Contributors: M. Cremer, E. Gonthier, J. Duprat, J.-C. Faugères, T. Courp

Date: 2007-02-01

sediment cores across the Sao Tomé system (core location in Fig. 2). ...core) and temporal (average for glacial and interglacial sediments) variability...carbonate-rich sediment are lighter. «Sl» and «sl» stand for the silt ...sedimentation rates ...Quaternary...fraction) in the sediment cores. Data in Table 5. ...sediment records allow addressing the paleoceanographic changes that took...sediment...sedimentation rates. Cores location in Fig. 2. ...sediment cores across the Sao Tomé system (core location in Fig. 2). Lithologic...sediment dynamics that prevailed on this system during the late Quaternary...Carbonate record and sediment structures (X radiograph) in selected sequences...sediment dynamics that prevailed on this system during the late Quaternary...sedimentation. According to the location of the cores at the present day...sediment cores. Data in Table 5. ...sedimentation rate during glacials) the sediment records (chiefly the ...late glacial could be associated to Heinrich events, when NADW production...Spatial (average by core) and temporal (average for glacial and interglacial...Late Quaternary variability of the sedimentary record in the Sao Tome ...cores at the present day interface between NADW and AABW, we infer that...sediment cores located across a deep channel-levee system in the South ... Very few sediment records allow addressing the paleoceanographic changes that took place on orbital and/or sub-Milankovitch time scales in the South–West Atlantic. Here, a set of sediment cores located across a deep channel-levee system in the South Brazilian basin (3700–3900 m depth) is used to infer the sediment dynamics that prevailed on this system during the late Quaternary and to relate this pattern to climate changes. The spatial distribution of deposits (changes in mineralogy, texture, structure, and sedimentation rate according to the morphology) indicates bulk of sediment supplies is distributed on the Sao Tomé system by bottom advective processes. The silty–sandy layers, originate undoubtedly from turbidity currents whereas the fine-grained muds and oozes, that form the major part of the deposits, are controlled by deep geostrophic currents. In addition to variations forced by the orbital cycles, (more turbidites, less carbonates and higher sedimentation rate during glacials) the sediment records (chiefly the CaCO3 record) document outstanding higher frequency regional changes in sedimentation. According to the location of the cores at the present day interface between NADW and AABW, we infer that changes in sedimentation are related to pulses of AABW versus NADW production. These changes, commonly marked by asymmetric carbonate pattern of about 10 kyr, suggest that the relative influence of NADW versus AABW followed, throughout the last 190 kyr, a repetitive sequence of progressive increase and sharp decrease. The rather sharp shut down observed during the late glacial could be associated to Heinrich events, when NADW production stopped, but similar events are also well expressed during MIS 5, MIS 6 and at the end of MIS 7.

Contributors: A. Anil Kumar, V. Purnachandra Rao, S.K. Patil, Pratima M. Kessarkar, M. Thamban

Date: 2005-10-15

...sediment-dominated sections of the cores off Saurashtra–Ratnagiri, followed...cores on the western margin of India. Geology after Rao and Wagle (1997...late Quaternary...late Quaternary...Do...1997). ...sediments of the eastern Arabian Sea: Evidence for late Quaternary climatic...sediments in GC1. (B) Down-core variations of sedimentological parameters...sediment sections of the cores ...Down-core variations of MS in GC11. ...Down-core variations of MS in core GC14 and GC15. ...sediments were determined for 15 gravity cores recovered from the western...sediments off Indus–Gulf of Kachchh and then Mangalore–Cape Comorin....GC13. ...the sediments in GC1. (B) Down-core variations of sedimentological parameters...sediments...sediments reflect the land-derived input and, in general, are the highest...Down-core variations of MS in GC11. ... Rock-magnetic measurements along with grain size, acid-insoluble residue (AIR), organic carbon (OC), CaCO3 and δ18O of the planktonic foraminifers of the sediments were determined for 15 gravity cores recovered from the western continental margin of India. Magnetic susceptibility (MS) values in the surficial sediments reflect the land-derived input and, in general, are the highest in terrigenous sediment-dominated sections of the cores off Saurashtra–Ratnagiri, followed by the sediments off Indus–Gulf of Kachchh and then Mangalore–Cape Comorin.

