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”

GEOVIDEN_1_2016

Front page illustration by Stefan Sølberg, GEUS.

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Triassic-Jurassic fossils from Scania: (I) dinosaur tracks

The Triassic-Jurassic transition of Scania has been one of my favourite research subjects since I was a student back in the late 1980ies. Back then I once again came in touch with the sedimentary rock escarpments of my hometown when working on two small research projects. I got to revisit slopes and outcrops where I used to play as a child, weathered but beautiful and home to bats and various spiders and various insects.  Far from a safe playground but as kids, we loved the “wild” sanctuary within the city. Maybe that is where I first fell in love with geology?

If I had known back then when I was a kid, what creatures had actually roamed my “hometown area” during the latest Triassic, Rhaetian, I would probably have been even more fascinated by those rocks. But back then, fossils and dinosaurs was not common knowledge.

Eventhough the Rhaetian and Hettangian (earliest Jurassic) sedimentary rocks of Scania have been extensively quarried for coals and clays during many centuries, no dinosaur fossil bones have ever been recovered. But dinosaur trace fossils of the ichnogenus Grallator have been recovered at several localities, see e.g. Gierlinski and Ahlberg 1994. In this paper the authors describe two different Grallator ichnospecies from various localities in NW Scania. The larger Grallator sp. cf. giganteus, which measures 32 cm in length, and the smaller 15-26 cm long Grallator soltykovensis.

Grallator soltykovensis (LO5463t) from the uppermost Rhaetian at southern Vallåkra. Photograph of original housed at the Department of Geology, Lund University. Drawing of the same specimen from Gierlinski and Ahlberg (1994).

 To date, the Scanian Grallator-trackmakers are unidentified. The Scanian Grallator tracks were defintely made by biped dinosaurs and display between three and four digits, three pointed forward and one backwards. The presence of many tracks of various size (between 15 and 35 cm in length) at southern Vallåkra (no longer exposed outcrop) suggest they were left by a herd, or pack if they were carnivors, of juvenile and adult individuals (Gierlinski and Ahlberg, 1994). My own research on dating the Triassic-Jurassic boundary (by palynology) sediments clearly shows that the tracks were all made during the Rhaetian. Hence, we do not know if the dinosaur-taxa that left these tracks survived the end-Triassic mass extinction event. 

 Hopefully one day someone will recover the fossil bones of the dinosaurs that left these amazing tracks and roamed the latest Triassic Scanian landscape.

Ode to an abandoned quarry…No.1.

“Oh in thy darkest hour rest

Let Earth be thy humble grave

Remembering the glory days

For green and dewey grass

and willow trees and water

will comfort thee”

 

Lunnom Quarry

Lunnom Quarry in July 2005 (Photo: Leif Johansson)

I mourn the loss of the Lunnom Quarry, this classical Rhaetian (uppermost Triassic) excursion locality that was closed down in 2008. During the last couple of decades numerous geology students have visited the quarry and studied the quarry walls, where a ca 9m thick exposed coal-bearing succession opened a window into the past. There, we could observe how a once marine lagoonal clay had been turned into underclay as the sea had retreated and allowed the plants to invade and form a swamp on the former sea floor. Fossilized plant remains, large and small rootlets, tree trunks, leaves and seeds…the remnants of a 200 million year old dinosaur swamp. 

The coal at Lunnom was first mentioned in 1744 and for centuries the coal was economically important. However, since 1964 it was instead the aluminum-rich underclay that was quarried for high-quality ceramics.

When the quarry wasclosed down in 2008 it was due to environmental issues as acidic water from the claypit leaked into a nearby brook causing mass kill of fishes.

The Lunnom Quarry was also (and still is although it is no longer accessible) the type locality for the rare but beautiful dinoflagellate cyst, Lunnomidinium scaniense Lindström, which I described in 2002.

Lunnomidinium scaniense Lindström 2002

When I last visited the quarry site in the summer of 2010 it had turned into a small green lake, beautiful in its own way, but…

The Lunnom Quarry will be sorely missed by many geologists!