In order to prepare a new, refined edition of the International
Stratigraphic Guide, the International Commission on Stratigraphy
concentrated its effort on the re-definition of national stratigraphic
codes. In the framework of the Geological Stratigraphical Sections and
Points Programme, this work is associated with searching for
international and regional key sections. Until the International
Geological Congress in Oslo (2008), all 88 GSSP points should be
defined.
In the context of this research programme, the stratigraphic revision
of classical Phanerozoic profiles and areas is especially invited.
Germany was the area, where the classical studies of Alberti, von
Buch, Frech, Geinitz, Geyer, Quenstedt, Schindewolf, Strombeck, and
many other founders of stratigraphy as a scientific discipline were
done. From this point of view, the recent book edited by Manfred
Menning & Andreas Hendrich in Newsletters on Stratigraphy (41:
Explanations to Stratigraphic Table of Germany, 2005) deserves special
interest.
This book has been compiled due to the common effort of 88 authors
from 38 institutions. It consists of 28 chapters dealing with problems
of stratigraphic study of individual Phanerozoic time slices in
Germany. The explanations are accompanied by numerous sketches and
tables on 405 pages of the text, and by 16 coloured tables in the
appendix. In spite of the unifying effort of the editors, individual
chapters substantionally differ one from another in style, method and
in approach to the subject of study. In fact, the text chapters could
be grouped into five parts (Teminological Introduction, Early
Paleozoic to Pennsylvanian, Permian and Triassic, Jurassic and
Cretaceous, Cenozoic).
Two introductory chapters were written by M. Menning (together with
F.F. Steininger). They deal with the trends in German stratigraphy,
schools and concepts, development of terminology, and stratigraphical
knowledge as a whole in the last three years (since 2002, when the
first concept of a new stratigraphical scale was published). Since
that time, the Devonian, Triassic and Late Jurassic tables have
considerably changed. In the community of German stratigraphers, there
is still some oposition to Salvador’s and Hedberg’s concepts.
Moreover, the German Cambrian, Ordovician, Devonian, Carboniferous and
Permian divisions differ from the Global Time Scale of Harland & Ogg.
Although an agreement was reached that the terms "Thuringian",
"Saxonian" and "Autunian" are unclear and not recommended for futher
use, a judgement that the terms "Buntsandstein", "Muschelkalk" or the
"Keuper" should be considered as "obsolete and terminologically
incorrect" is still a matter of debate. A new lithostratigraphical (?)
term "Folge" has been introduced. Lutz et al. (1999) defined this term
as ΄the time section (more-or-less equal to the formation), limited by
quasi-isochronous surfaces of different origin‘. However, the meaning
of this term is varying in the use of different authors.
Early Paleozoic and Carboniferous stratigraphical problems are
discussed by 21 authors in the five following chapters. Their text is
written in old routine style, in which the mixing of
lithostratigraphical and chronostratigraphical terms and the use of
jargon ("deutsche Proterozoikum", "Profil des Neoproterozoikum",
"Existenz von Kambrium","sibirische Unterkambrium","deutsche
Kambrium","Fazies des deutschen Devon","Graptolithen-Schiefern
überlagern das Silur" ...) is frequent. The authors suggest the term
"Silesium" for Pennsylvanian, despite of its base lies deeper than the
top of the Mississippian. They designate the thickness in meters of
Mississippian stages, and of the "Sedimentary Silesian" as well (thus
in the meaning of lithostratigraphic units!).
The following eight chapters form part of the most important
contribution of the book. They deal with Permian and Triassic
stratigraphical problems. In spite of the long history of problems
with the diachronism of biostratigraphical indicators, many troubles
with the correlation (called here the "Paternoster-Stratigraphie"),
the German sequence starting with the Rothliegend up to the Keuper
deposits is one of the best studied European Phanerozoic sequences now
and it evokes many interesting thoughts. The Permian to Triassic
infilling of the Mid European Basin should be the most com104 plete
and one of the most continuous Pm/Tr sequences (37 Myr) anywhere. The
Pm/Tr boundary should be indicated by microsferuls in the Calvőrde
Folge. What a pity that the tables illustrating the division,
structure and correlation of the sequences are arranged not very
systematically, being placed rather far from the text...
The term "Folge" in use of these authors is close to
cyclostratigraphic unit. In Rothliegendes and Zechstein, they
represent "Sohlbankzyklen 1. Ordnung" - megacycles with duration of
0.5-2 Myr, (consisting of Milankovich long eccentricity cycles), which
are recorded as rock bodies limited by "quasi-isochronous" surfaces
("sie begrenzen Abfolgen von Schichten, die, wenn auch nicht exakt
gleichzeitig, so doch innerhalb einer bestimmen Zeitscheibe abgelagert
wurden"). In Muschelkalk, the "Folgen" have the character of
"quasi-isochronous" formations. These formations were situated
centrally in the basin: they were neighbours of typical diachronous
formations along the basin marginal parts. The allostratigraphy of the
Muschelkalk is based on the marker horizons called here the
"Leitbänke" or "Leitflächen" ( =time reference or
time-correlation horizons).
