Institut für Ostseeforschung Warnemünde
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Peter Feldens - research topics and publications

Geology of the Baltic Sea

The Baltic Sea remains a geologically difficult area, especially its Late Pleistocene and Holocene evolution. In many places, prior morphological landscapes are preserved on the seafloor. In this regard, we analyze the Fehmarn Belt area in Feldens & Schwarzer (2012). Preserved glacial features, so-called eskers resulting from subglacial meltwater flows, are identified in Feldens et al. (2013). An interesting, but younger morphological feature is the transition from sand ribbons to underwater dunes, likely active during salt water inflows from the North Sea. The transition from one feature to the other is controlled by sediment available for transport (Feldens et al. 2015). The subsurface – and thus the geological history – of shallow waters is very difficult to analyze. Kreuzburg et al (2018) attempt to bridge the land-water interface to study the continuation of former peatlands into the Baltic Sea, and thus contribute to the development of regional sea level curves. Of course, also the deeper basins of the Baltic Sea can be interesting, and I was happy to contribute with acoustic data (recorded during very bad weather conditions onboard FS Poseidon) to the very interesting study of Katharina Häusler et al. (2018), dealing with Mn-carbonate formation in the Baltic Sea’s deepest basin, the Landsort Deep.

  • Feldens, P., Diesing, M., Schwarzer, K., Heinrich, C., Schlenz, B. (2014).Occurrence of flow parallel and flow transverse bedforms in Fehmarn Belt (SW Baltic Sea) related to the local paleomorphology. Geomorphology 231, 53-62.
  • Feldens, P., Schwarzer, K. (2012) The Ancylus Lake stage of the Baltic Sea in Fehmarn Belt: Indications of a new threshold? Continental Shelf Research 35, 43-52.
  • Feldens, P., Diesing, M., Wilken, D., Schwarzer, K. (2013). Submarine eskers preserved on Adler Grund, south-western Baltic Sea. Baltica 26(2), 137-144.
  • Häusler, K., Dellwig, O., Schnetger, B., Feldens, P., Leipe, T., Moros, M., Pollehne,  F., Schönke, M.,  Wegwerth, A., Arz ; HW.(2018)Massive Mn carbonate formation in the Landsort Deep (Baltic Sea): Hydrographic conditions, temporal succession, and Mn budget calculations. Marine Geology DOI::10.1016/j.margeo.2017.10.010
  • Kreuzburg, M., Ibenthal, M., Janssen, M., Rehder, G., Voss, M., Naumann, M., Feldens, P. (accepted) Submarine continuation of a coastal peatland in the southern Baltic Sea and its Holocene development. Frontiers in Earth Science

Geology of the Red Sea 

Over the years, I had the opportunity to work in the Red Sea with great colleagues. We learned a lot on the movement of salt glaciers. The salt glaciers – thick evaporitic sequences -  were emplaced in prior to the rifting of the Rd Sea. Feldens & Mitchell 2015 give detail into the movement mechanics, while Mitchell et al. (2017) addresses the effects on salt glacier topography. The dissolution of the evaporites in the Red Sea deeps causes an interesting stratification in the water column above. This is analyzed by Albarakati et al. (2016). An interesting morphological feature we found on the seafloor is a large field of pockmarks. Here, we measured thermogenic methane that had to permeate through the evaporitic sequence, which is not normally possible. Details on this can be found in Feldens et al. 2016. During the field work, I could contribute to work led by N. Augustin regarding the evolution of the Red Sea rifts. More information on the development of the Red Sea oceanic crust is found in Augustin et. al  2014 and 2016.

