- Email: [email protected]
Sedimentary evolution and climate history of Zambezi River sediments since Marine Isotope Stage 3
494
Abstracts / Quaternary International 279-280 (2012) 462–565
resolution sedimentary analysis and soil micromorphology. A borehole and geomorphological survey of the site links the sedimentary record with the archaeology enabling mapping of the palaeo-landscape and defining the potential role of changing sea level. A robust chronological framework was established by integrating AMS radiocarbon assays of the organic sediments with OSL dating of minerogenic sediment sequences. The chronology suggests that the stratigraphy provides a record of environmental change from the Late glacial and the Holocene. The richness of palaeoenvironmental data generated from Stronsay has allowed for an unparalleled depth of understanding of environmental change and human activity in this region of the north Atlantic. It is proposed that this approach provides a template for future palaeoenvironmental and archaeological investigations. FROM SURFACE TO DEEP WATER HYDROLOGY CHANGES DURING ABRUPT CLIMATE CHANGES OVER THE LAST 20,000 YEARS Amandine Aline Tisserand. University of Bergen/Bjerknes Centre for Climate R, Norway E-mail address: [email protected]
Climate models predict weakening of the MOC (Meridional Overturning Circulation) in response to climate instabilities. Changes in the MOC influences heat transport from Tropics to high-latitude in the Atlantic Ocean. When weakening of the MOC, climate models show warm pool centered in Tropical Atlantic Ocean. In order to test this hypothesis, we produce timeslice records (Modern, Holocene, Younger-Dryas, Bolling Allerod, Heinrich 1, Last Glacial Maximum) along North Western Brazilian depth transect, sensitive enough to detect the main components of the MOC. We have been applying Mg/Ca-paleotemperature and stable isotopes to three intermediate depth cores (GS07-150-17/1GC - GS07150-18/2GC - GS07-150-20/2GC). These cores are bathed (respectively 1000 - 900 - 700 meters deep) within the Antarctic Intermediate Water (AAIW). Combining d18O and Mg/Ca from epifaunal and infaunal benthic foraminiferal species (C. wuellerstorfi and U. peregrina) and from planktic foraminiferal species (G. ruber, G. trilobus, G. glutinata, G. siphonifera, G. truncatulinoides dex.), we access paleo-environmental records of surface, sub-surface, thermocline depth and deep-water changes from the Last Glacial Maximum (LGM) throughout the deglaciation to the present. We document that in relation to changes in MOC large variation in thermocline depth and temperatures in the upper tropical ocean, large variations documenting that the tropics below the upper surface is very sensitive region to MOC changes. A RELATIVE SEA-LEVEL CURVE FROM SUB- AND INTER-TIDAL DEPOSITS OF SE VIETNAM: CATASTROPHIC EARLY HOLOCENE SHELF FLOODING Rik Tjallingii. NIOZ - Royal Netherlands Institute for Sea Research, Netherlands E-mail address: [email protected]
Sea-level change is a central parameter in the climate system and strongly controlling s sedimentation in coastal regions and on continental margins. Therefore, deglacial sea-level changes and particularly deglacial MeltWater Pulses (MWPs) require a profound understanding. We present a compilation of sub- and inter-tidal sediment records from the SE Vietnamese margin that forms the northern border of the Sunda Shelf system, as a continuation of the Sunda Shelf sea-level history. Incised-valley deposits of the broad and low-gradient SE Vietnamese margin allow tracking of deglacial coast-line migrations. This compilation displays a relatively constant rate of sea-level rise of w9 mm/yr between 14.3 and 9.2 ka BP and shows no significant discontinuity during the MWP-1B period. However, the newly compiled record indicates an accelerated of sea-level rise after 9.2 ka BP that culminated in a dramatic pulse-like sea rise of 36 mm/yr between 8.8 to 8.2 ka BP. Sea-level rose from -26 to -7 m below present mean sea level (mbsl) during this phase, which coincides with MWP-1C. This sea-level jump is apparent from other SE Asian sediment records but is not observed in the most complete sea-level records of Tahiti and Barbados. The acceleration of sea-level rise at this time explains the fast and extensive Holocene flooding from the SE Vietnamese outer shelf to the Cambodian lowlands. After this pulse-like rise, sea-level
