«Changing Polar Regions 25th International Congress on Polar Research March 17-22, 2013, Hamburg, Germany German Society for Polar Research Edited by ...»
the westernmost boundary of the mobile belt is characterized by a major dextral transpressional shear zone. In central DML, a major magnetic anomaly, the Forster anomaly, was interpreted as a cryptic suture of the EAAO (Riedel et al. 2012). The area where the Forster anomaly crosses the DML mountains is poorly investigated so far, but appears to coincide with a major strike slip shear zone in the southern Kurze Mts. and the occurrence of major Ediacaran granulite bodies. East of the Forster anomaly, the magnetic anomaly pattern changes significantly and typical Maud type crust is not present any longer. GEA II targeted a range of nunataks between Sør Rondane and central DML that had never been visited previously (from Blåklettane and Bergekongen in the E to Urna and Sørsteinen in the W). These nunataks are dominated by medium- to high-grade metasedimentary and metavolcanic rocks of possibly Neoproterozoic age, including abundant marble and graphite schists. Sør Rondane in eastern DML, is dominated by two distinct blocks separated by the dextral Main Shear Zone. The northwestern block is still part of the eastern EAAO, where new SHRIMP zircon data from metamorphic rims provide ages of ca. 560 Ma. The southeastern block is made up of a TTG terrane, which provides "Changing Polar Regions" - 25th International Congress on Polar Research 2013 four new SHRIMP zircon dates between 990-980 Ma, interpreted as igneous crystallization ages (oceanic arc).
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 IDENTIFICATION OF BIOGEOCHEMICAL PROVINCES IN THE
SOUTHERN OCEAN BY SPATIAL MODELING OF GEOCHEMICAL,
SEDIMENTOLOGICAL AND BIOLOGICALDATA – THE APPROACH
Compared to biogenic silica, little is known about benthic particulate organic carbon fluxes in situ in the Southern Ocean, a key region for the global marine carbon cycle.
Because of the lack of data, the Southern Ocean south of 60° is still excluded from the global carbon budget calculations. Our knowledge of rates and spatio-temporal variability is patchy, therefore coupling of these processes into regional or global models remains difficult and error prone. Meanwhile the public availability and dissemination of biological, geochemical and sedimentological research data as well as multivariate analysis methods applied in marine sciences is undergoing major developments, towards improving interdisciplinary data analysis.
This poster aims to illustrate the approach of modeling benthic particulate organic carbon fluxes which is the objective of the DFG-Priority Programme SPP 1158 project started in December 2012. For this purpose, correlating parameters as biogenic silica, benthic organisms and other environmental parameters will be used which mimic the geochemical situation as proxies. Biogeochemical provinces in the Southern Ocean combining in situ measurements, experiments and multivariate models, will indicate areas of defined oxygen and carbon fluxes by GIS-based statistical modeling methodology. These provinces are also needed to quantify potential species occurrence and biomass and can be used to optimize sampling strategies during scientific expeditions. The spatial distribution and the dimensions of the Southern Ocean provinces will reduce the gap of knowledge regarding the global geochemical cycles. Furthermore, the exploration of the spatial variation regarding the location and extent of the provinces which are to be expected due to global warming contribute to the prediction of quantitative changes in geochemical fluxes in the Southern Ocean.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 PROVENANCE OF THE PERMIAN TAKROUNA FORMATION,
ANTARCTICA - IMPLICATIONS ON BASIN GEOMETRY AND
During the Late Carboniferous and Permian a series of sedimentary basins occupied the eastern margin of Gondwana. Many uncertainties exist regarding the extent and nature of some of these basins. In northern Victoria Land the Takrouna Formation presents the fossil record of the northern part of this basin system, exposed within an outcrop belt with an E-W extension of 125 km and an N-S length of more than 160 km. The up to 300 m thick succession of siliciclastic deposits documents the onset of sedimentation after the Late Carboniferous to Early Permian glaciation of Gondwana.
The Takrouna Formation includes fluvial conglomerates, sandstones and carbonaceous fine-grained rocks that were deposited in a braided river system, draining towards Tasmania.
This study combines heavy mineral with new U-Pb age data of the Takrouna Formation. CL imaging of the zircons, a typologic study and detrital zircon dating, populations of the sandstones have been performed for sections of five mountain ranges. Both metamorphic and igneous sources must be considered for the detrital zircons. Populations with Grenvillian and early Paleoproterozoic zircon ages, as well as rare older Archean ages are present in all samples. The most abundant age population reveals Pan-African zircons. One key aspect regarding the basin extent can be concluded from heavy-mineral data. The heavy-mineral contents include zircon, tourmaline, rutile, garnet, epidote-group minerals, hornblende, titanite, apatite and minor amounts of anatase and monazite. The abundance of the different heavy minerals show systematic variations related to stratigraphy as well as regional trends.
