Looking back millions of years into the earth's history with computed tomography
July 27, 2023 | Gina Naujokat
A sedimentary slab from the Holstein Rock was to be examined for its fossil content using computed tomography. Latest CT technology provided results no one had expected.
Earth sciences and, in particular, paleontology provide us insights into our earth's past and exciting information about changes in our habitat over millions of years back. Species possibly long extinct paint pictures of life long before the dawn of humankind in environments and vegetation drastically different from today. Not only dinosaur finds should inspire our imaginations, but much more micrometer-scale fossils proving the drastic changes our planet has undergone. And we marvel at the insights scientists have already gained and their conclusions about our future.
Dr. Ulrich Kotthoff, Head of Paleontology at the Leibniz Institute for the Analysis of Biodiversity Change in Hamburg, and a team of researchers from the University of Hamburg's Micropaleontology Department, the Foraminifera.eu Lab, and the LIB recently visited the Comet Yxlon Application Factory to see what today's X-ray technology can do for their research. A sedimentary slab from the Holstein Rock, a specific sandstone found primarily in eastern Schleswig-Holstein, was to be examined for its fossil content using computed tomography.
Up to now, such examinations have been realized mainly by destroying the rock, which, however, always entails the risk of damaging the contained fossils too. Therefore, non-destructive examination is an attractive alternative if the device can achieve the required resolution. As a matter of fact, new technological possibilities could provide results that nobody had expected at that moment: Besides the larger snails, even an accumulation of millimeter-sized foraminifera shells became visible. Foraminifera are single-celled organisms occurring in marine habitats such as oceans or salt marshes. The oldest foraminifera found are about 540 million years old. Scientists can read the tiniest changes in the respective environmental conditions from their shells and thus look far back into climate and ocean evolution.
The fossil plate brought in by the researchers, got scanned in the high-resolution computed tomography system FF35 CT. A three-dimensional overview of the plate was generated using the conventional circular trajectory in the QuickScan mode of the Vista software. The 3D dataset generated had a voxel size of 50 µm and provided the researchers with initial insights from inside the test object at familiar resolution.
Using the ZoomScan from the VistaX Package, a detail detectability improvement by a factor of 10 was realized. With a small voxel size of only 7 µm, millimeter-sized shells of foraminifera in an unexpected accumulation could now be detected in the rock.
Fig. 4-6: VistaX ZoomScan "opens new horizons" - millimeter-sized foraminifera next to the snail shells.
Much faster to perform, however, is the LayerScan included in the VistaX Pro Package, a Comet Yxlon computed laminography technology that creates high-resolution layers of flat parts without the need for 360° rotation. LayerScan achieved a voxel size of 5 µm.
The direct comparisons on scale:
Fig. 8: Vista QuickScan vs. VistaX ZoomScan
Fig. 9: Vista QuickScan vs. VistaX Pro LayerScan
The possibilities of advancing X-ray technology bring exciting insights to science and, at the same time, raise expectations for the future. Dr. Ulrich Kotthoff is enthusiastic:
"The most surprising thing for me and my colleagues was the ability to recognize foraminifera shells besides the significantly larger snails. In addition to the possibility of studying these microfossils without destroying the rock, it is exciting to be capable of determining their volume fraction of the rock. Should an even higher resolution get achieved, a more precise determination of the foraminifera would actually be possible. Going further, we could examine a few more pieces of the same rock from other sites to see if the foraminifera and snail density is similar at all sites or if there are regional differences. At best, when the microfossils get identified more precisely, we could also infer the former water depth."
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