Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30°N

Crustal Thickness on the Mid-Atlantic Ridge: Bull's-Eye Gravity Anomalies and Focused Accretion.

Spreading segments of the Mid-Atlantic Ridge show negative bull's-eye anomalies in the mantle Bouguer gravity field. Seismic refraction results from 33 degrees S indicate that these anomalies can be accounted for by variations in crustal thickness along a segment. The crust is thicker in the center and thinner at the end of the spreading segment, and these changes are attributable to variations...

Structure of oceanic core complexes: Constraints from seafloor gravity measurements made at the Atlantis Massif

[1] Using the DSV Alvin, the relative seafloor gravimeter ROVDOG was deployed at 18 sites on the Atlantis Massif (located at the ridge-transform intersection of the MidAtlantic Ridge and the Atlantis Transform Fault near 30 N, 42 W). These data along with previously collected shipboard gravity and bathymetry provide constraints on the density structure of this oceanic core complex. A series of ...

Dominance of one bacterial phylotype at a Mid-Atlantic Ridge

Microbial community structure in natural environments has remained largely unexplored yet is generally considered to be complex. It is shown here that in a Mid-Atlantic Ridge hydrothermal vent habitat, where food webs depend on prokaryotic primary production, the surface microbial community consists largely of only one bacterial phylogenetic type (phylotype) as indicated by the dominance ofa si...

Locating the spreading axis along 80 km of the Mid-Atlantic Ridge south of the Atlantis Transform

The zone of active eruptive fissuring (the “spreading axis”) is investigated at an accretionary segment of the Mid-Atlantic Ridge. High-resolution side-scan images are used to produce a detailed geologic map of the median valley floor of Segment 18, located immediately south of the Atlantis Transform (30oN). The spreading axis is defined by distinguishing between primary eruptive vents (seamoun...

Evolution of the accretion processes along the Mid-Atlantic Ridge north of the Azores since 5.5 Ma: An insight into the interactions between the ridge and the plume