Arkell.1956.Jurassic..

io8 WESTERN GERMANY
Of almost equal renown are the superbly preserved and prepared reptile
skeletons of the Upper Lias at Holzmaden, at foot of the Swabian Alb
(Hauff, 1921, 1953). Yet a third show-piece of palaeontology, even on a
world view, are the famous Goldschnecken of the Franconian Callovian.
Quantities of small ammonites are preserved as limonitic casts of the
septate inner whorls bearing only the pearly layer of the shell; there
results an iridescence like opal and a colour like gold, sometimes deepening
to copper.
The Swabian Alb is the type example of a simple scarp landscape.
It is also the birthplace of zonal stratigraphy and of the scientific study
of ammonites from the systematic and stratigraphical points of view, for
it was the scene of the labours of Leopold von Buch, F. A. Quenstedt,
and Albert Oppel. Von Buch in 1837 divided the Jurassic into Lower
FIG. 13.—Section through the Swabian Alb, generalized. On right, sponge rock
is shown diagrammatically (Schwammfelsen). From Dacque, after Engel.
Jurassic, Lias or Black Jura, Middle or Brown Jura, and Upper or White
Jura, and established three subdivisions of each. Quenstedt, who for
more than fifty years worked and taught at Tubingen University, used
the Greek letters alpha to zeta for six subdivisions of each of von Buch's
three main divisions. But although these subdivisions were lithological,
Quenstedt (1845-9, 1858, 1883-8) was the real founder of the scientific
study of ammonites and an acute observer of their distribution. It was his
pupil Oppel (1856-8, 1862-3), however, who founded the zonal system of
classification and opened the possibility of correlation over theoretically
unlimited distances. He shook himself free of Quenstedt's alphas, betas
and gammas, but they have nevertheless remained in local use to this day
because of their precision and convenience. As a basis for local work
they are by far superior to the ill-starred stages used in the Franco-Swiss
Jura (Argovian, Rauracian, Sequanian), which mean something different
with every author and have led to a geological babel. Oppel's zonal
system was first tried out by Waagen in his masterly maiden work (1864).
Besides the classics mentioned, important early works of a lesser order,
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