- Email: [email protected]
Holocene sea-level and climatic variability along the African Red Sea coast: Impacts on an ancient Egyptian civilization and implications for future coastal response to climate change
Abstracts / Quaternary International 279-280 (2012) 121–232
conjunction with other palynological and geochemical tracers in order to characterize spatial patterns with respect to ice cover, freshwater input and nutrient cycling. Our dataset includes 38 cyst types, which demonstrates more diverse communities than typically found in the Arctic. We distinguish three distinct dinoflagellate cyst groups in eastern, western and northern regions of the bay, respectively, and discuss their taxonomical, trophical and ecological characteristics. Furthermore, we highlight the importance of gentle sample processing methods, taxonomical precision and ecologically meaningful approaches in geological application of dinoflagellate cysts.
193
of ancient glacial advances. By applying this approach we can greatly improve the age constraints for these and other Quaternary glacial sequences in Patagonia and offer rare insight into the terrestrial climate in the southern mid-latitudes throughout the Quaternary. HOLOCENE SEA-LEVEL AND CLIMATIC VARIABILITY ALONG THE AFRICAN RED SEA COAST: IMPACTS ON AN ANCIENT EGYPTIAN CIVILIZATION AND IMPLICATIONS FOR FUTURE COASTAL RESPONSE TO CLIMATE CHANGE Christopher Hein. Boston University, United States
RETROSPECTIVE PERSPECTIVE ON VEGETATION RESPONSES TO CLIMATE CHANGE: POSTGLACIAL TREE POPULATION DYNAMICS IN NORTHERN EUROPE Maija Heikkilä. University of Manitoba, Canada E-mail address: [email protected]
The equilibrium vs. disequilibrium between postglacial climate and vegetation has been debated for decades. Today, it is a topical issue, as understanding species range shifts and ecosystem responses under predicted climate change scenarios will be a crucial future undertaking. We employed lake sediment pollen and isotopic tracers in order to investigate large-scale responses of ecosystems to postglacial climate changes in northern Europe. The pollen records manifest changes in the abundances of plant communities, whereas the oxygen-isotope records reflect moisture balance that is mainly controlled by evaporation during the open-water season, which in turn, is often a function of summer temperatures. In addition, oxygenisotope stratigraphies can help untangling seasonal signals related to deeper snowpacks and ample spring snowmelt. Our results suggest that postglacial population expansions of common tree species in northern Europe were in dynamic equilibrium with climate and that migration delays, competition and disturbances did not play a significant role in the spatial and temporal scales examined here. A remarkable exception to this pattern may be the postglacial spread of Norway spruce (Picea abiesL. Karst) and related development of the modern boreal ecosystem that cannot be explicitly explained by current evidence of postglacial climate changes. Moreover, our results manifest strikingly rapid vegetation responses to climate change, which contrasts with the traditional view of weak or delayed responses of tree species to climate change. Even though continental-scale spread of species from far-away dispersal loci may be relatively slow, species presence as scattered refuge populations or diffuse local stands may have been sufficient to account for rapid invasions and population expansions in concert with climate changes. However, if scattered populations are not provided, tree populations may not be alert enough to keep track of predicted rates of future climate change.
E-mail address: [email protected]
Archeological investigations along a carbonate / conglomerate terrace located 600 m landward of the shoreline at Mersa / Wadi Gawasis have uncovered the existence of an ancient Egyptian harbor and documented the world's earliest (w4 kya) archaeological evidence of long distance seafaring. Wave-cut notches discovered along the shoreline confirm a sitespecific rheological model for the northern the Red Sea and reveal the existence of a 0.5 – 2 m highstand of sea level at 5 cal. kyr BP. Sedimentological, malacological, radiocarbon, and foraminiferal analyses indicate that this resulted in the formation of a tidal lagoon adjacent to the occupation sites. This paleo-bay received infrequent freshwater inputs, as evidenced by the presence of 6 m of multiple fining-upward sequences medium to fine lagoonal sediments. A narrow coral-beach rock platform and tidal flat sediments are found ubiquitously along the periphery of the paleo-bay. Early bay closure was driven by sediment inputs from the adjacent wadi, enhanced by the wetter climate of the African Humid Period. However, bay area reconstructions indicate that closure was initiated prior to the highstand, during a period of relatively rapid sea-level rise, thus demonstrating the dominance of sedimentary processes. Following the highstand, coincidental slowly falling sea level and climatic aridization allowed for the establishment of the Egyptian harbor. During the late Holocene, shoreline progradation was dominated by falling sealevels, driven by isostatic processes. These results demonstrate the complex interactions and temporal shifts in the relative contribution of various global (sea level), regional (climate, sea level), and local (sedimentation, bathymetry) controls on the coastal evolution of the Red Sea and how these controls dictated the response of a complex civilization. Furthermore, they highlight the crucial role played by sedimentation in governing coastal response to changing sea levels. EUROPEAN CLIMATE CHANGE AT THE END OF THE LAST GLACIATION: CHIRONOMID–BASED TEMPERATURE RECONSTRUCTION ON A CONTINENTAL SCALE Oliver Heiri. University of Bern, Switzerland
EXPOSURE SURFACES
DATING
ANCIENT
PATAGONIAN
GLACIAL
OUTWASH
Andrew Hein. University of Edinburgh, United Kingdom E-mail address: [email protected]
