HR: 0800h
AN: GP11D-0881    [Abstracts]
TI: Evolution Of The Alpha Ride, The Arctic Ocean, On The Basis Of The Geohistorical Analysis Of The Magnetic Anomalies
AU: * Gurevich, N I
EM: gur@vniio.nw.ru
AF: Geological Institute of the Russian Academy of Sciences, 7, Pyzhevsy lane, Moscow, 119017 Russian Federation
AU: Merkouriev, S A
EM: SAM@ns1480.spb.edu
AF: SPbF IZMIRAN, Muchnoy per.,2, BOX 188 , St.Petersburg, 191023 Russian Federation
AB: A new magnetic anomaly map of the Amerasian Basin has been created owing to a joint reprocessing of the Russian and American aeromagnetic data [Glebovsky, Kovacs at all., 2000]. This model produced the base for the magnetic data interpretation on the more qualitative level. As a result three series of seafloor spreading-type magnetic anomalies have been identified within the area of the Alpha Ridge and the adjacent part of the Canada Basin [Gurevich et all, 2003]. Their sources were formed from three spreading centers (SC). Two spreading centers: the western and the eastern, are situated at the axial part of the Alpha Ridge, the third one - the southern, is located on the southern slope of the Alpha Ridge and on the adjacent part of the Canada Basin. The triple junction of these SC had been located in the central part of the recent Alpha Ridge. The geohistorical analysis of these magnetic anomalies is fulfilled using an original computer programs. In consequence of this analysis: the geochronological characteristics are specified; the kinematic characteristics of the oceanic floor movement are determined and the main stages of the area evolution are found. The magnetic anomalies M16r (140 Ma), which signify the position of all three SC, and pair anomalies M20r (146.5 Ma) and M23r (151.5 Ma) are identified enough sure for all three SC and pair anomalies M30r (157.5 Ma) - fore the eastern and the southern SC. Finite and differential Euler poles of the lithospheric plates rotation were calculated for all three SC from best-fit pair magnetic anomalies. All the poles are concentrated around the Nares strait and at the northeastern part of the Ellesmere island. Angle and linear spreading rates were calculated using Euler poles. The calculation has showed that all three SC had low spreading rates. Three stages of the area evolution are found on the basis of the plate tectonic reconstruction for the periods 146.5, 151.5 and 157.5 Ma ago. The first stage, slightly earlier 157.5 Ma ago: the initiation of the oceanic crust formation to the north-west from the recent shelf of the Prince Patrick island. The second stage, from about 157.5 Ma ago: SC had advanced to the north-east; the oceanic crust was forming from one SC. The third stage, from slightly earlier 151.5 Ma ago to 140 Ma ago: the oceanic floor spreading from three SC took place, 140 Ma ago spreading ceased in this area. During the third stage the triple junction of the spreading centers was not stable and changed from type "ridge - ridge - ridge" to type " ridge - ridge - transform". The intraplate volcano-tectonic activity of the oceanic floor that created the Alpha Ridge was t8he fourth stage of the area evolution The kinematic characteristics of the spreading imply of crustal compression in the north of the Greenland and in the north-east of the Ellesmere island and of crustal stretching in the area of the Queen Elizabeth Islands, that agrees with their geological structure. The main stages of the Amerasian Basin evolution correspond by age to unconformities that A. Embry determined in the Mesozoic strata of the Sverdrup Basin [Embry, 1991]. The work has been supported by the Russian Foundation for basic Research (Grant 01-05-65481).
DE: 1517 Magnetic anomaly modeling
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting