On the end-Triassic mass extinction – In Danish

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”

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Front page illustration by Stefan Sølberg, GEUS.

“What lies beneath…”

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.

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Sose Bay in October 2013 (Photo: Lars Henrik Nielsen, GEUS)

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.

section before and after

Left: a small weathered coastal section. Right: Same section after rinsing. (Photo: Sofie Lindström, GEUS)

 

 

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Wave ripples (Photo: Gunver K. Pedersen, GEUS)

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.

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One of the dinosaur tracks described by Clemmensen et al. (2014). (Phoyo: Sofie Lindström, GEUS)

 

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.

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Numerous thin vertical roots penetrating a thick sand layer (Photo: Sofie Lindström, GEUS).

 

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?

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The drill site and equipment (Photo: Gunver K. Pedersen, GEUS).

 

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.

kernehenter kommer til syne

The core catcher brings up a new core (Photo: Gunver K- Pedersen, GEUS).

 

John tager kerne ud af kernerør

John Boserup checkes the bottom of a core (Photo: Gunver K. Pedersen, GEUS).

 

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.

Trias rødt ler stedvis grønt stedvis sandet

Red and green clay and some sand at the bottom of a core (Photo: Gunver K. Pedersen, GEUS).

 

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.

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 Sealed red plastic pipes  containing the cored succession of the Sose-1 well (Photo: Gunver K. Pedersen, GEUS).

 

 

To be continued…

 

 

 

Silence = work in progress – update on our TJ-boundary project

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 🙂

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The newly arrived Sose-1 core boxes at GEUS in November 2014. The sealed pipes contain the sedimentary cores from the drilling. At this stage no one knows what the sedimentary succession in the pipes look like. (Photo: John Boserup, GEUS)

 

 

 

Drilling through Triassic-Jurassic boundary strata

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! 🙂

Beautiful Hettangian (lowermost Jurassic) clays and sands at Sose Bugt, Bornholm, Denmark (Photo: Sofie Lindström)

Beautiful Hettangian (lowermost Jurassic) clays and sands at Sose Bugt, Bornholm, Denmark (Photo: Sofie Lindström)

Updates on our TJ-boundary project

The Triassica site has been silent because I have been on vacation and on a great five week fieldwork to North Greenland – which was great except for the fact that I missed out on the apparently best Swedish summer in years, and now autumn is on its way…

Scenery from North Greenland summer 2013 (Photo by Sofie lindström)

Scenery from North Greenland summer 2013 (Photo by Sofie Lindström)

Here are some news from our Geocenter Denmark financed Triassic-Jurassic (TJ) boundary project:

We have published a new paper on the Rhaetian coals of southern Sweden, which amongst all the interesting data also includes a beautiful artistic reconstruction of a Rhaetian forest mire: 

Petersen, H.I, Lindström, S., Therkelsen, J., Pedersen, G.K. 2013. Deposition, floral composition and sequence stratigraphy of the uppermost Triassic (Rhaetian) coastal coals, southern Sweden. International Journal of Coal Geology 116-117, 117-134.

We are now also advertising for a PhD-student for our TJ-boundary project, a collaboration between three institutes within Geocenter Denmark: the Geological Survey of Denmark and Greenland (GEUS), the  the Department of Geosciences and Natural Resource Management (DGN) at Copenhagen University, and the Department of Geosciences at Århus University. The PhD-position is placed at the Department of Geosciences and Natural Resource Management (DGN), and the successful candidate will perform research on high-resolution chemo- and cyclostratigraphic analysis with the goal of deciphering local to global changes of environmental redox and carbon cycle perturbations through the end Triassic (Rhaetian) early Jurassic (Pliensbachian), and assessing the pacing of the ecosystem pertubation. You can read the full description here.

We are looking forward to receiving applications from potential candidates 🙂