  • Albarakati, A., McGinnis, D. F., Ahmad, F., Linke, P., Dengler, M., Feldens, P., Schmidt, M. und Al-Farawati, R. (2016) Thermal small-steps staircase and layer migration in the Atlantis II Deep, Red Sea. Arabian Journal of Geosciences 9:392 DOI 10.1007/s12517-016-2399-5.
  • Augustin A., van der Zwan FM, Devey CW, Ligi M, Kwasnitschka T, Feldens P, Bantan RA, Basaham AS (2016) Geomorphology of the central Red Sea Rift: Determining spreading processes. Geomorphology http://dx.doi.org/10.1016/j.geomorph.2016.08.028
  • Augustin, N., Devey, C.W., van der Zwan, F.M., Feldens, P., Tominaga, M., Bantan, R.A., Kwasnitschka, T. (2014) The rifting to spreading transition in the Red Sea. Earth and Planetary Science Letters 395, 217-230.
  • Feldens, P., Mitchell, N.C. (2015). Salt flows in the central Red Sea. In: The Red Sea: The Formation, Morphology, Oceanography and Environment of a Young Ocean Basin (Eds. Rasul, N.M.A., Stewart, I.C.F.) Springer Earth System Sciences.
  • Feldens, P., Schmidt, M., Mücke, I., Augustin, N., Al-Farawati, R., Orif, M., Faber, E. (2016). Expelled subsalt fluids form a pockmark field in the eastern Red Sea. Geo Marine Letters, doi: 10.1007/s00367-016-0451-9
  • Mitchell, N.C., Ligi, M., Feldens, P., Hübscher, C (2017) Deformation of a young salt giant:  Regional topography of the Red Sea Miocene evaporites: effects of salt tectonic and isostasy. Basin Research 29(S1) 352-369 DOI: 10.1111/bre.12153

The Antarctic, the South-China Sea

While not participating in the field work, I had the opportunity to contribute to the very interesting data analysis for projects in the South China Sea and the Antarctic. Miluch et al (2021) and Xiong et al. (2020) use (among other approaches) seismic data to reconstruct a Delta offshore the Hainan island in the South China Sea. Anne Wölfl et al. (2016) use classical set of hydroacoustic data and sediment samples to study the effects of glaciers retreat on submarine morphology  in an Antarctic fjord. 

  • Miluch, J., Osadczuk, A., Feldens, P., Harff, J., Maciag, L., Chen, H. (2021). Seismic profiling-based modeling of geometry and sedimentary architecture of the Late Pleistocene delta in the Beibu Gulf, SW of Hainan Island (South China Sea), Journal of Asian Earth Sciences 205, 104611 10.1016/j.jseaes.2020.104611
  • Xiong, P., Dudzińska-Nowak, J., Harff, J., Xie, X., Zhang, W., Chen, H., Tao, J., Chen, H., Miluch, J., Feldens, P., Maciąg, L., Osadczuk, A., Meng, Q., Zorita, E., Modeling paleogeographic scenarios of the Last Glacial Cycle as a base for source-to-sink studies: an example from the northwestern shelf of the South China Sea, Journal of Asian Earth Sciences (2020), doi:https://doi.org/10.1016/j.jseaes.2020.104542
  • Wölfl, A-C., Wittenberg, N., Feldens, P., Hass, HC., Betzler, C., Kuhn, G. (2016) Submarine landforms related to glacier retreat in a shallow Antarctic fjord.Antarctic Science

Submarine Archeology

Unfortunately, this highly interesting category only has one entry. I hope to do more work in this field in the future. I was invited by Tina Wunderlich and Dennis Wilken to contribute to the identification of drowned remnants of Norse harbours in Greenland. It turned out more difficult than we expected, the results are written down in Wilken et al. (2019). 

  • Wilken, D., Wunderlich, T., Feldens, P., Coolen, J., Preston, J., Mehler, N. (2019) Investigating the Norse Harbour of Igaliku (Southern Greenland) Using an Integrated System of Side-Scan Sonar and High-Resolution Reflection Seismics Remote Sensing 11(16), 1889

