A team of scientists from Goethe University Frankfurt, the University of
Warsaw, the State Authority for Mining, Energy and Geology (LBEG) in Hanover,
and from other institutions world-wide, has found what researchers have been
searching for worldwide for more than 20 years in Salzgitter-Salder: A
geological formation that perfectly represents the transition from the
Cretaceous Turonian to the Coniacian Age. The team has characterised the former
limestone quarry so precisely that it is now considered a global reference
point for the turn of the ages 89.4 million years ago. This was announced by
the International Union of Geological Sciences, which awarded the stratotype
profile the title "Global Stratotype Section and Point" (GSSP).
FRANKFURT/HANNOVER. The international
team of geoscientists led by Prof. Silke Voigt from the Goethe University
Frankfurt, Prof. Ireneusz Walaszczyk from the University of Warsaw and Dr André
Bornemann from LBEG have thoroughly investigated 40 metres of the geological
strata sequence in the former limestone quarry at Hasselberg. The researchers
determined that this is only sequence in the transition between Turonian and
Coniacian without gaps and it therefore represents a perfect rock sequence to
serve geoscientists from all over the world as a reference for their research -
a "Global Stratotype Section and Point (GSSP)" or, in the jargon of
geosciences, a "golden nail".
Certain group of bivalve mollusks of the family
Inoceramidae, first appeared in the Coniacian, and are found in large numbers
in Salder. In Bed 46 of the quarry, the German-Polish scientific team found the
oldest appearance of the Inoceramid species Cremnoceramus
deformis erectus, which marks the time boundary. Careful studies also
revealed other microfossils and a characteristic change in the ratio of the
carbon isotopes 12C and 13C, a so-called negative anomaly
in the carbon cycle.
"This means that variable geological sequences,
such as marine shelf sediments in Mexico or the deep sea in the tropical
Atlantic, can now be compared and classified in time," explains Prof.
Silke Voigt. "This is important in order to be able to make an exact
chronological classification even in the case of incomplete successions and
ultimately to see, for example, what the climate was like at a certain time in
the past in different places in the world."
Professor Ireneusz Walaszczyk says: "The sequence
in Salzgitter-Salder prevails over other candidates, for example from the USA, India,
Madagascar, New Zealand and Poland, because we have a perfect rock boundary sequence
here over 40 metres, with a well-defined record of events which took place in
this interval of geological time."
"The Zechstein Sea left behind massive salt
layers in the North German Basin more than 250 million years ago,"
explains André Bornemann. "The rock layers deposited later exerted
pressure on these salt layers, some of which bulged up into large salt domes, deforming
younger layers in the process. Salder is located near such a salt dome, so that
here the fossil-rich rock layers of the Cretaceous period are steeply upright,
resulting in a wonderful profile that is very accessible for scientific
investigations. That's why we at LBEG have designated this place as a geotope,
and this is one of the most important geopoints of the Harz-Braunschweiger
Land-Ostfalen UNESCO Global Geopark."
In the limestone quarry at Hasselberg near Salder in
the north-east of the Salzgitter mountain range, limestone and marl used to be
quarried for the cement industry and later for ore processing. Today, it is the
location of a well-known biotope and geotope which is the property of the Stiftung
Naturlandschaft (Natural Landscape Foundation) and established by the BUND
regional association of Lower Saxony. While the care of the quarry site has
been entrusted to the Salzgitter district group of BUND, the
Harz-Braunschweiger Land-Ostfalen UNESCO Global Geopark looks after the
geoscientific part of the quarry. The quarry is not freely accessible for
nature conservation reasons, but guided walks are occasionally offered.
90 million years ago, in the second half of the
Cretaceous, it was tropically warm on Earth: the ice-free poles ensured high
sea levels, and Central Europe consisted of a cluster of islands. In the sea,
ammonites developed a tremendous variety of forms, while dinosaurs reigned on
land. The first flowering plants began to compete with horsetails and ferns. About
89.39 million years ago, the climate began to cool slightly, sea levels began
sink, and a new period in Earth history, the Coniacian, replaced the Turonian.
Voigt S, Püttmann T, Mutterlose J,
Bornemann A, Jarvis I, Pearce M, Walaszczyk, I (2021) Reassessment of the Salzgitter-Salder section as a potential stratotype
for the Turonian–Coniacian Boundary: stable carbon isotopes and cyclostratigraphy
constrained by nannofossils and palynology. Newsl Stratigr, 54/2, 209–228, https://doi.org/10.1127/nos/2020/0615
I., Čech, S., Crampton, J.S., Dubicka, Z., Ifrim, C., Jarvis,
I., Kennedy, W.J., Lees, J.A., Lodowski, D., Pearce, M. Peryt, D.,
Sageman, B., Schiøler, P., Todes, J., Uličný, D.,
Voigt, S., Wiese, F., With contributions by, Linnert, C., Püttmann, T.,
and Toshimitsu, S. (2021) The Global Boundary Stratotype Section and Point
(GSSP) for the base of the Coniacian Stage (Salzgitter-Salder, Germany) and its
auxiliary sections (Słupia Nadbrzeżna, central Poland; Střeleč, Czech Republic; and El
Rosario, NE Mexico).
Episodes 2021; 44(2): 129-150l. https://doi.org/10.18814/epiiugs/2020/020072
Salzgitter-Salder: A perfect rock boundary
sequence over 40 metres. (Photo: Silke Voigt, Goethe University Frankfurt)
GSSP in Salzgitter-Salder: Layer 46 marks
the transition from the Cretaceous Turonian to the Coniacian Age. Photo and
montage: Silke Voigt, Goethe University Frankfurt. Fossil: Walaszczyk et al.
Professor Silke Voigt
Goethe University Geocentre
Tel: +49 69 798-40190
Professor Ireneusz Piotr Walaszczyk
Institute for Historical and Regional
Geology and Paleology
Dr André Bornemann
May be contacted through
LBEG, Communications office
Tel.: +49 511 643-2274