative to previously obtained conventional 14C dates. Bomb-affected sediment appears variably distributed within floodplain soils and in the ground soil of a colluvial section. Mass wasted deposits, with AMS 14C ages spread over the last few centuries, appear related to Little Ice Age (LIA) changes in climate, corroborated by pollen records. Further, these AMS-14C dated beds calibrate weathering of secondary Fe-Al oxihydroxides over the first half a millennium of weathering time.

Atmospherically produced beryllium-10 in annually laminated late-glacial sediments of the North American Varve Chronology

Abstract. We attempt to synchronize the North American Varve Chronology (NAVC) with ice core and calendar year timescales by comparing records of atmospherically produced 10Be fallout in the NAVC and in ice cores. The North American Varve Chronology (NAVC) is a sequence of 5659 varves deposited in a series of proglacial lakes adjacent to the southeast margin of the retreating Laurentide Ice Sheet between approximately 18 200 and 12 500 years before present. Because properties of NAVC varves are related to climate, the NAVC is also a climate proxy record with annual resolution, and our overall goal is to place the NAVC and ice core records on the same timescale to facilitate high-resolution correlation of climate proxy variations in both. Total 10Be concentrations in NAVC sediments are within the range of those observed in other lacustrine records of 10Be fallout, but 9Be and 10Be concentrations considered together show that the majority of 10Be is present in glacial sediment when it enters the lake, and only a minority of total 10Be derives from atmospheric fallout at the time of sediment deposition. Because of this, an initial experiment to determine whether or not 10Be fallout variations were recorded in NAVC sediments by attempting to observe the characteristic 11-year solar cycle in short varve sections sampled at high resolution was inconclusive: short-period variations at the expected magnitude of this cycle were not distinguishable from measurement scatter. On the other hand, longer varve sequences sampled at decadal resolution display centennial-period variations in reconstructed 10Be fallout that have similar properties as coeval 10Be fallout variations recorded in ice core records. These are most prominent in glacial sections of the NAVC that were deposited in proglacial lakes and are suppressed in paraglacial sections of the NAVC that were deposited in lakes lacking direct glacial sediment input. We attribute this difference to the fact that buffering of 10Be fallout by soil adsorption can filter out short-period variations in an entirely deglaciated watershed, but such buffering cannot occur in the ablation zone of an ice sheet. This implies that proglacial lakes whose watershed is mostly glacial may effectively record 10Be fallout variations. We attempted to match centennial-period variations in reconstructed 10Be fallout flux from two segments of the NAVC with ice core fallout records. For both records, it is possible to obtain matches that result in acceptable correlation between NAVC and ice core 10Be fallout records, but the best-fitting matches for the two segments disagree, and only one of them is consistent with independent calendar year calibrations of the NAVC and therefore potentially valid. This leaves several remaining ambiguities in whether or not 10Be fallout variations can, in fact, be used for synchronizing NAVC and ice core timescales, but these could most likely be resolved by higher-resolution and replicate 10Be measurements on targeted sections of the NAVC.

ASSESSING THE STRATIGRAPHIC INTEGRITY OF PLANKTIC AND BENTHIC 14C RECORDS IN THE WESTERN PACIFIC FOR Δ14C RECONSTRUCTIONS AT THE LAST GLACIAL TERMINATION

ABSTRACTThere is a growing database of radiocarbon (14C) reconstructions from biogenic carbonate taken from marine sediment cores being used to investigate changing ocean circulation and carbon cycling at the end of the last great ice age. Reported here are 14C results from a marine core taken in the Makassar Straits of the western equatorial Pacific that was intended to test whether there was evidence of geologic carbon release to the ocean during the glacial termination. A thorough investigation of planktic and benthic 14C ages with stable isotopes and CT-scans revealed extensive burrowing in the upper 2 m of the core that displaced younger sediments downward by more than half a meter into the glacial section of the core. The vertical displacement is evident in both planktic and benthic fossils. However, the extent of displacement and the stratigraphic disturbance became evident only after multiple measurements of different species and genera. A CT-scan prior to sampling would be an effective screening tool to avoid sampling problem cores such as this.

