During Saturday core drilling at Sose bugt continued slowly. Because the sedimentary succession is fairly unconsolidated we are drilling with a technique that encase the cored sediments in 1,5 m long pipes. This means that it is only possible to investigate the cored sediments at the top or bottom of each core section. Typical Early Jurassic whitish sands and grey clays had been cored during the first three days of drilling. On Saturday we were closing in on two prominent seismic horizons, one which we suspected could be the top of the Triassic redbeds. At 91 m there were still grey clays but also coal. But at 95 m the top of the core showed dark grey clays, while the bottom consisted of light green sand and clay typical for the Upper but not the uppermost Triassic. We had finally reached the Triassic!
Drilling will continue for a few more hours tomorrow until the geophysical logging equipment arrives. We are all very excited and can’t wait to get the cores back to GEUS so that we can study them. Almost 95 m of Lower Jurassic and hopefully also uppermost Triassic (Rhaetian) near coastal sedimentary strata which we think will provide us with additional information on the end-Triassic mass extinction and the biotic recovery that followed.
Sose Bugt on Bornholm is a beautiful place (photo: S. Lindström)
The Sose Bugt outcrop and our on-site technician.
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!
Beautiful Hettangian (lowermost Jurassic) clays and sands at Sose Bugt, Bornholm, Denmark (Photo: Sofie Lindström)
Thursday afternoon at the EGU2014 was totally dedicated to the session “Volcanism, Impacts, Mass extinctions and Global environmental change” in which I also presented a talk. The session contained a total of eleven oral presentations covering various subject within the above mentioned topics. The first four talks were on the volcanism of the Siberian Traps and the end-Permian mass extinction event.
In the first talk, Seth Burgess presented new high-resolution geochronological data for the intrusives of the Siberian Traps. Burgess and his colleagues had used the same analysis and standards on not only zircons from the Siberian Traps, but also on zircons from the ash-layers bracketing the end-Permian mass extinction level at the GSSP Meishan in China. According to these new datings all the dated intrusives post-date the end-Triassic mass extinction event. Seth Burgess stated that although these data could be taken as “the nail in the coffin for the theory that the intrusive activity caused the mass extinction” he didn’t believe that they did. He then went on to explain that the majority of the intrusives of the Siberian Traps are situated at depths and those that have been dated are the ones that are accessible, probably producing a biased record.
This was good news for the second speaker, Henrik Svensen, who presented a talk on the sill-induced evaporite and coal metamorphism of the Siberian Traps. Svensen and colleagues showed that the Siberian Traps contain very thick sills that have been emplaced into both coal-bearing sediments and salt deposits, with the potential for degassing of both green house gases (CH4, CO2), aerosols (SO2), and ozone destructive gases (CH3Cl, CH3Br), which could explain the end-Permian biotic crisis.
A fuzzy picture of Henrik Svensen and his audience.
The number 1 highlight of Tuesday was the Arthur Holmes medal lecture by Kevin C.A. Burke: Plume Generation Zones On The Core Mantle Boundary: their origin and what they tell about how the Earth works – and how it has worked.
Kevin Burke giving his medal lecture at the EGU2014
Burke, who due to health issues had to remain seated during his hour-long lecture, captivated his audience with his warm and humoristic and insightful review on how and where in the Earth’s interior volcanic plumes are formed. If you are interested in large igneous provinces, flood basalts, hot spots etc I strongly recommend you to check out the streamlined talk at the EGU2014 website.
This year I am attending the European Geisciences Union General Assembly or for short the EGU2014 meeting in Vienna, Austria, 27 April – 2 May. The EGU meetings are BIG! Geoscientists everywhere! More than 600 sessions, workshops and short courses. A multitude of geotopics with something for everyone.
I arrived yesterday, so I have only attended half a session so far, but I have seen plenty of posters and met many colleagues. Today I am especially looking forward to the Arthur Holems Medal lecture by Kevin C.A. Burke on “Plume Generation Zones on the core mantle boundary: their origin and what they tell us about how the Earth works – and how it has worked”. And also to spend the afternoon at session SSP2.3: “Late Palaeozoic and Mesozoic stratigraphy, paleoceanography and paleoclimate” (sponsored by the IAS).
I am also co-author on a poster in the session “Rifts and rifted margins: The sedimentary, volcanic and crustal architecture”, so I have to check out that. The poster is entitled “Pre-breakup age of East Greenland Ridge strata” by Tove Nielsen, Morten Bjerager, Sofie Lindström, Henrik Nøhr-Hansen, Tine L. Rasmussen (Abstract).
It’s going to be a busy but fun day