Netherlands Journal of Geosciences — Geologie en Mijnbouw | 86 – 3 | 165 - 177 | 2007 History of geological mapping of the Holocene Rhine-Meuse delta, the Netherlands H.J.A. Berendsen† The Netherlands Centre for Geo-Ecological Research (ICG), Faculty of Geosciences, Department of Physical Geography, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, the Netherlands. † Henk Berendsen passed away on May 14, 2007. Manuscript received: October 2005; accepted: January 2007 Abstract A brief overview is given of the history of geological mapping of the Holocene Rhine-Meuse delta. The first accurate map of the delta, based on field observations, was made by Vink (1926). The geological map of the Netherlands, scale 1 : 50,000, made by the ‘Geologische Stichting’ (1927 - 1938) under the supervision of P. Tesch totally neglected Vink’s work, and was a step backwards with regard to the mapping of the Holocene delta. Between 1940 and 1965, the Wageningen group of soil scientists produced detailed regional soil maps, that had a strong ‘geogenetic’ component. In the 1960’s a revolutionary ‘profile type legend’ was introduced by the Netherlands’ Geological Survey. This allowed to map not only the outcropping sediments, but the whole Holocene succession, which gave more insight into the geological history. Over the past 30 years, the Rhine-Meuse delta has been studied extensively by students of physical geography at Utrecht University. More than 250,000 borehole descriptions, 1500 14C dates and over 36,000 archeological artifacts with associated ages (collected by the National Service for Archaeological Heritage) have accumulated, resulting in the largest database of a delta in the world. The production of detailed maps has been crucial to the solution of many scientific problems. The use of GIS has greatly enhanced geological and geomorphological mapping, and subsequently, understanding of the evolution of the Holocene Rhine-Meuse delta. A new detailed digital elevation map of the Netherlands, based on very accurate laser-altimetry data, will enable us to map larger areas in greater detail, with greater accuracy, and in a much shorter period of time. Keywords: geological maps, Holocene, Rhine-Meuse delta, fluvial systems, avulsions Introduction In this paper, an overview is given of the history of geological mapping of the Holocene Rhine-Meuse delta, and Geological, geomorphological and soil mapping by individuals how mapping has contributed to the scientific understanding or by national organizations has been the basis for under- of the evolution of the delta. The aim of this paper is to show standing the evolution of the Rhine-Meuse delta ever since how progress was made over the years with regard to the the first maps were produced. Maps have not only been crucial understanding of the Holocene delta evolution, using different to scientific work, but also to numerous practical applications, mapping techniques, better drilling methods, increasing like construction, infrastructure, extraction of minerals and technical facilities, and a gradually growing understanding of water, environmental planning, reallotment and agriculture. processes governing the geological evolution. It is shown that This applies especially to maps that have been produced by avulsion was a key process in the development of the delta. the Geological Survey of the Netherlands and the ‘Stichting voor Bodemkartering’ (Soil Survey of the Netherlands). For Staring’s geological map overviews of national mapping programs of these institutions, and their aims and products the reader is referred to, e.g., Oele The first overview of surficial geology of the Netherlands et al. (1983) or Berendsen (2004a, 2005). was given by Staring’s (1858 - 1867) geological map of the Netherlands Journal of Geosciences — Geologie en Mijnbouw | 86 – 3 | 2007 165 Netherlands, on a scale of 1 : 200,000. The map included infor- were applied only 20 years later by others (mainly soil mation on agricultural land use. Although this map has been scientists). Vink realized, that sand is deposited in the river very influential, especially in education, it did not show much bed, clay further away from the channel and peat formation detail of the Holocene Rhine-Meuse delta, and only few field occurs far from the river, where little sediment is deposited. observations could be made to produce it. These simple assumptions enabled him to accurately map most of the subrecent channel belts, using an iron rod that he could Vink’s work stick into the ditches. If the iron rod met virtually no resistance he knew there was peat, if there was considerable resistance The first map of part of the delta that was based on detailed there was clay, and if it was impossible to penetrate the field observations, was published in the trail-blazing Ph.D. substrate, there was sand. His excellent observations are still thesis ‘De Lekstreek’ by Vink (1926), Fig. 1. His map was the valid at the present time, although most of his explanations result of purely scientific work. It was the first map that are now