Large bedrock slope failures in a British Columbia, Canada fjord: first documented submarine sackungen

Very large (>60×106 m3) sackungen or deep-seated gravitational slope deformations occur below sea level along a steep fjord wall in central Douglas Channel, British Columbia. The massive bedrock blocks were mobile between 13 and 11.5 thousand radiocarbon years BP (15,800 and 13,400 BP) immediately following deglaciation. Deformation of fjord sediments is apparent in sedimentary units overlying and adjacent to the blocks. Faults bound the edges of each block, cutting the glacial section but not the Holocene sediments. Retrogressive slides, small inset landslides as well as incipient and older slides are found on and around the large failure blocks. Lineations, fractures and faults parallel the coastline of Douglas Channel along the shoreline of the study area. Topographic data onshore indicate that faults and joints demarcate discrete rhomboid-shaped blocks which controlled the form, size and location of the sackungen. The described submarine sackungen share characteristic geomorphic features with many montane occurrences, such as uphill-facing scarps, foliated bedrock composition, largely vertical dislocation and a deglacial timing of development.

Reflection of global late glacial and Holocene paleoclimate oscillations in the palynological record from bottom sediments of Tavatui Lake (Middle Urals)

The palynological analysis of the reliably dated core section of bottom sediments from Tavatui Lake revealed consistency between the chronology and succession of Late Pleistocene and Early Pliocene events (GI-a/b, CS-1, GH-11.2) in the Middle Urals and the North Atlantic region. It is established that the Holocene thermal maximum (5.3–8.0 cal. ka ago) in the Middle Urals was characterized by high temperatures and humidity. The initial stage of the Subboreal cooling was reffered to the interval of 4.5–5.3 cal. ka ago. The data obtained provided grounds for the conclusion that the palynological record in the Tavatui Lake section reflects in detail global and regional climate oscillations, which allows it to be used as a Holocene and late glacial reference section, as well as for predicting the behavior of the natural system of the Middle Urals in response to future climate change.

Coupled ocean–land millennial-scale changes 1.26 million years ago, recorded at Site U1385 off Portugal

While a growing body of evidence indicates that North Atlantic millennial-scale climate variability extends to the Early Pleistocene, its impact on terrestrial ecosystems has not been established. Here we present ultra-high resolution (70–140year) joint foraminiferal isotopic and pollen analyses from IODP Site U1385 off Portugal, focusing on a short glacial section of Marine Isotope Stage 38, ~1.26millionyears ago. Our records reveal the presence of millennial-scale variability in the coupled ocean–atmosphere–land system in the North Atlantic and provide the first direct evidence for the response of western Iberian vegetation to abrupt climate changes in the Early Pleistocene. The magnitude and pacing of changes bear significant similarities to Dansgaard–Oeschger variability of the last two glacials.

The oxygen and carbon isotopic signatures of biogenic carbonates in Gerzensee, Switzerland, during the rapid warming around 14,685 years BP and the following interstadial

The stable isotope signature of ostracods, molluscs, and charophyte remains from the late glacial section of a shallow core from lake Gerzensee, Switzerland, is analyzed along with the bulk carbonate isotope composition in a multi-proxy study aiming to document the biotic responses to the first strong warming ca. 14.6ka ago after full glacial conditions. The main goal of our contribution is to understand the climatic significance of the oxygen-isotope variations in and between the different carbonate species and ideally provide a quantitative estimate of the oxygen isotopic composition of meteoric precipitation, which then could be translated to mean temperature estimates. Corrected for the respective vital offsets, the different carbonates show almost identical oxygen-isotope ratios for the time preceding and after the rapid transition from Greenland climate stages GS2 to GI1, indicating low and seasonally constant water temperatures at the sediment–water interface for this period. In the following the difference between cold season and warm-season carbonates increases gradually, pointing to a summer–winter temperature difference of roughly 10K at the end of GI1. We conclude that this gradual water-temperature increase is independent of climate and is mainly due to sedimentation, shallowing the sediment–water interface, eventually accentuated by a gradual decrease of Gerzensee's water level during GI1. Corrected for the isotope fractionation induced by the long term trend of such water temperature change, the higher resolved δ18O record from the bulk carbonates allows calculation of the presumed oxygen–isotope ratio of former lake water (δ18OL), which shows striking similarity to the record from Ammersee. Introducing a tentative hydrological correction close to the present day offset between δ18OL and the oxygen–isotopes in meteoric precipitation (δ18OP), we propose a quantitative δ18OP and mean air temperature record for the Gerzensee region.

