3D/4D seismic reflection imaging of the internal structure of the magmatic-hydrothermal system at the East Pacific Rise 9°50’N
In summer 2008 we conducted the first 3D multi-channel seismic investigation aboard the R/V Langseth, the new seismic ship operated by Lamont. The goals of our program are to create an accurate 3D seismic reflection image of the magmatic-hydrothermal system at the EPR ISS by imaging the structure of the axial magma chamber (AMC) lid and shallow oceanic crust at a resolution, geometric accuracy, and scale comparable to seafloor observations of hydrothermal, biological, and volcanic activity. 3D migration techniques now commonly in use will allow us to construct geometrically accurate high-resolution images of the magma system and its distribution in the subsurface, while 3D amplitude variation with offset (AVO) analysis will allow us to determine the seismic properties (e.g., velocity, density, Poisson’s ratio) that are proxies for the porosity and fluid content of the magma body. The 6 km offset of the hydrophone streamers will permit a detailed 3D characterization of the thickness and velocity of seismic Layer 2A and the upper part of Layer 2B. Our 3D seismic study will establish a baseline image of the magma body and upper crust in this region against which changes in geometry and physical properties can be detected in the future using 4D time-lapse seismic imaging technology. This work is funded by the National Science Foundation and is a collaboration with researchers at WHOI and Dalhousie. For more information visit our cruise web site here.
A multi-channel seismic reflection investigation of axial crustal structure and alteration of the upper crust at the Juan de Fuca spreading center
This project supported the first regional investigation of crustal structure along the axis and flanks of the Juan de Fuca Ridge (JdF) using modern multichannel seismic (MCS) techniques (cruise EW0207). Despite the extensive mapping, sampling and hydrothermal studies carried in the region for the past 25 years, and the evidence for ongoing volcanic activity, remarkably little has been known about the sub-seafloor structure of the JdF Ridge. The aims of our study were to determine the location, size and physical properties of crustal magma bodies along the JdF and relate these properties to the recent eruptive history of the ridge; measure the variation in velocity and thickness of the shallowest crust (seismic layer 2A/2B) to constrain crustal emplacement models; and characterize the alteration history of the upper crust (seismic layer 2A/2B) as a function of sedimentation history, crustal age and basement relief. Seismic data reveal magma bodies beneath all segments of the Juan de Fuca Ridge and underlie all mapped vents fields indicating the hydrothermal system along this intermediate spreading ridge is a magmatically driven system, similar to that found on the faster spreading ridges. Possible melt sills are imaged at the base of the crust, consistent with the multiple sill hypothesis for the formation of ocean crust. The data also indicate that the axial rift valley along this intermediate spreading ridge is the result of magmatic processes within the upper crust rather than tectonic extension of the crust during amagmatic periods. This work is funded by the NSF and is a collaboration with researchers at WHOI and SIO. Some papers resulting from this work are:
Carbotte, S.M., M. Nedimovic, J.P. Canales, G.M. Kent, , A.J. Harding, M. Marjanovic, Variable crustal structure along the Juan de Fuca Ridge: influence of on-axis hot spots and absolute plate motions. G-Cubed, Vol. 9, doi:10.1029/2007GC001922. 2008. PDF Full resolution versions of Figure 3a-c.
Carbotte, S.M., R. S. Detrick, A. Harding, J.P. Canales, J. Babcock, G. Kent, E. Van Ark, M. Nedimovic, J. Diebold, Rift topography linked to magmatism at the intermediate spreading Juan de Fuca Ridge. Geology, 34, 209–212, 2006. PDF
Canales, J. P, Robert S. Detrick, S. M. Carbotte, Graham M. Kent, John B. Diebold, Alistair Harding, Jeffrey Babcock, Mladen Nedimovic, and Emily van Ark Upper Crustal Structure and Axial Topography at Intermediate-Spreading Ridges: Seismic Constraints from the Southern Juan de Fuca Ridge, JGR, 110, B12104, doi:10.1029/2005JB003630, 2005.
