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.

Time to colour the fossil record…

Since the dawn of palaeontology, researchers and artists have strived to reconstruct ancient extinct life forms. By combining the fossil remains with knowledge of anatomy or botany pioneers like Henry de la Beche (1796-1855) and Charles R. Knight (1874-1953)  envisioned the forms and colours of prehistoric life on Earth (read more about palaeoartists here) and brought us the first ideas on what e.g. dinosaurs may have looked like.

Recently, palaeontological research have broken new ground by identifying melanin – a black, brown or red colour pigment that occurs in both animals and plants – in fossils. Since Jakob Vinther and colleagues published their paper “Plumage Color Patterns of an Extinct Dinosaur” more reports of preserved melanin-residues in fossils have surfaced. Two of the latest deal with: pigment in a 50 million year old fossil fish eye (Lindgren et al. 2012) and in a 160 million year old fossil squid ink sac (Glass et al. 2012).

The fossil record will never be the same 😉

However, we will always need reconstructions and paintings depicting the past. Check out this wonderful webpage with beautiful palaeo-scenery: Evolutionary routes

Everybody’s talking about methane…

It actually started 16 years ago when Gerald R. Dickens and his colleagues published their paper on oceanic methane hydrate dissociation and the Palaeocene-Eocene Thermal Maximum (PETM). Their hypothesis that release of methane gas stored in oceanic sediments was the cause of the negative carbon-isotope excursion at the end of the Palaeocene and hence the trigger of the global warming recorded at the PETM, got scientists working on climate change and mass extinction around the world to suddenly set their old theories aside and focus on this new one.

Burning natural gas which consists of methane to 80% (Left) and a methane molecule (right).

Today, it seems, everybody’s talking about methane, CH4, this very potent greenhouse gas. From methane stored in clathrates underneath the ocean floor, or frozen by permafrost in the circum- Arctic or Antarctic tundra ( e.g. De Conti et al. 2012), to cattle or even farting dinosaurs during the Mesozoic, it poses a severe threat to life on Earth if released in large quantities. Hence, many scientific papers (see e.g. Payne et al. 2004 and references therein, and Ruhl et al. 2011) have argued that methane must have played a role in the end-Permian and end-Triassic mass extinctions, which are both associated with negative carbon-isotope excursions indicating input of light carbon (carbondioxide or methane from volcanoes or other sources).

My colleagues and I have studied the Triassic-Jurassic (T/J) boundary of the Denmark and compared that to a well known T/J boundary succession in England. In these two areas the carbon-isotope records exhibit three negative excursions separated by two intervals with more positive carbon-isotope values. What we have found is that the most profound floral changes on land and amongst organisms in the epicontinental sea that once covered these two areas, commenced within the first positive interval, i.e. between the first negative carbon-isotope peak and the second (most prominent) one. At the same level as the second negative carbon-isotope peak, which has been attributed to methane injection by e.g. Ruhl et al. 2011, the flora does not seem to be affected but is instead recovering, while organisms in the ocean continue to suffer. Hence our study suggests a more complex scenario…

You can read our paper (or just the abstract) or the press release.

On this day in Edinburgh 286 years ago…

…James Hutton, the father of modern geology and the understanding of deep time, was born.

James Hutton (1726-1797), part of a painting by Sir Henry Raeburn.

Without his sharp observations on the geology around the Edinburgh area and the Scottish Highlands, we might never have learned that Earth was vastly older than previously thought. In 2005 a group of students from Lund University and I were graciously guided around the fantastic geology around Edinburgh by Professor Euan Clarkson, who told us many stories about the life and times of James Hutton. A truly wonderful excursion! 🙂

Hutton’s unconformity at Siccar Point (Photo by Sofie Lindström 2005).

 One of the localities was Siccar Point with “Hutton’s unconformity”, where Devonian Old Red Sandstone (345 million years old) overlie Silurian greywackes (425 million years old) with an angular unconformity (see above), which we visited during a rather grey day with very strong winds that almost blew us off the cliff.

My three then students and our gracious guide visiting Siccar Point in 2005 (copyright Sofie Lindström).

Happy Birthday James Hutton!