Provenance and temporal variability of ice rafted debris in the Indian sector of the Southern Ocean during the last 22,000 years

Ice rafted debris (IRD) records were studied in two sediment cores (SK200/22a and SK200/27) from the sub-Antarctic and Polar frontal regime of the Indian sector of Southern Ocean for their distribution and provenance during the last 22,000 years. The IRD fraction consists of quartz and lithic grains, with the lithic grains dominated by volcaniclastic materials. IRD content was high at marine isotope stage 2 but decreased dramatically to near absence at the Termination 1 and the Holocene. The concentration of IRD at glacial section of the core SK200/27 was nearly twice that of SK200/22a. Moreover, IRD were more abundant at the last glacial maxima (LGM) in SK200/27 with its peak abundance proceeding by nearly two millennia than at SK200/22a. It appears that an intensification of Antarctic glaciation combined with a northward migration of the Polar Front during LGM promoted high IRD flux at SK200/27 and subsequent deglacial warming have influenced the IRD supply at SK200/22a. Quartz and lithic grains may have derived from two different sources, the former transported from the Antarctic mainland, while the latter from the islands of volcanic origin from Southern Ocean. Sea-ice, influenced by the Antarctic Circumpolar Current is suggested to be a dominant mechanism for the distribution of lithic IRD in the region.

Nutrient conditions in the subpolar North Atlantic during the last glacial period reconstructed from foraminifera‐bound nitrogen isotopes

Surface nitrate concentration is a potentially useful diagnostic in reconstructing the past circulation of high‐latitude North Atlantic waters. Moreover, nutrient consumption in the North Atlantic surface impacts the atmospheric concentration of carbon dioxide. To reconstruct nutrient conditions in the subpolar North Atlantic region during the last ice age, a record of foraminifera‐bound δ15N was measured in Neogloboquadrina pachyderma (sin.) from core V28‐73 south of Iceland (57.2°N, 20.9°W). Foraminifera‐bound δ15N is up to 2‰ lower during the last ice age than during the Holocene, suggesting as much as ~25% less complete nitrate consumption during the former. This is consistent with stronger light limitation associated with a deeper summer surface mixed layer, perhaps related to the formation of Glacial North Atlantic Intermediate Water previously suggested to have occurred near the core site. However, three single‐point maxima in δ15N in the glacial section and the sharp deglacial δ15N rise coincide with Heinrich event layers. This suggests that increased water column stratification during Heinrich events, presumably due to surface freshening, reduced the nutrient supply from below and led to nearly complete nitrate consumption in the summertime mixed layer. The Heinrich layers in V28‐73 are not accompanied by δ18O minima in either N. pachyderma (sin.) or Globigerinoides bulloides, which we tentatively attribute to extreme mixed‐layer shoaling. The reconstructed subpolar North Atlantic upper water column changes—both glacial/interglacial and millennial—are inverse to those inferred for the Antarctic.

Authigenic, detrital and diagenetic minerals in the Laguna Potrok Aike sediment sequence

The ∼100 m-long Laguna Potrok Aike sediment sequence yielded a record spanning the Last Glacial period to the Holocene. This paper presents and discusses two aspects of the mineralogy of the lake. The first aspect is based on a semi-quantitative X-ray diffraction analysis of bulk and clay mineralogical assemblages. Minor mineralogical changes are observed throughout the glacial section suggesting relatively uniform sediment sources. The transition into the Holocene is characterized by increasing fluxes of endogenic calcite thought to relate to lower lake levels. The second aspect is based on analysis of uranium-series disequilibria in diagenetic vivianite from the glacial section. U-series ages were expected to yield minimum ages for the host-sediment. Unfortunately, very little authigenic U is present in vivianite grains. The low primary productivity of the lake and thus low organic carbon fluxes might have prevented the development of strong redox gradients at the water-sediment interface and thus reduced diagenetic U-uptake into the sediment. One vivianite sample, at a 56.9 m composite depth, yielded enough authigenic uranium to calculate a 230Th-age of 29.4 ± 5.9 ka (±2σ). This age is younger than the one indicated by the radiocarbon chronology. It is thus concluded that a relatively late diagenetic evolution of the U–Th system characterizes the recovered vivianite minerals. The authigenic U displays a very high excess in 234U (over 238U) with an activity ratio of 4.58 ± 0.58 (±2σ). It suggests that it originates from the transfer of highly fractionated U from surrounding detrital minerals through very low U-content pore waters.

