This spring an entire issue of the Danish Geoscience journal Geoviden was dedicated to our research project “The Triassic–Jurassic boundary: Impact of a Large Igneous Province on the geobiosphere”. Geoviden is a popular science magazine aimed at high school students and everyone else interested in geology and geography. Our issue is called “A crisis in the history of life” and presents the background, hypothesis and progress of our Geocenter Denmark financed project. Unfortunately for non-Scandinavian readers it is in Danish. It is richly illustrated and covers various aspects of our research. It can be downloaded for free using this link, so feel free to check it out: Geoviden No 1 2016: “En krise i livets historie”
The Sose Bay area on the Danish island of Bornholm is a beautiful place. Here, the lush greens of the partly forested coastline with its white sandy beaches meets the Baltic Sea, and at the horizon there is nothing but sky.
Early Jurassic rocks crop out along the coast; the sands and clays still soft after 200 million years, revealing a multitude of sedimentary structures when scraped free of their weathered surfaces.
The most continuous sedimentary succession in the coastal cliff is exposed east of Sose Odde. It comprises a c. 24 m thick section including restricted marine, eustarine, lacustrine and fluvial deposits, and was described in detail by Surlyk et a. (1995). The outcropping succession belongs to the Sose Bugt Member of the Rønne Formation, which was assigned a Hettangian–Sinemurian (Early Jurassic) age based on its fossil palynological (spores, pollen, microalgae) content. In 2014, Clemmensen et al. described the presence of steep-walled, flat- to concave-bottomed depressions, with a raised ridge at each side, that were interpreted as dinosaur tracks.
The dinosaur tracks are found in layers interpreted to have been deposited in small streamson a large coastal plain. Clemmensen et al. (2014) suggest that the dinosaurs may have preferred to use shallow channels as paths. The succession also contains thin coal seams and layers penetrated by numerous vertical roots, remnants of 200 million year old vegetation.
So these are the sediments that lie immediately beneath our feet when we walk the fields at Sose Bay, below a thin cover of Quaternary sediments. But what lies beneath? Would sediments deposited before, during and after the end-Triassic mass extinction be present?
In order to find out, we performed a core drilling in the Sose Bay area, with the aim to reach typical red and green coloured Late Triassic sediments – and hopefully Triassic–Jurassic boundary sediments.We drilled with a core drilling technique that sealed the sedimentary cores in plastic pipes.
By checking the bottom of each pipe when they were brought to the surface, it was possible to see when the red and green Triassic had been reached. At a depth of 110 m below ground, we reached red Triassic sediments.
But because the cores were sealed in red plastic pipes, we still had no idea how complete the drilled succession would be. All we could do was wait until the cores had been transported back to GEUS.
To be continued…
I realised the other day that it has been ages since I last posted something on Triassica. Why is that? Sometimes life gets in the way and you have to direct your attention elsewhere. The simple explanation is that I have been far too busy.
Anyway, I decided it is time to break the silence, so I will try to publish some posts about how our Geocenter Denmark financed research project on the Triassic-Jurassic boundary is progressing. A lot of fun things have happened since we drilled the Sose-1 well on Bornholm in October 2014, hoping to find Triassic-Jurassic boundary strata – so stay tuned, updates are coming 🙂
Our core drilling through the Triassic-Jurassic boundary at Sose Bugt on Bornholm is progressing faster than expected. The drilling commenced Wednesday and we have already reached a depth of 64 m. Just like the outcrop succession along the beach, the deposits that mainly consist of sand, heteroliths and clay are faurly unconsolidated. The biggest challenges so far have been a siderite and a loose sand layer. None of these two were successfully cored.
Our on-site technician is providing updates for us and we are ready to take the next ferry to Bornholm as soon as we get close to our target depth. With the current drilling speed this may happen sooner than expected 🙂
On Tuesday next week we launch our new core drilling project. This time we are going to drill through the lowermost Jurassic sedimentary succession at Sose Bugt on the Danish island of Bornholm, with the aim to reach uppermost Triassic rocks. Despite many excellent geological studies in the area it is not clear if the Triassic-Jurassic boundary is preserved on the Sose Fault block, but the presence of Hettangian-Sinemurian strata in the coastal cliffs at Sose Bugt and Upper Triassic green and red clays along parts of the coast make it an ideal area to drill for the TJB.
Our core drilling project is funded by Geocenter Denmark and is a part of our research project on the end-Triassic mass extinction event. The core drilling will provide us with new research material, hopefully both of the mass extinction interval and of the recovery in the earliest Jurassic.
Quite excited about this! 🙂