Head of the laboratory - doctor G.Z. Gurary 

Main results of the laboratory for the last four years run as follows:

1. Tectonics

1.1. It is found that the Omulev block and Okhotsk-Chukotka volcanic belt did not move with respect to Eurasia and North America since the Late Jurassic and Late Cretaceous, respectively [Alexutin et al., 1999]. In contrast, upper Jurassic-lower Cretaceous oceanic cherts on the northern coast of the Sea of Okhotsk accumulated at a latitude of 35°N on the Izanagi plate and docked to the Eurasia margin in the early Late Cretaceous; the Izanagi-Farallon boundary is shown to be much to the east from its earlier suggested position [Bazhenov et al., 1999];

1.2. It is shown that large counterclockwise rotations in the Tien Shan fold belt are accounted for by two-stage strike-slip deformation in Permian-early Mesozoic time [Bazhenov et al., 1999];

1.3. Reconstructions of the Turkestan ocean in the Tien Shan [Burtman et al., 1998a] and the Irtysh-Zaisan ocean in North Kazakhstan [Burtman et al., 1998b] were constructed for the Devonian.

1.4. Original paleolatitudes and subsequent motions of the Campanian-Maastrichtian Achayvayam-Valagina island arc of Central Kamchatka and the Cretaceous-Eocene Kronotsky island arc of East Kamchatka were established [Levashova et al., 1997; 1998; 1999].

1.5. It is demonstrated that Upper Riphean rocks of the western zone of the Bashkir anticlinorium (South Urals) were folded only in the Carboniferous-Permian; fold propagation is traced in this area [Shipunov, 1997].

1.6. With the aid of numerical simulation, it is shown that the most powerful modifications of the fold test do not detect up to 30% of postfolding overprint even for favorable fold geometry. A method of analysis of reliability of fold test results for a paleomagnetic data set derived from a certain fold geometry is suggested [Shipunov, Muraviev, 1999].

2. Stratigraphy

2.1. Magnetostratigraphic scale of the Caspian region is constructed and correlated with the global magnetochronological scale; the Miocene-Pliocene boundary is shown to coincide with the top of the Pontian stage in this region [Gurary et al., 1995].

3. Fine structure of geomagnetic field

3.1. Field behavior during the initial stage of the Tvera-Gilbert transition was studied; it is found that two quasi-stationary states, «VGP patches» after K. Hoffman, are characterized by VGP clusters near North America and Australia. Each patch lasted for ca. 1 ky, and the 100° field switch between the patches took less than 60 years [Gurary and Kudasheva, 1995];

3.2. The study of the stationary geomagnetic field of the Matuyama chron and Jaramillo subchron showed that no partial remagnetization can account for the VGP confinement to a single band; instead, the pattern observed is well explained by co-existing main reversing dipole and non-reversing equatorial dipole. Field intensity during the above intervals is found to match the pattern established by Valet and Meynadier (1993) in the peri-equatorial parts of the Indian and Pacific oceans [Gurary et al., 1999].