Contributors: A Kuijpers, S.R Troelstra, M.A Prins, K Linthout, A Akhmetzhanov, S Bouryak, M.F Bachmann, S Lassen, S Rasmussen, J.B Jensen

Date: 2003-03-30

core is not represented. The core location, where water depth is 620 m...sediment Fe/K ratio. Results of 14C measurements are also shown. Note ...core DS97-7P with whole-core MS, calcium carbonate content, relative abundance...core DS97-4P with grain size (>63 μm) distribution, whole-core MS, XRF...the sediment waves, indicates contour-parallel bottom currents (shown ...sediment transport and mass flow deposition, which is concluded to be ... log of core DS97-7P with whole-core MS, calcium carbonate content, relative...Late Quaternary sedimentary processes and ocean circulation changes at...Pliocene–Quaternary sedimentary sequence. ...late Quaternary depositional processes and bottom current activity on ...late Quaternary depositional processes and bottom current activity on ...sedimentation...core of south flowing LSW between 800 and 1500 m (after Dickson and Brown...sediment core information. The seabed data demonstrate the occurrence ... A study has been made of late Quaternary depositional processes and bottom current activity on the Southeast Greenland margin, using seismic, sub-bottom profiling and deep-tow side-scan sonar data as well as sediment core information. The seabed data demonstrate the occurrence of strong, southerly bottom currents prevailing on the slope and rise. Well-defined longitudinal bedforms indicate maximum mean near-bottom current velocities of up to at least 1.0 m/s at the depth stratum of Labrador Sea water (800–1500 m). Similarly strong currents occur in Denmark Strait overflow water (DSOW) at the base of the slope, whereas more basinward the maximum DSOW flow speed is lower. Iceberg plow marks were found down to about 700 m water depth. Both at the shelf edge and on the lower slope and rise the seafloor morphology is indicative of downslope sediment transport and mass flow deposition, which is concluded to be a typically glacial feature. After generally more sluggish deep-water circulation during the last glacial maximum, DSOW basin ventilation was re-established shortly before 13.3 ka. On the shelf, in front of the retreating Greenland ice margin, permanent or semi-permanent sea ice conditions prevailed until about 12.5 ka. At that time increased Irminger Current activity had resulted in warming, and East Greenland Current (EGC)-controlled iceberg drift increased. No evidence was found for a return to extreme glacial conditions or a ceasing of DSOW flow during the Younger Dryas. Abundant coarse IRD collected at greater water depth from shallow sub-seabed strata has a provenance mainly in the northern part of East Greenland (68–73°N), which demonstrates the existence of a pre-Holocene EGC system initially extending to beyond the shelf edge.

Contributors: Pierre Giresse, Henri Pauc, Jacques Déverchère

Date: 2009-05-01

sediment cores indicate that turbidite sequences are both thicker and ...sediment cores. ...Sediment cores...cores retrieved from the Algerian margin from Oran to 80km east of Algiers...Late Quaternary... profiles of sediment cores from the Algiers area: KMDJ01 (a), KMDJ02 ...sediment core implying various origin of the gravity flow (eustatic change...sediment cores indicate a decreasing frequency of turbidite sequences ...sediment gravity-flow deposits on the western Algerian margin during late...sediment rates of seven studied sediment cores. Thickness of debris flow...profiles of sediment cores from the Chenoua–Tenes area: KMDJ06 (a), KMDJ07...Late Quaternary...position of analysed sediment cores. ...sediment cores from the Chenoua–Tenes area: KMDJ06 (a), KMDJ07 (b), KMDJ08...position of analysed sediment cores. (B). Detailed maps of the Chenoua–Tenes...accumulation sediment rates of seven studied sediment cores. Thickness...sediment cores from the Algiers area: KMDJ01 (a), KMDJ02 (b), KMDJ03 (...sediment gravity-flow deposits and their sources. At the foot of the slope...sediment cores. (B). Detailed maps of the Chenoua–Tenes area locating ... Seven piston cores retrieved from the Algerian margin from Oran to 80km east of Algiers were studied to identify sediment gravity-flow deposits and their sources. At the foot of the slope, five sediment cores indicate a decreasing frequency of turbidite sequences from the transgressive systems tract to the highstand systems tract resulting in lower off-shelf sediment fluxes during the last highstand episode. There is an approximately log-normal frequency distribution of bed thickness that increases for larger grain-size class, but this relationship is frequently altered by truncation of the top of the turbidite sequence. In the deep basin off Algeria, two sediment cores indicate that turbidite sequences are both thicker and more preserved than at the foot of the slope and are observed through the entire sediment core implying various origin of the gravity flow (eustatic change, seismicity).

