Rocks from the Cascade Seamount: an archive of the unzipping of Gondwana and the initiation of the ACC?
Mundana, R and Johnson, SC and Whittaker, JM and Carey, R and Sauermilch, I and Fox, JM, Rocks from the Cascade Seamount: an archive of the unzipping of Gondwana and the initiation of the ACC?, AGU Chapman Conference 2017 Abstracts, 29 January-03 February, Hobart, Tasmania (2017) [Non Refereed Conference Paper]
The Cascade Seamount, on the East Tasman Plateau, is enigmatic with regard to its formation
and subsidence history. Understanding the timing and rate of subsidence of the region is an
important factor for determining the initiation of the Antarctic Circumpolar Current.
Currently situated ~2000m below sea level, the Seamount has archived much of this history.
However, our understanding of its evolution is limited by poorly constrained samples
recovered from two separate locations. One, from a fishing excursion, recovered rocks from
various unknown locations on the seamount while an ODP drill hole collected samples on the
East Tasman Rise ~23km from the Seamount (~2000m bsl). The two, limited, sample sets
comprise of shallow water sediments but have led to opposing subsidence histories for the
area being proposed. Fundamentally, it is the ODP drill hole that has been used as the only
constraint for the area in the tectonic modeling that has been conducted (Stickley et al. 2004).
The recent RV Investigator voyage to the Cascade Seamount (August, 2016) aimed to
elucidate this problem through high-resolution mapping and dredging with the aim to further
understand and characterize the Seamount. We present the initial results of the macro- and
micro-features of the rocks recovered from the top and flanks of the Seamount. The highresolution
bathymetry data identified a series of terraces on the flanks of the Seamount from
which a series of shallow water sedimentary rocks and conglomeratic units were recovered.
Here, we describe these rocks, and discuss their formation. These descriptions and
interpretations, coupled with the new geophysical data, provide a critical insight into the
subsidence history of the Seamount. The ability to understand the history of the Cascade
Seamount and the East Tasman Plateau provides a new and important tie-point in
understanding the final stages of the regional evolution and initiation of the Antarctic