Special issue statement. This article is part of a special issue published on the occasion of the 70th anniversary of E&G Quaternary Science Journal (EGQSJ). The special issue celebrates the journal's notable contribution to Quaternary research by revisiting selected milestone articles published in the long history of EGQSJ. The German Quaternary Association (DEUQUA) presents translations of the originals and critical appraisals of their impact in tandem anniversary issues of DEUQUASP and EGQSJ, respectively.

Original article: https://doi.org/10.3285/eg.02.1.04

Translation: https://doi.org/10.5194/deuquasp-3-35-2021

Woldstedt addressed the issue of river terraces by describing critical evidence for each of the formational scenarios and ended by presenting a scheme for terrace formation that integrates much of that evidence (Fig. 1). This scheme is perceptive, widely applicable and relevant to present concepts. Nevertheless, he noted that “Die im Vorstehenden gemachten Ausführungen bieten mehr Problemstellungen als Lösungen” [The explanations given above offer more problems than solutions] (Woldstedt, 1952, p. 44) and looked forward to the results of future investigations.

Figure 1Redrawn version of Fig. 2 from Woldstedt (1952) with the addition of representative cross sections.

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The effects of climatic processes on terrace formation are examined with evidence from the Saale and Elbe regions of central Germany and the Thames and Somme regions of southern England and northern France. Within the framework of the climatic model, Woldstedt considered that the primary process for the formation of these terraces is deposition of glacial and periglacial deposits during periods of cold climate and erosion during periods of “passive” warm climates and that these activities are tuned to the glacial–interglacial cycles as identified by Penck and Brückner (1909). However, he was critically aware that this model is challenged because terrace deposits may be composed of both cold and warm climate sediments. He was aware that some of the warm climate proxies included in the terrace deposits may not be in situ, but he rejected derivation as a general explanation and stressed the fact that a single terrace may contain evidence of different climates and that this material may be located at either the bottom or the top of the sediment body. Furthermore he noted that the relative position of these warm and cold sediment units may vary within a catchment and between river systems.

In order to explain this apparent anomaly, he identified the importance of sea level as a factor able to control the process of deposition or erosion at the lower part of river systems. According to this proposition, a rise in sea level would cause a reduction in the gradient of the channel in the lower part of a river, resulting in aggradation during interglacials. At the same time, incision would characterise the development of the upper reaches. In contrast, during glacials when sea level was low, incision would take place in the lower parts of catchments due to a steepening of the channel and aggradation would take place in the upper reaches due to increased sediment supply from periglacial and glacial processes. The extent of incision or aggradation through a catchment would depend upon the duration of the period of low sea level, gradient of the seabed in the exposed offshore zone and the duration of the depositional processes in the upper reaches. He also took care to note that the tuning between the rise in sea level and sedimentation would not coincide directly with the climate at the river mouth, as there would be a lag in sea-level rise due to the time taken for global ice masses to melt. Likewise, he stressed that the rate of sea-level rise would determine the pattern of sedimentation. A rapid rise would submerge the river mouth, and sediment would be located offshore, so that aggradation in the lower part of the river valley would be limited. The effects of these processes are summarised in Fig. 1, which is based on Fig. 2 of Woldstedt (1952), and it is evident that the processes of terrace development are very complex.

Woldstedt examined the issue of a solely tectonic origin for river terraces by reference to work done on the river Rhine, in which it had been proposed that deposition took place during periods of tectonic stability and incision occurred during periods of uplift that tilted the river towards the sea. He rejected this model because it failed to take into account the consequences of sea-level change and variations in sediment supply caused by glaciation and periglaciation. Nevertheless, he fully acknowledged that tectonic activity would be a factor responsible for terrace formation but that it needed to be validated by available evidence.

In addition to the mechanisms described above, Woldstedt responded to the proposal that terraces would develop due to the blockage of a river by an ice sheet. He examined this issue by reference to the river Weser in northern Germany, in which it was recognised that an ice dam had created a proglacial lake in the river valley upstream of the Scandinavian ice margin. Paul Woldstedt reasoned that this process would have resulted in the formation of a delta in the proglacial lake and that this would be of restricted extent, not significantly affecting existing river terraces. He also noted that it would be capable of being differentiated from terraces by the presence of deltaic topset and foreset sedimentary structures, supporting his case with a figure showing a stratigraphic succession indicating river gravels, overlain by lake sediments, and capped by glacial and glaciofluvial deposits. His proposition has been vindicated and expanded by recent work of Winsemann et al. (2015). Furthermore he noted that the subsequent deposition downstream of the ice dam would have a different lithological composition from material deposited in terraces in the upper part of the catchment.

The recognition that the pattern of terrace development varies along the length of a river catchment was a fundamental contribution to geomorphology and Quaternary science (Fig. 1). This premise requires that any study of river terraces must be aware of the potentially infinite variety of erosional/depositional permutations and approach the subject with this constraint in mind. The following section considers how science has responded to this requirement.

The article processing charge was funded by the Quaternary scientific community, as represented by the host institution of EGQSJ, the German Quaternary Association (DEUQUA).

This paper was edited by Markus Fuchs and reviewed by one anonymous referee.