Nedimovic, M Carbotte, S. Harding, A, Detrick, R.S., Canales, P.J., Kent, G. M., Tischer, M., Diebold, J., J. Babcock, Frozen subcrustal magma lenses, Nature 436, 1149-1152, 2005. PDF
Magmatic segmentation of the mid-ocean ridge and links to plate kinematics
Modern digital data compilations provide opportunities to examine local properties within a global context, revealing new relationships and insights into underlying processes. Over 70% of the global mid-ocean ridge has now been mapped with multibeam sonars and much of this data is synthesized and publicly available within the Ridge Multibeam Synthesis. This global compilation reveals a correlation between ridge axis morphology and migration of the ridge axis relative to the underlying mantle. Ridge morphology is believed to be linked to the architecture and volume of mantle melt supplied to the spreading center. The relationships observed between ridge morphology and the absolute motion of the plate boundary, indicates that variations in melt delivery to mid-ocean ridges arise from the geometry and motion of the plates. Papers describing this work include:
Supak, S., Carbotte, S.M., and K. C. Macdonald, 2007, Influence of ridge migration and proximity to hot spots on the morphology of slow- and intermediate-spreading centers. Geochem. Geophys. Geosyst..8 Q01010, doi:10.1029/2006GC001387, 2007. PDF
Katz, R., M Spiegelman, SM Carbotte, Ridge migration, asthenospheric flow and the origin of magmatic segmentation in the global mid-ocean ridge system, GRL 31, doi:10.1029/2004GL020388, 2004. PDF
Carbotte, S.M., C. Small, and K. Donnelly, The influence of ridge migration on the magmatic segmentation of mid-ocean ridges, Nature, 429, 743-746, 2004. PDF
High resolution mapping within the Hudson River Estuary
Modern geophysical mapping techniques and extensive bottom sampling have been used to characterize the river bottom and underlying sediments from the New York Harbor to Troy. A record of human occupation in the Hudson Valley since colonial times is preserved in the river bottom including evidence of ship wrecks, dredge spoils and channels, anchor drag marks, cable crossings and other markings. Subbottom profiling data reveal ancient oyster beds once harvested by local indigenous populations buried within the sediments of the Hudson south from Haverstraw Bay. The subbottom images and cores also provide evidence for changes in sedimentation through the region going back thousands of years. The mapping work was conducted in collaboration with researchers at SUNY Stony Brook and Queens College and funded by the New York State Department of Environmental Conservation (DEC). On-going research has been funded by the Hudson River Foundation. Some papers describing this work include:
Carbotte, S.M., R.E. Bell, W.B.F. Ryan, C. McHugh, A. Slagle, F. Nitsche, J. Rubenstone,. Environmental change and oyster colonization within the Hudson River estuary linked to Holocene climate. Geo-Marine Letters 24: 212–224 DOI 10.1007/s00367-004-0179-9, 2004. PDF
Slagle, A.L., W.B.F. Ryan, S.M. Carbotte, R. Bell, F.O. Nitsche, and T. Kenna, Estuary infilling controlled by limited accommodation space in the Hudson River, Marine Geology, 2006. PDF
Nitsche, F. O., W.B.F Ryan, S.M. Carbotte, R.E. Bell, A.Slagle, C. Bertinado, R. Flood, T. Kenna, C. McHugh, Regional Patterns and Local Variations of Sediment Distribution in the Hudson River Estuary, Estuarine, Coastal and Shelf Science, 71, 259-277, 2007. PDF
Read more about the Hudson River Mapping Project at
OTHER RECENT RESEARCH
Multichannel seismic reflection studies of the South-East Indian Ridge.
In 2001 we conducted a multi-channel seismic study of the SEIR (EW0114) to investigate variations in crustal structure associated with the marked variations in ridge morphology found along this constant intermediate spreading rate ridge. Read more here PDF
Seismic study of the shallowest, most robust East Pacific Rise: magmatic and spreading rate influences on axial and young ocean crustal structure.
During cruise EW9503 we conducted a multi-channel seismic reflection study of the East Pacific Rise from 15°30-17°N. In this region spreading rate is constant at a fast-intermediate rae, but ridge structure differs dramatically between two adjoining ridge segments. Results from this study are described in Carbotte et al 2000 PDF and Carbotte, et al 1998. PDF
Exploiting digital elevation models to study deformation and volcanic processes at Mid-Ocean Ridges.
In this study we use ultra-high resolution bathymetry data collected with ABE from the East Pacific Rise at 18°S to study the role of tectonic stretching and magmatic subsidence in the formation of the axial depression found at this ridge segment. Read more here PDF