Structural geology and tectonic significance of basin-fill sedimentary rocks, of ice-transported boulders therein and of volcanics recovered by ANDRILL cores in the McMurdo Sound region: Implications for the Cenozoic tectonic and glacial/climatic evolution of the Ross Sea region
Zusammenfassung der Projektergebnisse
The ANtarctic Geological DRILLing Program (ANDRILL) drilled a 1285 m long stratigraphic core of middle Miocene to Pleistocene age (AND-1B) from a platform located on Ross Island in the McMurdo Ice Shelf sector of the Ross Ice Shelf in the 2006/07 season. Primary target was a thick succession of glacimarine, terrigenous, volcanic, and biogenic sediments that were deposited in a flexural moat depression formed by loading of the Ross Island volcanic complex. The drill site was located close to the southern end of the Terror Rift of the Victoria Land Basin within the Cenozoic West Antarctic Rift System (WARS). The western termination of the WARS is represented by the Transantarctic Mountains front that forms an asymmetric rift shoulder segmented by numerous transverse and oblique faults and has experienced several phases of uplift and denudation in the Cenozoic. Primary goals of the project were the analysis of natural fractures in the core and the reconstruction of kinematics and dynamics of rifting, related faulting history, and palaeostrain/- stress states in the western Ross Sea in Neogene to Recent times, as well as the state of the contemporary stress field based on the record of drilling-induced fractures. More than 4300 fractures were logged. Drilling-induced fractures included abundant subhorizontal extension fractures as well as 410 steeply dipping, petal, petal-centerline, and core-edge fractures with a maximum density of 5 fractures/m. A total of 1475 natural fractures were recorded and include faults, brecciated zones, veins, and clastic intrusions. Faults show mostly normal sense of movement, although there are also some subordinate reverse faults present in the core. The latter could be related to glaciotectonic processes. Veins include slickenfiber veins along faults, openingmode fibrous veins, pressure shadows on clast margins, and complex microvein webs within fault zones. Strain analyses of mechanically twinned calcite in veins and faults were performed in Neogene (13.6 to 4.3 Ma) strata of the core. Strain ellipsoids have prolate and oblate geometries with principal shortening and extension strains between -7 to 9%, respectively. Negative expected values are ≤25% in most samples. Therefore, homogeneous coaxial strain is mainly characterized by subvertical shortening at relatively shallow depths most likely due to lithostatic loading in an Andersonian normal faulting stress regime during sedimentary and ice sheet burial under relatively low stresses. Twinning due to horizontal contraction within a strike-slip dominated setting may be caused by layer-parallel shortening in only two samples; however, local inhomogeneous strain/stress is also possible. This widely observed absence of layer-parallel shortening may indicate that horizontal contraction as predicted by several transtensional rifting models was lacking or too weak to cause widespread overprint by non-coaxial strain. Average NW-SE oriented extension subparallel to different indicators of Neogene extension is shown by oriented samples and fits well into (i) an orthogonal rifting scenario within a NNE trending rift segment and (ii) geodynamic models predicting rifting in a general right-lateral transtensional regime. The widely observed absence of non-coaxial layer-parallel shortening is in favor for possibility (i), although it may also suggest strain partitioning within a transtensional rift setting within the Terror Rift.
Projektbezogene Publikationen (Auswahl)
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(2007): Das ANDRILL McMurdo Ice Shelf Project 2006/07: Eine geologische Forschungsbohrung im Rossmeer, West-Antarktis.- Arbeitskreis Geologie der Polargebiete in der Deutschen Gesellschaft für Polarforschung und FKPE-Arbeitsgruppe „Geophysik der Polargebiete“, 29. Arbeitstreffen in Leipzig, 27./28. April 2007, Überblick mit ausgewählten Beiträgen, 20-21
Läufer, A.L.
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(2007): Fracture logging of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica. In Naish, T., Powell, R., and Levy, R. (Eds.), Studies from the ANDRILL, McMurdo Ice Shelf Project, Antarctica—Initial Science Report on AND-1B. Terra Antartica, 14(3):175–184
Wilson, T., Paulsen, T., Läufer, A. & Millan, C.
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(2008), Brittle fractures in AND-1B core, McMurdo Ice Shelf, Antarctica: A record of Neogene rifting or glaciotectonic deformation? Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract C33A-05
Wilson, T.J., Paulsen, T.S., Millan, C., Läufer, A., McKay, R. & ANDRILL MIS Science Team
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(2008): Drilling-induced petal-centerline and core-edge fractures in Antarctic sedimentary rock cores: A robust indicator of contemporary stress.- 3rd World Stress Map Conference, Proceedings, 42, Potsdam, 15.-17. October 2008
Wilson, T.J., Paulsen, T.S., Jarrard, R., Schmitt, D., Moos, D., Millan, C., Läufer, A. & Pierdominici, S.
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(2009): Contemporary stress data from induced fractures in the AND-1B sedimentary rock core, McMurdo Ice Shelf, Antarctica.- In: Dow, M., Fischbein, S., Levy, R., Naish, T., Powell, R., ANDRILL McMurdo Ice Shelf Project Science Integration Workshop - Program and Abstracts. 10-13th February, 2009. Victoria University of Wellington. ANDRILL Contribution 12, Wellington, New Zealand, 64
Wilson, T., Paulsen, T., Jarrard, R., Läufer, A., Millan, C. & Schmitt, D.
