On the evidence for and against palaeolakes in some Lake District valleys

For over 200 years the lakes (and tarns) of the Lake District have been the focus of a considerable amount of geological/palaeoenvironmental research. Early work was concerned with establishing lake depths and recording details of shoreline configurations (e.g. Mill, 1895a, b), while later studies aimed at determining the origin and significance of lakes with respect to former ice-sheet and valley glaciation, and post-glacial environmental changes. Included in this research are the lake sediments which have yielded valuable data concerning: 1) the presence and longevity of mountain ice-masses in the Lateglacial period (14.7-11.7 ka BP; e.g. Pennington, 1996; Avery et al., 2019); 2) natural and human-induced landscape changes during the Holocene (<11.7 ka BP; e.g. Clare, 1999; Grosvenor et al., 2017); and 3) records of flood events spanning the last 500-1500 years (e.g. Chiverrell et al., 2019; Schillereff et al., 2019). The results of these studies demonstrate the importance of the lakes to understanding how the landscape has responded to both long- and short-term environmental perturbations, and how it may respond to current and future climate trends associated with a warming world.
In addition to these research issues, water bodies that no longer exist (i.e. palaeolakes) have also been subjected to various degrees of investigation, and it is with these features and their recognition and interpretation that this paper is concerned. Our reading of the literature relating to palaeolakes indicates that some of the associated landforms are in need of re-assessment regarding their mode of formation, while the significance of others has been underplayed in developing evolutionary models of post-glacial landscape change. We are also concerned that the existence of palaeolakes in some Lake District valleys is regarded as an undeniable truth, when in fact it appears that there is no substantive evidence for such lakes. Unfortunately, this has not stopped the myth being perpetuated in some ‘popular’ geological literature.
In this contribution we consider three themes relating to palaeolakes. We wish to emphasise that we have not undertaken any new fieldwork in relation to these themes. Rather, we base our comments on a combined total of ~100 years of field observations and discussion with other researchers. Some details accrue from basic map and field observations. Our intention is to highlight not only where we think additional work is needed but to encourage others to consider the implications of our comments and attempt to resolve the issues.