The third summer excavation at Bromacker came to an end at the weekend. Despite this year's very wet and changeable weather, the excavation team made numerous finds again this year, covering aspects of the entire Bromacker ecosystem and underlining that the site is unique in the world.
The excavation was complemented by a research drilling at the nearby Gallberg, which was carried out under the auspices of the Geosciences Institute of the University of Jena and the UNESCO Global Geopark Thüringen Inselsberg – Drei Gleichen.
At the Bromacker, the researchers opened a new excavation field and were able to gain further insights into new rock layers and a deep insight into the ecosystem 290 million years ago.
All in all, about 45 scientists and students spent four weeks excavating the reddish rock layer by layer and made 317 finds. Among them are geological structures such as dry cracks and raindrop marks as well as trace fossils – i.e. tracks, burrow systems and swim marks – and body fossils, which include plants, insects, arthropods and vertebrates.
This year's highlights include a new type of burrow system similar to those of today's lungfish and some amphibians, which most likely served as protection against adverse climatic conditions, such as drought. A total of three partial skeletons were discovered, as well as bones of rarer groups of early tetrapods, whose assignment to a species, however, will only be possible after their uncovering in the geoscientific workshops.
The excavation remained exciting until the very end: Ten minutes before the planned end of the excavation, the team found arm and finger bones from an unspecified ursaur, so that in the end the excavation team had to put in some overtime and late shifts. A plaster cap was made to remove, if possible, the complete coherent skeleton, which is now being prepared under controlled conditions.
BROMACKER project leader Prof. Jörg Fröbisch, PhD, from the Museum für Naturkunde in Berlin, says: "It is always fascinating that so many and novel finds are made in every Bromacker excavation year, which once again underlines the enormous potential of this fossil site for decades to come. Therefore, we are already looking forward to all future and hopefully somewhat drier excavations at the Bromacker."
Generally, the summer months are the best time for an excavation because dry conditions are optimal for breaking down the rock and identifying even very small fossils. This year, the rainy weather partly silted up or even flooded the excavation areas. Dr. Tom Hübner, project manager of the BROMACKER project in Gotha, says: "Nevertheless, we were able to work on most days, partly protected by pavilions and with the help of a team that showed great research spirit and a lot of stamina."
In the past weeks, not only the specialist community gained a more precise idea of what climate and geology might have looked like in the Tambach Formation 290 million years ago. Even non-specialists, amateur palaeontologists, schoolchildren and tourists have been able to get a better idea of the dinosaurs and the like.
Action days for families, public guided tours and direct communication at the excavation site made this possible. A total of about 1,600 people visited the Bromacker excavation. So anyone interested could look over the shoulders of the researchers – virtually or directly on site. Because: The Bromacker is there for everyone. Science communication accompanies the BROMACKER project on all levels and conveys the fascination of the topic and the enthusiasm of the researchers by means of state-of-the-art and experimental knowledge transfer formats.
"Guided tours were already fully booked in advance. We were very pleased that so many visitors were interested in the excavation again this year and that interest in the Bromacker and the region's earth-historical heritage continues unabated," says Maria Schulz, science communicator in the BROMACKER project.
About 600 visitors came to the Open Bore Day on 5 August alone. The research borehole was opened to the public as part of the family festival in Tambach-Dietharz. In addition to the guided tours, the BROMACKER stand on the Ochsenwiese was also very popular: at a microscopy station with thin sections of fossils from the Bromacker, interested visitors were given an insight into the project, and plaster figures and plaster casts of fossils and footprints from the Bromacker were available for painting. In this way, the team brought their research intentions closer to the residents of the town of Tambach-Dietharz and celebrated the successes achieved so far with them over a Thuringian grilled sausage.
In the meantime, the majority of the finds from last year have been processed and prepared. This includes a very significant find that has far exceeded the team's expectations. It is the remains of a early tetrapods from the diadectid group, which were apparently embedded in the chamber of a former burial system. Scratch marks on the chamber walls also prove for the first time that some early tetrapods systematically dug such chambers and retreated into them. It looks as if the early tetrapods discovered here had found its final resting place in its own burrow.
Drilling at Gallberg
This year the team drilled the borehole on the Gallberg near Tambach-Dietharz, at a location in the middle of the Tambach Basin. Last year, a first borehole was drilled at Hainfelsen and reached a depth of 250 metres.
During drilling, a water-cooled diamond drill bit moves deep into the rock and brings a cylindrical rod from the depths to the surface. This so-called drill core is then stored in a wooden core box. A core box with core weighs about 25 kilograms.
In the following, these rock samples are intensively processed, sampled and examined with the help of a wide variety of scientific methods. For example, the researchers make thin sections, carry out grain size analyses and geochemical analyses, determine the colour spectra and measure the magnetisability and natural radioactivity of the rocks. Afterwards, the data obtained from the drillings will be compared. In this way, a great deal of additional information, especially spatial information, can be obtained.
The aim of the approach is to reconstruct the landscape and climate 290 million years ago and thus the habitats of the primordial dinosaurs: When the researchers compare the rocks from both boreholes, they can answer important questions: Where were mountains and lowlands? How did the sedimentary debris get into the basin? Where did the rivers rise and where did they flow? How wide and how deep were they? Were the river basins constantly filled with water or did they dry up in summer? Were there climatic fluctuations?
The drilling at Gallberg is still ongoing. On Wednesday, 16 August, at 2 p.m., interested visitors can take part in a guided tour led by staff from Friedrich Schiller University Jena and learn more about the drilling technology and the geotechnical and geoscientific work. BOG staff will also be happy to answer questions about the drilling process at any time outside of the guided tours. The UNESCO Global Geopark Thuringia Inselsberg – Drei Gleichen will announce the exact end of drilling at www.geopark-thueringen.de.
Researchers and staff from the Museum für Naturkunde Berlin - Leibniz Institute for Evolutionary and Biodiversity Research (MfN), the Friedrich Schiller University of Jena, the UNESCO Global Geopark Thüringen Inselsberg – Drei Gleichen and the Stiftung Schloss Friedenstein Gotha are involved in the project, which is funded by Bundesministerium für Bildung und Forschung (BMBF).