A novel approach to varve counting using μXRF and X-radiography in combination with thin-section microscopy, applied to the Late Glacial chronology from Lake Suigetsu, Japan

The Lake Suigetsu 2006 Varved Sediment Core Project (SG06 Project) aims to contribute to the international terrestrial radiocarbon calibration model, extending it to >50,000 cal years BP using the new SG06 sediment record, which shows annual laminations (varves) for most of this period. For varve counting, a novel approach using high resolution X-ray fluorescence (μXRF) and X-radiography was applied, described here in detail for the first time, and applied to the Late Glacial sediments of core SG06. This new technique was carried out alongside conventional varve counting by thin-section microscopy (Schlolaut et al., 2012). This dual approach allows comparison of results from the two independent counting methods on metre to sub-mm scales, enabling the identification and characterisation of differences between the techniques, and quantification of their weaknesses. Combining the results produces a more robust chronology than either counting method could produce alone. The reliability of this dual approach is demonstrated by comparison of the combined chronology with the radiocarbon dataset of SG06, calibrated with the tree-ring derived Late Glacial section of IntCal09.

Millennial‐scale sea surface temperature and Patagonian Ice Sheet changes off southernmost Chile (53°S) over the past ∼60 kyr

Glacial millennial‐scale paleoceanographic changes in the Southeast Pacific and the adjacent Southern Ocean are poorly known due to the scarcity of well‐dated and high resolution sediment records. Here we present new surface water records from sediment core MD07‐3128 recovered at 53°S off the Pacific entrance of the Strait of Magellan. The alkenone‐derived sea surface temperature (SST) record reveals a very strong warming of ca. 8°C over the last Termination and substantial millennial‐scale variability in the glacial section largely consistent with our planktonic foraminifera oxygen isotope (δ18O) record of Neogloboquadrina pachyderma (sin.). The timing and structure of the Termination and some of the millennial‐scale SST fluctuations are very similar to those observed in the well‐dated SST record from ODP Site 1233 (41°S) and the temperature record from Drowning Maud Land Antarctic ice core supporting the hemispheric‐wide Antarctic timing of SST changes. However, differences in our new SST record are also found including a long‐term warming trend over Marine Isotope Stage (MIS) 3 followed by a cooling toward the Last Glacial Maximum (LGM). We suggest that these differences reflect regional cooling related to the proximal location of the southern Patagonian Ice Sheet and related meltwater supply at least during the LGM consistent with the fact that no longer SST cooling trend is observed in ODP Site 1233 or any SST Chilean record. This proximal ice sheet location is documented by generally higher contents of ice rafted debris (IRD) and tetra‐unsaturated alkenones, and a slight trend toward lighter planktonic δ18O during late MIS 3 and MIS 2.

High-resolution 14C dating of a 25,000-year lake-sediment record from equatorial East Africa

We dated a continuous, ∼22-m long sediment sequence from Lake Challa (Mt. Kilimanjaro area, Kenya/Tanzania) to produce a solid chronological framework for multi-proxy reconstructions of climate and environmental change in equatorial East Africa over the past 25,000 years. The age model is based on a total of 168 AMS 14C dates on bulk-organic matter, combined with a 210Pb chronology for recent sediments and corrected for a variable old-carbon age offset. This offset was estimated by i) pairing bulk-organic 14C dates with either 210Pb-derived time markers or 14C dates on grass charcoal, and ii) wiggle-matching high-density series of bulk-organic 14C dates. Variation in the old-carbon age offset through time is relatively modest, ranging from ∼450 yr during glacial and late glacial time to ∼200 yr during the early and mid-Holocene, and increasing again to ∼250 yr today. The screened and corrected 14C dates were calibrated sequentially, statistically constrained by their stratigraphical order. As a result their constrained calendar-age distributions are much narrower, and the calibrated dates more precise, than if each 14C date had been calibrated on its own. The smooth-spline age-depth model has 95% age uncertainty ranges of ∼50–230 yr during the Holocene and ∼250–550 yr in the glacial section of the record. The δ 13C values of paired bulk-organic and grass-charcoal samples, and additional 14C dating on selected turbidite horizons, indicates that the old-carbon age offset in Lake Challa is caused by a variable contribution of old terrestrial organic matter eroded from soils, and controlled mainly by changes in vegetation cover within the crater basin.