considered obsolete. This reinstates his proposition: showed coherent ‘river systems’ (channel belts) which provided “Facts are of lasting value, views are temporary”, a proposition a solid basis for beginning to understand the evolution of the that should be well remembered by present-day generations of Rhine-Meuse delta, even though little was known at that time students, who often seem to think that the explanation is about river processes. Vink stressed the importance of field more important than the facts, or worse, tend to adapt the observations. facts so that they fit the current theory. Nevertheless, the In one of his propositions, he stated: “Staring did not know master also had his weaknesses, as is now evident from his the river area from his own observations, and only had a proposition: “The common opinion, that shifts of river courses fragmented understanding of its literature” (all cited proposi- and the formation of new channels have occurred in the tions are translated from the Dutch). Although diplomacy was Holocene Rhine-Meuse delta, as in other deltas in the world, not one of his main assets, his statements generally were is contradicted by the facts”. Here, he seems to have mixed correct. Vink was a geography teacher with a profound scientific facts and interpretations in an inadmissable way, because we interest. Only during weekends he was able to map most of the now think that the facts unequivocally seem to tell us that western part of the delta. He produced the first detailed map avulsions (shifts of a river course to another location on the of a river delta in the world. In the Netherlands, his insights floodplain) were quite common. Fig. 1. Fragment of the Holocene channel belt map of Vink (1926). Blue hatch: channel belts, White: flood- basins. Numbers refer to the names of the channel belts and floodbasins. Original scale: 1 : 100,000. 166 Netherlands Journal of Geosciences — Geologie en Mijnbouw | 86 – 3 | 2007 In those days, it was thought that all Holocene rivers were 1942). The map aimed to give more detailed information than small remnants of gigantic glacial streams, and all Holocene Staring’s (1858 - 1867) geological map, more insight into the river systems were considered to be coeval. The depth at which origin of Quaternary sediments, and at the same time provide sand occurred was just a rough measure for the successive information on the lithology of surface deposits. It was also abandonment of the channels. Channels were considered to be meant to be used for all kinds of practical problems (Tesch, equivalent to channel belts, and no knowledge existed about 1942). The map was produced by a small group of people in a river processes and smaller-scale fluvial landforms like, e.g., relatively short and economically difficult time. It was quite point bars, swales, residual channels and crevasse splays. This an accomplishment at the time, but with regard to the mapping resulted in some weird explanations, and some rivers actually of the Holocene Rhine-Meuse delta it was a major step back- were considered to flow in the opposite direction. Nevertheless, wards, because it was obvious that Vink’s (1926) earlier work Vink’s contribution was both original and phenomenal. was totally neglected. The map showed channel belts as Unfortunately, his thesis was written in Dutch (as was common isolated ‘islands’ of sand (Fig. 2), whereas Vink (1926) had at that time), and hence it gained no international acclaim. already shown that these sands were connected and formed Vink continued to study the Rhine-Meuse delta, and extended part of a former river system. It is not clear why this happened. his map to the entire western part of the delta. These results Maybe Tesch was unaware of Vink’s work, or maybe he under- were published in 1956, shortly after his death, in a volumi- estimated its significance. Whatever the reason, it resulted in nous and at times exhilarating book (‘De Rivierstreek’, Vink, a geological map of the Holocene deltaic area that was obsolete 1956), in which he described humorous details of encounters even before it was published. Consequently, the map did in the field. However, by then, modern insights into river not contribute in any way to a better understanding of the processes had arisen, especially by the excellent work of Fisk evolution of the Holocene delta. (1947) in the Mississippi delta. These insights were absent from Vink’s second masterpiece, and this severely diminished Wageningen soil scientists the scientific value of that work. The period 1940 - 1965 was the era of the Wageningen school First geological map, scale 1 : 50,000 of soil scientists, led by Edelman. The first generation of soil maps had a strong ‘geogenetic’ component, making them a Between 1927 and 1938, the first nationwide geological map mixture of a soil map (with a strong lithological component), at a scale 1 : 50,000 of the Netherlands was published by the a geomorphological map and – to a lesser degree – a geological Geological Survey (at that time ‘Geologische Stichting’; Tesch, map.