decelerated continuously until mid-Holocene sea-level highstand was reached around 6.0 ka BP. SEDIMENTARY EVOLUTION AND CLIMATE HISTORY OF ZAMBEZI RIVER SEDIMENTS SINCE MARINE ISOTOPE STAGE 3 Rik Tjallingii. NIOZ - Royal Netherlands Institute for Sea Research, Netherlands E-mail address: [email protected]
The Zambezi River drainage area covers a considerable part of the South African subtropics that is influenced by multiple surface wind systems delivering precipitation form both the Atlantic and Indian Ocean. Surface sediments and sediment cores from the shelf area off the Zambezi River were used to identify sediment supply of Zambezi River and smaller coastal rivers over the last w45 kyr. We present XRF core-scanning data in combination with grain-size data of multiple sediment cores along the Zambezi margin between w400 m and w1300 m water depth and from the shelf area. These data documents decreasing lithogenic contribution after w 16 kyr BP related with the landward retreat of the Zambezi River mouth system. This decrease is followed by a northward migration of the suspended-sediments of the Zambezi River associated with progressive flooding of the Zambezi shelf and the initiation of the northward shelf currents. The bulk inorganic sediment composition is compared with organic geochemical proxies for the deepest sediment core PE304-80 (1329 m water depth; -18.24 S, 37.87 E) to simultaneously examine South-East African continental conditions and the SST history in the Mozambique Channel over the last w45 kyr. Both organic and inorganic geochemical proxies indicate pronounced millennial-scale lithogenic fluctuations occurring within Marine Isotope Stage 3, possessing a similar structure to Dansgaard-Oeschger (DO) events SEASONAL VARIATION IN RESOURCE ABUNDANCE AND ANATOMICALLY MODERN HUMAN ADAPTATIONS: THE BLUE HIGHWAYS PROJECT, NW ETHIOPIA Lawrence Todd. University of Texas, United States E-mail address: [email protected]
Investigation of modern human range expansion out of Africa requires integration of datasets from archaeology, physical anthropology, genetics, and the geosciences that span a wide range of geographic and temporal scales. The African record from this period ranges from the southern Cape to the Nile corridor and presents a diverse range of environmental setting from which to examine variation in Middle Stone Age (MSA) adaptations. The upper reaches of tributaries of the Blue Nile provide a unique setting in which seasonally dynamic resource availability provides an opportunity to examine the diversity of Anatomically Modern (AM) Human adaptive strategies, particularly to seasonal variation in riverine resources (both aquatic and terrestrial). Seasonal factors are currently not being investigated in other African setting. Recent research along tributaries of the Blue Nile in northwestern Ethiopia suggests that MSA groups targeted dryseason, resource-aggregating waterholes along trunk stream channels. This seasonal pulse of abundant resource was dependant on extremes in river flow driven by variation of rainfall in the adjacent highlands. Documentation of a series of surface sites and excavated contexts from a variety of settings along the Shinfa drainage in Northwest Ethiopia provides multiple datasets on MSA seasonal use of riverine settings and highlights the multiplicity of ecological interactions that have fostered and challenged AM humans along our expansion into the diversity of environments our species have occupied over that last 50,000 years. Hydrologic extremes in streamflow and watersources provide a long-term proxy bio-chemical and geo-archaeological records that when coupled with the archaeological data provide fine-grained temporal and ecological analysis AM humans on the doorstep of global expansion. EFFECT OF PLUVIAL LAKE CHANGES ON REGIONAL CLIMATE SENSITIVITY AND GLACIAL MASS BALANCE IN CENTRAL UTAH Claire Todd. Pacific Lutheran University, United States E-mail address: [email protected]