The Keuper Group contains more than thirty lithostratigraphic units.
The "Folgen" in the Keuper are allostratigraphic units - the
definition of their boundaries should be focused not on the facies
changes, but on the marker horizons, which, according to
sedimentological indicators, are supposed to represent isochronous
surfaces. It is noteworthy that the rock record represents less than
50 \% of the time in these sequences. Therefore, both formation and
"Folge" represent different but complementary views on the same rock
pile, and their boundaries may cross over one another.
In summary, the "Dyas to Rhaetian" sequence should be represented by
33 "quasi-isochronous Folgen" (with a duration of 0.4 to 3.5 Myr)
consisting of 230 eccentricity cycles. Rotliegende precession 20 kyr
cycles are grouped into eccentricity 100 kyr cycles, 400 kyr
"long-eccentricity" cycles and these form 2.8 Myr long "Folgen"
(Parchim-, Mirow-, Dethlingen-, Hannover-, Zechstein-Folge). The 58
Buntsandstein cycles (duration of 6 Myr) have a short eccentricity
(100 kyr) character. The Lower Muschelkalk (2.8 Myr) comprises twenty
eight short eccentricity - parasequences, the Middle Muschelkalk (1.2
Myr) consists of 13 cycles, the Upper one (1.6 Myr) of 14-16 cycles.
The Keuper comprises 40 cycles separated by 6 large gaps (the largest
one, called the "Altkimmerische Hauptdiskordanz" lasted 12 Myr). The
Keuper resembles the Rotliegende Group - they both lasted up to 40 Myr
(twice as long as the Muschelkalk, Buntsandstein and Zechstein groups
together), with frequent gaps. The Norian and Visean represent the
longest stages of the whole Phanerozoic history. However, the Keuper
sedimentary record (consisting of 40 cycles with sedimentary rate of
30-40 mm/kyr) contains more than 20 gaps (0.5 to 12 Myr long) and
paleosoils.
Three chapters are devoted to the Jurassic stratigraphy. New
chronostratigraphic data show that the Late Jurassic lasted 15 Myr
(Kimmeridgian 6.5 Myr, Oxfordian 4 Myr, Tithonian 4 Myr). The authors
stress chronical problems with the identification of boundaries
(Rhaetian Sandstone vs. Hettangian Psilonotus Sandstone,
Toarcian-Aalenian ´Posidonienschiefer¡, Tithonian-lower Berriasian
Purbeck Facies). Classical terms like Liassic, Dogger and Malm have a
provisional status only. They are rather equivalent to
lithostratigraphic terms Ith-, Hildesheim- and Herford Group in
northern Germany. In southern Germany, names like ´Schwarzer-,
Brauner-, Weisser Jura Gruppe¡ are proposed. However, these
designations are not concordant with the international terminology and
are mixed with other jargon-like expressions in the text (Süddeutscher
Jura, globaler Jura). The use of formal lithostratigraphic terminology
is also wrong in several examples (Angulatenton Fm, Angulatensandstein
Fm, Grypheensandstein Fm, Numismalismergel Fm, Ostreenkalk Fm,
Psilonotenton Fm, etc.).
The Cretaceous lithostratigraphic units contain many local names
without modern re-definitions. Moreover, they are not hierarchically
arranged. Formalized unit names occur in several regions (Lower
Saxonia) only. Jargon expressions are frequent (überwiegend in
Schriebkreide Fazies entwickelte Oberkreide, Kreide von
Norddeutschland, Sächsische Kreide, süddeutsche Kreide, alpinen
Kreide). The stratigraphy is based on classical biostratigraphy; the
description of sediments mostly lacks any sequence- or
cyclostratigraphic interpretation. Three megasequences are recognized
(Berriasian to Lower Albian, middle Albian to Lower Coniacian and
middle Coniacian to Maastrichtian) and interpreted as a consequence of
the Alpine tectonism.
The remaining nine chapters deal with Tertiary (including Quaternary)
stratigraphy. They discuss sequences of partial basins (Lower and
Upper Rhine Valley, north-western, eastern and southern Germany,
Hessian Depression, Mainz Basin, Alpine units). Although many local
developments exist, two principal sedimentary megacycles have
developed due to the Alpine orogenesis (Paleocene-Lower Eocene and
Oligocene-Upper Neogene). It is only a pity that the authors keep a
descriptive approach (lithological and stratigraphical description
with paleogeographical implications) and sequence stratigraphic,
climatic and cyclostratigraphic aspects are only mentioned.
In spite of a few weak points, the book is very important contribution
to international discussion on modern trends in the Phanerozoic
stratigraphy. The authors expressed a (modest) purpose of the
Stratigraphical Table to serve as a stable basis for German Basin
stratigraphy for at least five to ten years. I am convinced that this
task has been succesfully fulfilled and that their common work
documents the admirable progress in German stratigraphical reasearch.
Jozef Michalík, Slovak Academy of Sciences, Bratislava
Geologica Carpathica, February 2007, 58, 1, 103-104
can be downloaded
Open Access (paper can be downloaded for free)
Inhaltsbeschreibung