@article {Cameselle2015, title = {{The continent-ocean transition on the northwestern South China Sea}}, journal = {Basin Research}, year = {2015}, pages = {n/a{\textendash}{\textendash}n/a}, issn = {0950091X}, doi = {10.1111/bre.12137}, url = {http://doi.wiley.com/10.1111/bre.12137}, author = {Cameselle, Alejandra L and Ranero, C{\'e}sar R and Franke, Dieter and Barckhausen, Udo} } @article {Cameselle2014, title = {{The continent-ocean transition of the rifted South China continental margin}}, journal = {EGU General Assembly Conference Abstracts}, volume = {16}, year = {2014}, month = {may}, pages = {14917}, url = {http://adsabs.harvard.edu/abs/2014EGUGA..1614917C}, author = {Cameselle, Alejandra L. and Ranero, C{\'e} and sar R. and Franke, Dieter and Barckhausen, Udo} } @article {Cameselle2013a, title = {{The continent-ocean transition of the Pearl River margin}}, journal = {AGU Fall Meeting Abstracts}, volume = {-1}, year = {2013}, month = {dec}, pages = {06}, abstract = {Rifted continental margins form by lithospheric extension and break-up. The continent to ocean transition (COT) architecture depends on the interplay between tectonic and magmatic processes, and thus, to study the COT variability of different systems is key to understand rifting. We use MCS data and magnetic lineations across the Pearl River margin (PRM) of South China Sea to investigate a previously poorly defined COT. The structure of the PRM presents different amounts of extension allowing the study of conjugate pairs of continental margins and their COT in a relative small region. We reprocessed about 2250 km of MCS data along 4 regional, crustal-scale lines and found that 3 of them possibly display the COT. The time-migrated seismic sections show differences in internal reflectivity, faulting style, fault-block geometry, the seismic character of the top of the basement, in the geometry of sediment deposits, and Moho reflections, that we interpret to represent clear continental and oceanic domains. The continental domain is characterized by arrays of normal faults and associated tilted blocks overlaid by syn-rift sedimentary units. The Moho is imaged as sub-horizontal reflections that define a fairly continuous boundary typically at 8-10 s TWT. Estimation of the thickness of the continental crust using 6 km/s average velocity indicates a \~{}22 km-thick continental crust under the uppermost slope passing abruptly to \~{}9-6 km under the lower slope. Comparatively the oceanic crust has a highly reflective top of basement, little-faulting, not discernible syn-tectonic strata, and fairly constant thick aness (4-8 km) defined by usually clear Moho reflections. The COT occurs across \~{}5-10 km narrow zone. Rifting resulted in asymmetric conjugate margins. The PRM shows arrays of tilted fault blocks covered by abundant syn-rift sediment, whereas the conjugate Macclesfield Bank margin displays abrupt thinning and little faulting. Seismic profiles also show a change in the tectonic structure from NE to SW. On the two NE- most lines, crustal thinning and break-up occur over 20-40 km wide segments. To the SW, continental extension occurred over a comparatively broader \~{}100-110 km segment of tilted fault-block structure. We interpret, that this 3D structural variability and the narrow COT was caused by the lateral NE to the SW propagation of a spreading center. In the NE, early spreading center propagation during ongoing rifting stopped continental stretching, causing an abrupt break-up and a narrow COT to seafloor spreading. Later arrival of spreading center propagated to the SW, resulted in a comparatively broader segment with fault-block structures of extended continental crust. However, the COT to clear oceanic crust is narrow. Spreading center propagation in the basin is however not a simple phenomena and ridge jumps and abrupt cessation of spreading contributed to form narrow COT that laterally change to highly thinned continental crust segments. We suggest that the tectonic architecture of continental extension and the abrupt COT along the PRM have been controlled by 3D oceanic spreading center propagation to a degree larger than by the local lithospheric structure during rifting.}, keywords = {8105 TECTONOPHYSICS Continental margins: divergent}, url = {http://adsabs.harvard.edu/abs/2013AGUFMOS23E..06C}, author = {Cameselle, Alejandra L. and Ranero, Cesar R. and Franke, Dieter and Barckhausen, Udo} } @article {Harris2010a, title = {{Thermal regime of the Costa Rican convergent margin: 1. Along-strike variations in heat flow from probe measurements and estimated from bottom-simulating reflectors}}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {11}, number = {12}, year = {2010}, month = {dec}, pages = {n/a{\textendash}n/a}, abstract = {The thermal structure of convergent margins provides information related to the tectonics, geodynamics, metamorphism, and fluid flow of active plate boundaries. We report 176 heat flow measurements made with a violin bow style probe across the Costa Rican margin at the Middle America Trench. The probe measurements are collocated with seismic reflection lines. These seismic reflection lines show widespread distribution of bottom-simulating reflectors (BSRs). To extend the spatial coverage of heat flow measurements we estimate heat flow from the depth of BSRs. Comparisons between probe measurements and BSR-derived estimates of heat flow are generally within 10\% and improve with distance landward of the deformation front. Together, these determinations provide new information on the thermal regime of this margin. Consistent with previous studies, the margin associated with the northern Nicoya Peninsula is remarkably cool. We define better the southern boundary of the cool region. The northern extent of the cool region remains poorly determined. A regional trend of decreasing heat flow landward of the deformation front is apparent, consistent with the downward advection of heat by the subducting Cocos Plate. High wave number variability at a scale of 5-10 km is significantly greater than the measurement uncertainty and is greater south of the northern Nicoya Peninsula. These heat flow anomalies vary between approximately 20 and 60 mW m-2 and are most likely due to localized fluid flow through mounds and faults on the margin. Simple one-dimensional models show that these anomalies are consistent with flow rates of 7-15 mm yr-1. Across the margin toe variability is significant and likely due to fluid flow through deformation structures associated with the frontal sedimentary prism. Copyright 2010 by the American Geophysical Union.}, keywords = {fluid flow, heat flow, Middle America Trench, subduction zones}, issn = {15252027}, doi = {10.1029/2010GC003272}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-78650544794\&partnerID=tZOtx3y1}, author = {Harris, Robert N. and Grevemeyer, Ingo and Ranero, Cesar R. and Villinger, Heinrich and Barckhausen, Udo and Henke, Thomas and Mueller, Christian and Neben, Soenke} } @article {Harris2010, title = {{Thermal regime of the Costa Rican convergent margin: 2. Thermal models of the shallow Middle America subduction zone offshore Costa Rica}}, journal = {Geochemistry, Geophysics, Geosystems}, volume = {11}, number = {12}, year = {2010}, month = {dec}, pages = {n/a{\textendash}n/a}, abstract = {At the Costa Rica margin along the Middle America Trench along-strike variations in heat flow are well mapped. These variations can be understood in terms of either ventilated fluid flow, where exposed basement allows fluids to freely advect heat between the crustal aquifer and ocean, or insulated fluid flow where continuous sediment cover restricts heat advection to within the crustal aquifer. We model fluid flow within the subducting aquifer using Nusselt number approximations coupled with finite element models of subduction and explore its effect on temperatures along the subduction thrust. The sensitivity of these models to the initial thermal state of the plate and styles of fluid flow, either ventilated or insulated, is explored. Heat flow measurements on cool crust accreted at the East Pacific Rise are consistent with ventilated hydrothermal cooling that continues with subduction. These models yield much cooler temperatures than predicted from simulations initialized with conductive predictions and without hydrothermal circulation. Heat flow transects on warm crust accreted at the Cocos-Nazca spreading center are consistent with models of insulated hydrothermal circulation that advects heat updip within the subducting crustal aquifer. Near the trench these models are warmer than conductive predictions and cooler than conductive predictions downdip of the trench. Comparisons between microseismicity and modeled isotherms suggest that the updip limit of microseismicity occurs at temperatures warmer than 100{\textdegree}C and that the downdip extent of microseismicity is bounded by the intersection of the subduction thrust with the base of the overriding crust. Copyright 2010 by the American Geophysical Union.}, keywords = {fluid flow, subduction zones, thermal model}, issn = {15252027}, doi = {10.1029/2010GC003273}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-78650528793\&partnerID=tZOtx3y1}, author = {Harris, Robert N. and Spinelli, Glenn and Ranero, Cesar R. and Grevemeyer, Ingo and Villinger, Heinrich and Barckhausen, Udo} } @article {Barckhausen2008, title = {{Birth of an intraoceanic spreading center}}, journal = {Geology}, volume = {36}, number = {10}, year = {2008}, pages = {767}, abstract = {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 Nazca plate by 20{\textdegree}clockwise, and a large increase in Pacific-Cocos plate velocity in the middle Miocene. {\textcopyright} 2008 The Geological Society of America.}, keywords = {Central Pacific, Farallon breakup, Galapagos hotspot, Magnetic anomalies}, issn = {0091-7613}, doi = {10.1130/G25056A.1}, url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-54949104690\&partnerID=tZOtx3y1}, author = {Barckhausen, Udo and Ranero, Cesar R. and Cande, Steven C. and Engels, Martin and Weinrebe, Wilhelm} }