Scotia arc kinematics from GPS geodesy

Abstract

GPS crustal velocity data from the Scotia and South Sandwich plates, transform azimuths, spreading data, and an updated earthquake slip vector catalog provide the first Scotia and South Sandwich plate Euler vector estimates not dependent on closure as the GPS data tie them to the global plate circuit. Neither the GPS data, which sample limited portions of the plates, nor the geologic data, which are not tied to the global spreading circuit, are sufficient individually to define the Euler vectors. As Scotia plate GPS measurements do not sample the stable plate interior, plate boundary deformation field modeling is necessary for Euler vector estimation. Our South America‐Antarctic and Scotia‐South Sandwich Euler pole estimates agree with previous estimates from either GPS or geologic data. Our South America‐Scotia Euler vector, however, is significantly different and near the South America‐Antarctic Euler vector producing an approximately coaxial motion of Scotia between South America and Antarctica.

Collisional model for rapid fore‐arc block rotations, arc curvature, and episodic back‐arc rifting in subduction settings

“…Kinematic data that exist (some GPS, earthquake slip vectors, transform orientations, magnetic lineations) show that the Sandwich Plate rotates about a distant pole (>2000 km away) relative to the subducting South America Plate [Thomas et al, 2003;Smalley et al, 2007]. Moreover, rifting rates on the east Scotia Ridge remain fairly constant along its length (6-7 cm/a) supporting the assertion that the Sandwich Plate rotates about a distant pole relative to the Scotia Plate [Thomas et al, 2003].…”

Tectonic reconstructions for paleobathymetry in Drake Passage

“…13, as in the 17 Ma reconstruction, the plate circuit at 10 Ma is completed using a rotation that is designed to avoid overlap between the Phoenix and Magallanes plates. The rotation is slight, and the strain it insinuates on the South Scotia Ridge is very similar to that by the present-day GPS-derived rotation of Smalley et al (2007). We interpret this as an indication of the onset of modern-like motion following ridgecrest-trench collisions in the northwest Weddell Sea and deactivation of Scan and Jane basins as sites of plate divergence.…”

“…Used separately or in combination, the two techniques agree on the presence of two independently-moving plates inside the Scotia Arc, the larger Scotia Plate in the west and, further east, the smaller Sandwich Plate, which diverge from one another at the north-striking east Scotia ridge along 30°W (Forsyth, 1975;Pelayo and Wiens, 1989;Smalley et al, 2003Smalley et al, , 2007Thomas et al, 2003). Smalley et al (2007) show that the use of GPS data much reduces the uncertainties in solutions for the directions and rates of motions between these plates and their larger neighbours outside the Scotia Arc. These motions are distinct from those of the surrounding South American and Antarctic plates owing to slow transform motions on the North and South Scotia ridges, and subduction of South American lithosphere beneath the Sandwich Plate.…”

“…The reconstruction features 70 km of overlap between the northwest corner of the South Orkney Microcontinent and the western end of the South Scotia Ridge. This overlap may be a consequence of deformation of these parts of the ridge as part of the present ScotiaAntarctic plate boundary (Smalley et al, 2007) or by extension during the opening of Powell Basin (Eagles and Livermore, 2002).…”

The global relevance of the Scotia Arc: An introduction

“…2, 3). Opening of the gateway has influenced the oceanographic flows between the Pacific and Atlantic oceans and, hence, as has been widely speculated, the climatic evolution of the Southern Ocean and Antarctica and global climate change in general (Kennett 1977, Barker, 2001Livermore et at., 2005, 2007, Dalziel et al, 2013bMartos et al, 2013, among others). This gateway is also very important for mantle dynamics since, together with the Caribbean Arc, it is the main potential gateway for the asthenopheric flow between the shrinking Pacific and the expanding Atlantic oceans (Alvarez ,1982;Russo and Silver, 1994;Pearce et al, 2001;Leat et al, 2004;Haase et al, 2011;Dalziel et al, 2013a;Lynner and Long, 2013;Martos et al, 2014a).…”