Abstracts / Quaternary International 279-280 (2012) 462–565
resolution sedimentary analysis and soil micromorphology. A borehole and geomorphological survey of the site links the sedimentary record with the archaeology enabling mapping of the palaeo-landscape and defining the potential role of changing sea level. A robust chronological framework was established by integrating AMS radiocarbon assays of the organic sediments with OSL dating of minerogenic sediment sequences. The chronology suggests that the stratigraphy provides a record of environmental change from the Late glacial and the Holocene. The richness of palaeoenvironmental data generated from Stronsay has allowed for an unparalleled depth of understanding of environmental change and human activity in this region of the north Atlantic. It is proposed that this approach provides a template for future palaeoenvironmental and archaeological investigations. FROM SURFACE TO DEEP WATER HYDROLOGY CHANGES DURING ABRUPT CLIMATE CHANGES OVER THE LAST 20,000 YEARS Amandine Aline Tisserand. University of Bergen/Bjerknes Centre for Climate R, Norway E-mail address: [email protected]
Climate models predict weakening of the MOC (Meridional Overturning Circulation) in response to climate instabilities. Changes in the MOC influences heat transport from Tropics to high-latitude in the Atlantic Ocean. When weakening of the MOC, climate models show warm pool centered in Tropical Atlantic Ocean. In order to test this hypothesis, we produce timeslice records (Modern, Holocene, Younger-Dryas, Bolling Allerod, Heinrich 1, Last Glacial Maximum) along North Western Brazilian depth transect, sensitive enough to detect the main components of the MOC. We have been applying Mg/Ca-paleotemperature and stable isotopes to three intermediate depth cores (GS07-150-17/1GC - GS07150-18/2GC - GS07-150-20/2GC). These cores are bathed (respectively 1000 - 900 - 700 meters deep) within the Antarctic Intermediate Water (AAIW). Combining d18O and Mg/Ca from epifaunal and infaunal benthic foraminiferal species (C. wuellerstorfi and U. peregrina) and from planktic foraminiferal species (G. ruber, G. trilobus, G. glutinata, G. siphonifera, G. truncatulinoides dex.), we access paleo-environmental records of surface, sub-surface, thermocline depth and deep-water changes from the Last Glacial Maximum (LGM) throughout the deglaciation to the present. We document that in relation to changes in MOC large variation in thermocline depth and temperatures in the upper tropical ocean, large variations documenting that the tropics below the upper surface is very sensitive region to MOC changes. A RELATIVE SEA-LEVEL CURVE FROM SUB- AND INTER-TIDAL DEPOSITS OF SE VIETNAM: CATASTROPHIC EARLY HOLOCENE SHELF FLOODING Rik Tjallingii. NIOZ - Royal Netherlands Institute for Sea Research, Netherlands E-mail address: [email protected]
Sea-level change is a central parameter in the climate system and strongly controlling s sedimentation in coastal regions and on continental margins. Therefore, deglacial sea-level changes and particularly deglacial MeltWater Pulses (MWPs) require a profound understanding. We present a compilation of sub- and inter-tidal sediment records from the SE Vietnamese margin that forms the northern border of the Sunda Shelf system, as a continuation of the Sunda Shelf sea-level history. Incised-valley deposits of the broad and low-gradient SE Vietnamese margin allow tracking of deglacial coast-line migrations. This compilation displays a relatively constant rate of sea-level rise of w9 mm/yr between 14.3 and 9.2 ka BP and shows no significant discontinuity during the MWP-1B period. However, the newly compiled record indicates an accelerated of sea-level rise after 9.2 ka BP that culminated in a dramatic pulse-like sea rise of 36 mm/yr between 8.8 to 8.2 ka BP. Sea-level rose from -26 to -7 m below present mean sea level (mbsl) during this phase, which coincides with MWP-1C. This sea-level jump is apparent from other SE Asian sediment records but is not observed in the most complete sea-level records of Tahiti and Barbados. The acceleration of sea-level rise at this time explains the fast and extensive Holocene flooding from the SE Vietnamese outer shelf to the Cambodian lowlands. After this pulse-like rise, sea-level
