the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Harmonising and mapping Patagonian Shelf seabed sediment data
Abstract. Maps of seabed sediment distribution on global continental shelves are useful for a wide range of applications, including for habitat mapping, predicting sedimentary carbon stocks, and providing insight into past and present oceanographic conditions and the processes influencing sediment transport and deposition. Whilst some continental shelves have relatively well mapped seabed sediments, others lack publicly available, harmonised datasets. The Patagonian Shelf, also known as the Argentine Shelf, is one of the world’s largest continental shelves, but there is currently no database that has compiled publicly available seabed sediment data. In this paper we collate and harmonise existing published and open-access seabed grain size data for the Patagonian Shelf. The paper combines both quantitative and qualitative data from published and grey literature and translates these data into two modified Folk sediment classification schemes. Ordinary Kriging is used to map the spatial distribution of different sediment classes across the shelf and allows us to assess uncertainty in the predictions of seabed sediment type. Overall, our sediment maps agree well with previously published maps over the central and northern shelf. Key differences are the classification of shell-rich sediments, and the spatial distribution of coarse sediments, particularly over the southern shelf. The latter would be further resolved with greater sampling of seabed sediments in the region. The data products produced for this study are grain size point data for the shelf and interpolated Geographic Information System (GIS) layers of seabed sediments and associated prediction errors. These are freely available for download via Zenodo (Roseby et al., 2026; https://doi.org/10.5281/zenodo.19111158).
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Status: final response (author comments only)
- RC1: 'Comment on essd-2026-220', Anonymous Referee #1, 22 Apr 2026
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RC2: 'Comment on essd-2026-220', Anonymous Referee #2, 20 Jul 2026
Roseby et al., bring together a variety of data sets collected between 1973 and 2023 from across the Patagonian shelf to facilitate simple mapping of the sediment type following the Folk class. The combined dataset is a useful resource and has the potential to be the foundation of future studies.
Overall, the manuscript is well written and and the figures are of high quality. The methodological approach to gather to compile the data is solid and well documented. However greater clarity is required concerning the grain size analysis:
- Folk classification description could be clearer - The modified Folk-5 scheme differs from previous applications because mud >90% is isolated as a separate category. The rationale is reasonable, but the exact thresholds should be listed in a table in the main text or Sup Mat rather than relying mainly on Figure 2.
- Approximately 78% (380 of 486) of observations are qualitative descriptions that were translated into Folk classes using expert judgement. Although two researchers independently classified samples, there is no confusion matrix or uncertainty estimate for translation of descriptions and no sensitivity analysis showing how classification choices affect mapped outputs.Given that most data are qualitative, this uncertainty may be more important than interpolation uncertainty.
- The authors note that shell-hash samples were excluded from Folk coding while many shelly sediments were assigned to sand classes.
This decision may affects comparisons with previous maps and has the potential to bias sediment proportions towards sands. This approach requires stronger justification and clearer documentation.
The interpolation of the data using Kriging approaches is simple, but I believe there are some issues that need clarified.
- The authors assign numerical codes to sediment classes and then perform Ordinary Kriging on those codes before reclassifying the output. This is problematic as Folk classes are ordinal/categorical, not continuous numerical variables. Kriging assumes numerical continuity and meaningful distances between values. Alternative approaches such as indicator kriging, multinomial classification models, or interpolation on the underlying %gravel-%sand-%mud fractions would produce more robust mapping.
- There is a lack of validation data. Model evaluation appears based on ArcGIS interpolation diagnostics (RMSE, Mean Error, R²) these test the quality of model but not how it replicates the real world. Good model statistics does not equal a good map. The use of independent technique such as K-fold cross-validation or hold-out testing would provide greater confidence in the maps.
- Missing details on the variogram. Ordinary Kriging results depend strongly on - Variogram model type, nugget, sill, range parameters.
These are not reported in the manuscript therefore reproducing the interpolation therefore appears difficult.
- The manuscript states that Ordinary Kriging was the “most appropriate” method.
However, Table 2 shows very small differences between interpolation approaches, and Simple Kriging sometimes performs similarly or slightly better in some metrics. The wording should be softened.
Citation: https://doi.org/10.5194/essd-2026-220-RC2
Data sets
Harmonising and mapping Patagonian Shelf seabed sediment data [Data set] Z. A. Roseby et al. https://doi.org/10.5281/zenodo.19111158
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The manuscript entitled “Harmonising and mapping Patagonian Shelf seabed sediment data” gathers about 500 surface sediment data to provide a reliable map of the Argentinean shelf. Worth noting that those types of mapping are crucial for several studies, such as habitat mapping and geohazards. Nevertheless, the authors make a major mistake when they treat the Patagonian shelf as a synonym for the Argentinean shelf. In fact, the Argentine shelf is much larger than the Patagonian area, and the manuscript must be corrected accordingly.
The second aspect deals with Table 1. It is not clear which data were obtained from the samples in which the GSA method was classified as a “description”. Indeed, most of the samples fall into this GSA method. In the case of Oliva (2020), the GSA method is “NA” (not available). Which data were used in this case?
Concerning the kriging interpolation, I wonder which semivariogram model was used. I am not familiar with ArcGIS, and I do not know whether there is a basic model for determining the extent of a zone of influence for a given georeferenced value.
In summary, the manuscript has value, but some methodological aspects need clarification before acceptance.