Source, timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis

Haapaniemi, A.I., Scourse, J.D., Peck, V.L., Kennedy, H., Kennedy, P., Hemming, S.R., Furze, M.F.A., Pieńkowski, A.J., Austin, W.E.N., Walden, J., Wadsworth, E. & Hall, I.R. 2010: Source, timing, frequency and flux of ice‐rafted detritus to the Northeast Atlantic margin, 30–12 ka: testing the Heinrich precursor hypothesis. Boreas, Vol. 39, pp. 576–591. 10.1111/j.1502‐3885.2010.00141.x. ISSN 0300‐9483.Increased fluxes of ice‐rafted detritus (IRD) from European ice sheets have been documented some 1000–1500 years before the arrival of Laurentide Ice Sheet (LIS)‐sourced IRD during Heinrich (H) events. These early fluxes have become known as ‘precursor events’, and it has been suggested that they have mechanistic significance in the propagation of H events. Here we present a re‐analysis of one of the main cores used to generate the precursor concept, OMEX‐2K from the Goban Spur covering the last 30 ka, in order to identify whether the British–Irish Ice Sheet (BIIS) IRD fluxes occur only as precursors before H layers. IRD characterization and planktonic foraminiferal δ18O measurements constrained by a new age model have enabled the generation of a continuous record of IRD sources, timing, frequency and flux, and of local contemporary hydrographic conditions. The evidence indicates that BIIS IRD precursors are not uniquely, or mechanistically, linked to H events, but are part of the pervasive millennial‐scale cyclicity. Our results support an LIS source for the IRD comprising H layers, but the ambient glacial sections are dominated by assemblages typical of the Irish Sea Ice Stream. Light isotope excursions associated with H events are interpreted as resulting from the melting of the BIIS, with ice‐sheet destabilization attributed to eustatic jumps generated by LIS discharge during H events. This positive‐feedback mechanism probably caused similar responses in all circum‐Atlantic ice‐sheet margins, and the resulting gross freshwater flux contributed to the perturbation of the Atlantic Meridional Overturning Circulation during H events.

Synchronizing ice cores from the Renland and Agassiz ice caps to the Greenland Ice Core Chronology

Four ice cores from the Agassiz ice cap in the Canadian high arctic and one ice core from the Renland ice cap in eastern Greenland have been synchronized to the Greenland Ice Core Chronology 2005 (GICC05) which is based on annual layer counts in the DYE‐3, GRIP and NGRIP ice cores. Volcanic reference horizons, seen in electrical conductivity measurements (ECM) have been used to carry out the synchronization throughout the Holocene. The Agassiz ice cores have been matched to the NGRIP ice core ECM signal, while the Renland core has been matched to the GRIP ice core ECM signal, thus tying the cores to GICC05. Furthermore, it has been possible to synchronize the Renland ice core to NGRIP‐GICC05 in the glacial period back to 60,000 years b2k (years before A.D. 2000), on the basis of a matching of transitions between stadials and interstadials. This work brings the total number of ice core records that have been rigorously tied to the GICC05 timescale up to nine. Renland annual layer thicknesses are increasing with depth during the period from 7 to 8.5 ka b2k, a highly unusual observation only matched by a similar thickness increase in the glacial section of the Renland core some 60 ka ago. Annual layer thicknesses in the Agassiz ice cores point to a well‐developed Raymond bump in the Agassiz ice cap.

Glacial water mass geometry and the distribution of δ13C of ΣCO2 in the western Atlantic Ocean

Oxygen and carbon isotopic data were produced on the benthic foraminiferal taxa Cibicidoides and Planulina from 25 new piston cores, gravity cores, and multicores from the Brazil margin. The cores span water depths from about 400 to 3000 m and intersect the major water masses in this region. These new data fill a critical gap in the South Atlantic Ocean and provide the motivation for updating the classic glacial western Atlantic δ13C transect of Duplessy et al. (1988). The distribution of δ13C of ΣCO2 requires the presence of three distinct water masses in the glacial Atlantic Ocean: a shallow (∼1000 m), southern source water mass with an end‐member δ13C value of about 0.3–0.5‰ VPDB, a middepth (∼1500 m), northern source water mass with an end‐member value of about 1.5‰, and a deep (>2000 m), southern source water with an end‐member value of less than −0.2‰, and perhaps as low as the −0.9‰ values observed in the South Atlantic sector of the Southern Ocean (Ninnemann and Charles, 2002). The origins of the water masses are supported by the meridional gradients in benthic foraminiferal δ18O. A revised glacial section of deep water δ13C documents the positions and gradients among these end‐member intermediate and deep water masses. The large property gradients in the presence of strong vertical mixing can only be maintained by a vigorous overturning circulation.

