HR: 1340h
AN: GP43B-0860    [Abstracts]
TI: Different magnetostratigraphic approaches: Lake Baikal sediments and the J/K boundary strata in the Tethyan realm
AU: * Pruner, P
EM: pruner@gli.cas.cz
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AU: Housa, V
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AU: Kadlec, J
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AU: Chadima, M
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AU: Schnabl, P
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AU: Slechta, S
AF: Institute of Geology, Academy of Sciences, Rozvojova 135, Prague, 16502 Czech Republic
AB: Rock magnetic and paleomagnetic parameters were studied on two cores drilled in the Academician Ridge, Lake Baikal, Russia. The rock magnetic parameters were used to identify variations in the concentration, grain size and mineralogy of the magnetic material. Three intervals of deviating declinations and inclinations with steep totally reversed inclinations are clearly present in the cores. The ChRM directions were clearly dominated by normal polarity indicating the Brunhes Chron age of the sediments. The observed excursions were interpreted as the Blake excursion, the Iceland Basin excursion and the Biwa II excursion. The reversal excursions fall within the intensity minima. On the basis of the identification of excursions we correlated the magnetostratigraphic results (relative paleointensity and polarity) from the Lake Baikal sediments to comparable data sets from ODP site 984. Data obtained from the cores indicate the age of deposits up to 300 ka. Comparing the variations of the paleointensity records the mean sedimentation rate in the range of 3 - 4 cm/ka can be estimated. The result of magnetostratigraphic and micropalaeontological investigations of the Jurassic/Cretaceous boundary strata in the Tethyan realm (Brodno - Slovakia, the Bosso Valley - Italy, and Puerto Escano - Spain) can be reasonably intercorrelated. Reverse subzones proposed to be named "Kysuca Subzone" in M20n and "Brodno Subzone" in M19n were precisely localized in all studied profiles. All the magnetozones and subzones can be related to the M-sequence of marine magnetic anomalies. At the locality of Brodno, the interpreted duration of the transition between N - R (R - N) polarity falls into the range of 5 - 10 ka. Stratigraphically significant calpionellid events occupy an identical position in relation to magnetozones and subzones derived in all the three sections. The base of the calpionellid zone Crassicolaria coincides with the base of the "Kysuca Subzone". Appearance of the species Calpionella grandalpina represents a significant horizon; it lies immediately below the base of the magnetozone M19r in all sections. The base of the standard zone Calpionella was used for the definition of the J/K boundary in calpionellid stratigraphy.
UR: http://www.gli.cas.cz/Departments/paleomagnet/projects.htm
DE: 1513 Geomagnetic excursions
DE: 1520 Magnetostratigraphy
DE: 1521 Paleointensity
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting