Palaeoreconstruction of the Amazon River freshwater and sediment discharge using sediments recovered at Site 942 on the Amazon Fan

A continuous reconstruction of palaeoclimate has been generated for the last 12 000 C-14 yr BP, from ODP site 942 (5 degrees 45'N, 49 degrees 6'W at a water depth of 3346 m), drilled to the west of the Amazon Fan. Records from the site suggest that during the Younger Dryas, the Amazon Basin was extremely dry, and Amazon River discharge was low. This increased aridity is hypothesised to be due predominantly to reduced precipitation. In addition, there is evidence for a discharge event at the end of the Younger Dryas, coeval with Termination 1B, that produced an estimated Amazon River outflow equivalent to present-day values, and an increase in sediments derived from the Andes. The timing of this event, coincident with the warming of the Andean Ice Sheet, suggests that it was at least partly driven by meltwater produced by the retreat of Andean glaciers, but also required an increase in regional rainfall resulting from changes in climate. Site 942 also demonstrates that the sediment input to the western part of the Amazon Fan from the river ceased between 9900 and 9500 C-14 yr BP, at a time when sea level was 40-50 m below the present level. If this value is truly indicative of the sea levels at which the sediment supply to the fan switched 'off', then it is far greater than the 30 m below current sea-level suggested previously. Copyright (C) 2000 John Wiley & Sons, Ltd.

[1]  A. Morton,et al.  Amazon Fan sands: implications for provenance , 2000 .

[2]  M. Maslin,et al.  Composition and circulation of bottom water in the western Atlantic Ocean during the last glacial, based on pore-water analyses from the Amazon Fan , 1999 .

[3]  A. Mix,et al.  Reassessment of ice-age cooling of the tropical ocean and atmosphere , 1999, Nature.

[4]  Alan C. Mix,et al.  Foraminiferal faunal estimates of paleotemperature: Circumventing the No‐analog problem yields cool Ice Age tropics , 1999 .

[5]  Gerold Wefer,et al.  The deglacial history of the western tropical Atlantic as inferred from high resolution stable isotope records off northeastern Brazil , 1999 .

[6]  Andrew C. Morton,et al.  Processes controlling the composition of heavy mineral assemblages in sandstones , 1999 .

[7]  A. Mix,et al.  Pleistocene Precipitation Balance in the Amazon Basin Recorded in Deep Sea Sediments , 1999, Quaternary Research.

[8]  M. Maslin,et al.  Late Quaternary Vegetation and Climate Change in the Amazon Basin Based on a 50,000 Year Pollen Record from the Amazon Fan, ODP Site 932 , 1999, Quaternary Research.

[9]  M. Maslin,et al.  Sea-level –and gas-hydrate–controlled catastrophic sediment failures of the Amazon Fan , 1998 .

[10]  Gerold Wefer,et al.  Correlated Millennial-Scale Changes in Surface Hydrography and Terrigenous Sediment Yield Inferred from Last-Glacial Marine Deposits off Northeastern Brazil , 1998, Quaternary Research.

[11]  A. Solow,et al.  Correlation between rate of sea-level change and frequency of explosive volcanism in the Mediterranean , 1997, Nature.

[12]  P. Colinvaux,et al.  A Long Pollen Record from Lowland Amazonia: Forest and Cooling in Glacial Times , 1996, Science.

[13]  U. Pflaumann,et al.  SIMMAX : a modern analog technique to deduce Atlantic Sea Surface Temperatures from planktonic foraminifera in deep sea sediments , 1996 .

[14]  W. Junk,et al.  Quaternary geology of the Amazonian Lowland , 1995 .

[15]  T. Sowers,et al.  Climate Records Covering the Last Deglaciation , 1995, Science.

[16]  E. Mosley‐Thompson,et al.  Late Glacial Stage and Holocene Tropical Ice Core Records from Huascar�n, Peru , 1995, Science.

[17]  M. Maslin,et al.  Surface water temperature, salinity, and density changes in the northeast Atlantic during the last 45,000 years: Heinrich events, deep water formation, and climatic rebounds , 1995 .

[18]  C. Hoorn,et al.  Andean tectonics as a cause for changing drainage patterns in Miocene northern South America , 1995 .

[19]  Andrew C. Morton,et al.  Identifying provenance-specific features of detrital heavy mineral assemblages in sandstones , 1994 .

[20]  J. Jouzel,et al.  Comparison of oxygen isotope records from the GISP2 and GRIP Greenland ice cores , 1993, Nature.

[21]  J. Jouzel,et al.  Evidence for general instability of past climate from a 250-kyr ice-core record , 1993, Nature.

[22]  A. Chivas,et al.  Carbon isotope indicators of catchment vegetation in the Brazilian Amazon , 1992 .

[23]  E. Bard,et al.  U-Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years , 1990, Nature.

[24]  E. Bard,et al.  Calibration of the 14C timescale over the past 30,000 years using mass spectrometric U–Th ages from Barbados corals , 1990, Nature.

[25]  C.J.F. ter Braak,et al.  Diatoms and pH Reconstruction , 1990 .

[26]  R. Fairbanks.  A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation , 1989, Nature.

[27]  P. Colinvaux.  Ice-age Amazon revisited , 1989, Nature.

[28]  M. Bevis,et al.  Amazon cone isotopic stratigraphy: evidence for the source of the tropical freshwater spike , 1988 .

[29]  J. Duplessy,et al.  Variations in mode of formation and temperature of oceanic deep waters over the past 125,000 years , 1987, Nature.

[30]  R. Pacanowski,et al.  A model of the seasonal cycle in the tropical Atlantic Ocean , 1986 .

[31]  Philip L. Richardson,et al.  Mapping climatological seasonal variations of surface currents in the tropical Atlantic using ship drifts , 1986 .

[32]  J. Damuth,et al.  Morphology, sedimentation processes, and growth pattern of the Amazon Deep-Sea Fan , 1983 .

[33]  P. E. Potter,et al.  Petrology, Chemistry, and Texture of Modern River Sands, Amazon River System , 1983, The Journal of Geology.

[34]  S. Levitus.  Climatological Atlas of the World Ocean , 1982 .

[35]  J. Damuth,et al.  The climate-related diachronous disappearance of Pulleniatina obliquiloculata in late quaternary sediments of the Atlantic and Caribbean , 1978 .

[36]  J. Damuth.  Late Quaternary sedimentation in the western equatorial Atlantic , 1977 .

[37]  J. Damuth.  Quaternary climate change as revealed by calcium carbonate fluctuations in western Equatorial Atlantic sediments , 1975 .

[38]  J. Damuth,et al.  Amazon Cone: Morphology, Sediments, Age, and Growth Pattern , 1975 .

[39]  C. Summerhayes,et al.  Quaternary Sedimentation on the Amazon Continental Margin: A Model , 1975 .

[40]  R. Clayton,et al.  Oxygen isotope fractionation in divalent metal carbonates , 1969 .

[41]  J. Haffer.  Speciation in amazonian forest birds. , 1969, Science.

[42]  W. G. Metcalf,et al.  Origin of the Atlantic Equatorial Undercurrent , 1967 .

[43]  R. Gibbs.  The Geochemistry of the Amazon River System: Part I. The Factors that Control the Salinity and the Composition and Concentration of the Suspended Solids , 1967 .

[44]  M. Ewing,et al.  Atlantic Deep-Sea Sediment Cores , 1961 .

[45]  G. Wollin,et al.  Micropaleontological and isotopic determinations of Pleistocene climates , 1956 .

[46]  S. Burns,et al.  Isotopic evidence for late Quaternary climatic change in tropical South America , 2000 .

[47]  M. Maslin.  Equatorial western Atlantic Ocean circulation changes linked to the Heinrich events: deep-sea sediment evidence from the Amazon Fan , 1998, Geological Society, London, Special Publications.

[48]  M. Maslin,et al.  Stable isotope records from ODP Sites 932 and 933 , 1997 .

[49]  S. Cisowski,et al.  12. AN EXAMINATION OF THE PALEOINTENSITY RECORD AND GEOMAGNETIC EXCURSIONS RECORDED IN LEG 155 CORES 1 , 1997 .

[50]  M. Maslin,et al.  38. BIOSTRATIGRAPHY AND SEDIMENTATION RATES OF THE AMAZON FAN 1 , 1997 .

[51]  M. Maslin,et al.  Synthesis of stratigraphic correlations of the Amazon fan , 1997 .

[52]  J. Wehmiller,et al.  22. DATA REPORT: AMINO ACID RACEMIZATION GEOCHRONOLOGICAL STUDIES OF SELECTED LEG 155 SAMPLES 1 , 1997 .

[53]  J. Damuth,et al.  Sedimentary facies and associated depositional elements of the Amazon fan , 1997 .

[54]  M. Maslin,et al.  16. ISOTOPIC STRATIGRAPHY OF AMAZON FAN SEDIMENTS 1 , 1997 .

[55]  D. Long,et al.  MASS-TRANSPORT DEPOSITS OF THE AMAZON FAN , 1997 .

[56]  C. Pirmez,et al.  Morphology and structure of Amazon Channel , 1995 .

[57]  R. H. Meade.  Suspended sediments of the modern Amazon and Orinoco rivers , 1994 .

[58]  P. Reimer,et al.  Extended 14C Data Base and Revised CALIB 3.0 14C Age Calibration Program , 1993, Radiocarbon.

[59]  J. Syvitski,et al.  Principles, methods, and application of particle size analysis: SediGraph technique , 1991 .

[60]  J. King,et al.  SEDIMENTARY MAGNETISM, ENVIRONMENTAL MAGNETISM, AND MAGNETOSTRATIGRAPHY , 1991 .

[61]  J. Duplessy,et al.  Surface salinity reconstruction of the north-atlantic ocean during the last glacial maximum , 1991 .

[62]  Anthony Smith.  Explorers of the Amazon , 1990 .

[63]  N. Shackleton.  Oxygen isotopes, ice volume and sea level , 1987 .

[64]  J. Servain,et al.  Climatic atlas of the tropical Atlantic wind stress and sea surface temperature: 1980-1984 , 1987 .

[65]  J. Damuth,et al.  Amazon Fan, Atlantic Ocean , 1985 .

[66]  J. C. Castro,et al.  Stratigraphic And Structural Framework Of The FOZ D0 Amazonas Basin , 1978 .

[67]  A. Bé.  An ecological, zoogeographic and taxonomic review of recent planktonic foraminifera , 1977 .

[68]  Nilva G. Kipp,et al.  New Transfer Function for Estimating Past Sea-Surface Conditions from Sea-Bed Distribution of Planktonic Foraminiferal Assemblages in the North Atlantic , 1976 .

[69]  N. Shackleton.  Attainment of isotopic equilibrium between ocean water and the benthonic foraminifera genus Uvigerina: isotopic changes in the ocean during the last glacial , 1974 .

[70]  J. Damuth,et al.  Equatorial Atlantic Deep-Sea Arkosic Sands and Ice-Age Aridity in Tropical South America , 1970 .