Habitat Mapping

During the last years, a larger percentage of my work was concerned with seafloor mapping, by improving the ways in which we can use and interpret acoustic data to understand the seafloor. It is clear that even now (2021), we only use a small percentage of the information included in data recorded by current hydrographic instruments. In 2012, we found that artefacts in side scan sonar backscatter mosaics were an impediment to automatic classification attempts, and developed a method based on 2D Fourier Filtering to remove directional noise from the data (Wilken et al. 2012) (interestingly, that paper was recently cited in brain research, further showing that the big image processing problems are ubiquitous). More technical work also includes the use of an inclined and potentially rotating echo sounders to detect buried objects, a big problem in applied work e.g., for cable detection (Schneider von Deimling et al. 2016). On the surface, a big controlling factor for acoustic surveys is seafloor roughness. Here, we used underwater laser line-scanning to determine surface roughness, and later related scatter, in North Sea sediment covered by tubeworms (Mischa Schönke et al. 2017 and 2019). This research was triggered by the observation of Christoph Heinrich et al. (2016), that tubeworms and their seasonal changes in abundance can be clearly measured by side scan sonar backscatter. In a related work, I analyze the impact of acoustic incidence angle on textures derived from backscatter maps (Feldens 2017). It turns out that the effect of survey geometry cannot be neglected when using texture to identify subtle seafloor features. In another view at the topic, we utilized multi-spectral data to improve the interpretation of acoustic data, and to get a more complete view of the seafloor (Feldens et al. 2018). This multi-spectral approach is highly promising, especially given technological advancement of multibeam echo sounders, and I hope to return to the topic in the near future. 

More applied habitat mapping was topic of Silke Glogowski et al. (2015), where we mapped a field of cold water corals offshore Morocco, and Karolina Czechowska et al. (2020), where we attempted to map Black Coral Gardens offshore Lanzarote. The former study clearly represents preliminary results, since we found the difficile branches of the Black Corals Gardens difficult to discern in traditional backscatter maps, but found the use of water column scatter for mapping purposes promising. I also put here the impressive work by Kristina Enders, tracing the mobility of microplastic near Warnemünde, where I could contribute to the mobility constraints (Enders et al. 2020). 

New regulations by the EU triggered a need to map boulders in the Baltic Sea. Given how many there are, this is hugely challenging. Svenja Papenmeier et al (2020) give a review of the problem. It became clear that both the resolution of current remote sensing systems is insufficient for the task and the time required for manual interpretation is prohibitive. Therefore, we explored the use of neural networks for automatic boulder identification (Feldens et al. 2019) and improvement of image resolution (Feldens 2020). Clearly, neural networks work and can be tool to automate the processes, but additional work is required to create training databases. A comparison between side scan sonar and multibeam echo sounder derived datasets is given in Feldens et al. 2021.   

