The tectonic evolution of the transition zone from the Pacific Ocean to the Atlantic Ocean is closely linked with the destruction of the American–Antarctic continental bridge in the Scotia Sea. The ...western segment of the bridge combines the Terror, Pirie, and Bruce banks, as well as the Protector and Dove basins between them. Modeling—primarily based on original geological and geophysical materials—of linear magnetic anomalies and calculation of the floor kinematics in these basins have made it possible for the first time to reveal that the collapse of the western segment of the American–Antarctic continental bridge occurred 18–25 Ma ago via a two-stage separation of the Pirie Rise from the Bruce Rise with the formation of the Dove Basin and a two stage separation of the Terror Rise from the Pirie Rise with the formation of the Protector Basin.
Age of the Scan Basin (Scotia Sea) Schreider, Al. A.; Schreider, A. A.; Galindo-Zaldivar, J. ...
Oceanology (Washington. 1965),
03/2017, Volume:
57, Issue:
2
Journal Article
Peer reviewed
Integrated geological and geophysical analysis of the anomalous magnetic field along with the previously unpublished profiles of Spanish expeditions onboard the R/V
Hesperides
and international ...databases of geomagnetic data processed in the context of the global tectonics concepts made it possible to identify paleomagnetic anomalies C11–C15 and compile the first map of the bottom geochronology of the Scan Basin. Unlike in earlier known publications, the paleoaxis of spreading does extend northeast, but approximately at an angle of 345°. According to calculations, spreading began 35.294‒35.706 Ma ago during chron C15r, and the spreading paleoaxis was abandoned 29.527‒29.970 Ma ago during chron C11n.2n. Thus, the destruction of the American–Antarctic bridge in the region joining the Bruce and Discovery banks with formation of oceanic crust in the Scan Basin started about 36 Ma ago. Regular spreading of the bottom has been continuing for about 6 Ma at a average rate close to 1.8 cm/year.
The study of the sedimentary body of the Bransfield Strait has made it possible to identify several sedimentary complexes, to construct the first electronic charts for the acoustic basement, and to ...establish four stages of the evolution of its floor, which updates the previous knowledge about the formation of the strait. At the first stage, there was an increase in tension stresses that were accompanied by the local splits of the continental crust at the periphery of the Antarctic Peninsula. At the second stage, a graben-like structure filled with the Lower stratigraphic complex was formed northward of the Antarctic Peninsula. At the third stage, the continuing processes of extension led to intensive explosive activity of the growing volcanic structures and filling of the graben with sediments of the Middle seismostratigraphic complex. The fourth stage, which has continued until recently, is characterized by quasi-linear localization of the major centers of volcanic activity in the band closer to the South-Shetland Islands and the formation of the Upper seismostratigraphic sedimentary complex. The evolution of the floor of the Bransfield Strait reflects the process of penetration of the American-Antarctic ridge to the continental lithosphere of the Antarctic Peninsula for the last million years.
Structure of the Bransfield strait crust Schreider, Al. A.; Schreider, A. A.; Galindo-Zaldivar, J. ...
Oceanology (Washington. 1965),
02/2015, Volume:
55, Issue:
1
Journal Article
Peer reviewed
Data on the high heat flow, active volcanism, and extensional folding, in combination with modeling of the gravity and magnetic anomalies and earthquake focal mechanisms, indicate that the Bransfield ...strait floor represents a zone of lithosphere extension forming in the Antarctic Peninsula. The most important structural element of the strait floor is the neovolcanic zone near the South Shetland Islands and the diapirism zone near the Antarctic Peninsula. The discussed stages of rifting of the Bransfield floor reflect the propagating of the American-Antarctic Ridge into the continental lithosphere of the Antarctic Peninsula. The propagating causes thrusting of the South Shetland Island arc onto the peripheral part of the relict Phoenix plate, which is accompanied by the seismicity in the South Shetland trench.
The separation of Ceylon from Antarctica Schreider, Al. A.; Schreider, A. A.; Boiko, A. N. ...
Oceanology (Washington. 1965),
08/2011, Volume:
51, Issue:
4
Journal Article
Peer reviewed
The geometry of the junction between Ceylon and Antarctica during the Gondwanaland breakup is still under discussion. Analysis of the available geological-geophysical materials has allowed the ...peculiarities of Ceylon separation from Antarctica to be characterized, the new paleogeodynamical reconstruction to be elaborated, and a prognosis of the tectonic structure and mineral resources in the areas of Antarctic coast that were adjacent to Ceylon to be made.
The first map of the acoustic basement and the new map of chrons C1-C5E for the region of the East Scotia mid-ocean ridge have been made. The analysis of the maps and the calculations have indicated ...that the sea-floor spreading at the ridge’s flanks started in its southeast in the interval of chrons C5Er-6An (18.52–20.17 Ma BP). The maximal spreading rate (5.3 cm/year) was in the interval of chrons C5Bn-C5Br (14.78–15.97 Ma BP). Then, the spreading rate was slow and increased again from 3–6 Ma BP until the present. The spreading in the last 1–2 Ma was accompanied by the propagating of the axes southwards in the E1, E2, and E4 segments and northwards in the E8 and E9 segments.
The first map of the acoustic basement and a new map of the C
4
-C
12
chrons are made for the area of the paleospreading West Scotia Ridge. The analysis of the constructed maps and the calculations ...showed that the bottom growth in the ridge axes began in the southeast in the interval of chron C
12r
(31.116–33.266 Ma B.P.). In the period of chron C11r (30.217–30.627 Ma), a hundred-kilometer northwestward jump of the spreading axis occurred. The maximal values of the bottom growth (about 6.3 cm/yr) were in the interval of chrons C6–C6B (18.748–22.546 Ma); then, the spreading began to fade. In the time of chron C3n.1r (3.300–4.493 Ma B.P.), the axis of the paleo-mid-oceanic ridge died. The spreading was accompanied with northeastward propagating of the axes, and the propagating proper had an impulse character.
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