There is a detailed record of glacial moraines and outwash terraces in Argentine Patagonia. These landforms reflect advances of the Patagonian Ice Sheet over the past w1 million years. Recent geochronologic work in the Lago Pueyrredón Valley utilizing cosmogenic nuclide surface exposure methods has shown the outwash terraces can be used to determine the timing of ancient glacial events. Here there is evidence of outwash surface stability for at least 260 thousand years based on 10Be concentrations in sediment on and within these surfaces. We recently extended this outwash sediment dating approach to even older glacial surfaces. The new data from surface cobbles suggest glacial advances occurred at around 600 thousand years and at around 1.2 million years. There is geologic evidence of instability on the oldest dated surface. Despite this it appears that some individual clasts have survived on its surface since their initial deposition over one million years earlier, assuming the dated outwash terrace is indeed correlative with tills constrained by 40Ar/39Ar ages elsewhere in Patagonia. In this environment it appears the outwash terraces are relatively stable landforms that can be directly dated to determine the timing
E-mail address: [email protected]
In Europe climatic conditions at the end of the last ice age were affected by a number of abrupt temperatures shifts, including the rapid transitions to warmer climate at the beginning of the Lateglacial Interstadial and the Holocene, and the cooling at the start of the Younger Dryas cold period. The amplitude and spatial pattern of Lateglacial changes in temperature can provide information about the forcing factors of these climate shifts and about processes affecting the European climate system during a transition to warmer climate. However, spatially resolved datasets describing temperature change across the European continent during the Lateglacial period at centennial or higher time resolution and based on the same standardized approach are presently not available. We aim to develop such a standardized dataset based on records of past summer temperature reconstructed from fossil chironomid assemblages in lake sediments. A combination of regional calibration datasets provided the basis for a chironomid-based inference model for July air temperature that covers the range of temperatures and chironomid assemblages expected for Europe during the Lateglacial. This model, which is based on modern chironomid assemblages from 274 lakes in Norway and Switzerland and associated observed values of mean July air temperature, was then used to produce temperature records from Estonia, Denmark, Ireland, the Netherlands, southeastern France, Western Spain, southern Switzerland,
conjunction with other palynological and geochemical tracers in order to characterize spatial patterns with respect to ice cover, freshwater input and nutrient cycling. Our dataset includes 38 cyst types, which demonstrates more diverse communities than typically found in the Arctic. We distinguish three distinct dinoflagellate cyst groups in eastern, western and northern regions of the bay, respectively, and discuss their taxonomical, trophical and ecological characteristics. Furthermore, we highlight the importance of gentle sample processing methods, taxonomical precision and ecologically meaningful approaches in geological application of dinoflagellate cysts.
193
of ancient glacial advances. By applying this approach we can greatly improve the age constraints for these and other Quaternary glacial sequences in Patagonia and offer rare insight into the terrestrial climate in the southern mid-latitudes throughout the Quaternary. HOLOCENE SEA-LEVEL AND CLIMATIC VARIABILITY ALONG THE AFRICAN RED SEA COAST: IMPACTS ON AN ANCIENT EGYPTIAN CIVILIZATION AND IMPLICATIONS FOR FUTURE COASTAL RESPONSE TO CLIMATE CHANGE Christopher Hein. Boston University, United States
RETROSPECTIVE PERSPECTIVE ON VEGETATION RESPONSES TO CLIMATE CHANGE: POSTGLACIAL TREE POPULATION DYNAMICS IN NORTHERN EUROPE Maija Heikkilä. University of Manitoba, Canada E-mail address: [email protected]
The equilibrium vs. disequilibrium between postglacial climate and vegetation has been debated for decades. Today, it is a topical issue, as understanding species range shifts and ecosystem responses under predicted climate change scenarios will be a crucial future undertaking. We employed lake sediment pollen and isotopic tracers in order to investigate large-scale responses of ecosystems to postglacial climate changes in northern Europe. The pollen records manifest changes in the abundances of plant communities, whereas the oxygen-isotope records reflect moisture balance that is mainly controlled by evaporation during the open-water season, which in turn, is often a function of summer temperatures. In addition, oxygenisotope stratigraphies can help untangling seasonal signals related to deeper snowpacks and ample spring snowmelt. Our results suggest that postglacial population expansions of common tree species in northern Europe were in dynamic equilibrium with climate and that migration delays, competition and disturbances did not play a significant role in the spatial and temporal scales examined here. A remarkable exception to this pattern may be the postglacial spread of Norway spruce (Picea abiesL. Karst) and related development of the modern boreal ecosystem that cannot be explicitly explained by current evidence of postglacial climate changes. Moreover, our results manifest strikingly rapid vegetation responses to climate change, which contrasts with the traditional view of weak or delayed responses of tree species to climate change. Even though continental-scale spread of species from far-away dispersal loci may be relatively slow, species presence as scattered refuge populations or diffuse local stands may have been sufficient to account for rapid invasions and population expansions in concert with climate changes. However, if scattered populations are not provided, tree populations may not be alert enough to keep track of predicted rates of future climate change.