decelerated continuously until mid-Holocene sea-level highstand was reached around 6.0 ka BP. SEDIMENTARY EVOLUTION AND CLIMATE HISTORY OF ZAMBEZI RIVER SEDIMENTS SINCE MARINE ISOTOPE STAGE 3 Rik Tjallingii. NIOZ - Royal Netherlands Institute for Sea Research, Netherlands E-mail address: [email protected]
The Zambezi River drainage area covers a considerable part of the South African subtropics that is influenced by multiple surface wind systems delivering precipitation form both the Atlantic and Indian Ocean. Surface sediments and sediment cores from the shelf area off the Zambezi River were used to identify sediment supply of Zambezi River and smaller coastal rivers over the last w45 kyr. We present XRF core-scanning data in combination with grain-size data of multiple sediment cores along the Zambezi margin between w400 m and w1300 m water depth and from the shelf area. These data documents decreasing lithogenic contribution after w 16 kyr BP related with the landward retreat of the Zambezi River mouth system. This decrease is followed by a northward migration of the suspended-sediments of the Zambezi River associated with progressive flooding of the Zambezi shelf and the initiation of the northward shelf currents. The bulk inorganic sediment composition is compared with organic geochemical proxies for the deepest sediment core PE304-80 (1329 m water depth; -18.24 S, 37.87 E) to simultaneously examine South-East African continental conditions and the SST history in the Mozambique Channel over the last w45 kyr. Both organic and inorganic geochemical proxies indicate pronounced millennial-scale lithogenic fluctuations occurring within Marine Isotope Stage 3, possessing a similar structure to Dansgaard-Oeschger (DO) events SEASONAL VARIATION IN RESOURCE ABUNDANCE AND ANATOMICALLY MODERN HUMAN ADAPTATIONS: THE BLUE HIGHWAYS PROJECT, NW ETHIOPIA Lawrence Todd. University of Texas, United States E-mail address: [email protected]
Investigation of modern human range expansion out of Africa requires integration of datasets from archaeology, physical anthropology, genetics, and the geosciences that span a wide range of geographic and temporal scales. The African record from this period ranges from the southern Cape to the Nile corridor and presents a diverse range of environmental setting from which to examine variation in Middle Stone Age (MSA) adaptations. The upper reaches of tributaries of the Blue Nile provide a unique setting in which seasonally dynamic resource availability provides an opportunity to examine the diversity of Anatomically Modern (AM) Human adaptive strategies, particularly to seasonal variation in riverine resources (both aquatic and terrestrial). Seasonal factors are currently not being investigated in other African setting. Recent research along tributaries of the Blue Nile in northwestern Ethiopia suggests that MSA groups targeted dryseason, resource-aggregating waterholes along trunk stream channels. This seasonal pulse of abundant resource was dependant on extremes in river flow driven by variation of rainfall in the adjacent highlands. Documentation of a series of surface sites and excavated contexts from a variety of settings along the Shinfa drainage in Northwest Ethiopia provides multiple datasets on MSA seasonal use of riverine settings and highlights the multiplicity of ecological interactions that have fostered and challenged AM humans along our expansion into the diversity of environments our species have occupied over that last 50,000 years. Hydrologic extremes in streamflow and watersources provide a long-term proxy bio-chemical and geo-archaeological records that when coupled with the archaeological data provide fine-grained temporal and ecological analysis AM humans on the doorstep of global expansion. EFFECT OF PLUVIAL LAKE CHANGES ON REGIONAL CLIMATE SENSITIVITY AND GLACIAL MASS BALANCE IN CENTRAL UTAH Claire Todd. Pacific Lutheran University, United States E-mail address: [email protected]