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The Kola Superdeep Drillhole and the nature of seismic boundaries
Author(s) -
Pavlenkova N.I.
Publication year - 1992
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1992.tb00456.x
Subject(s) - geology , seismology
The Kola Superdeep Drillhole was drilled through 7 km of Proterozoic rocks of the Pechenga structure and 5 km of the Archean basement in the Baltic Shield to 12 km depth. The results of drilling revealed a significant heterogeneity of physical properties of the crystalline rocks and a surprisingly high porosity and water content throughout the section. Seismic wide‐angle reflection data, obtained in the region of the hole, were used to delineate the volcanic‐sedimentary layers of the Pechenga structure and the intersecting faults. These studies revealed also a subhorizontal boundary at a depth of 7 km of uncertain origin. Core sampling implies that this boundary is associated with a change in core pressure, with higher porosity and with velocity anisotropy. A change in rock fissuring and in the fluid regime correlates with a velocity inversion zone reached by the hole at a depth of 4.5 km.