The fantasy of Glacial Lake Nevern

The glacial lakes assumed (by the BRITICE team) to have existed in NE Pembrokeshire and the Teifi Valley.  There is good evidence for "Glacial Lake Teifi" in the published literature, even though its outlines may not have coincided with those shown here -- but "Glacial Lake Nevern" is pure fantasy, dreamed up almost a century ago, and it should have no place in a supposedly scientific research document.

Last night I was checking out some of the features mapped on the BRITICE Chrono map of Devensian features in the British Isles -- which is flagged up as THE definitive map.   I was amazed to find that the version currently available on the web still shows "Glacial Lake Nevern" -- a feature that has not a scrap of evidence in support of it, as many of us have been pointing out for half a century or more. There are no shorelines, no rafted deposits, no varved lake clays or other sediments, no moraines marking the position of an ice dam, and no evidence of any sort relating even to a short-lived body of standing water that covered the area proposed.  In short, Glacial Lake Nevern was a fantasy from the beginning, dreamed up by Charlesworth because he was obsessed with glacial lakes and overflow channels..........

On the map, the lake is shown as covering Cilgwyn, Felindre Farchog, Crosswell, Brynberian, Penygroes and the whole of the low-lying area on the north flank of Mynydd Preseli, with an outlet or "overflow" into Cwm Gwaun.  

This is quite extraordinary.  How is it that Chris Clark and his colleagues in the supposedly high powered BRITICE team have simply perpetrated a myth that is a century old in a publication that is supposed to represent all the latest sophisticated science?  Don't ask me what the answer is -- ask them! 

It's rather sad, after all my criticisms of archaeologists for the perpetration of assorted bluestone myths including the human transport myth, the quarrying myth and the lost circle myth, that I now have to accept that in my own field -- glacial geomorphology -- there are other myths almost a century old that are still being flagged up in spite of the vast accumulation of evidence showing that they are speculative and even nonsensical.

All that having been said, there is limited evidence for meltwater lake clays on Brynberian Moor, and I have discussed the likely extent of "Glacial Lake Brynberian" as a short-lived feature associated with ice wastage and ice edge retreat northwards down a reverse slope.  There might have been one lake a few kilometres long, or a series of short-lived smaller lakes impounded by detached masses of wasting glacier ice.  Such short-lived lakes might have existed in multiple locations during the catastrophic melting of the LGM ice in West Wales.

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See this:

Sunday, 26 November 2017

BRITICE Glacial Map 2 -- a mixed blessing

https://brian-mountainman.blogspot.com/2017/11/britice-glacial-map-2-mixed-blessing.html

This is what I said:

The outlines of Glacial Lake Teifi more or less coincide with what we see in assorted published papers, but the other information shown on the map is very scanty indeed for the Cardigan - Moylgrove area. That must disappoint many of the authors who have published their research findings, with considerable local detail on the record. When we zoom in on Preseli and the hypothetical area of "Lake Nevern" we find even more problems. Why is "Lake Nevern" shown at all? So far as I am aware, nobody since Charlesworth in 1929 has taken it at all seriously, and many papers by a variety of authors have shown that the "evidence" for it does not withstand scrutiny. The paper authors site "George 1970"as their source of information, but George was simply citing (very uncritically) Charlesworth, and provided no evidence for this so-called lake. Careless. As readers of this blog will know, there are a few places where thin laminated (lake?) sediments appear to be present on the northern flank of Preseli, but they are better explained by short-lived ponding of meltwaters in complex terrain in a dead-ice environment. I have called this "Lake Brynberian" -- a possible small lake of limited duration and extent. There are other fluvioglacial landforms and moraines in this area which are in the literature. They should have been mapped, but have not been. And where did that impounded lake at Pontfaen come from? I am aware of no evidence in support of it.

https://brian-mountainman.blogspot.co.uk/2015/05/lake-brynberian-further-thoughts.html

The impression is gained that this map has been produced by researchers accessing satellite and bibliographic data and sitting in front of computer screens, unlike the BGS bedrock and sedimentary map for the UK which has been based largely upon the field notes of surveyors working in the field. Black mark for BRITICE, and glowing praise for the BGS. In the abstract to the paper, the authors state: "All published geomorphological evidence pertinent to the behaviour of the ice sheet is included, up to the census date of December 2015." That is patently not true. There are abundant references in the literature (just a few of them by me, and many others as well) that have clearly not been consulted.

The explanation of how the "glacial lake" information was added to the map:

https://onlinelibrary.wiley.com/doi/full/10.1111/bor.12273

BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet
Chris D. Clark, Jeremy C. Ely, Sarah L. Greenwood, et al
Boreas: 29 August 2017
https://doi.org/10.1111/bor.12273

The cited lake evidence used by the BRITICE researchers is said to have come from this source:

https://www.sciencedirect.com/science/article/abs/pii/S1040618211004320?via%3Dihub

Quaternary International
Volume 260, 18 May 2012, Pages 115-142

Middle and Late Pleistocene glacial lakes of lowland Britain and the southern North Sea Basin

Della K.Murton and Julian B.Murton

........ and their source was TN George, in the British Regional Geology of 1970, who in turn cited Charlesworth's 1929 paper on the South Wales End-moraine.  At no stage in this process of citations of older work was any critical scrutiny applied, as I noted in the following blog post:

https://brian-mountainman.blogspot.com/2014/09/the-gwaun-jordanston-meltwater-channel.html