E-mail address: [email protected]
Archeological investigations along a carbonate / conglomerate terrace located 600 m landward of the shoreline at Mersa / Wadi Gawasis have uncovered the existence of an ancient Egyptian harbor and documented the world's earliest (w4 kya) archaeological evidence of long distance seafaring. Wave-cut notches discovered along the shoreline confirm a sitespecific rheological model for the northern the Red Sea and reveal the existence of a 0.5 – 2 m highstand of sea level at 5 cal. kyr BP. Sedimentological, malacological, radiocarbon, and foraminiferal analyses indicate that this resulted in the formation of a tidal lagoon adjacent to the occupation sites. This paleo-bay received infrequent freshwater inputs, as evidenced by the presence of 6 m of multiple fining-upward sequences medium to fine lagoonal sediments. A narrow coral-beach rock platform and tidal flat sediments are found ubiquitously along the periphery of the paleo-bay. Early bay closure was driven by sediment inputs from the adjacent wadi, enhanced by the wetter climate of the African Humid Period. However, bay area reconstructions indicate that closure was initiated prior to the highstand, during a period of relatively rapid sea-level rise, thus demonstrating the dominance of sedimentary processes. Following the highstand, coincidental slowly falling sea level and climatic aridization allowed for the establishment of the Egyptian harbor. During the late Holocene, shoreline progradation was dominated by falling sealevels, driven by isostatic processes. These results demonstrate the complex interactions and temporal shifts in the relative contribution of various global (sea level), regional (climate, sea level), and local (sedimentation, bathymetry) controls on the coastal evolution of the Red Sea and how these controls dictated the response of a complex civilization. Furthermore, they highlight the crucial role played by sedimentation in governing coastal response to changing sea levels. EUROPEAN CLIMATE CHANGE AT THE END OF THE LAST GLACIATION: CHIRONOMID–BASED TEMPERATURE RECONSTRUCTION ON A CONTINENTAL SCALE Oliver Heiri. University of Bern, Switzerland
EXPOSURE SURFACES
DATING
ANCIENT
PATAGONIAN
GLACIAL
OUTWASH
Andrew Hein. University of Edinburgh, United Kingdom E-mail address: [email protected]
There is a detailed record of glacial moraines and outwash terraces in Argentine Patagonia. These landforms reflect advances of the Patagonian Ice Sheet over the past w1 million years. Recent geochronologic work in the Lago Pueyrredón Valley utilizing cosmogenic nuclide surface exposure methods has shown the outwash terraces can be used to determine the timing of ancient glacial events. Here there is evidence of outwash surface stability for at least 260 thousand years based on 10Be concentrations in sediment on and within these surfaces. We recently extended this outwash sediment dating approach to even older glacial surfaces. The new data from surface cobbles suggest glacial advances occurred at around 600 thousand years and at around 1.2 million years. There is geologic evidence of instability on the oldest dated surface. Despite this it appears that some individual clasts have survived on its surface since their initial deposition over one million years earlier, assuming the dated outwash terrace is indeed correlative with tills constrained by 40Ar/39Ar ages elsewhere in Patagonia. In this environment it appears the outwash terraces are relatively stable landforms that can be directly dated to determine the timing
E-mail address: [email protected]
In Europe climatic conditions at the end of the last ice age were affected by a number of abrupt temperatures shifts, including the rapid transitions to warmer climate at the beginning of the Lateglacial Interstadial and the Holocene, and the cooling at the start of the Younger Dryas cold period. The amplitude and spatial pattern of Lateglacial changes in temperature can provide information about the forcing factors of these climate shifts and about processes affecting the European climate system during a transition to warmer climate. However, spatially resolved datasets describing temperature change across the European continent during the Lateglacial period at centennial or higher time resolution and based on the same standardized approach are presently not available. We aim to develop such a standardized dataset based on records of past summer temperature reconstructed from fossil chironomid assemblages in lake sediments. A combination of regional calibration datasets provided the basis for a chironomid-based inference model for July air temperature that covers the range of temperatures and chironomid assemblages expected for Europe during the Lateglacial. This model, which is based on modern chironomid assemblages from 274 lakes in Norway and Switzerland and associated observed values of mean July air temperature, was then used to produce temperature records from Estonia, Denmark, Ireland, the Netherlands, southeastern France, Western Spain, southern Switzerland,