Lindeque, Ansa; Martos, Yasmina M; Gohl, Karsten; Maldonado, Andrés (2012): Seafloor spreading magnetic anomaly isochron map compilation for the Weddell Sea and Scotia Sea [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.777453,

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Supplement to: Lindeque, A et al. (2013): Deep-sea pre-glacial to glacial sedimentation in the Weddell Sea and southern Scotia Sea from a cross-basin seismic transect. Marine Geology, 336, 61-83, https://doi.org/10.1016/j.margeo.2012.11.004

The deep sea sedimentary record is an archive of the pre-glacial to glacial development of Antarctica and changes in climate, tectonics and ocean circulation. Identification of the pre-glacial, transitional and full glacial components in the sedimentary record is necessary for ice sheet reconstruction and to build circum-Antarctic sediment thickness grids for past topography and bathymetry reconstructions, which constrain paleoclimate models. A ~3300 km long Weddell Sea to Scotia Sea transect consisting of multichannel seismic reflection data from various organisations, were used to interpret new horizons to define the initial basin-wide seismostratigraphy and to identify the pre-glacial to glacial components. We mapped seven main units of which three are in the inferred Cretaceous-Paleocene pre-glacial regime, one in the Eocene-Oligocene transitional regime and three units in the Miocene-Pleistocene full glacial climate regime. Sparse borehole data from ODP leg 113 and SHALDRIL constrain the ages of the upper three units. Compiled seafloor spreading magnetic anomalies constrain the basement ages and the hypothetical age model. In many cases, the new horizons and stratigraphy contradict the interpretations in local studies. Each seismic sedimentary unit and its associated base horizon are continuous and traceable for the entire transect length, but reflect a lateral change in age whilst representing the same deposition process. The up to 1240 m thick pre-glacial seismic units form a mound in the central Weddell Sea basin and, in conjunction with the eroded flank geometry, support the interpretation of a Cretaceous proto-Weddell Gyre. The base reflector of the transitional seismic unit, which marks the initial ice sheet advances to the outer shelf, has a lateral model age of 26.6-15.5 Ma from southeast to northwest. The Pliocene-Pleistocene glacial deposits reveals lower sedimentations rates, indicating a reduced sediment supply. Sedimentation rates for the pre-glacial, transitional and full glacial components are highest around the Antarctic Peninsula, indicating higher erosion and sediment supply of a younger basement. We interpret an Eocene East Antarctic Ice Sheet expansion, Oligocene grounding of the West Antarctic Ice Sheet and Early Miocene grounding of the Antarctic Peninsula Ice Sheet.

We compiled a seafloor spreading magnetic anomaly isochron map for the Weddell Sea and Scotia Sea from published literature to:

1. constrain basement ages,

2. obtain a spreading age range for each basin that the WS-SS seismic transect crosses and

3. to deduct the ages of the oldest sediments that lie on the basement.

Magnetic anomaly picks were sourced from authors where available (e.g. König and Jokat, 2006) and imported into GIS ArcMap 10. Published anomaly and isochron maps (e.g. Bohoyo et al., 2002; Maldonado et al., 2007) were georeferenced and the isochrons precisely digitized, to fill the regions where actual magnetic data picks were unavailable.

Conflicting opinions exist between studies in the same basin e.g. in the Powell basin between Eagles and Livermore (2002) and Suriñach et al. (1997) due to ambiguous data and allow for alternative age interpretations. In such cases where isochrons of different authors overlapped or disagreed, the most recent publication or data that fitted best with the regional trend were favoured.

Data can be downloaded as GMT file (version 5) and as a complete ArcMap 10 shapefile collection with metadata.