Müller, R. Dietmar and Cande, Steven C. and Stock, Joann M. and Keller, William R. (2005) Crustal structure and rift flank uplift of the Adare Trough, Antarctica. Geochemistry, Geophysics, Geosystems, 6 (11). 2005GC001027. ISSN 1525-2027 http://resolver.caltech.edu/CaltechAUTHORS:MULggg05
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The Adare Trough, located 100 km northeast of Cape Adare, Antarctica, represents the extinct third arm of a Tertiary spreading ridge between East and West Antarctica. It is characterized by pronounced asymmetric rift flanks elevated up to over 2 km above the trough's basement, accompanied by a large positive mantle Bouguer anomaly. On the basis of recently acquired seismic reflection and ship gravity data, we invert mantle Bouguer anomalies from the Adare Trough and obtain an unexpectedly large oceanic crustal thickness maximum of 9–10.5 km underneath the extinct ridge. A regional positive residual basement depth anomaly between 1 and 2.5 km in amplitude characterizes ocean crust from offshore Victoria Land to the Balleny Islands and north of Iselin Bank. The observations and models indicate that the mid/late Tertiary episode of slow spreading between East and West Antarctica was associated with a mantle thermal anomaly. The increasing crustal thickness toward the extinct ridge indicates that this thermal mantle anomaly may have increased in amplitude through time during the Adare spreading episode. This scenario is supported by a mantle convection model, which indicates the formation and strengthening of a major regional negative upper mantle density anomaly in the southwest Pacific in the last 50 million years. The total amount of post-26 Ma extension associated with Adare Trough normal faulting was about 7.5 km, in anomalously thick oceanic crust with a lithospheric effective elastic thickness (EET) between 3.5 and 5 km. This corresponds to an age between 3 and 5 million years based on a thermal boundary layer model and supports a scenario in which the Adare Trough formed soon after spreading between East and West Antarctica ceased, confined to relatively weak lithosphere with anomalously thick oceanic crust. There is little evidence for major subsequent structural activity in the Adare trough area from the available seismic data, indicating that this part of the West Antarctic Rift system became largely inactive in the early Miocene, with the exception of minor structural reactivation which is visible in the seismic data as offsets up to end of the early Pliocene.
|Additional Information:||Copyright 2005 by the American Geophysical Union. Received: 24 May 2005; Revised: 23 August 2005; Accepted: 27 September 2005; Published: 23 November 2005. This work was supported by National Science Foundation grants NSF OPP 0126334 (to Stock) and OPP-01-26340 (to Cande) and by an Australian Research Council IREX grant (to Müller). We thank Bernhard Steinberger for providing outputs from his mantle convection model published in Steinberger et al. . Two anonymous reviews improved the quality of the paper substantially.|
|Subject Keywords:||Adare Trough; Antarctica; depth anomaly; extinct ridge; flexure; rift; 0930 Exploration Geophysics: Oceanic structures; 3010 Marine Geology and Geophysics: Gravity and isostasy (1218, 1222); 3035 Marine Geology and Geophysics: Midocean ridge processes|
|Official Citation:||Müller, R. D., S. C. Cande, J. M. Stock, and W. R. Keller (2005), Crustal structure and rift flank uplift of the Adare Trough, Antarctica, Geochem. Geophys. Geosyst., 6, Q11010, doi:10.1029/2005GC001027.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Archive Administrator|
|Deposited On:||20 Dec 2005|
|Last Modified:||26 Dec 2012 08:42|
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