Contributors: Zhongyuan Chen, Baoping Song, Zhanghua Wang, Yongli Cai

Date: 2000-01-15

sediment cores, vibrocores, surficial samples and seismic track line. ...sediment distribution. Belt A, delta front fine sand and silt, with trough...the core Cj4. Zone c, the warmest temperature period starting at ca. 7000...sediment sequences reveal a general trend of climate warming from early...late Pleistocene sediments in front of the estuarine depocenter. Gravity...core Cj4. Indicated 14C dates are based from Chen and Wang (1994). ...showing the location of sediment cores, vibrocores, surficial samples ...late Quaternary stratigraphy...Late Quaternary evolution of the sub-aqueous Yangtze Delta, China: sedimentation...sediment belts (A–D) of the Yangtze sub-aqueous delta are defined from...text. ...Sediment distribution of the sub-aqueous Yangtze Delta. Four sediment ...late Quaternary sub-aqueous Yangtze Delta. N, number; S, species; R, rare...S...late Pleistocene period (Ren and Zhen, 1980). ...late Quaternary stratigraphy of the delta consists from bottom upward ...late Quaternary stratigraphy...sediment loading within the depocenter is the major factor in causing ...sediment distribution...lithostratigraphic log of the late Quaternary sub-aqueous Yangtze Delta ... Four sediment belts (A–D) of the Yangtze sub-aqueous delta are defined from the sea-bottom sediment distribution. Belt A, delta front fine sand and silt, with trough cross stratification; Belt B, prodelta silty clay and clayey silt, with abundant burrowing and rich in organic matter; Belt C, prodelta to continental shelf sand–silt–clay, with thin layers of sand and clay interbedded; and Belt D, late Pleistocene relict sands (medium to fine grained), mixed with shell fragments. The late Quaternary stratigraphy of the delta consists from bottom upward of: late Pleistocene terrigenous (fluvial and lacustrine) sand and mud; Holocene transgressive silt, prodelta clay and delta front fine sand and silt. In addition, four pollen-spore zones (a–d) derived from these sediment sequences reveal a general trend of climate warming from early to late Holocene. The Zone c, distributed primarily within the prodelta muds, provides evidence for a temperature maximum starting at ca. 7000 years B.P. (Atlantic period). This indicates that the delta initiation was essentially coeval with the climate optimum in early Holocene. Sub-bottom seismic surveys reveal three (I–III) acoustic facies. Facies I and II are characterized by seaward remobilization of water-saturated Holocene prodelta muds; facies III is composed of highly-contorted late Pleistocene strata and mud diapirs that erupted from deep-seated late Pleistocene sediments in front of the estuarine depocenter. Gravity subsidence due to Holocene sediment loading within the depocenter is the major factor in causing the deformation of underlying unconsolidated strata. Furthermore, the sub-aqueous Yangtze Delta proper is now obviously diverting to southeast owing to the long-term, tectonically induced southward shift of the river mouth, and to the marine currents associated with the Coriolis effect. We thus predict that the large Chongming island in river mouth area will have been coalesced with the northern Yangtze coast in the recent future.