  • Czechowska,K., Feldens, P.,  Tuya, F. , Cosme de Esteban,M.,  Espino, F.,  Haroun, R.,   Schönke, M. and  Otero-Ferrer, F. (2020) Testing Side-Scan Sonar and Multibeam Echosounder to Study Black Coral Gardens: A Case Stud from Macaronesia. Remote Sensing 12, 3244. 
  • Enders, K., Käppler, A., Biniasch, O., Feldens, P., Stollberg, N., Lange, X., Fischer, D., Eichhorn, K.-J., Pollehne, F., Oberbeckmann, S., and Labrenz, M., 2019, Tracing Microplastics in Aquatic Environments Based on Sediment Analogies: Scientific Reports v. 9
  • Feldens, P. (2017) Sensitivity of texture parameters to acoustic incidence angles in multibeam backscatter. IEEE Geoscience and Remote Sensing Letters.  DOI: 10.1109/LGRS.2017.2756258 
  • Feldens, P., Schulze, I., Papenmeier, S., Schönke, M., Schneider von Deimling, J. (2018). Improved Interpretation of Marine Sedimentary Environments using Multi-Frequency Multibeam Backscatter Data. Geosciences. 
  • Feldens, P., Darr, A., Feldens, A., Tauber, F. (2019) Detection of Boulders in Side Scan Sonar Mosaics by a Neural Network. Geosciences 9(4) 159.  https://www.mdpi.com/2076-3263/9/4/159
  • Feldens, P. (2020)  Super Resolution by Deep Learning Improves Boulder Detection in Side Scan Sonar Backscatter Mosaics. Remote Sensing 12(14), 2284.
  • Feldens, P.. Westfeld, P., Valerius, J., Feldens, A., Papenmeier, S. (2021) Automatic detection of boulders by neural networks: A comparison of multibeam echo sounder and side-scan sonar performance. 10.23784/HN119-01 https://www.dhyg.de/images/hn_ausgaben/HN119.pdf
  • Glogowski, S., Dullo, W-C., Feldens, P., Liebetrau, V., von Reumont, J., Hühnerbach, V., Krastel, S., Wynn, R.B., Flögel, S. (2015). The Eugen Seibold coral mounds offshore Morocco: oceanographic and bathymetric boundary conditions of a newly discovered cold-water coral province. GeoMarine Letters 35(4) 1-13.
  • Heinrich, C., Feldens, P., Schwarzer, K., (2017) Highly dynamic biological seabed alterations revealed by side scan sonar tracking of Lanice conchilega beds offshore the island of Sylt (German Bight). Geomarine Letters 37(3) 289-303. DOI: 10.1007/s00367-016-0477-z
  • Papenmeier, S., Darr, A., Feldens, P., Michaelis, R. (2020): Hydroacoustic Mapping of Geogenic Hard Substrates: Challenges and Review of German Approaches. Geosciences, 10, 100. DOI: 10.3390/geosciences10030100.
  • Schneider von Deimling, J., Held, P., Feldens, P., Wilken, D. (2016) Effects of using inclined parametric echosounding on sub-bottom acoustic imaging and advances in buried object detection. Geomarine Letters DOI: 10.1007/s00367-015-0433-3
  • Schönke, M., Feldens, P., Wilken, D., Papenmeier, S., Heinrich, C., Schneider von Deimling, J., Held, P., Krastel, S. (2017) Impact of Lanice conchilega on seafloor microtopography off the island of Sylt (German Bight, SE North Sea).Geo-Marine Letters 37(3) 305-318  doi:10.1007/s00367-016-0491-1
  • Schönke, M., Wiesenberg, L., Schulze, I., Wilken, D., Darr, A., Papenmeier, S., Feldens, P. (2019) Impact of Sparse Benthic Life on Seafloor Roughness and High-Frequency Acoustic Scatter. Geosciences 9(10), 454
  • Wilken, D., Feldens, P., Wunderlich, T., Heinrich, C. (2012). Application of 2D Fourier Filtering for the elimination of stripe noise in side scan sonar mosaics. GeoMarine Letters 32(4), 337-347.

Natural Hazards

During my PhD thesis at CAU Kiel and as a PostDoc in the Marine Geophyiscs groupt at CAU, I coud work on two different marine hazards: Tsunami and submarine gravity flows. Our work on tsunami focused on deposits left by the 2004 Indian Ocean Tsunami in Thailand. It turned out surprisingly difficult to identify and characterize the offshore deposits, fundamentally different from onshore deposits. Our initial results are reported in Feldens et al. (2009), my first paper serving as an example of how to not do it, since we found our interpretations of the data were a bit too enthusiastic and could not be confirmed later on. A description of the sediment composition in a tsunami-affected area is given in Feldens et al (2012), while Sakuna et al. (2012) analyzed the geochemical characteristics of these deposits. Very interesting is the origin of the tsunamigenic deposits. Here, Yvonne Milker et al. (2013) used foraminiferal transfer functions to determine the origin of sediments. It confirmed our initial hypothesis that – at least in our investigation area – the majority of preserved sediments result from less than 30 m water depths, much less than theoretically possible. A further difficulty is the differentiation from tsunami deposits and flash floods, which increase due to deforestation and potentially climate change. An analysis of the different feature of these sediments is given in Sakuna et al. (2015). Finally, the distribution of polyaromatic hydrocarbons and their use as a tsunami proxy is discussed by Siwatt Pongpiachan et al. (2013).

