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

Abstract

Follow this and additional works at: http://digitalcommons.unl.edu/geosciencefacpub Part of the Earth Sciences CommonsThis Article is brought to you for free and open access by the Earth and Atmospheric Sciences, Department of at DigitalCommons@University of Nebraska -Lincoln. It has been accepted for inclusion in Papers in the Earth and Atmospheric Sciences by an authorized administrator of DigitalCommons@University of Nebraska -Lincoln.Fielding, Christopher R.; Whittaker, Joanne; Henrys, Stuart A.; Wilson, Terry J.; and Naish, Timothy R., "Seismic facies and stratigraphy of the Cenozoic succession in McMurdo Sound, Antarctica: Implications for tectonic, climatic and glacial history" (2008 AbstractIntegration of data from fully 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 the West Antarctic Rift. The Early Rift phase (Eocene to Early Oligocene) is recorded by wedges of strata confined by early extensional faults, and which contain seismic facies consistent with drainage via coarse-grained fans and deltas into discrete, actively subsiding grabens and half-grabens. The Main Rift phase (Early Oligocene to Early Miocene) is represented by a lens of strata that thickens symmetrically from the basin margins into a central depocenter, and in which stratal events pass continuously over the top of the Early Rift extensional topography. Internal seismic facies and lithofacies indicate a more organized, cyclical shallow marine succession, influenced increasingly upward by cycles of glacial advance and retreat into the basin. The Passive Thermal Subsidence phase (Early Middle Miocene) is recorded by an evenly distributed sheet of strata that thickens somewhat into the depocenter but is continuous across and over the earlier rift strata to the margins of the basin. Internally, it contains similar facies to the underlying Main Rift, but preserves more evidence for clinoform sets and large channels, and in core comprises many short, condensed and strongly top-truncated stratal cycles with continued, periodic glacial influence. These patterns are interpreted to record accumulation under similar environmental conditions but in a regime of slower subsidence. The Renewed Rifting phase (Middle Miocene to Recent, largely unsampled by coring thus far) is represented by intervals that thicken significantly into the basin depocenter and that are complicated by evidence of magmatic activity (McMurdo Volcanic Group). This succession is further divided into lower and upper intervals, separated by a major unconformity that displays increasing angular discordance towards the western basin margin and Transantarctic Mountain Front. The youngest part of the stratigraphy was accumulated under the influence of flexural loading imposed by the construction of large volcanic edifices, and was formed in an environment in which little sediment was supplied from the western basin margin, su...

Sequence stratigraphy of the ANDRILL AND-2A drillcore, Antarctica: A long-term, ice-proximal record of Early to Mid-Miocene climate, sea-level and glacial dynamism

“…The base of the stratified interval at 122.86 mbsf may coincide with a widely-correlated seismic stratigraphic event (Red reflector, Bclino of Fielding et al, 2008a) that is interpreted to record a Pliocene relative sea-level high at ~ 5.0-4.0 Ma. Composite Sequence 13 (< 5.0 Ma to > 750 ka), which contains inferred unconformities, represents an incomplete record of the Pliocene.…”

“…Also, integration of drilling records with an extensive array of seismic reflection data has allowed division of the VLB stratigraphy into a series of age-constrained tectono-stratigraphic units reflecting discrete phases of basin-forming activity. The principal phases are 1) Early Rift (34-29 Ma), 2) Main Rift (29-24 Ma), 3) Passive Thermal Subsidence (24-13 Ma), and 4) Renewed Rifting (Terror Rift: 13 Ma to present) (Fielding et al, 2006(Fielding et al, , 2008aHenrys et al, 2007).…”

Tectonic history of mid-Miocene to present southern Victoria Land Basin, inferred from seismic stratigraphy in McMurdo Sound, Antarctica

“…Six post-17 Ma regional unconformities and volcanic horizons have been mapped across the McMurdo Sound seismic grid and define basin wide regional seismic intervals with bounding unconformities (Fielding et al, 2007). An interpreted west to east seismic cross section profile ( (Brancolini et al, 1995;Bartek et al, 1996;Hamilton et al, 2001;Wilson et al, 2004).…”

“…Faults commonly reach the seafloor at the basin edges although seafloor fault scarps are not pronounced in swath data (Wilson et al, 2004). This post-Early Miocene phase of rifting accommodates up to ~3.5 km of sediment along the central axis of the (Fielding et al, 2007) for key to seismic reflector coding scheme. The thermal subsidence phase between the purple-grey (Re) and light green (Rg) reflectors and Terror Rift formation is above the light green reflector (Rg to seafloor).…”

“…The goal of the cruise was to gain a better understanding of the kinematics and ages of the neotectonic events of the Terror Rift through acquisition of multi-channel and single-channel reflection seismic, magnetic, gravity, and bathymetric data (Hall et al, 2007). Here we focus on McMurdo Sound where we draw on the stratigraphic framework already established (Whittaker, 2005;Fielding et al, 2006;Fielding et al, 2007) to address the following question; does the structure and architecture of the stratigraphic record provide evidence of Neogene rifting of the West Antarctic Rift and the VLB?…”