1 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet2 Geology, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet
an appraisal of existing seismic data
We present a digital model SibCrust of the crustal structure of the Siberian craton (SC) and the West Siberian basin (WSB), based on all seismic profiles published since 1960 and sampled with a nominal interval of 50 km. Data quality is assessed and quantitatively assigned to each profile based on acquisition and interpretation method and completeness of crustal model. The database represents major improvement in coverage and resolution and includes depth to Moho, thickness and average P-wave velocity of five crustal layers (sediments, and upper, middle, lower, and lowermost crust) and Pn velocity. Maps and cross sections demonstrate strong crustal heterogeneity, which correlates weakly with tectono-thermal age and strongly with tectonic setting. Sedimentary thickness varies from 0-3 km in stable craton to 10-20 km in extended regions. Typical Moho depths are 44-48 km in Archean crust and up-to 54 km around the Anabar shield, 40-42 km in Proterozoic orogens, 35-38 km in extended cratonic crust, and 38-42 km in the West Siberian basin. Average crustal Vp velocity is similar for the SC and the WSB and shows a bimodal distribution with peaks at ca. 5.4 km/s in deep sedimentary basins and ~ 6.2-6.6 km/s in parts of the WSB and SC. Exceptionally high basement Vp velocities (6.8-7.0 km/s) at the northern border between the SC and the WSB indicate the presence of magmatic intrusions and are proposed to mark the source zone of the Siberian LIP. The cratonic crust generally consists of three layers and high-velocity lowermost crust (Vp ~ 7.4 km/s) is observed only locally. Pn velocities are generally ~ 8.2 km/s in the SC and WSB and abnormally high (8.6-8.9 km/s) around kimberlite fields. We discuss the origin of crustal heterogeneity and link it to regional crustal evolution.
Tectonophysics, 2013, Vol 609, p. 154-183
Crustal structure; Moho; Seismic velocities; Siberian craton; West Siberian basin