Contributors: Müller, Peter J, Cepek, Martin, Ruhland, Götz, Schneider, Ralph R

Date: 1997-10-19

Late Quaternary: Reconstruction of Budget and Currents...late Quaternary periods when this species was scarce or absent because...Late Quaternary: Reconstruction of Budget and Currents...late Quaternary coccolith datum levels: Validation by oxygen isotopes....late Quaternary sediment core from the Walvis Ridge and compared the results...Quaternary sediments may be subject to bias if algae with different temperature...late Quaternary sediments from the Walvis Ridge: Implications for the ...late Quaternary sediments from the Walvis Ridge: Implications for the ...late Quaternary sediment core from the Walvis Ridge and compared the results...late Quaternary coccolith datum levels: Validation by oxygen isotopes....core record while the coccolithophorid study was confined to the last ...late Quaternary sediments from the Walvis Ridge...late Quaternary periods when this species was scarce or absent because ... Abstract: Sea surface temperatures (SSTs) derived from the alkenone UK'37) record of Quaternary sediments may be subject to bias if algae with different temperature sensitivities have contributed to the sedimentary alkenone record. The alkenone-derived SST records are usually based on a UK'37-temperature relationship which was measured in culture experiments using the coccolithophorid Emiliania huxleyi (F.G. Prahl, L.A. Muehlhausen and D.L. Zahnle, 1988. Further evaluation of long-chain alkenones as indicators of paleoceanographic conditions. Geochim. Cosmochim. Acta 52, 2303-2310). To assess possible effects of past species changes on the UK'37-temperature signal, we have analyzed long-chain alkenones and coccolithophorids in a late Quaternary sediment core from the Walvis Ridge and compared the results to SST estimates extracted from the d18O record of the planktonic foraminifer Globigerinoides ruber. Alkenones and isotopes were determined over the entire 400-kyr core record while the coccolithophorid study was confined to the last 200 kyr when the most pronounced changes in alkenone content occurred. Throughout oxygen-isotope stages 6 and 5, species of the genus Gephyrocapsa were the predominating coccolithophorids. E. huxleyi began to increase systematically in relative abundance since the stage 5/4 transition, became dominant over Gephyrocapsa spp. during stage 3 and reached the highest abundances in the Holocene. Carbon-normalized alkenone concentrations are inversely related to the relative abundances of E. huxleyi, and directly related to that of Gephyrocapsa spp., suggesting that species of this genus were the principal alkenone contributors to the sediments. Nevertheless, SST values obtained from the UK'37-temperature relationship for E. huxleyi compare favourably to the isotope-derived temperatures. The recently reported UK'37-temperature relationship for a single strain of Gephyrocapsa oceanica (J.K. Volkman. S.M. Barrett, S.I. Blackburn and E.L. Sikes, 1995. Alkenones in Gephyrocapsa oceanica: Implications for studies of paleoclimate. Geochim. Cosmochim. Acta 59, 513-520) produces unrealistically high SST values indicating that the temperature response of the examined strain is not typical for the genus Gephyrocapsa. This is supported by the C37:C38, alkenone ratios of the sediments which are comparable to average ratios reported for E. huxleyi, but significantly higher than for the G. oceanica strain. Most notably, the general accordance of the alkenone characteristics between sediments and E. huxleyi persists through stages 8 to 5 and even in times that predate the first appearance of this species (268 ka; H.R. Thierstein, K.R. Geitzenauer and B. Molfino, 1977. Global synchroneity of late Quaternary coccolith datum levels: Validation by oxygen isotopes. Geology 5, 400-404). Our results suggest that UK'37-temperature relationships based on E. huxleyi produce reasonable paleo-SST estimates even for late Quaternary periods when this species was scarce or absent because other alkenone-synthesizing algae, e.g. of the genus Gephyrocapsa. Category: geoscientificInformation Source: Supplement to: Müller, Peter J; Cepek, Martin; Ruhland, Götz; Schneider, Ralph R (1997): Alkenone and coccolithophorid species changes in late Quaternary sediments from the Walvis Ridge: Implications for the alkenone paleotemperature method. Palaeogeography, Palaeoclimatology, Palaeoecology, 135(1-4), 71-96, https://doi.org/10.1016/S0031-0182(97)00018-7 Supplemental Information: Not Availble Coverage: EVENT LABEL: * LATITUDE: -20.104000 * LONGITUDE: 9.185833 * DATE/TIME: 1988-03-02T00:00:00 * ELEVATION: -2209.0 m * Penetration: 12 m * Recovery: 10.79 m * LOCATION: Walvis Ridge, Southeast Atlantic Ocean * CAMPAIGN: M6/6 * BASIS: Meteor (1986) * DEVICE: Gravity corer (Kiel type)

