Beschreibung
The correlation of drilling results with the regional geology is one of the major tasks within many ICDP drilling projects. This task is challenging, because of a resolution gap between drilling measurements, which resolve in the cm-scale whereas measurements which investigate the geology surrounding the borehole, e.g. surface seismic, resolve objects at its best in a range of tens of meters. Especially events with high complexity such as the Caledonian orogeny are difficult to understand on these scales. Our project bundle combines oriented borehole magnetic and high resolution seismic measurements to investigate the Caledonian orogeny and its temporal evolution along the COSC-2 drill hole. In this way we intend to fill the resolution gap which still prevents in many drilling projects an exact correlation of drilling results with the regional geology.
Within our projects we will obtain important complementary data about the structural setting in the surrounding of the COSC-2 drill hole from high-resolution borehole and surface seismic and 3C borehole magnetic measurements. The added scientific value will be generated by an innovative approach combining the benefits of seismic information with those of directional magnetic information obtained by using 3C sensors and a sophisticated reorientation system. The integrated interpretation of the data will reduce the ambiguity that is inherent in both methods when applied separately. The combination of surface seismic measurements and three-component borehole magnetic data to interpret complex structures were done in 2008 in the ICDP project Outokump Deep Drill Hole. However, additional combination with high resolution VSP data will further decrease the ambiguity in interpretation of the magnetic anomalies.
Compared to existing magnetic surveys, the inclusion of seismic data into the magnetic interpretation will yield a more reliable and detailed estimate about the magnetization direction for each rock unit in an expanded range of up to 200 m distance to the borehole. On the other hand, the identification of magnetized rock will help to differentiate between rock units not resolvable by seismic means. Since the magnetization directions contain information about the tectonic evolution of the host rocks, and thus about the character of deformation. These approaches will be used to advance the understanding of the deep structure and development during collision underriding plate Baltica, which is one key goal of the COSC project.