⁴⁰Ar-³⁹Ar incremental heating experiments were performed on volcanic rocks recovered by drilling during Ocean Drilling Program Leg 152, southeast Greenland Margin (63°N), and Deep Sea Drilling Project Leg 81, southwest Rockall Plateau (56°N). Both of these legs drilled into thick sections of submerged lava flows, known as seaward-dipping reflector sequences,...
Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has the temporal
but not the isotopic characteristics usually attributed to a mantle plume. The earlier volcanic products of
the hotspot, from eight volcanoes in the Cobb-Eickelberg seamount (CES) chain, show a westward age
progression away from...
Persistent, long‐lived, stationary sites of excessive mantle melting are called hotspots. Hotspots leave volcanic trails on lithospheric plates passing across them. The global constellation of fixed hotspots thus forms a convenient frame of reference for plate motions, through the orientations and age distributions of volcanic trails left by these melting...
Determination of reliable crystallization ages by
K-Ar methods for young (<1 Ma), fresh basalts from the
seafloor has been frustrated by several effects. The small
amounts of radiogenic ⁴⁰Ar developed over these timescales in
such low-K rocks are difficult to resolve from predominantly
atmospheric ⁴⁰Ar. An additional concern is that...
A volcanic sequence almost 700 meters thick has been sampled in the Punaruu valley on the island of
Tahiti, southern central Pacific Ocean. Detailed paleomagnetic results have been obtained from 123 sites. Three
reversals are recorded in this sequence. Age determinations (K-Ar) indicate that the youngest reversal corresponds
to the...
Magnetic and gravity modelling was completed along two E-W transects offshore central Oregon. These models indicate that the backstop-forming western edge of the Siletz terrane has a seaward dip of approximately 40° to 49° at 44°48'N, shallowing to ~28° at 44°1 1 'N. This is a well-determined result, given available...
At the submerged margins of the North Atlantic, andesitic to dacitic and basaltic volcanic rocks occur together. The silicic rocks were derived by processes requiring the presence of continental crust (crustal anatexis and/or contamination of mafic magmas) while the majority of the basaltic lavas had little or no contact with...
Lavas from seamounts of the central Galápagos Platform and the Carnegie Ridge increase in age with distance from the western edge of the platform, consistent with a hotspot model for the generation of these features. The areal distribution of seamount ages suggests that the pattern of dispersed volcanism seen on...
Bathymetry and gravity data collected during Legs 5, 6, and 7 of the 1993 GLORIA Expedition and the recently released 2-min altimetry-derived global gravity grid are used to determine the effective elastic thickness of the lithosphere along the Easter Seamount Chain (ESC). Forward modeling, admittance, and coherence methods yield consistent...