SEISMIC ATTRIBUTE ANALYSES REVEAL A RECORD OF HIGHER RESOLUTION ANTARCTIC CRYOSPHERE DYNAMICS

Understanding relationships between past variations in cryosphere evolution and global climate change improve our understanding of the impact of future climate change. The Ross Sea continental margin received ~25% of the drainage from both East and West Antarctic Ice Sheets since the late Oligocene. The large proportion of ice volume change contained in the stratigraphy of this margin makes the record an excellent “barometer” of past Antarctic cryosphere dynamics.

Seismic stratigraphic analysis of data from this margin was used to decipher the depositional and erosional history in the Ross Sea. This stratigraphy is directly related to variations in drill core properties, temporal and spatial lithofacies changes and depositional environments. Stratigraphic analysis of multi-channel seismic (MCS) data is limited by its low resolution, relative to Single Channel and Multibeam Data. To improve resolution and our ability to test hypotheses on the presence of Milankovitch-scale glacial sequences, we performed Spectral Decomposition on MCS profiles. This revealed thin-bed interfaces that are tuned and not visible in Standard Amplitude sections and revealed higher-frequency spatial and temporal variations in seismic facies that may be related to climate changes identified in core. Seismic Attribute Analyses (Instantaneous Frequency and Instantaneous Amplitude) conducted on spectrally decomposed profiles reveals subtle changes in seismic characteristics not detected in standard MCS data and that are associated with gradual increases in bed thickness and impedance contrast related to changes in depositional conditions and source proximity. Identification of these temporal and spatial variations distinguish temperate to polar subglacial facies and important differences in ice sheet and climate conditions. Additionally, lateral changes in Spectrally-Decomposed Reflection Surface Texture reveal hidden sequence bounding unconformities and changes in distance from sediment source.