A crustal model and its tectonic implication on the evolution of the Pacific margin of the northern Antarctic Peninsula

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The Shackleton Fracture Zone (SFZ) and the South Shetland Trench (SST) are prominent bathymetric structures in the Southeast Pacific off Antarctic Peninsula. The SFZ comprises a high ridge and a deep trough. The SFZ ridge was probably formed by the uplift of low-density material like serpentinite. Two phases of deformation observed in the trough suggest that (1) a large-scale crustal faulting due to transtensional movement along the SFZ during Drake Passage opening before 6 Ma formed the deep trough, and (2) recent contractional structures around the trough are indicative of the present convergence between the Scotia and Antarctic plates. The angle of subduction of oceanic crust in the SST increases from southwest to northeast along the SST as its age increases from southwest to northeast. Because thick accumulation of sediments is not expected in active trenches with a horst and graben structure, the presence of thick trench-fill sediments (up to 1300m) over a horst and graben structure in the South Shetland Trench (SST) indicates that they accumulated after the cessation of subduction at about 4 Ma.
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