A major input of material derived from distinct local sources filling a pre-existing topography must be assumed for the stratigraphic lower parts of all sections. The examination of garnet varieties indicates low- to medium-grade metamorphic source rocks that reveal an unknown source, located to the east of the study area. However, in most cases the heavy-minerals can be related to sources equivalent to rocks found in the basement or in the vicinity of northern Victoria Land. Similar heavy-mineral assemblages are present in sandstones of the Permian Weller Coal Measures in southern Victoria Land. Based on these results our paleogeographic model suggests a trough-shaped elongated basin with a basin margin of unknown composition to the east. A connection of both the northern and southern part of the Victoria Basin or very similar sources can be concluded.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 ARCTIC CLIMATE AND SEA-ICE CHANGES OVER THE LAST
MILLENNIUM IN PALEO-RECONSTRUCTIONS AND MODEL
Arctic climate is characterized by pronounced variations on multidecadal to centennial time scales. Recent high-resolution reconstructions based on multiple terrestrial proxies and geological archives allow for an assessment of such variability over the last 2000 years. Model simulations carried out in the framework of the third phase of the Paleo Model Intercomparison Project (PMIP3) cover dedicated simulations over the last millennium that can be used to achieve a process-based understanding of the mechanisms behind the variability and to provide a large-scale context for local or regional reconstructions. The simulations demonstrate that both internal variability and the response to external forcing show aspects of Arctic amplification. The low-frequency character of the variability suggests a role of ocean dynamics and, in particular, changes in meridional heat transports in the ocean. We explore the role of ocean heat advection and atmosphere-ocean-sea ice coupling in driving such multidecadal variations in the Max Planck Institute Earth System Model.
Finally, we discuss the recent, unprecedented changes observed in the Arctic in the context of the climate evolution of the last millennium.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 MEASURING SOUTHERN OCEAN BENTHIC BIODIVERSITY:
DECADAL PROGRESS AND FUTURE CHALLENGES
The scarce information available on Southern Ocean biodiversity patterns suggest that they have been shaped by complex interactions of factors at varying scales;
long-term oceanographic and thermal isolation by the Antarctic Circumpolar Current coupled with recurrent glaciations probably drove vicariant speciation and endemism, whilst physical disturbance is thought to maintain (shelf) biodiversity at local to regional scales. Across ecological, and to some extent evolutionary time scales, the Southern Ocean seabed has been remarkably constant and had potentially experienced the least direct anthropogenic impact. Thus, it represents one of the most ‘natural laboratories’ to study organisms’ biodiversity, distribution and responses to changing climatic conditions.
We are now at a key period to assess and interpret biodiversity and distributions through amassed knowledge but we are also in a time of current and impending, potentially pivotal environmental change. So, one of the greatest challenges, not only in the Southern Ocean but globally, is probably to balance the conservation of, and an increasing demand to exploit its natural resources and services.
Achievements over the past ten years, especially in the course of the International Polar Year initiative, the Census of Marine Life as well as SCAR (Scientific Committee of Antarctic Research) programs, have considerably altered our perception of patterns and processes shaping the biodiversity of Southern Ocean benthos. Here I evaluate decadal progress in Antarctic benthic biodiversity research, discuss present research knowledge gaps and identify potential priorities for future research that will provide deeper insights into our understanding of the Southern Ocean ecosystem structure and function.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 CRUSTAL STRUCTURE OF THE AMUNDSEN SEA EMBAYMENT,
WEST ANTARCTICA: IMPLICATIONS FOR ITS TECTONIC
EVOLUTION FROM A GEOPHYSICAL DATASET.
The Amundsen Sea Embayment of West Antarctica is a centrepiece in understanding the history of the New Zealand – Antarctica breakup. This region plays a key role in plate kinematic reconstruction of the southern Pacific from the collision of the Hikurangi Plateau with the Gondwana subduction margin to the evolution of the West Antarctic Rift System. During two RV Polarstern cruises in 2006 and 2010, a large geophysical dataset was collected consisting of seismic refraction and reflection profiles, shipborne gravity and helicopter magnetic measurements. The data provide constraints on the crustal architecture, the structural evolution and the tectonic block formation during and after the Cretaceous continental breakup. We present two continental rise-to-shelf P-wave velocity models which were derived from forward travel-time modelling of ocean bottom hydrophone recordings which provide an insight into the crustal and upper mantle architecture beneath the Amundsen Sea Embayment for the first time. The sedimentary sequences and the basement were constrained by seismic reflection data. A 2-D density-depth model supports and complements the P-wave modelling. Observed P-wave velocities show 10 to 14 km thick crust of the continental rise and up to 28 km thick crust beneath the middle and inner shelf. The crust of the continental rise is characterized by a small gradient in thickness. Including horst and graben structures this can be associated with widemode rifting. A high velocity zone with velocities ranging between 7.1 and 7.6 km/s indicate magmatic underplating of variable thickness along the entire transect. We classify this margin as one of volcanic type rather than magma poor because of the high-velocity zone and seaward dipping reflectors observed from the seismic reflection data. We discuss the possibility of a serpentinized upper mantle caused by seawater penetration at the Marie Byrd Seamounts. The crustal structure, distinct zones in potential field anomalies indicate several phases of fully developed and failed rift systems and a possible branch of the West Antarctic Rift System in the Amundsen Sea Embayment.
"Changing Polar Regions" - 25th International Congress on Polar Research 2013 IRO-2 EISVORHERSAGE UND EIS-ROUTEN-OPTIMIERUNG