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The international team of geoscientists led by Prof. Silke Voigt from Goethe University in Frankfurt, Prof. Ireneusz Walaszczyk from the University of Warsaw and Dr André Bornemann from LBEG studied 40 meters in depth of the sequence of geological strata in the old limestone quarry in Hasselberg. The researchers determined that this is only a sequence in the transition from Turonian to Coniacian without gaps and therefore represents a perfect rock sequence to serve as a reference for geoscientists around the world for their research. – a “section and a global stratotype point (GSSP)” or, in geoscience jargon, a “golden nail”.
Certain groups of bivalve molluscs of the Inoceramidae family appeared for the first time 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 occurrence of the inoceramide species Cremnoceramus deformis erectus, which marks the time limit. Careful studies have also revealed other microfossils and a characteristic change in the ratio of 12C and 13C carbon isotopes, a so-called negative anomaly in the carbon cycle.
“This means that varying geological sequences, such as sediments from the marine shelf in Mexico or the deep tropical Atlantic, can now be compared and classified over 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 estates and finally see, for example, what the climate looked like at a certain point in time in the past in different parts of the world.”
Professor Ireneusz Walaszczyk says: “The Salzgitter-Salder sequence wins out over other candidates, for example from the United States, India, Madagascar, New Zealand and Poland, because we have here a perfect 40 meter rock border sequence, with a record of the events that took place in this geological time interval.
“The Zechstein Sea left huge layers of salt in the North German basin more than 250 million years ago,” explains André Bornemann. “The rock layers deposited later put pressure on these salt layers, some of which bulged into large salt domes, deforming the 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 strongly vertical, resulting in a wonderful profile which is very accessible for scientific research. That is why we at LBEG have designated this location as a geotope, and it is one of the most important geopoints of the Harz-Braunschweiger Land-Ostfalen UNESCO Global Geopark. “
Context:
In the Hasselberg limestone quarry near Salder in the northeast of the Salzgitter mountain range, limestone and marl were once mined for the cement industry and later for ore processing. Today it is the location of a well-known biotope and geotope which is owned by the Stiftung Naturlandschaft (Natural Landscape Foundation) and established by the regional association BUND of Lower Saxony. While the management of the quarry site has been entrusted to the Salzgitter district group of BUND, the Harz-Braunschweiger Land-Ostfalen UNESCO Global Geopark is taking care of the geoscientific part of the quarry. The quarry is not freely accessible for reasons of nature conservation, but guided walks are sometimes offered.
90 million years ago, in the second half of the Cretaceous, it was too hot on Earth: the ice-free poles kept the sea level high, and Central Europe was made up of a group of islands. In the sea, ammonites developed a wide variety of forms, while dinosaurs ruled the 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 level began to drop, and a new period in Earth’s history, the Coniacian, replaced the Turonian.
Source of the story:
Material provided by Goethe University Frankfurt. Note: Content can be changed for style and length.
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