Contributors: Papay Suparan, Rien A.C Dam, Sander van der Kaars, Theo E Wong

Date: 2001-07-15

palynological analysis of core D6 sediments (hscharacteristic lowland ...Late Quaternary environmental change studies. First, the geologic, morphologic...Mid-Late Holocene, a low-energy fluvial systems and swamps existed in ...Late Pleistocene and Holocene landform development, sedimentation and ...core sediments. All taxa are shown as a percentage of the total pollen...sediment starved floodbasins. (C) The marine erosion cliff in the coastal...Late Quaternary environmental change studies. First, the geologic, morphologic...Late Quaternary...core D6 sediments (hscharacteristic lowland rain-forest tree taxa on Halmaherah...Late Quaternary...sediments (core D6). Core samples were subsampled for texture, organic...sedimentation in humid tropical lowland environments on Halmahera island...Late Pleistocene or Holocene environmental conditions is difficult to ...Late Quaternary tropical lowland environments on Halmahera, Indonesia...confidence) ranges. The sequence of core D6 is discussed in the text. ...Kao River plain sediments (core D6). Core samples were subsampled for ...core D6 is discussed in the text. The locations of cores D6 and D7 are...flooded, sediment starved floodbasins. (C) The marine erosion cliff in...palynological analysis of D6 core sediments. All taxa are shown as a percentage...Late Pleistocene and Holocene landform development, sedimentation and ...sediments and the existence of natural grasslands in the coastal zone. ... Results of a case study of landform development and sedimentation in humid tropical lowland environments on Halmahera island, eastern Indonesia, are presented with the aim to better characterise tropical lowland environments in the context of Late Quaternary environmental change studies. First, the geologic, morphologic and environmental settings of the two areas, the interior Kao River plain and the Kao coastal zone (N. Halmahera), are presented. Subsequently, data concerning Late Pleistocene and Holocene landform development, sedimentation and coastal processes are discussed. Pleistocene landform development involved volcaniclastic sedimentation, base levelling of coastal lowlands, prolonged weathering and crust formation, coastal uplift and eustatic sea level change. A conspicuous ferricrete crust in the subsoil of the coastal plain is tentatively dated with 14C AMS analysis and isotopes of organic matter encapsulated in the soil ferricrete have been determined. Due to interacting sea level change, neotectonic uplift, climatic, hydrologic and vegetational change, unequivocal evidence for anomalous Late Pleistocene or Holocene environmental conditions is difficult to obtain. During the Mid-Late Holocene, a low-energy fluvial systems and swamps existed in the interior Kao River plain; a dense open swamp/swamp forest vegetation contributed to extremely high sedimentation rates in this depositional basin. Palynological analysis of the organic swamp deposits indicates little or no change in sedimentary environmental settings and swamp vegetations, and indications for early human presence in the area. In the coastal area accretion and delta progradation occurred after the Early-Mid Holocene formation of a marine erosion cliff. Tentative evidence for early human presence in the Kao area is derived from charcoal particle frequencies in sediments and the existence of natural grasslands in the coastal zone. As most of the geologic and environmental characteristics of the tropical lowlands in the Kao area are common in eastern Indonesia, the study provides useful information for ongoing research in the region.

Contributors: S.H. Lee, J.J. Bahk, S.K. Chough, G.G. Back, H.S. Yoo

Date: 2004-05-31

sedimentation caused by an interaction between bottom currents and mass...Location, water depth and length of sediment cores ...core sediments ...late Quaternary. Cross sections cut through the South Korea Plateau and...Late Quaternary sedimentation in the Ulleung Interplain Gap, East Sea ...core sections. For symbols on the right side, see Table 3. Core locations...adjacent areas during the late Quaternary. Cross sections cut through ...sedimentary facies in core sediments ...sediments. Based on vertical distribution of sedimentary facies together...core sediments can be divided into Units I (∼15 ka)....sediment cores (8.6–11.4 m long) together with age data of tephra layers...sediment cores ...cores. For location of cores, see Figs. 1B, 7B, 9D and 10. Solid triangles...Core sediments consist of various deposits of turbidites, muddy contourites... core sections. For symbols on the right side, see Table 3. Core locations... correlation of cores. For location of cores, see Figs. 1B, 7B, 9D and ... The Ulleung Interplain Gap (UIG) is a deep (2300–2700 m) passage which has served as a conduit for deep-water circulation between the Ulleung and Japan basins. A detailed analysis of Chirp (2–7 kHz) subbottom profiles (ca. 6270 line-km) and nine sediment cores (8.6–11.4 m long) together with age data of tephra layers and four AMS 14C from the UIG and the adjacent areas reveals complex sedimentation caused by an interaction between bottom currents and mass flows during the last- and post-glacial periods. From high-resolution subbottom data, rock basement, slide/slump/rock-fall deposits, mass-flow chutes/channels, mass-flow deposits, bottom-current deposits, and a large-scale bottom-current channel system are recognized. Core sediments consist of various deposits of turbidites, muddy contourites, manganiferous contourites, and pelagic/hemipelagic sediments. Based on vertical distribution of sedimentary facies together with a chronostratigraphic framework, core sediments can be divided into Units I (∼15 ka).

