Seismic facies and stratigraphy of the Cenozoic succession in McMurdo Sound, Antarctica: Implications for tectonic, climatic and glacial history

• Published in: Palaeogeography, Palaeoclimatology, Palaeoecology
• Main Authors: Fielding, CR, Whittaker, J, Henrys, SA, Wilson, TJ, Naish, TR
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Bv 2008
• Subjects: Earth Sciences; Geology; Marine Geoscience; McMurdo Sound; Victoria Land; Western Basin; Antarc*; Antarctica
• Online Access: https://doi.org/10.1016/j.palaeo.2007.08.016; http://ecite.utas.edu.au/84442

Integration of data fromfully cored stratigraphic holes with an extensive grid of seismic reflection lines in McMurdo Sound, Antarctica,has allowed the formulation of a new model for the evolution of the Cenozoic Victoria Land Basin of theWestAntarctic Rift. The Early Riftphase (Eocene to Early Oligocene) is recorded by wedges of strata confined by early extensional faults, and which contain seismic faciesconsistent with drainage via coarse-grained fans and deltas into discrete, actively subsiding grabens and half-grabens. TheMain Rift phase(Early Oligocene to Early Miocene) is represented by a lens of strata that thickens symmetrically from the basin margins into a centraldepocenter, and in which stratal events pass continuously over the top of the Early Rift extensional topography. Internal seismic facies andlithofacies indicate a more organized, cyclical shallow marine succession, influenced increasingly upward by cycles of glacial advance andretreat into the basin. The Passive Thermal Subsidence phase (EarlyMiddle Miocene) is recorded by an evenly distributed sheet of strata thatthickens somewhat into the depocentre but is continuous across and over the earlier rift strata to the margins of the basin. Internally, itcontains similar facies to the underlying Main Rift, but preservesmore evidence for clinoformsets and large channels, and in core comprisesmany short, condensed and strongly top-truncated stratal cycles with continued, periodic glacial influence. These patterns are interpreted torecord accumulation under similar environmental conditions but in a regime of slower subsidence. The Renewed Rifting phase (MiddleMiocene to Recent, largely unsampled by coring thus far) is represented by intervals that thicken significantly into the basin depocentre andthat are complicated by evidence of magmatic activity (McMurdo Volcanic Group). This succession is further divided into lower and upperintervals, separated by a major unconformity that displays increasing angular discordance towards the western basin margin andTransantarctic Mountain Front. The youngest part of the stratigraphy was accumulated under the influence of flexural loading imposed bythe construction of large volcanic edifices, and was formed in an environment in which little sediment was supplied from the western basinmargin, suggesting a change in environmental (glacial) conditions at possibly c. 2 Ma. The Cenozoic stratigraphy of the southern VictoriaLand Basin preserves archives of both climate change and the complex rift history of the basin, and coincidences between key stratal surfacesin seismic data and evidence for environmental change in drillcores suggest that tectonic and climatic drivers may be causally linked.