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(2009): Contemporary stress data from induced fractures in the AND-1B sedimentary rock core, McMurdo Ice Shelf, Antarctica.- In: Dow, M., Fischbein, S., Levy, R., Naish, T., Powell, R., ANDRILL McMurdo Ice Shelf Project Science Integration Workshop - Program and Abstracts. 10-13th February, 2009. Victoria University of Wellington. ANDRILL Contribution 12, Wellington, New Zealand, 64
Wilson, T., Paulsen, T., Jarrard, R., Läufer, A., Millan, C. & Schmitt, D.
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(2009): Natural fractures of the AND-1B core, McMurdo Ice Shelf Project, Antarctica.- In: Dow, M., Fischbein, S., Levy, R., Naish, T., Powell, R., ANDRILL McMurdo Ice Shelf Project Science Integration Workshop - Program and Abstracts. 10-13th February, 2009. Victoria University of Wellington. ANDRILL Contribution 12, Wellington, New Zealand, 46
Paulsen, T., Wilson, T., Läufer, A., Millan, C. & Jarrard, R.
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(2009): Obliquity-paced Pliocene West Antarctic Ice Sheet oscillations.- Nature, 458, 322-329
Naish, T., Powell, R., Levy, R., Krissek, L., Niessen, F., Pompilio, M., Scherer, R., Talarico, F., Wilson, G., Wilson, T., Browne, G., Carter, C., Cody, R., Cowan C., Crampton, J., Dunbar, G., Dunbar, N., Florindo, F., Gebhardt, C., Graham, I., Hannah, M., Harwood, D., Hansaraj, D., Henrys, S., Helling, D., Kuhn, G., Kyle, P., Läufer, A., Maffioli, P., Magens, D., Mandernack, K., McIntosh, W., McKay, R., Millan, C., Morin, R., Ohneiser, C., Paulsen, T.., Persico, D., Reed, J., Ross., J., Raine, I., Schmitt, D., Sagnotti, L., Sjunneskog, C., Strong, P., Taviani, M., Vogel, S., Wilch, T., Williams, T., Winter, D.
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(2010): Neogene deformation in the West Antarctic Rift in the McMurdo Sound region from studies of the ANDRILL and Cape Roberts drill cores.- American Geophysical Union, Fall Meeting 2010, abstract #C43B-0544
Paulsen, T.S., Wilson, T.J., Jarrard, R.D., Millan, C., Saddler, D., Läufer, A. & Pierdominici, S.
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(2010): Recent to contemporary stress of the West Antarctic Rift from drill core and volcanic alignment studies.- American Geophysical Union, Fall Meeting 2010, abstract #T13F-04
Paulsen, T. S., Wilson, T. J., Jarrard, R. D., Schmitt, D. R., Pierdominici, S., Montone, P., Millan, C., Läufer, A., Wonik, T. & Handwerger, D.
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(2012): Neogene tectonic and climatic evolution of the Western Ross Sea, Antarctica – Chronology of events from the AND-1B drill hole.- Global and Planetary Change, 96-97, 189-203
Wilson, G.S., Levy, R.H., Naish, T.D., Powell, R.D., Florindo, F., Ohneiser, C., Sagnotti, L., Winter, D.M., Cody, C., Henrys, S., Ross, J., Krissek, L., Niessen, F., Pompillio, M., Scherer, R., Alloway, B.V., Barrett, P.J., Brachfeld, S., Browne, G., Carter, L., Cowann, E., Crampton, J., DeConto, R.M., Dunbar, G., Dunbar, R., von Eynatten, H., Gebhardt, C., Giorgetti, G., Graham, I., Hannah, M., Hansaraj, D., Harwood, D.M., Hinnov, L., Jarrard, R.D., Joseph, L., Kominz, M., Kuhn, G., Kyle, P., Läufer, A., McIntosh, W.C., McKay, R., Maffioli, P., Magens, D., Millan, C., Monien, D., Moriny, P., Paulsen, T., Pollard, D., Raine,J.I., Riesselman, C., Sandroni, S., Schmitt, D., Sjunneskog, C., Strong, P., Talarico, F., Taviani, M., Villae, G., Vogel, S., Wilch, T., Williams, T., Wilson, T.J. & Wise, S.
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(2013): Rift history and kinematic records from Antarctic drill cores.- Antarctic Geologic Drilling Workshop, Houston, TX, USA, 07-08 November 2013
Paulsen, T., Wilson, T., Millan, C., Jarrard, R., Läufer, A. & Wonik, T.
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(2014): Kinematics of the Neogene Terror Rift: Constraints from calcite twinning strains in the ANDRILL McMurdo Ice Shelf (AND-1B) core, Victoria Land Basin, Antarctica.- Geosphere
Paulsen, T.S., Wilson, T.J., Demosthenous, C., Millan, C., Jarrard, R. & Läufer, A.