Lipid and lignin/cutin compounds in Lake Baikal sediments over the last 37 kyr: implications for glacial–interglacial palaeoenvironmental change

A stratigraphic study of total organic carbon (TOC) concentration, carbon isotopic composition of total organic matter (TOM), lipids ( n-alkanes, n-alkanols, n-alkanoic acids and sterols) and lignin/cutin compounds has been conducted for a Lake Baikal core (323-PC1) over the last glacial/interglacial. TOC concentrations (mg g −1 dry sediment) are low (2–4) in the glacial sections, but high (10–29) in the interglacial ones. The concentrations of land plant-derived compounds such as n-C 14 to C 28 ω-hydroxyalkanoic acids, lignin phenols ( p-hydroxyl, vanillyl and syringyl), total cutin acids, normalized to TOC in the interglacial, are 5–6 times higher than those in the glacial. Carbon isotopic compositions of TOM are −24 ± 0.9‰ in the glacial, while they are −27 ± 1.3‰ in the interglacial. The heavy isotope composition of TOM in the glacial might be due to a contribution from submerged plants and/or grasses. The light isotopic composition of TOM for the interglacial may be due to a contribution from both land plant- and phytoplankton (mainly diatom)-derived OM. Autochthonous organic carbon contents were estimated from the C/N ratio corrected for the effect of inorganic nitrogen and based on the assumption of C/N values of 8 for autochthonous and 25 for allochthonous OM. The estimation indicates that autochthonous OC comprises 74 ± 6% of TOC for the glacial and 72 ± 9% for the interglacial, respectively. Primary palaeoproductivity was estimated to be below 20 gC m −2 y −1 in the glacial (before 18 ka), but high (100–120 gC m −2 y −1) in the interglacial (11–8 ka), which is 10–30% higher than the modern values.

MIDDLETON, G. V. (ed.) 2003. Encyclopedia of Sediments and Sedimentary Rocks. Encyclopedia of Earth Sciences Series. xxx + 821 pp. Dordrecht, Boston, London: Kluwer. Price Euros 399, US $390, £250 (hard covers). ISBN 1 4020 0872 4

A book of this nature is always a challenge to a reviewer to find out just how comprehensive it really is. My first few hours of using this book were taken up with attempts to think of relatively obscure terms or concepts in sedimentary geology and then looking for them within the 821 pages of text. Overall I was reasonably satisfied that the subject area was well covered, although I was disappointed that neither ‘jokhul-haup’ nor ‘sandur’ seemed to have a mention when I reviewed the glacial sections, and when looking more broadly, the terms ‘palustrine’, ‘strandplain’ and ‘chenier ridge’ also appeared to be absent. At first I thought that there were more omissions, as I could not find terms like ‘dropstone’ and ‘adhesion ripple’ in the index, but it transpired that the index was at fault here and mention of these topics was to be found buried in articles. It was perhaps a little unfair of me to be deliberately looking for faults from the outset, but this approach did give me an insight into the organisation of the encyclopedia and an indication of how useful it might be to the casual (or indeed, intensive) user. I was not wholly impressed with what I found. The book is organized into approximately 250 topics about which an …

340,000-year centennial-scale marine record of Southern Hemisphere climatic oscillation.

In order to investigate rapid climatic changes at mid-southern latitudes, we have developed centennial-scale paleoceanographic records from the southwest Pacific that enable detailed comparison with Antarctic ice core records. These records suggest close coupling of mid-southern latitudes with Antarctic climate during deglacial and interglacial periods. Glacial sections display higher variability than is seen in Antarctic ice cores, which implies climatic decoupling between mid- and high southern latitudes due to enhanced circum-Antarctic circulation. Structural and temporal similarity with the Greenland ice core record is evident in glacial sections and suggests a degree of interhemispheric synchroneity not predicted from bipolar ice core correlations.