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)