Rotational Extension Model for the East Antarctic Fan-like Basal Pattern

The authors evaluated glacial erosion, rift propagation, and inherited lithospheric structures as causes of the East Antarctic Fan-like Basal Pattern (EAFBP). Low ice-surface speeds (<10 m yr?¹) and limited historic glacial valleys led them to reject erosion; rift propagation typical of mid-ocean ridges was deemed unsuitable, and inheritance alone could not generate radial geometry. They propose a two-phase rotational-extension model. Phase 1 features counter-clockwise fan-shaped extension about an Euler pole that formed the Aurora and Wilkes basins, with normal faults accommodating northward deepening and Transantarctic Mountains (TAM) rotating clockwise. Phase 2 adds secondary V-shaped and rectangular basins, a north-to-south increase in extensional strain (e_s < e_c < e_n), and segmentation of Western and Eastern Mawson sutures and TAM into three blocks each. A transcurrent en-échelon strike-slip fault system caps the fan, and TAM rotates ~20° around point DP. Compression reactivated Gamburtsev Mountains, adding uplift to their Alpine-type topography.

Nature

The model links the fan-shaped extension to the circular geometry of the conjugate Antarctic–Australian margins. Pull-apart basins that formed along the northern EAFBP edge may have evolved into short seafloor-spreading segments, driving west-to-east ridge propagation and shaping the fracture-zone distribution that partitions the Southeast Indian Ridge into five segments.

Nature

The transverse offsets could be interpreted as transfer faults rather than true strike-slip motion, a scenario deemed less probable. Limited seismic or drilling evidence for short spreading segments leaves the precise nature of the offsets and the extent of pull-apart basin development uncertain.

Nature

• “5) are generally low (<10 m yr–1) and geomorphological evidence suggests that glacial erosion by earlier ice sheets in the East Antarctic interior was selectively focused through existing valleys on a smaller scale than the features comprising the EAFBP28.” — Study Authors

Nature

• “The final rotation angle of the TAM around point DP is ? = ~20°.” — Study Authors

Nature

• “We propose that the rotational extension in the EAFBP was at least partially accommodated by compression in the Gamburtsev Mountains region, causing additional uplift and contributing to their youthful Alpine topography7.” — Study Authors

Nature

• “During the subsequent Antarctica–Australia rifting, these pull-apart basins may have driven west-to-east ridge propagation, producing the transfer faults responsible for the present-day fracture zone distribution and the partitioning of the Southeast Indian Ridge into five segments (Fig.” — Study Authors

Nature

Future work will focus on seismic surveys, ice-penetrating radar, and modeling to test the rotational-extension hypothesis and identify any short seafloor-spreading segments predicted by the model.

Nature