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Cande, SC, Patriat P, Dyment J.  2010.  Motion between the Indian, Antarctic and African plates in the early Cenozoic. Geophysical Journal International. 183:127-149.   10.1111/j.1365-246X.2010.04737.x   AbstractWebsite

P>We used a three-plate best-fit algorithm to calculate four sets of Euler rotations for motion between the India (Capricorn), Africa (Somali) and Antarctic plates for 14 time intervals in the early Cenozoic. Each set of rotations had a different combination of data constraints. The first set of rotations used a basic set of magnetic anomaly picks on the Central Indian Ridge (CIR), Southeast Indian Ridge (SEIR) and Southwest Indian Ridge (SWIR) and fracture zone constraints on the CIR and SEIR, but did not incorporate data from the Carlsberg Ridge and did not use fracture zones on the SWIR. The second set added fracture zone constraints from the region of the Bain fracture zone on the SWIR which were dated with synthetic flowlines based on the first data set. The third set of rotations used the basic constraints from the first rotation set and added data from the Carlsberg Ridge. The fourth set of rotations combined both the SWIR fracture zone constraints and the Carlsberg Ridge constraints. Data on the Indian Plate side of the Carlsberg Ridge (Arabian Basin) were rotated to the Capricorn Plate before being included in the constraints. Plate trajectories and spreading rate histories for the CIR and SWIR based on the new rotations document the major early Cenozoic changes in plate motion. On the CIR and SEIR there was a large but gradual slowdown starting around Chron 23o (51.9 Ma) and continuing until Chron 21y (45.3 Ma) followed 2 or 3 Myr later by an abrupt change in spreading azimuth which started around Chron 20o (42.8) Ma and which was completed by Chron 20y (41.5 Ma). No change in spreading rate accompanied the abrupt change in spreading direction. On the SWIR there was a continuous increase in spreading rates between Chrons 23o and 20o and large changes in azimuth around Chrons 24 and 23 and again at Chron 21. Unexpectedly, we found that the two sets of rotations constrained by the Carlsberg Ridge data diverged from the other two sets of rotations prior to anomaly 22o. When compared to rotations for the CIR that are simultaneously constrained by data from all three branches of the Indian Ocean Triple Junction, there is a progressively larger separation of anomalies on the Carlsberg Ridge, with a roughly 25 km misfit for anomaly 23o and increasing to over 100 km for anomaly 26y. These data require that there was previously unrecognized convergence somewhere in the plate circuit linking the Indian, Capricorn and Somali plates prior to Chron 22o. We quantify this motion by summing our new Capricorn-Somalia rotations with previously published rotations for Neogene India-Capricorn motion and for early Cenozoic Somali-India motion based solely on Carlsberg Ridge data. The most likely possibility is that there was motion within the Somalia Plate due to a distinct Seychelles microplate as young as Chron 22o. The sense of the misfit on the Carlsberg Ridge is consistent with roughly 100-150 km of convergence across a boundary passing through the Amirante Trench and extending north to the Carlsberg Ridge axis between anomalies 26y and 22o. Alternatively, there may have been convergence within the Indian Plate, either along the western margin of Indian or east of the CIR in the region of the current Capricorn-Indian diffuse plate boundary. Our work sharpens the dating of the two major Eocene changes in plate motion recognized in the Indian Ocean.

Barckhausen, U, Ranero CR, Cande SC, Engels M, Weinrebe W.  2008.  Birth of an intraoceanic spreading center. Geology. 36:767-770.   10.1130/g25056a.1   AbstractWebsite

The Cocos-Nazca spreading center is one of the few examples of the formation of a spreading center by splitting of oceanic lithosphere. It was created when the Farallon plate broke up in the early Miocene following the collision of the Pacific-Farallon spreading center with the North American continent. Much of the ancient Farallon plate corresponding to the area of opening is lost to subduction beneath Central America and South America, but new data from the conjugate area on the Pacific plate allow the first detailed reconstruction of the break-up process. The opening began after chron 7 (25 Ma) at a location of focused crustal extension caused by overlapping spreading centers that had evolved in response to a slight reorientation of a Pacific-Farallon ridge segment. Beginning at chron 6B (22.7 Ma), eastward progressing seafloor spreading started along an axis that most likely migrated toward the region of weak lithosphere created by the Galapagos hotspot. By chron 6 (19.5 Ma), plate splitting from the spreading center to the trench was complete, allowing the fully detached Cocos and Nazca plates to move independently. This kinematic change resulted in a significant ridge jump of the newly established Pacific-Nazca spreading center, a change in plate motion direction of the Nazea plate by 20 degrees clockwise, and a large increase in Pacific-Cocos plate velocity in the middle Miocene.

