Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Abstract

New multibeam bathymetry data are presented for the South Sandwich intra-oceanic arc which occupies the small Sandwich plate in the South Atlantic, and is widely considered to be a simple end-member in the range of intra-oceanic arc types. The images show for the first time the distribution of submarine volcanic, tectonic and erosional-depositional features along the whole length of the 540 km long volcanic arc, allowing systematic investigation of along-arc variations. The data confirm that the volcanic arc has a simple structure composed of large volcanoes which form a well-defined volcanic front, but with three parallel crosscutting seamount chains extending 38-60 km from near the volcanic front into the rear-arc. There is no evidence for intra-arc rifting or extinct volcanic lines. Topographic evidence for faulting is generally absent, except near the northern and southern plate boundaries. Most of the volcanic arc appears to be built on ocean crust formed at the associated back-arc spreading centre, as previously proposed from magnetic data, but the southern part of the arc appears to be underlain by older arc or continental crust whose west-facing rifted margin facing the back-arc basin is defined by the new bathymetry. The new survey shows nine main volcanic edifices along the volcanic front and ca. 20 main seamounts. The main volcanoes form largely glaciated islands with summits 3.0-3.5 km above base levels which are 2500-3000 m deep in the north and shallower at 2000-2500 m deep in the south. Some of the component seamounts are interpreted to have been active since the last glacial maximum, and so are approximately contemporaneous with the volcanic front volcanism. Seven calderas, all either submarine or ice-filled, have been identified: Adventure volcano, a newly discovered submarine volcanic front caldera volcano is described for the first time. All but one of the calderas are situated on summits of large volcanoes in the southern part of the arc, and most are associated with current or historic volcanic or hydrothermal activity. Shallow shelves around the islands are generally 1-10 km wide. Submerged banks up to 1100 m deep are interpreted as subsided erosional surfaces. Seamounts and emergent volcanoes experienced a range of mass wasting processes including by landsliding and smaller mass flows. KeywordsVolcanic arc, subduction zone, caldera, seamount, submarine volcanism The importance of the South Sandwich volcanic arcThe South Sandwich volcanic arc, situated in the South Atlantic ( Fig. 1), is a tectonically simple, active, intra-oceanic arc, and is ideally suited to studies of volcanic arc crustal structure, geochemical investigation of mantle processes above a subduction zone, and sedimentation in an early stage of arc evolution. The active arc is built largely on oceanic crust of the small Sandwich plate which formed about 10 Ma at the back-arc East Scotia ridge spreading centre . The arc is forming in response to steeply inclined subduction of the South American plate beneath the Sand...

Tectonic activity evolution of the Scotia‐Antarctic Plate boundary from mass transport deposit analysis

“…Thus, in addition to their greater quantity, the MTDs of Scan Basin are also larger than those of the western basins (Table 2 and Figure 8). This Journal of Geophysical Research: Solid Earth 10.1002/2015JB012622 Nelson et al, 2011], as is well described in volcanic ocean islands such as the South Sandwich Islands, Hawaii, Reunion Island, or Canary Islands, whose MTDs reach 600 km in length [Moore and Normark, 1994;Masson et al, 1998;Ollier et al, 1998;Leat et al, 2013].…”

“…This increase might be related to the presence of young volcanic constructs in Scan Basin and neighboring Discovery Bank [ Dalziel et al ., ; Eagles and Jokat , ; Pérez et al ., ]. Volcanic edifices are usually associated with large MTDs [ Lee et al ., ; Moore and Normark , ; Weaver et al ., ; Issler et al ., ; Nelson et al ., ], as is well described in volcanic ocean islands such as the South Sandwich Islands, Hawaii, Reunion Island, or Canary Islands, whose MTDs reach 600 km in length [ Moore and Normark , ; Masson et al ., ; Ollier et al ., ; Leat et al ., ].…”

Analysis of air mass back trajectories with present and historical volcanic activity and anthropogenic compounds to infer pollution sources in the South Shetland Islands (Antarctica)

“…The South Sandwich volcanic islands are the highest part of the intraoceanic Scotia Ridge, which is located in the South Atlantic. Its origin is related to the steeply inclined subduction of the South American plate beneath the Sandwich plate at a rate of 67-79 km/Ma (Leat et al 2013).…”

Tectonic and oceanographic control of sedimentary patterns in a small oceanic basin: Dove Basin (Scotia Sea, Antarctica)

“…Lodolo et al ., ; Maldonado et al ., ). The system remains active today along the volcanic South Sandwich Arc (Leat et al ., ). The present day Scotia Arc consists of continental blocks deriving from the break‐up of the continental bridge and the subsequent dispersion of fragments along the periphery of the Scotia Sea (Fig.…”

“…We relate these sedimentary changes to the intensification of bottom water circulation that followed the Mid‐Miocene Climate Optimum while ice sheet expansion took place in Antarctica due to global cooling (Tsuchi, ; Anderson, ; Zachos et al ., ; Bart, ). Sedimentary input and its widespread distribution may also reflect regional tectonic activity, which modified the southern Scotia Sea basinal configurations; the Scotia Arc re‐organisation followed changes in the back‐arc spreading centre related to decreased WSR spreading rates and activation of the ESR (Livermore et al ., ; Vanneste & Larter, ; Leat et al ., ; Nicholson & Georgen, ; Eagles & Jokat, ). At this time, some significant tectonic events took place, including collision of the Chile Ridge with the Chile Trench in southern South America (Cande & Leslie, ; Eagles & Scott, ).…”