Contributors: N. Fagel, L.Y. Alleman, L. Granina, F. Hatert, E. Thamo-Bozso, R. Cloots, L. André

Date: 2005-01-01

sediment cores. Analyses by ICP-AES (Mn content, data from Table 3a) or...Sediment...sediments from cores CON01-604 (Posolsky Bank), CON01-603 (Continent Ridge...Late Quaternary... investigated sediment cores (plotted from South to North). Modified from...diatom-samples in any of the core sediment samples. ...Late Quaternary...sediment core: the concretions are concentrated at specific depths along...sediments. While reflecting an early diagenetic signal, the source of ...sediment cores spanning two to four interglacial stages in the northern...sedimentation rates (e.g., Academician and Continent ridges). At the site...sedimentation rates, and porewater chemistry. We conclude that vivianite...geochemical signature of sediments from cores CON01-604 (Posolsky Bank...sediment cores (plotted from South to North). Modified from Hauregard,...sediments...core sediment samples. ...sedimentation rates, and it is not a proxy for lacustrine paleoproductivity...concretions in sediment core: the concretions are concentrated at specific... sediment cores. Analyses by ICP-AES (Mn content, data from Table 3a) ... In an effort to better understand vivianite formation processes, four Lake Baikal sediment cores spanning two to four interglacial stages in the northern, central and southern basins and under various biogeochemical environments are scrutinized. The vivianite-rich layers were detected by anomalous P-enrichments in bulk geochemistry and visually by observations on X-radiographs. The millimetric concretions of vivianite were isolated by sieving and analysed by X-ray diffraction, scanning electron microscope (SEM), microprobe, infrared spectroscopy, inductively coupled plasma atomic emission spectrometry and mass spectrometry (ICP-AES, ICP-MS). All the vivianites display similar morphological, mineralogical and geochemical signature, suggesting a common diagenetic origin. Their geochemical signature is sensitive to secondary alteration where vivianite concretions are gradually transformed from the rim to the center into an amorphous santabarbaraite phase with a decreasing Mn content. We analysed the spatial and temporal distribution of the concretions in order to determine the primary parameters controlling the vivianite formation, e.g., lithology, sedimentation rates, and porewater chemistry. We conclude that vivianite formation in Lake Baikal is mainly controlled by porewater chemistry and sedimentation rates, and it is not a proxy for lacustrine paleoproductivity. Vivianite accumulation is not restricted to areas of slow sedimentation rates (e.g., Academician and Continent ridges). At the site of relatively fast sedimentation rate, i.e., the Posolsky Bank near the Selenga Delta, vivianite production may be more or less related to the Selenga River inputs. It could be also indirectly related to the past intensive methane escapes from the sediments. While reflecting an early diagenetic signal, the source of P and Fe porewater for vivianites genesis is still unclear.

Contributors: Jaime Argollo, Philippe Mourguiart

Date: 2000-01-01

core TDI, Lake Titicaca; after Argollo and Mourguiart, 1995b, c). ...ostracod studies (core TDI, Lake Titicaca; after Argollo and Mourguiart...Late Quaternary climate history of the Bolivian Altiplano...late Pleistocene/Holocene paleoclimates and lake evolution based on a ...for core TD1, Lake Titicaca (from Mourguiart et al., 1995c). ...Sediment cores and outcrops from the Bolivian Altiplano are used to interpret...core TD1, Lake Titicaca (from Mourguiart et al., 1995c). ...Radiometric dates from Lake Titicaca cores and altiplanean outcrops. The...function on ostracods (cores TD1 and TJ from lakes Taraco-Guaqui and Chucuito...cores and altiplanean outcrops. The radiocarbon dates were calibrated ...cores TD1 and TJ from lakes Taraco-Guaqui and Chucuito, respectively; ... Sediment cores and outcrops from the Bolivian Altiplano are used to interpret late Pleistocene/Holocene paleoclimates and lake evolution based on a multi-proxy approach (ostracod content, palynology, sedimentology, and radiocarbon dating). Despite the different sensitivity of the lacustrine basins to environmental changes, interpreting the records in terms of paleohydrology, climate, and more especially timing of events is difficult. Notwithstanding these problems, Lake Titicaca in the north and Lake Pocoyu (Lake Poopó, salars of Coipasa and Uyuni) in the south reveal a similar evolution in general trends through the course of time. During the Minchı́n phase (until 30–26kyr BP), the Altiplano was wetter than present. The Last Glacial Maximum (ca. 26–14kyr BP), marked by cooler, drier conditions, was followed by a return to a wetter climate, interrupted by short arid events, between ca. 14 and 10.5kyr BP. Another cycle of aridity, between 10.5 and 8kyr BP, took place abruptly just after the humid Tauca phase. The mid-Holocene is interpreted as climatically unstable, with an alternation of humid and dry episodes. Since 3.9kyr BP, wetter conditions have persisted and intensified to the present. The data are interpreted in terms of changes in inter-tropical convergence zone extension (summer precipitation) and in polar air mass intensity (winter precipitation).