Bathymetric and Seismic Data, Heat Flow Data, and Age Constraints of Le Gouic Seamount, Northeastern Atlantic

Until the year 2019 only around 15% of the Earth’s seafloor were mapped at fine spatial resolution (<800 m) by multibeam echosounder systems (Wölfl et al., 2019). Most of our knowledge of global bathymetry is based on depths predicted by gravity observations from satellite altimeters. These predicted depths are combined with shipboard soundings to produce global bathymetric grids. The first topographic map of the world’s oceans so produced (Smith and Sandwell, 1997) had a resolution between 1 and 12 km, and subsequent improvements in data and filtering techniques led to several updates. The latest bathymetric grid of the General Bathymetric Chart of the Oceans (GEBCO_2020) uses the SRTM15+V2.0 data set, which has a grid spacing of 15 arc sec, equivalent to about 500 × 500 m at the equator (Tozer et al., 2019). This resolution does not imply that reliable depth data are available for each grid cell. There are vast areas of the oceans where the accuracy of these grids is limited by lacking shipborne multibeam data, which are needed for calibrating and ground-truthing predicted depths (Smith and Sandwell, 1994). The resolution and accuracy of the bathymetric grids are critical factors for global estimates of the number and size distribution of seamounts, in particular for small edifices of <1,000 m height (Wessel, 2001; Hillier and Watts, 2007; Kim and Wessel, 2011). A case in point is Le Gouic Seamount, located in the NE Atlantic about 100 km SW of Tropic Seamount on ca. 152 Ma crust, close to magnetic isochrone M24 (Bird et al., 2007). The seamount belongs to the Canary Island Seamount Province (CISP; van den Bogaard, 2013), also termed Western Saharan Seamount Province (WSSP) by some workers (e.g., Josso et al., 2019). It is listed in the Kim and Wessel (2011) seamount census with the ID KW-00902, located at 21.26216 ◦ W/23.0199 ◦ N, with a height of 498 m; hence it appears as a tiny cone in pre-2019 bathymetric grids (Figure 1a). After first mapping of large parts of the seamount by the French oceanographic survey vessel “Beautemps-Beaupré” in 2013, it is represented at its full height in the actual GEBCO_2020 grid, which is based on the SRTM15+V2.0 data set (Tozer et al., 2019). In this data report we present new multibeam bathymetric data for Le Gouic Seamount, mapping its full extent for the first time. The data were obtained during a transit of R/V METEOR cruise M146 in 2018. We also present a reflection seismic profile across the seamount that was shot during the mapping, and seafloor heatflow data obtained on a profile near the northeastern seamount base and co-located on the reflection profile. On the basis of this data we can place constraints on the age of the seamount, and speculate about possible rejuvenated magmatic activity.


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