Croon, MB, Cande SC, Stock JM.  2008.  Revised Pacific-Antarctic plate motions and geophysics of the Menard Fracture Zone. Geochemistry Geophysics Geosystems. 9   10.1029/2008gc002019   AbstractWebsite

[1] A reconnaissance survey of multibeam bathymetry and magnetic anomaly data of the Menard Fracture Zone allows for significant refinement of plate motion history of the South Pacific over the last 44 million years. The right-stepping Menard Fracture Zone developed at the northern end of the Pacific-Antarctic Ridge within a propagating rift system that generated the Hudson microplate and formed the conjugate Henry and Hudson Troughs as a response to a major plate reorganization similar to 45 million years ago. Two splays, originally about 30 to 35 km apart, narrowed gradually to a corridor of 5 to 10 km width, while lineation azimuths experienced an 8 degrees counterclockwise reorientation owing to changes in spreading direction between chrons C13o and C6C (33 to 24 million years ago). We use the improved Pacific-Antarctic plate motions to analyze the development of the southwest end of the Pacific-Antarctic Ridge. Owing to a 45 degrees counterclockwise reorientation between chrons C27 and C20 (61 to 44 million years ago) this section of the ridge became a long transform fault connected to the Macquarie Triple Junction. Following a clockwise change starting around chron C13o (33 million years ago), the transform fault opened. A counterclockwise change starting around chron C10y (28 millions years ago) again led to a long transform fault between chrons C6C and C5y (24 to 10 million years ago). A second period of clockwise reorientation starting around chron C5y (10 million years ago) put the transform fault into extension, forming an array of 15 en echelon transform faults and short linking spreading centers.

Muller, RD, Gohl K, Cande SC, Goncharov A, Golynsky AV.  2007.  Eocene to Miocene geometry of the West Antarctic Rift System. Australian Journal of Earth Sciences. 54:1033-1045.   10.1080/08120090701615691   AbstractWebsite

Tectonic models for the Late Cretaceous/Tertiary evolution of the West Antarctic Rift System range from hundreds of kilometres of extension to negligible strike-slip displacement and are based on a variety of observations, as well as kinematic and geodynamic models. Most data constraining these models originate from the Ross Sea/Adore Trough area and the Transantarctic Mountains. We use a new Antarctic continental crustal-thinning grid, combined with a revised plate-kinematic model based on East Antarctic-Australia-Pacific-West Antarctic plate circuit closure, to trace the geometry and extensional style of the Eocene-Oligocene West Antarctic Rift from the Ross Sea to the South Shetland Trench. The combined data suggest that from chron 21 (48 Ma) to chron 8 (26 Ma), the West Antarctic Rift System was characterised by extension in the west to dextral strike-slip in the east, where it was connected to the Pacific-Phoenix-East Antarctic triple junction via the Byrd Subglacial Basin and the Bentley Subglacial Trench, interpreted as pullapart basins. Seismic-reflection profiles crossing the De Gerlache Gravity Anomaly, a tectonic scar from a former spreading ridge jump in the Bellingshausen Sea, suggest Late Tertiary reactivation in a dextral strike-slip mode. This is supported by seismic-reflection profiles crossing the De Gerlache Gravity Anomaly in the Bellingshausen Sea, which show incised narrow sediment troughs and vertical faults indicating strike-slip movement along a north-south direction, Using pre-48 Ma plate circuit closure, we test the hypothesis that the Lord Howe Rise was attached to the Pacific Plate during the opening of the Tasman Sea, We show that this plate geometry may be plausible at least between 74 and 48 Ma, but further work especially on Australian-Antarctic relative plate motions is required to test this hypothesis.

Downey, NJ, Stock JM, Clayton RW, Cande SC.  2007.  History of the Cretaceous Osbourn spreading center. Journal of Geophysical Research-Solid Earth. 112   10.1029/2006jb004550   AbstractWebsite

[ 1] The Osbourn Trough is a fossil spreading center that rifted apart the Manihiki and Hikurangi Plateaus during Cretaceous time. Previous models of the Osbourn spreading center are based on data collected near the trough axis, and therefore only constrain the history of the Osbourn spreading center during the last few Ma of spreading. Our data set includes multibeam data collected northward to the Manihiki Plateau, allowing us to examine seafloor morphology created during the entire active period of the Osbourn spreading center, as well as several additional multibeam data sets that provide the opportunity to examine the relationship between the Osbourn paleospreading center and the Cretaceous Pacific-Phoenix ridge. The axial gravity of the trough is similar to the gravity found at other extinct slow-intermediate spreading rate ridges. Magnetic field measurements indicate that spreading at the trough ceased during Chron C34. Abyssal-hill trends indicate that spreading during the early history of the Osbourn spreading center occurred at 15 degrees- 20 degrees. The east-west component of this spreading explains the modern east-west offset of the Manihiki and Hikurangi Plateaus. Spreading rotated to 2 degrees - 5 degrees prior to extinction. Abyssal-hill RMS amplitudes show that a decrease in spreading rate, from > 7 cm/yr to 2 - 6 cm/yr full-spreading rate, occurred similar to 2 - 6 Ma prior to ridge extinction. Our data analysis is unable to determine the exact spreading rate of the Osbourn spreading center prior to the slowing event. The temporal constraints provided by our data show that the Osbourn spreading center ceased spreading prior to 87 Ma or 93 Ma, depending on whether the Manihiki and Hikurangi Plateaus rifted at 115 Ma or 121 Ma. Our model resolves the conflict between regional models of Osbourn spreading with models based on trough characteristics by showing that spreading at the Osbourn spreading center was decoupled from Pacific-Phoenix spreading.