In terms of submarine slides, I could contribute to projects offshore Morocco and Canada. Offshore Morocco, Sebastian Krastel et al. (2016) and Wei Li et al. (2018) analyze the flow properties of landslides in the Agadir Canyon, while an overview of landslides on the NW continental margin is given by Krastel et al (2018). Using the unique opportunity of recorded flow speeds of a slide offshore Canada (due to broken telephone cables) combined with extensive sediment sampling and acoustic data analysis, Chris Stevenson et al. (2018) constrain the sediment concentration of a large submarine gravity flow. Due to the (practically) unpredictable time and location of these flows, these physical parameters are basically impossible to measure in situ.

  • Feldens, P., Schwarzer, K., Szczuciński, W, Stattegger, K., Sakuna, D., Somgpongchaiykul, P. (2009).Impact of 2004 Tsunami on Seafloor Morphology and Offshore Sediments, Pakarang Cape, Thailand. Polish Journal of Environmental Studies 18(1): 63-68
  • Feldens, P., Schwarzer, K., Sakuna, D., Szczucinski, W., Somgpongchaiykul. (2012) Sediment distribution on the inner continental shelf off Khao Lak (Thailand) after the 2004 Indian Ocean Tsunami. Earth Planets Space 64, 875-887.
  • Li, W., Krastel, S., Alves, T.M., Urlaub, M., Mehringer, L., Schürer, A., Feldens, P., Gross, F., Stevenson, C.J., Wynn, R.B. (accepted). The Agadir Slide offshore NW Africa: Morphology, emplacement dynamics, and potential contribution to the Moroccan Turbidite System. Earth and Planetary Science Letters. 
  • Milker, Y., Wilken, M., Schumann, J., Sakuna, D., Feldens, P., Schwarzer, K., Schmiedl, G. (2013). Sediment transport on the inner shelf off Khao Lak (Andaman Sea, Thailand) during the 2004 Indian Ocean tsunami and former storm events: Evidence from foraminiferal transfer functions. Natural Hazards and Earth System Sciences 13(12) 3113-3128
  • Krastel, S., Wynn, R.B., Feldens, P., Schürer, A., Böttner, C., Stevenson, C., Cartigny, M.J.B., Hühnerbach, V., Unverricht, D. (2015) Flow Behaviour of a Giant Landslide and Debris Flow Entering Agadir Canyon, NW Africa. In: Submarine Mass Movements and their Consequences, Publisher: Springer International Publishing, pp.145-154
  • Krastel, S., Li, W., Urlaub, M., Georgiopoulou, A., Wynn, RB, Schwenk, T., Stevenson, C., Feldens, P. (2018). Mass wasting along the NW African continental margin. Geological Society, London, Special Publications 477
  • Pongpiachan, S., Tipmanee, D., Deelaman, W., Muprasit, J., Feldens, P., Schwarzer, K. (2013). Risk assessment of the presence of polycyclic aromatic hydrocarbons (PAHs) in coastal areas of Thailand affected by the 2004 tsunami. Marine Pollution Bulletin 76(1-2)
  • Sakuna, D., Szczuciński, W., Feldens, P., Schwarzer, K., Khokiattiwong, S. (2012) Sedimentary deposits left by the 2004 Indian Ocean tsunami on the inner continental shelf offshore Khao Lak, Andaman Sea (Thailand). Earth Planets and Space 64, 931-943.
  • Sakuna, D., Feldens, P., Schwarzer, K., Khokiattiwong, Stattegger, K. (2015) Internal structure of event layers preserved on the Andaman Sea continental shelf, Thailand: Tsunami vs. Storm and Flash flood deposits. Natural Hazards and Earth System Science 15, 1181-1199
  • Stevenson, C., Feldens, P., Georgiopoulou, A., Schönke, M., Krastel, S., Piper, DJW, Lindhorst, K., Mosher, D. (2018) Reconstructing the sediment concentration of a giant submarine gravity flow. Nature Communications 9, 2616.