Saturday, 16 November 2013

The Scheidig (1934) map of World-wide loess distribution

In 1934 Alfred Scheidig of the Saxon Mining Academy in Freiberg(Sa.) published his book 'Der Loess und seine geotechnischen Eigenschaften'. The book contained a map of worldwide loess deposit distribution (fig.5) which became and has remained the standard map of loess distribution. Now, nearly 2014, 80 years after the initial publication it is a good time for a close look at the map, and an assessment of its continuing value.
The first worldwide map is believed to be that of Keilhack (1920). This was a very simple map; it accompanied Keilhack's estimate that 9.3% of the surface of the continental crust is covered by loess. Scheidig (1934) offered considerable detail and divided loess into definite (nachgewiesen) deposits and possible/probable deposits ( wahrscheinlich oder moglich). The map was used by Woldstedt (1960) in his Quaternary treatise- it is the standard map of loess distribution. Woldstedt made a few small changes- his map comes 'mit geringfugigen Anderungen', as does our reproduction.
In 1965, for the Boulder INQUA Congress, N.I.Kriger prepared a worldwide loess distribution map. This does not compare well with the Scheidig map. Kriger chose an unfortunate base map projection; Scheidig (perhaps inadvertently) chose a good Mercator-like projection. Mercator tends to emphasize the mid-latitude zones, which is where the loess occurs. Woldstedt changed the base projection slightly- and did not improve on the original. Trofimov (2001) followed Scheidig (1934)- there has been no better version. Abelev & Abelev (1968) reproduced Scheidig (1934) as an exact reproduction.

No comments:

Post a Comment